Astronomers talk about all the amazing discoveries they’re making but sometimes, it turns out, they were wrong. After decades and centuries of discoveries, how have they changed their minds?

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THANK YOU! - Fraser and Dr. Pamela

(This is an automatically generated transcript)

Fraser Cain [00:01:19] Astronomy Cast episode 700. The Things We Got Wrong. Welcome to Astronomy Cast for weekly facts space during the cosmos, where we help you understand not only what we know, but how we know what we know. I'm Fraser Cain. I'm the publisher of Universe Today. With me, as always, is Doctor Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmic Quest. Hey, mama. How are you doing? 

Pamela Gay [00:01:42] I am doing well. I am still recovering from American Thanksgiving. I know you got Thanksgiving out of out of the way back in October, but we're a little behind down here. 

Fraser Cain [00:01:55] Well, I mean, I am now experiencing American Thanksgiving in situ. I am surrounded by Americans experiencing Thanksgiving. Well, well, we just huddle up and watch Apple TV shows. But but now I think we've gotten through the other side of this, and now life's going to return to normal. Is something else really big and consumerist between now and the end of the year. So everything should be fine. 

Pamela Gay [00:02:17] I need to get Santa hats for the skeletons in the yard. 

Fraser Cain [00:02:20] There are Santa hats on on the cactus is here. It's hilarious. Yeah. People put like, you know, you've got some little saguaro cactus and someone's put multiple Santa hats on each one of the little heads of the cactus. Yeah, it's it's no. 

Pamela Gay [00:02:35] One giant googly eyes to put on cacti like you can or just like, giant eyes out of felt that you can slide over the needles without harming the. Yeah. Oh, this so needs to be like a midnight hack. 

Fraser Cain [00:02:49] That sounds good. 

Pamela Gay [00:02:50] I need teenagers. 

Fraser Cain [00:02:53] Astronomers talk about all the amazing discoveries they're making, but sometimes it turns out they were wrong. After decades and centuries of discoveries, how have they changed their minds? And I think I want to clarify, because when you pitch the story, I'm like, when we were wrong or when astronomy was wrong, and it was clear when, yes, it was when astronomy was wrong. 

Pamela Gay [00:03:14] And we reported on it. 

Fraser Cain [00:03:17] And we reported on it. Yeah, yeah. So we're wrong by proxy. Exactly, exactly. 

Pamela Gay [00:03:22] We never make mistakes. 

Fraser Cain [00:03:24] Yep, yep. All right. So, you know, you've got a bunch in your mind. I know I will be able to throw some in addition, on top of that, where do you wanna start? 

Pamela Gay [00:03:34] Planetary formation. Okay. Just. We don't know how it works. 

Fraser Cain [00:03:41] Sure, but what was the original idea for how planetary formation worked? 

Pamela Gay [00:03:45] So when we started this show. Well, so the original idea going way back was you have a solar nebula, and this part was still fine. Still fine? Where? Where a collapsing molecular cloud fragments into solar system blobs. Size varies with solar system collapses down, begins to spin. Because it's spinning, it flattens just like pizza dough. And in this disk of swirling material in the core where it's densest, you get a star. Further out, you get planets and everything forms where it is. With the rocky planets forming and staying near the star, the gassy planets forming and staying in the outer parts of the solar system, and then icy junk. It's the migratory stuff that decides it needs to come in and make a light show now and then. 

Fraser Cain [00:04:42] Right? And so where we have planets now is where the planets form. They scooped up the material within their region, and you got a planet. And where there wasn't enough material, you didn't get planets or material was stolen. And so in the last couple of decades, how has this picture changed? 

Pamela Gay [00:05:04] Well, in in the 1990s, we started realizing there are worlds orbiting other stars. The first discovery was actually of basically rocky objects going around and around a pulsar. Then we had discovery of 51 peg, having a. Object half the size of Jupiter, with less than half the orbital radius of Mercury going around a young star, not two. Hugely different from our own sun, and according to all of our understanding of all of the solar systems that should be out there, this should not be an option. And as we found more and more worlds throughout the 90s and 2000s, we kept finding things that did not match our own solar system. And so new models were needed that allowed things to migrate. And once astronomers got to thinking about planetary migration, they also gave a good hard stare at our own solar system. And they were also starting to worry about things like, why was there an era in the past that appears to have significantly more cratering than other epics in the past? So why was this one set of a billion years particularly violent? And a group of researchers gathered together in the city of Nese, France, built this idea that you could have massive amounts of planetary migration where worlds could migrate both inwards due to, dynamical friction and absorbing material as they went. Or you could have gravitational rearranging with the notion that at some point in our solar system's history, Saturn and Neptune were nice and politely in resonance with one another and started flinging Uranus and Neptune and many other things all about the solar system. 

Fraser Cain [00:07:18] And so, I mean, this is the nice model, not the nice model niece. And this model is not the nice model. Oh, no, she's named after the place in France. And I mean, I think where the revolution came was with the development of next generation telescopes, both on the ground and in space. So on the ground we have alma. And alma is this incredibly sensitive instrument that's looking in the microwave. And it is sorry in the submillimeter sorry, almost. This incredible instrument is looking in the submillimeter. And it is seeing through the gas and dust into newly forming planetary systems. And we've got these images, dozens of newly forming planetary systems where you see the the collections where new planets are forming. And now suddenly, instead of just having one solar system that we know of, that we have it all mapped out. Now we see dozens of these things at various stages and different configurations, allowing them to compare and contrast the different models and say, oh, I. In fact, this nice model planet migration makes a ton of sense. And then we've got this whole new revolution in in planet hunting telescopes, Kepler, which died too soon, and Tess, which are showing us how many of these hot Jupiters there are out there. It's not a one time 51 pack. There is a there are dozens, dozens, hundreds of these hot Jupiters. So clearly migration is one of the dominant processes that are happening in solar systems. 

Pamela Gay [00:08:52] But it turns out even the nice model is incomplete. With the nice model, it's super easy to create a solar system that has, for instance, all of our Kuiper Belt objects with their wild and crazy elliptical and very inclined orbits. But it's very hard to create all the Kuiper Belt objects, all of the Trojans that are on fairly circular orbits, Trojans we can get to via Jupiter, centaurs, though centaurs in the plain of our galaxy on fairly circular orbits just don't fall naturally out of the nest model. And then when we start looking at the mass distribution of these objects, it again makes even less sense. So there's something completely missing. And then we're finding solar systems that are developing on timescales that don't make any sense to us. Where with with the nice model and the solar nebula model, you have this young star turning on slash cleaning with light pressure, the solar system around it. And when you start comparing the timescales that we're now finding that stars turn on and the timescales that massive planets form, we need a way to get more material into the inner solar system of these forming systems faster, or those gas giants just can't creep fast enough to explain their size. 

Fraser Cain [00:10:35] And so what's the mechanism that's been developed for this there? 

Pamela Gay [00:10:40] So they're now starting to think, and this is where where I'm personally very much of the we don't really understand planetary formation school of thought. But the thing that's making the most sense is that just like galaxies sometimes form in a sudden collapse of a massive amount of mass, perhaps solar systems form in a much faster collapse. And we had previously thought, and if you have a faster collapse, you feed them more matter and faster. 

Fraser Cain [00:11:12] Yeah. And I think this is the part that was really surprising to astronomers is how fast this process seems to go. Like the thought was it would take a million years that the planet would slowly drift around in this region, slowly accrete material bigger and bigger, have impact. But now it looks like it's it happens in tens of thousands of years, maybe thousands of years, maybe hundreds of years that it just comes together so quickly. Yeah, like a instant collapse into a planet. And then you've got this clearing out. And I think that's really exciting because now you don't have so much tension between the activity of the star. You have the mass turning into the planets in their appropriate places almost as quickly as it's possible to happen. And I think that gives us a lot more latitude for the planets being able to form before the star is able to kick everything out. 

Pamela Gay [00:12:03] And so we're now at this point where we see people, instead of saying that solar systems are formed with an accretion disk model, that they're instead formed with a collapsed disk model. And I, I have to admit. I kind of feel like both will be an answer, because it keeps turning out that both is always the answer in our universe. 

Fraser Cain [00:12:25] And also dust. 

Pamela Gay [00:12:27] And also dust. 

Fraser Cain [00:12:28] Right? Yeah. Which to you later on, I'm sure. 

Pamela Gay [00:12:31] Yeah. 

Fraser Cain [00:12:32] Yeah, yeah. Okay. Well, I think that's great. All right. What's the next mystery that astronomers were kind of wrong about? 

Pamela Gay [00:12:41] I feel like long gamma ray bursts really need some attention. 

Fraser Cain [00:12:47] Because what is a long gamma ray burst? 

Pamela Gay [00:12:50] So. So we discovered back in the 1960s that various regions of our sky just feel the need to flash out gamma ray energy in a way that to a detector that simply goes detection. No detection. Not where detection looks rather like our enemies are launching nuclear weapons, which is bad that. With further study over the past many decades, we've now been able to go not just where burst, but also how long, what frequency, and all sorts of different details. And we've begun to realize that gamma ray bursts broadly appear to come in short duration and long duration. And and for the longest period of time in the early 2000s, the argument was, these long ones must be some sort of a supernova event. And this came from our ability to find leaves thanks to telescopes like Swift go from. There's gamma ray bursts in this giant area of the sky to flipping over X-ray detectors and go, okay, the x rays are coming from the smaller area looking with an optical detector and then seeing, oh, it's actually this thing right here and figuring out there's something that looks like a supernova going on. And so we're going to say a special fraction of supernovae are pointed directly at us and causing gamma ray bursts. So that's where we started the story. 

Fraser Cain [00:14:32] And so that's what that's what we used to think was that the gamma ray burst was, was that the beam was directed at us. 

Pamela Gay [00:14:41] And that was the only special thing. 

Fraser Cain [00:14:44] Right? Okay. 

Pamela Gay [00:14:45] So yeah. Yeah. But the problem with that, we don't see enough things exploding. If that's if that's all that's going on. Right. So so we, we know there's a certain number of supernovae that go off every year. We know what kinds most of them are. We know how many gamma ray bursts go off and we can match them. And if you assume that the things producing supernovae and gamma ray bursts have a completely random orientation on the sky, a random spin rotation of the thing that goes boom, you can calculate what fraction of supernovae should be giving off gamma ray bursts. And in the number of gamma ray bursts seems to be significantly too low. So then people started arguing. Well, these must be specially super rotating supernovae. But then the question becomes, why are these spinning so differently from everything else? 

Fraser Cain [00:15:52] And I think it's really important to sort of make that distinction. The difference between a supernova and a gamma ray burst is like the gamma ray bursts are just ludicrously bright. That they are. We are seeing them so bright from half a universe away compared to regular old boring supernova which explode with a, you know, mediocre amount of enormous energy. 

Pamela Gay [00:16:17] They only give off as much energy as the solar system, and they're within, whereas the gamma rays are like, I shall be the brightest thing in the sky. This. 

Fraser Cain [00:16:24] Yeah. Yeah. Yeah. Gamma ray burst will give off as much energy as the entire galaxy for a while. Like it's off the charts, while a supernova merely gives off the entire light of a, you know, a sun for 100 years or something like some long amount, but it's just next level. And so, like, how did this, I guess, what made this story or this. Yeah, more complicated. So we started to get a sense that there was actually a lot more to this than we knew. 

Pamela Gay [00:16:54] Well, folks started to notice things like when you look in detail at some of the gamma ray bursts that have been close enough that we could start doing that, it was realized, well, this one over here kind of looks like there was a binary star involved. So there are some people that are saying perhaps what we're seeing is star goes supernova. If it has a companion star like a neutron star. So a stellar remnant as a companion, the mass feeding on to that will create a disk that generates jets. So maybe that can explain some of them. And it's those jets that are gamma rays. And the physics for that worked super well. And it starts to explain why we see the numbers that we see. And so we're starting to see papers that are like, okay, is this due to binary star systems. But we're still trying to figure this out. And there there is also this weird thing that we're starting to realize where when you use different kinds of gamma ray telescopes that may examine more or less of the gamma ray part of the spectrum. The split between we're going to call this a long gamma ray burst, and a short gamma ray burst appears at a different time. So with some data, with some telescopes, it's like anything longer than two seconds probably has a supernova involved in the system that's going gamma ray other telescopes. It's point eight seconds. So this tells us we have a lot to figure out about what is what is the full distribution of light across all the colors coming out of these things. And how do you explain that? Why is why is it producing different colors at different times for different periods of time? And. Is it one kind of thing or many kinds of things? We still have a lot to figure out, and I think what we have learned, just like with planetary formation, is we thought we knew what was going on. But the universe is more creative than we are and our understanding is incomplete and was wrong. 

Fraser Cain [00:19:12] I mean, what's kind of amazing when I sort of think back at the very beginning and I'm sure we have a show, but this is like gamma ray bursts. There was a thing called gamma ray bursts, and then it got split into two. And so you had short gamma ray bursts and long gamma ray bursts. And it really looks now like the short gamma ray bursts are due to colliding neutron stars, you know, or a neutron star in a white dwarf or a neutron star or a black hole. Some kind of collision. While the long gamma ray bursts are these biggest stars in the universe exploding a supernova. But then we're getting in. Now, just in the last couple of years, we're getting these things being broken, sliced even more. Like maybe you're getting these short gamma ray bursts into neutron star, neutron star, neutron star, white dwarf. White dwarf. Right. Black hole. Right. You're getting this this sub categorization. And then you're getting the same thing with the gamma ray bursts. And we're seeing these really weird and kind of interesting scenarios that mean there's probably something even more complicated going on than just big star go boom that you're seeing based out of a boom near another star, big star go boom, because it gobbled up a different star. Like, like, yeah, things are getting weird. And and so as always, I think, like, I feel like that is the story that we hear, that it's always so common. Right? Is that the thing that we thought was a was one classification, when you really understand it better, suddenly gets split up into all these little pieces. And so again, I think it's, you know, back with the planetary migration concept, it is the revolution in in observation techniques. We have better gamma ray observatories, better X-ray observatories, better ground observatories, even, you know, neutron neutrino observatories are being brought on worldwide collaborations between astronomers able to turn their telescopes on the same target at the same time. And this what was this monolithic mystery has become a pile of little mysteries. Each one is a little better solved than the monolithic side of things. And so I agree, it's it's a really fascinating journey. All right. I think one of the big ones that you've been thinking a lot about is this did the supermassive black hole or the galaxy come first towards galaxies, collections of small pieces that came together. Do they. Yeah. Monolithically take us back to sort of early astronomy cast days. Think back to younger you. 

Pamela Gay [00:21:34] What did man what. 

Fraser Cain [00:21:35] Was your synthesis of the science at the time? 

Pamela Gay [00:21:38] Well, I mean, what what we'd been taught and what many who don't follow that part of the literature still hold on to because I don't think we're loud enough sometimes, when things change, is this idea that galaxies either form in the wholesale collapse of a giant pocket of material into a galaxy, so different sized pockets of material create different galaxies, or or you have little tiny things form that have to merge together to get big galaxies. And we were really taught it was either or. And the answer is, as always, both where we are now finding giant galaxies in the early universe that could only have formed via massive collapse of giant blobs of material. But then we see there's still small stuff today. We see things merging today, growing today. And so it's really looking like with stars, you had this distribution where massive things were fewer, tiny things where multiple dynamics kicked in, smaller things kept merging, so they took up less. Basically, when you're a whole lot of little things, the probability of collisions is much higher than when you have a small number of big things. So like in solar system formation, we're like, oh yeah, it started out with a gazillion planetesimals and they just kept colliding until we got planets. Well, it's now looking like we had a gazillion tiny galaxies, and they just kept merging until we ended up with big things. And so both the answer is both. And then like we totally are confused currently on the timescales and the order of operations for, for supermassive black holes. 

Fraser Cain [00:23:44] But like this is one of the most vexing problems for astronomy and cosmology. To the point that quest. Right. Like this is like up until this point, all you had was Hubble Space Telescope being able to occasionally see lensed galaxies at the very limits of its optics. This mystery was unfolding at a place that that Hubble couldn't see, that none of our telescopes on Earth could see that there was there was hints, but they're just like enough to give questions, but not enough to give answers. And so the whole purpose of Webb was to just help answer this question. And so here we are now, a year and a half into full operations and operations of this telescope. And we are getting these answers. And as you said, it turns out the answer is more complicated than anyone expected. It's not a simple, you know, you know, dwarf galaxy merger folks. You were right. Giant collapsed region, folks. You were right. No, it's it's a mixture of both. And so we're seeing these dwarf galaxies, and yet we're also seeing these giant galaxies that seem to have merged come together too quickly than anyone expected. And so wonderfully, the reality is more complicated and more interesting and more nuanced than anyone had ever believed. 

Pamela Gay [00:25:03] And this is your reminder scientists don't know everything. We want to know everything. And along the way, our our data isn't always as good as it needs to be to tell us the actual truth about the universe, and the details we fill in on our own often simplify things far too much. 

Fraser Cain [00:25:25] Yeah, so. 

Pamela Gay [00:25:26] Yeah, it's complicated. 

Fraser Cain [00:25:28] And it's funny, though, because you got to take a stab at it. Like you can see from scientists though, like like we're seeing this thing. We're trying to figure out how this works based on what we know. This is how it probably came together. And then it's that based on what we know. And then we learn a bunch of new things like, oh, this is more complicated than we thought. This is more nuanced. This has more shades of gray. This is a more complicated story than we believed. And yet the answer is so much more satisfying. And it's it's always wonderful to hear that. And I wish we could figure out some way in advance to know, oh, here's some stuff that seems simple. It's expected to be complicated, right? And it's, you know, it just it always surprises. 

Pamela Gay [00:26:09] That both and is the thing that always gets me. It it used to be that people argued, well, either our understanding of gravity is incomplete or there's dark matter and now there's room for both and and so both just. All the different sciences collaborate to get us where we are. 

Fraser Cain [00:26:30] Yeah, totally. Super fun. It's interesting, like, you know, this is sort of what astronomers were wrong about. And like, I wonder, like, what were they right about white dwarfs. 

Pamela Gay [00:26:41] We were really, really good with white dwarfs. We understand white dwarfs. 

Fraser Cain [00:26:46] I mean, even black hole event horizons. Right? Like once you open your eyes and telescope image. Yeah. Yeah. The speed of light. Me being the speed of gravity. Like it wasn't till the kilonova that we got that final confirmation. So, you know, there's a lot of really interesting predictions that were made. And even in our time in doing this job, that those predictions have proven out in ways that are really satisfying. 

Pamela Gay [00:27:13] Gravitational waves. We finally proved. 

Fraser Cain [00:27:16] Gravitational waves exist. Yeah. Yeah, yeah. Man, there's so many things that that we could go the other way around and say, what were astronomers right about? Yeah, I love it. 

Pamela Gay [00:27:26] Compact objects were really good with compact objects. 

Fraser Cain [00:27:31] All right. Well, maybe that's another show at some point. Oh, thanks, Pamela. 

Pamela Gay [00:27:34] Thank you. And thank you so much to all of the folks out there in our audience that donate through Patreon and, and make everything go. So this week I would like to thank in particular James Roger, Sam Brooks and his mom, Sean Martz, D, Nat Detweiler, Kimberly Reich, Jesus, Trina, Paul D Disney, Jeff Wilson, Tim Gerrish, Michelle Cullen, Janelle aka Veronica cured Dwight Elk, Gabriel Galvin, Benjamin Davies, Brian Kilby, Jordan Turner don't blame me Paul Esposito, Bob Czapski, Ruben McCarthy, Robert Hundley, time Lord, IRA Ryan Thorson, Jason. Kerr, Kadokawa. Christian Goldy, Daniel Donaldson, Frank Stewart, Jeff McDonald and Lee Harborne. Thank you all so very much, and thank you for forgiving me on my pronunciation. 

Fraser Cain [00:28:37] And thanks for helping us get to 700. Yeah yeah yeah it's amazing. Thanks everyone and we'll see you next week. 701. 

Pamela Gay [00:28:48] Yep. Bye bye. Astronomy cast is a joint product of the Universe Today and the Planetary Science Institute. Astronomy cast is released under a Creative Commons attribution license. So love it, share it, and remix it. But please credit it to our hosts, Fraser Cain and Doctor Pamela Gay. You can get more information on today's show topic on our website. Astronomy. Cars.com. This episode was brought to you. Thanks to our generous patrons on Patreon. If you want to help keep the show going, please consider joining our community at Patreon.com Slash Astronomy Cast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomy Cast. 

Recorded live during the CosmoQuestX 2023 Hangout-a-Thon on November 5.

How the time flies. It’s been over a year since JWST went operational, with other missions joining the fun. What new insights have we gained about the Universe thanks to these powerful new tools?

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Fraser Cain [00:00:59]  Astronomy cast. Episode 698 New Insights into the universe. Welcome to Astronomy Cast, a weekly facts based journey through the cosmos where we help you understand not only what we know, but how we know what we know. I'm Fraser Cain, I'm the publisher of Universe Today. With me, as always, is Doctor Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmic Quest. Hey, Bill, how you doing? 

Pamela Gay [00:02:11] I am doing well enough. We are currently in our. Oh, dear. We are currently in our 26 of our 32 hour fundraiser for Cosmic Quest. An astronomy cast partner. Patreon is down. It's down for astronomy cast is down for Cosmic Quest. Our donations are down. The economy isn't good. A lot of people are worried about war, but the humans that work for us still have bills to pay. And everyone working for Astronomy Cast is okay enough. So we're doing good. We had a question, but over on Cosmic Quest we're struggling a bit more and we had this horrible realization that across everything we do, it's like 1% of the people donate. And and we want to give everything away for free. But if everyone who downloaded an episode last week donated $4 once, we'd be good for the entire year. Yeah. Good. 

Fraser Cain [00:03:21] Yeah. 

Pamela Gay [00:03:22] And so unfortunately, with that, only about 1% donate. We're here begging. Yes. Hi. Hi. If you would like to donate, we'll have all of the links in the discussion over on YouTube. And. 

Fraser Cain [00:03:43] But just in general, go to Cosmo Quest x.org/request.org. 

Pamela Gay [00:03:48] Or. 

Fraser Cain [00:03:49] Cosmo quest.org/donate donate. And you can kick a couple of bucks our way. And of course, Cosmo Quest provides all kinds of educational services, runs community, and helps with developing citizen science projects. And so all of these are valuable and important. And we pay people salaries to do this work. And so if you want to help us out, please go to Cosmo quest.org/donate. How the time flies. It's been over a year since his went operational with other missions. Joining the fun. What new insights have we gained about the universe thanks to these powerful new tools? Doesn't doesn't the time really feel like it's flying? I mean, July 2022 was when we got the first light images from GBC and here we are now. We did an episode all about one full year of web observations. We are now in November, so another three four months on top of of that. And science marches on. And I mean, really, we've been getting like in the beginning, everyone's kind of excited and, and people were getting ahead of the arrow over the end of their skis. People were making instant claims that maybe took a little need a little more research to look into. And so I think this is a great time for us to think more deeply about what we've learned about the universe now that we are this far into the era. 

Pamela Gay [00:05:26] And and what I love is, I think the biggest thing that I've walked away from all the, jet papers with is a even stronger feeling that the universe is an improv artist that really likes to say yes. And. It seems like every time we've ever had a. Well, it's this or it's this, the answer keeps being both. 

Fraser Cain [00:05:55] Both? 

Pamela Gay [00:05:56] Yeah. And my favorite example of this was one of the first papers to threaten to revolutionize cosmology. Was was one of the ones that looked at all his, images of galaxy clusters in deep fields and basically said, there's bigger stuff out there than there should be. There's brighter stuff out there than there should be there for. The universe must be forming bigger, brighter things sooner, faster than we expected. And the follow up observations have been like, well, some of them aren't where we thought they were. Some of them are doing things different than what our models assume, so they're actually fine. And yeah, some of these really don't make sense. And I'm loving it, right? 

Fraser Cain [00:06:44] I mean, for sure, like within days of G2 was going live, I was looking through the various papers coming out of both journals, as well as all the stuff that's on archive, which is always sort of a bit of a dangerous game, you know, because it's all preprint. And, and you were seeing people see galaxies that were like 200 million years after the Big Bang, 230 million years, 170 million years after the Big Bang. And like, that's astonishing. That is so much earlier than Webb. Those are so much earlier than Hubble. And and then and so like that was exciting. And it was still just like, you know, we think we saw a galaxy that's that was the beginning and the end of the paper at that age. But then you got that round of, of paper saying what we're seeing, these galaxies are too big, too soon, that every model of our understanding of the cosmology of the universe, none of them predicted this. 

Pamela Gay [00:07:44] And what wasn't mentioned in a lot of the coverage of that discovery was the fact that they base the size of the galaxies on how luminous they appeared at their distance, and an assumption of the size distribution of the stars. So like. When you look at a galaxy in our modern universe, there's going to be a whole lot of tiny stars, a whole lot of medium sized stars, but not quite as many. And as you get bigger and bigger along that initial mass function, you get fewer and fewer stars. And so when we see a system that's a specific luminosity, it gives off a certain amount of light. And we measure how bright it appears. And that allows us to figure out how big it actually is. Based on this assumption of the distribution of masses of stars. 

Fraser Cain [00:08:47] Yeah. And so as more work was done, as more science was done, as the spectroscopy came in, as people were able to analyze these galaxies in more detail, all of these extreme observations about the galaxies started to go away. Yeah. And where we are now. And like, I don't think people know this, that where we are now is that everything is fine, everything is exciting, but everything is fine. 

Pamela Gay [00:09:16] And my favorite part of this was the mix of how we got there. And I'm just going to keep detailing this out. So it turned out that a couple of the systems being looked at, they had a different distribution of colors than initially assumed. And since we were doing broadband photometry for the images, you get colors but not spectral lines. And you can use that to estimate the distance to an object. But if you don't know correctly, with the mix of stars, you're going to misplace your galaxy. And so a few of the galaxies were just misplaced. And once we got spectra that allowed us to see specific atomic lines, measured the specific distances, those objects got a whole lot closer and a whole lot less suspicious. 

Fraser Cain [00:10:09] Right. Yeah. And that, like certain kinds of surveys of this early universe, told you that, like, were preferential towards making some galaxies look bigger, but not revealing some of the other ones that would have been in the same field of view. And so you were just seeing some of the bigger ones and that was starting to skew the results. And then the other thing is, you know, a lot of really interesting theories have also been put out. Like for example, well, early on in the universe, star formation probably went in pulses. And so you're seeing something that isn't just the continuous starlight from a giant galaxy, you're seeing one of these galaxies. It's going into this, this flare up of of star formation. And the other thing that's been really interesting as well is the interactions between the galaxies. So there's a lot of papers coming out talking about quenching, about how galaxies with active galactic nuclei are blasting out material that is then shutting down star formation in nearby galaxies. And so it's all of these nuanced discoveries that are adding a lot of really interesting texture to the things that astronomers already knew about, about the early universe. That's the real. That's the real part that I think you should be focusing on. If you're you're listening to this, you know, that that that nuance is now being worked out. And that's where the real progress is getting made. You're not overturning the big Bang. You are discovering how galaxies, when they were merged together, were interacting with each other to cause mayhem, which is really interesting. 

Pamela Gay [00:11:49] And a nuance almost feels like it's too cautious of a word. It's it's one of these things where we. Ran computer models that came up with a certain set of results allowed for a certain set of possibilities, and we as human beings failed to be creative enough to include in all the details that needed included in. And because of that, we we simply failed to imagine things that now we look at what the universe is actually doing and it's like, oh yeah, that's obvious. Who should have thought of that? And, and so our, our own failure to include all the needed complexity meant that we didn't understand what we saw the first time. But on the second and third glance, it was like, oh yeah, okay, this is cool. We're fine. 

Fraser Cain [00:12:44] I mean, I'll give you one really interesting kind of practical example is, which is these outflows that that galaxies have these outflows coming from them, as I said, that quench their their nearby neighbors and shut down star formation. And so you can have some galaxy that is putting out all of this radiation and all these particles and then and then their neighbors are not being able to go to the same amount of star formation. And astronomers weren't sure what was the source of these outflows, like one possibility that it could be supernovae, another possibility that it could be, mergers, you know, star formation. And then another possibility is that it could be material that's coming out of active galactic nuclei. And then they were able to now. With, you know, they're fairly certain this is coming from the the black holes from the active galactic nuclei, not the super not the star formation. And that requires resolution. That requires being able to do really good spectroscopy on your galaxies to get a sense of, of what the source is. And so there are all of these mysteries, you know, if you sat down cosmologists and just said, like, give me your top 20 mysteries, the beginning of the universe, they'll have a bunch of them and they'll sell that, you know, what is the source of galactic outflows? And Webb is so precise that it is now providing evidence to each one of these mysteries to lead this conversation further. And I think that's man, that is just something that's just not making the headlines, which is too bad. 

Pamela Gay [00:14:17] And I think we have to give credit where credit is due. Accretion disks are the real baddies of the universe. Yeah, the supermassive black holes are just sitting there going, I'm spinning in a big. And this in flowing material is forming a spinning disk that is hot. It has nuclear reactions going on. It's generating extraordinarily powerful magnetic fields that are driving these powerful jets. And the light from these accretion disks moving outwards in some cases can destroy star formation within the galaxy. The accretion disk lives in, and the jets popping out has the potential to hit other galaxies and end star formation. Nam, don't be afraid of the black holes. Be afraid of those. Under acknowledged accretion disks. Traveling the universe with them. 

Fraser Cain [00:15:18] Yeah, yeah. And so again, I'm kind of having trouble putting this to words, but just be patient. Yeah. And and enjoy the ride as these mysteries get solved one after the other. Now we're going to talk about this some more in a second. But it's time for a break. 

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Fraser Cain [00:17:10] And we're back. So let's get a little closer to home now. And and I would say one of the biggest mysteries that is now being solved right in front of our eyes is rogue planets. 

Pamela Gay [00:17:23] Yes. 

Fraser Cain [00:17:23] And and Webb gave us one of the most exciting announcements based on this. 

Pamela Gay [00:17:31] The Orion Nebula. Yeah, is full of star formation. We know this. We love it because of this. It is extremely dense in star formation, and it is apparently a world knock world situation gravitationally because there are thousands of planets just hanging out, not directly affiliated with any one star. This this isn't enough to solve dark matter. Don't, at any rate. But if it is enough to really allow us to realize there is a vast quantity of small, cold, round stars moving through our galaxy, that the only way we can possibly see it outside of star forming regions like Orion or Carina. We need to look at Carina more, please. Is. Unfortunately through gravitational lensing events, and so far that I know of, we haven't found any rogue planets that way. So this is this is a population that was unknown. 

Fraser Cain [00:18:46] We know of 100. We know of about 100 rogue planets through gravitational microlensing. 

Pamela Gay [00:18:51] I stand corrected because he reads more research papers than I do some weeks. 

Fraser Cain [00:18:57] Yeah, yeah. And so that, you know, this new snapshot from of the Orion Nebula, they found hundreds, like more than 500 rogue planets, Jupiter sized, Saturn sized, bigger. And many of these, about 9% are in binary star. Relationships and you've got two. Rogue Jupiters orbiting one another. And they had hints that this was the case from Spitzer and Herschel, which are, you know, far infrared instruments. But they didn't have this level of detail. And so now they will to this. And these are just the big ones. Like for every rogue Saturn there's going to be ten rogue Earths. And so now like in the past we would think, oh, you know, maybe there's a couple of rogue planets per system. And now there are probably more rogue planets than stars. More, maybe more rogue planets than planets. Crazy. 

Pamela Gay [00:20:05] Wild. 

Fraser Cain [00:20:06] Yeah. 

Pamela Gay [00:20:07] So. So we've really found hundreds using just gravitational lensing. 

Fraser Cain [00:20:12] We found out we've got 100 through gravitational microlensing. Yeah. 

Pamela Gay [00:20:16] Wow. Okay. I clearly am missing a corner of literature. 

Fraser Cain [00:20:20] Yeah. There's 100 known rogue planets before this new discovery of 540, like, announced in one paper. 

Pamela Gay [00:20:31] And and that's the other side of the story, is it's getting to the point that unless your entire job is keeping track of this. Thank you. Fraser. 

Fraser Cain [00:20:42] Yeah, yeah, it's all I do. 

Pamela Gay [00:20:44] The stories on the rogue planets in Orion didn't mention the rogue planets that were micro lensed in general. And so it's getting hard to keep track of all the different things we're learning in all the different ways. And one of the most powerful tools we have for advancing astronomy is getting people who work in different disciplines in the same room, comparing what they learned in different ways, and seeing how that information fits together. And it's getting harder and harder to do that every day. 

Fraser Cain [00:21:17] Yeah. It's funny because I almost sometimes play that role and like when I'm interviewing somebody, I'm like, oh, like, what about this paper over there? And like, I hadn't heard about that. And I send them in the paper, you know, because they weren't aware this other team had made this discovery over on that side. It's like it is really hard. I think this is one of the things that if we had AI telling us things that might be also useful to what we're working on right now, that would be very helpful. 

Pamela Gay [00:21:41] And not hallucinating. 

Fraser Cain [00:21:43] Yeah. Yeah. So we talked about rogue planets. We've talked about new galaxies, digital universe. Let's talk a bit about exoplanets. 

Pamela Gay [00:21:52] So we're finally going to start seeing the potential from Tess that had been counted on. And she just he was able to confirm its first exoplanet. So so for those of you who don't remember the story, the original plan for Tess was it would launch about the same time as J. UST the two of them would be working in coordinated planning the entire time, such that when Tess finds a world in the process of transiting, there'd be the capacity to steer over and go yes or no by looking at the atmosphere. And this is just such a fabulous story. And then Tess got to orbit and it's like, I'm here by myself, right? And Tess tested amazing work. Ground based astronomers have been doing crazy, amazing stuff, figuring out how to get as close as they could to what it was planned for for us to be doing. But finally we're there. We're we're able to do this. And. Yeah. I'm just sort of like task. Do the thing. Yeah. And and Jagdwurst, with its ability to look at atmospheres, has been confirming all sorts of molecules, atoms, things we weren't expecting around planets. Kelt nine V is my favorite. It seems to have every weird hot atom that you can only see under extremely high temperatures. And I'm loving it. What's your. 

Fraser Cain [00:23:33] Favorite? Well, I mean, just like all of it is my favorite because prior to G. He there was a couple of exoplanet observations done with Spitzer. Poorly like, it could just barely analyze the atmosphere of a planet that was transiting in front of its star. And so we knew of just a couple of examples like, yes, it has an atmosphere, and we think there's like some chemicals in that atmosphere no more, you know, no more data. But with gravity, it's finding really solid lines of carbon dioxide, carbon monoxide, oxygen, water, water, sulfur dioxide, all of these chemicals, and then weird ones like quartz, like glass clouds and things like that. And so you're just getting, like, every planet that they turn on and, and gathering of data, they map its atmosphere, which like, like again, we just we get so used to this, right, that by the way, there is a telescope that that is currently mapping the atmosphere of planets orbiting other stars so that we know what's in them. Now, obviously, we know we haven't found stuff that makes us think there's life there. The Trappist one systems are all coming up airless, but still it's phenomenal that this happens. And so each one, you know, you see a new a new paper comes out and you're like, oh, this is so cool. And imagine there will be this day in the future where we will have analyzed thousands, tens of thousands that we will know, sort of at a statistical level, what chemicals are in the atmospheres of planets. And this is this is how beginning, you know, right now there is maybe ten that have been done so far, but it's just going to snowball into the future. And and so each one is just so great. 

Pamela Gay [00:25:27] And the other side of this is like from alma, we've gotten amazing details on planetary disks in the process of forming worlds around young guest stars. J t is taking us a step earlier in some cases, and allowing us to see that first breath, that class zero protostars in disks with lights and seeing the structure of the interstellar medium around them. And so we're starting to improve the different kinds of snapshots we have where we can see the story of. And here's where they turn on, and here's where the worlds form and here's where if you have enough stars forming together, they fling worlds everywhere. Space is messy and you're getting more glimpses of it. 

Fraser Cain [00:26:26] Yeah. So you've got this situation where you go from nothing, a giant cloud of gas, and then on the other side, you've got a star with all of its planets. It's blowing everything away. And then there is that moment. And people always ask me that question like, you know, like, how long does it take for a star to ignite? And, you know, what do you mean by ignite? Is sort of the question I always come back with because it takes some time. But but literally, you were seeing that 100,000 years where you go from cold gas cloud to hot, not in the middle with infrared. That's what data is T is perfect for. And so you're seeing these little slices of star formation at different points at the, at the specific scale. Like we see these like ha big hero objects. Yeah. But then at the grander scales, as you said, the Carina Nebula, the Tarantula Nebula, the Orion Nebula, the Eagle Nebula, like the most dramatic nebula that we know of, the ones that are on all of our phones, all of our computer backgrounds, we are seeing, we're just looking with, like, X-ray vision right into these, in these nebulae and seeing all of the stars that are forming that would have just been opaque in a visible light telescope. 

Pamela Gay [00:27:41] And that's wonderful, because with s t all the things that we're used to seeing with our backyard telescopes. That is blocked. The light of what's beyond. We can now start to at least see into with some of these giant molecular clouds and the galactic center brick and all of these other structures that we just didn't know that and we knew they were there. We knew they were full of molecules. We knew they were cold, and now we can see at least a little ways into them and start to understand all the steps, using all the wavelengths of light, because we have a new wavelength to explore. 

Fraser Cain [00:28:28] Yeah. There was a paper that came out where astronomers had been put together all of their plans for doing an infrared investigation around the supermassive black hole at the heart of the Milky Way, home to 150 hours to study the motions of all of the stars going around the black hole, the gas clouds that around there, the weird regions of star formation that are way too close to the center of the Milky Way. Yeah. And so for a year or two, there will be even more of these. And when you think about the fact that we'll probably have this telescope for 20 years, yeah, it's going to be just year after year after year of these kinds of discoveries and announcements. It's, it's a good time. This I you remember I said before was the golden age of astronomy. No, no, no, this we are now in the golden. 

Pamela Gay [00:29:13] Age of astronomy. No, we still need to get Vera Rubin doing her survey. 

Fraser Cain [00:29:18] And Euclid and Nancy Grace. 

Pamela Gay [00:29:20] Was right, as those three. 

Fraser Cain [00:29:23] Instruments working together are going to be just phenomenal. And, you know, we're going to see the first color pictures from Euclid. By the time you listen to this, they will have been released and we're waiting for that. 

Pamela Gay [00:29:35] It's an impatient time. And some of the most impatient people out there right now are the folks that just in the past couple of weeks, have submitted new cycle proposals to Jay Austere, saying, this is what we want to see next. Yeah, that was second three right? Yes. Yeah. 

Fraser Cain [00:29:54] They had to submit cycle three. Amazing. 

Pamela Gay [00:29:57] And and so now we have the potential to start seeing follow up observations on the initial images. We get to start seeing the more telescopes come online, the more follow up to the more concepts that we have the potential to get to follow up. So it was a very awkward sentence for very awesome science. 

Fraser Cain [00:30:17] More follow up, more better. Pamela, thank you. 

Pamela Gay [00:30:22] Thank you, and thank you so much to all of our patrons out there who get ad free versions of every episode, and make it possible for us to pay our staff who keep us rational and sane. So this week I would like to thank Jordan Young, Steve, invite Jeanette Wenk, bora anthro level Saji Kemmler, Andrew plasterer ed Boogieing that Brian Cagle, David. Trog, Gerhard. Schweitzer, David. Buzz parsec. Zero. Chell, Laura Olson, Robert Fuller's my Joe Holstein, Richard. Drum, Liz. Howard, Adam. A nice brown. Gordon. Doers. Who's in the room with me? Alexis. Wanderer and 101 Felix. Good. Kim bear and Astro sets. William Andre gold, Roland Vollmer. Madame, all of you, thank you for supporting us at the. We're sorry. Pamela will likely mispronounce your name level. They don't teach phonics so well in this country. 

Fraser Cain [00:31:26] Is that in Astronomy Cast, like in our Patreon tiers? That should be one of them for sure. 

Pamela Gay [00:31:31] It's eight. Yeah, I think we need to rename that tier. 

Fraser Cain [00:31:34] I like it. All right. Thanks everyone and we'll see you next week for bye. 

Pamela Gay [00:31:44] Astronomy cast is a joint product of the Universe Today and the Planetary Science Institute. Astronomy cast is released under a Creative Commons Attribution license. So love it, share it, and remix it. But please credit it to our hosts, Fraser Cain and Doctor Pamela Gay. You can get more information on today's show topic on our website. Astronomy. Cars.com. This episode was brought to you thanks to our generous patrons on Patreon. If you want to help keep the show going, please consider joining our community at Patreon.com Slash Astronomy Cast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomy Cast. 

JWST Might Have Spotted the First Dark Matter Stars (Stephaie Pappas, Scientific American)

Webb Reveals Intricate Details in the Remains of a Dying Star (Webb Space Telescope)

Pairs of rogue planets found wandering in the Orion Nebula (Physics World)

James Webb Telescope to Unravel Mysteries of Crystal Ball Nebula (James Webb Discovery)

Supermassive Dark Star candidates seen by JWST (Cosmin Ilie, Jillian Paulin, and Katherine Freese, 2023, Proceedings of the National Academy of Sciences, Vol 120, No 30)

Nebulae News (Science Daily)

One of JWST’s top jobs is to peer deeper into the Universe than ever before, watching as the first galaxies came together. Surprisingly, astronomers found galaxies that seemed much more mature than expected, much earlier than it was believed possible. What’s going on and what does it mean for cosmology?

(This is an automatically generated transcript)

Fraser Cain [00:01:50] Astronomy Cast Episodes 684 two big two soon massive early galaxies defy expectations. Welcome to Astronomy Cast for weekly fact space journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I'm Fraser Cain and the publisher of Universe Today. With me, as always, is Doctor Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmic Quest. Hey, Pamela, how you doing? 

Pamela Gay [00:02:14] I am doing well. I love the fact that you can say that exactly the same every single time. It's it's delightful. 

Fraser Cain [00:02:24] I'm just reading from a script. 

Pamela Gay [00:02:25] Except you said episodes, and I love that the content for this singular episode is so great that it needs to be referred to as a plural. 

Fraser Cain [00:02:34] Do you see episode 684? 

Pamela Gay [00:02:36] You did. It was delightful. 

Fraser Cain [00:02:38] But episode. Episode 684. Episodes 684. Now, like I said, episode. It's just it. Just the way I say it is exactly the same. So I've been playing with the Merlin app, which is this bird. App that you can get and sell on your phone, and it lets you like report sightings. And it's great for ornithologists to be able to count birds and so on. And the the has a gadget that you put on to it. That will do recording sounds. Yeah. And so you just put it outside and you listen for bird sounds and then they just as it hears a bird, it just adds it to this database in front of you. And so you're, you're hearing these birds sing all around you and you're like, oh, that's a chickadee. Oh, that's a junco. Oh, that's a toee. And and then you get rare birds too. And I had so much fun. And then and what's been amazing is, is that now we're starting to hear these birds and we look, you know, with like, oh, there's a ten injure. And I've never seen a tanager. Never heard of a tanager before. And then you look up pictures, you know, like what a great bird. And then suddenly a couple of days later, you see the bird and you're just like, that's a tanager. Yeah. Like he landed on our fence. And Carl and I were both just, like, watching him just oohing and eyeing at this beautiful bird. Beautiful. Bright orange. Yellow like a like a tropical bird. But in the, in the temperate rainforest. So, I highly recommend this, this app, if you are interested in birds at all. The it's called Merlin and it just, it's just it's so much fun. And then find some friend to get into birds and and ship with. And then you just like be on my life list. It's 57 birds. My life list is 76 birds. So highly recommended. 

Pamela Gay [00:04:35] That that is that is absolutely amazing. We we actually, here in Edwardsville, we're able to accidentally prove a research paper. I read a paper a number of years ago about how songbirds are less likely to live near busy streets because their song gets drowned out. And I have an identical bird feeder to one of my friends who recently moved to town, and she lives far enough back from all of the busy roads and this super quiet little neighborhood that backs up on the high school. And she gets songbirds all the time. And I never get any songbirds in two miles apart. And the only difference in our neighborhoods is how busy the streets are. And, so it's weird is how localized things like that have allowed research to be done. And now we're seeing the results proved out. 

Fraser Cain [00:05:27] It's called theory proof. That's amazing. Yeah. One of Ghost's top jobs is to peer deeper into the universe than ever before. Watching as the first galaxies came together, surprisingly, astronomers found galaxies that seemed much more mature than expected, much earlier than it was believed possible. What's going on? And what does this mean for cosmology? Okay, so like, why does he so good for this job? Why is it the perfect machine for seeing early into the universe? 

Pamela Gay [00:05:55] Well, it's that whole infrared thing that we're just going to keep bringing up over and over and over. Light From Young Stars is peaking in the ultraviolet. But because the universe is expanding, and the further away you look, the more stuff there is between us and that to be expanding. We see the most distant parts of our universe as moving very fast away from us, which shifts all that ultraviolet light all the way through, visible and into the infrared, where it's easily apparent to the James Webb Space Telescope. Now, the thing is that there's the other side of this, which is you need something with high resolution cameras, because right now, our best way, not our only way, but our best way of imaging these things is to look at galaxy clusters that I use their mass to bend light towards us, that otherwise would have gone to other parts of the universe, and that added light from the event light, magnifies the brightness of these distant objects. But we need the high resolution, and we still need the light gathering power of the massive mirror of J ust to make out those faint smudges of light that are getting gravitationally lensed. 

Fraser Cain [00:07:22] So. So the galaxies that we're seeing, these ones, these impossible galaxies that we'll talk about in a second. They're being seen thanks to the gravitational lensing. Or is he able to just see some of these just with its raw capability? 

Pamela Gay [00:07:40] It's it's capable of seeing it through the raw capability. But we first started seeing them and we have seen the largest number of them so far through this gravitational lensing. It's it's basically the low hanging fruit. It takes fewer orbits. And you can honestly get a whole lot more science for the hour. If you look at a galaxy cluster, because you get the galaxy cluster and you get everything that's in the background of the galaxy cluster. 

Fraser Cain [00:08:09] Right? 

Pamela Gay [00:08:10] So by the numbers, that's how we've seen the most. 

Fraser Cain [00:08:12] And it's almost like the first time they turned this on, they found a bunch of these really big galaxies. And they're studying them. But they're are deeper like all sky. They're not all sketches but deep field surveys, like what happened with the Hubble Space Telescope in the works. Yeah, hopefully we'll see a lot more of this kind of stuff and get a better sense of like it's like a survey of them, as opposed to seeing the low hanging fruit, the weird stuff right away. 

Pamela Gay [00:08:39] And the stuff that was lucky enough. I don't know if that's the right word. We were lucky enough, was aligned to allow gravitational lensing. That that's one of the the statistical frustrations is if you look at a mostly empty patch of the sky, like they did with the Hubble Deep Field, like they're now doing with shelves, t that deep field. And you look and you look and you look and you look, you can say in this volume of space, which is a cone that increases as you look back, there is this population visible. And, and it's a by volume measurement of what's visible as a function of brightness. So you're not going to see the fainter stuff for the stout, but you're still going to know in that volume of space what is typically going to be seen now with, with J s t. They're looking at galaxies that just happened to be oriented just right behind these clusters that they're light, that in some cases originated just a few hundred million years after the Big Bang. Their light has been bent our way, and we're not necessarily seeing their neighbors or neighbors didn't necessarily have all the right geometry. Right. So it's it's not that same careful volume, limited statistical sample. 

Fraser Cain [00:09:58] And what were they expecting to see. Like I'm sure as they put they probably spent more time building models trying to make expectations figure out their calibration before they took those first images. What was sort of the the default. Astronomical expectation of what they would see. 

Pamela Gay [00:10:19] So. So what we're guilty of always doing is looking at the cosmic microwave background, which is the rabbit hole. We shall not go down. And looking at the modern universe and figuring out what had to happen to get from the distribution of little tiny, denser and less dense distribution in the cosmic microwave background to our current large scale structure, and we make assumptions about, okay, so if you have this mix and you have dark matter that has this temperature, and you see this happening at this point in the universe and this happening at this point in the universe than in the section of universe we know nothing about in time. Right? These things must have happened. Right? And and so we made assumptions based largely on the distribution of hot and cold patches in the cosmic microwave background. And we expected that there would be a very small number of large ish galaxies forming that resembled the distribution of hotter spots in the cosmic microwave background. We figured there'd be a whole lot of itty bitty little tiny stuff, and there was more matching the average distribution of warmer spots in the cosmic microwave background. 

Fraser Cain [00:11:44] So? So astronomers looked at the cosmic microwave background. They see these warmer spots. They correspond to denser regions of the early universe, the place where you would expect large amounts of mass to come together. And then you calculate the number of hot spots versus the number of cold spots. And that tells you about what the mixture of big galaxies to small galaxies should be. Because those hot spots, big spots, are going to turn into big galaxies, while the less dense. But obviously it's not a 1 to 1 right correlation because you can't see like what that part of the cosmic microwave background radiation turned into. Yeah, it's a different time. It's you're you're seeing simultaneously one part of the universe that is older, that you're seeing a different place. And so it's like a statistically, you see one thing over here and that allows you to expect what you might see over on this other part of the sky. 

Pamela Gay [00:12:44] And we base a whole lot off of this, this general idea that the universe looked at, at a large enough scale and averaged is the same everywhere. So as long as you look at a big enough chunk, each big enough chunk will have the same amount of stuff in the same population of stuff in it. Just like grabbing a cup of sand at different points on the beach, you're going to have the same distribution of grains. One might end up with a glass bubble in it. One might end up with a dead crab in it, right? Right. But more or less, you will have the same distribution in each cupful of universe as cup full of sand. 

Fraser Cain [00:13:28] It's like fishing in Stardew Valley, right? You just keep fishing. Yeah, you're going to get lots of the one kind of fish. And then every now and then you get the rare kind of fish, but you just keep at it and the statistics sort of pile up. So okay, so they had this sort of expectation like this based on the density over density regions of the early universe. This is the kind of structure, large scale structure of the universe that we should see. What did they say? 

Pamela Gay [00:13:57] Well, first I saw some really big things and they're like, yeah, those are easy to see statistics. It's all right. We're still okay here. And then I kept looking. And they kept seeing really big stuff. 

Fraser Cain [00:14:12] Right? 

Pamela Gay [00:14:13] And it started to hit the point where I was just like, okay, so there is something clearly wrong with our theories or with what we expect a dark matter to be or with all of the above, because there are more large things than the cosmic microwave background seems able to support. So what is going on, right? And like literally the entire astronomical community had a moment of oh dear or excitement, pick one. But it was it was a moment of emotion for all of us. 

Fraser Cain [00:14:46] Right? But so I mean, when they saw them, it's like these could be like a complete fluke that we just happened to see a part of the, you know, we happen to or. 

Pamela Gay [00:15:01] More of. 

Fraser Cain [00:15:01] Them kept happening. You know, we kept putting our hand in the water and we kept pulling out dead crabs like, yeah, you know, there's a chance that you could keep pulling out dead crabs, but you'd expect to pull out just deeper seawater every now and then. Rocks or. Yeah, yeah, a little bit of seaweed. So. So then what could be going on that would give you these, these larger galaxies than expected? 

Pamela Gay [00:15:26] So people started reaching for all the different tools in the cosmological tool bag. There was the well, maybe dark matter had a different temperature than we thought. And cold dark matter is dead, which confused me deeply, because if you make it colder, then you end up with more big things. There was dark matter is not what we thought it was at all. Arguments. There was. Well, maybe there was just more stuff. Or maybe things aren't where we thought because we're not understanding the spectra, right? There was a whole lot of it can't possibly be where we think we're seeing things. And in a few cases, that was both the actual answer. And then the theorists with the big computers got involved and started rerunning their models with greater granularity. And this is one of the things that I'm really enjoying watching. What happens with everything from weather models to plate tectonics to cosmological models is it used to be we thought we were doing awesome when we modeled a galaxy with 10,000 points of matter to see how it evolved. And yeah. 

Fraser Cain [00:16:47] With a star can have one. A galaxy can have 100 billion stars. And. Right. Not to mention distribution of gas. 

Pamela Gay [00:16:55] And dust and dark matter. 

Fraser Cain [00:16:57] And dark matter and globular clusters and and rogue planets and black holes and influences from nearby galaxies. 

Pamela Gay [00:17:07] So theorists started doing the okay. So what happens if we increase the granularity of our models? What happens if we have a mix of hot and cold dark matter? What happens if and we started seeing some of the more wild explanations for what is causing dark energy in my opinion. Where we saw folks working on models for things like what if dark energy is a function of black holes? So there wasn't dark energy prior to there being black holes and. We don't know what the truth is, but one of the remarkable things that is happening is we are seeing more and more computer models capable of saying, yeah, I it looks like we can get there from here. It looks like the temperature on average that we thought was dark matter is actually the temperature of the dark matter. Just maybe it's built up of more constituents. And and so you have the folks in the middle going, it's not what we expected, but it doesn't ruin our understanding of the universe. You have the folks that are jubilant on the other side going, the universe is totally different. Yeah, everything is bigger than it should be. It's Texas, but in space they don't actually say that. That's right. It came into my head. Yeah. And then you have on the other side, the people are like, physics is weird. We have found weird physics. We are going to change our understanding of physics. And and I have to admit, I'm one of the people that is sitting on the sideline going. More data, please. Yeah. 

Fraser Cain [00:18:59] More data please. I mean, this is like, any one of those possibilities is exciting, right? Yeah. That, you know, these new computer simulations and I, you know, we did a couple stories on this on on Universe Today. Like, they like in the past, they've they've simulated fairly large chunks of the universe at a lower resolution. And instead they, they were able to make with some, some of the most powerful supercomputers on Earth, a very detailed simulation of a very small part of the universe, and found that the kinds of galaxies that are turning up in this data are, are fit within the the way the universe might have behaved. Or the models could be wrong. Right. Like like, you know, I mean, models are just models and. So maybe the. But at least you're starting to make constraints like the most out there ideas you can sort of go, no, you know, dark matter can't have this temperature. No, galaxies couldn't have formed this. Like, you can start to put some constraints and then you have this playing space in between. And then as you say, right. It could be new physics, which is great. Like you imagine if there if that if there were new way like if dark matter is a combination of forces that if it is different than anyone ever expected that the universe was accelerating at different rate at different times, that there are different compositions of the universe are different, like, this is all great, this would all be wonderful. So however it turns out it's so early that all you can do is just keep gathering information. It might be that we're going to look at, you know, after the fifth g t ultra deep field has been released, the huge swaths of the sky have been mapped down. And the survey of galaxies is is really well understood. But we're just we're not there yet. And so it's just it's too early to say anything about anything ever. 

Pamela Gay [00:20:53] And what's super cool though is folks are starting to look in all the different wavelengths. I mean, some wavelengths are just not going to be useful. Gamma rays. You can't really study the early universe in gamma rays because the gamma rays have shifted to something else. But. We are in an age where we have meerkat coming online, where we have AI. With an unimaginable future, the Square Kilometer Array. We're starting to build bigger and bigger optical systems. And the way things work in astronomy is you need some piece of data to say, it is worth it to give me time on this super expensive, limited resource telescope to explore this idea with. Without that fragment of data, you can't get the time. Yeah, well, jethro's t quite by accident is getting amazing results saying, yeah, we need to look at this a little bit closer, which is opening the door to use some of these other limited resource systems to look deeper and deeper and deeper and try and understand across the wavelengths just what was going on. And I am really looking forward to the suite of telescopes that are going to have ten years from now, where we start seeing early results from Square Kilometer Array, where we're starting to get results from the Lsst, and where Jerry West has had enough time on orbit to start completing some of these deep fields and then doing the follow up observations. Right now, we're not entirely sure what's going on, other than we keep seeing really big things that seem to be in the first few hundred million years of the universe. Maybe we think, and they're big. 

Fraser Cain [00:22:47] So I don't know. Did you hear the most recent turn of the story? So, like, we'd been like ghosts. He finds galaxies that are too big too soon, and then. Yeah. And then. 

Pamela Gay [00:22:59] Then there is a correction to the distance. And then it was where. Then there was a no, wait. We have these other four Galaxy models. 

Fraser Cain [00:23:06] These are. 

Pamela Gay [00:23:06] Truly that far. 

Fraser Cain [00:23:07] Away. Yeah. And then yeah. So we've confirmed that's exactly right. Yeah. And then and then the these models say no, actually these are perfectly well fit within the distribution data that you would expect. Nothing bizarre going on here. And the latest twist and turn is, is that some researchers went through and carefully examined the images and, and think that those galaxies may be 3 to 10 times more massive than originally believed. 

Pamela Gay [00:23:35] Holy expletive. Batman. 

Fraser Cain [00:23:38] Yeah. Yeah. Right. So. And there's just like, it's such a mess right now. It's this exciting, wonderful ness with with just this sort of it's like this renaissance of time of, of disc, of discovery with, you know, like you just this firehose of data. There's just been, you know, barfed out onto the table, and astronomers are trying to pick through it and make sense of it. 

Pamela Gay [00:24:11] And the, the most data is basically through a carnival mirror, which is what's partially making this so difficult. 

Fraser Cain [00:24:20] Yeah. Using gravitational lensing, which is could not be harder. 

Pamela Gay [00:24:25] No. 

Fraser Cain [00:24:25] Yeah. 

Pamela Gay [00:24:25] No, I mean, you can imagine we we talked a couple episodes back about the, the ultra diffuse low luminosity galaxies and the these are systems that are big and splurged out and have like 10 to 100 times fewer stars in our galaxy over the same volume space. And we can see that because we can directly image and image and image and image to see that splurge. Now, if you looked at this through a carnival mirror, it might get contracted in one direction, spread out in the other, and you're trying to work backwards to figure out what that was. And all you know is how much light there is. Not with the original distribution of that light was. And so you might end up working out. Oh, that was just like a normal dwarf galaxy. Instead of this spread out volume of light, trying to reverse engineer geometry when you don't totally understand the the gravity of the situation, by which I mean the literal gravity of that inconvenient galaxy. 

Fraser Cain [00:25:39] No pun intended. Yeah, yeah. And so I think, like right now we are right in the middle of one of these mysteries, and it's one of these things that that five when we do our five year. What happened to those Impossible Galaxies episode. 

Pamela Gay [00:25:55] Yeah. 

Fraser Cain [00:25:56] In you know, around episode 1000, we will be able to come back around and go, oh, it turns out this is what it was. And now we have a really good concrete information. It turned out to be this, or it turned out to be that the Lambda CDM model has been completely overturned. And and now we're in completely brand new territory. We are in the, you know, the unpleasant, not even unpleasant. Like the exciting thing for the quantum mechanics, right? Like nobody ordered quantum mechanics. Nobody does that. That's how the universe worked and yet does deal with it. And, and this is where we could be going next. 

Pamela Gay [00:26:33] Very exciting. Since we added this episode to the calendar, the field has changed four times. 

Fraser Cain [00:26:40] Yes! Yeah. Yeah. Yeah. We planned this episode three months ago. 

Pamela Gay [00:26:46] Yeah. Yeah. And at that point, we knew that there were definitely four galaxies in the first few hundred million years that were incontrovertibly large. Yeah. And then everything else has happened since then. 

Fraser Cain [00:27:01] Yeah. So crazy. So fun. I love it. I can't wait to see where this goes next. It's just like to I always this analogy of like, you're watching a sports game or like a mystery movie and you don't know the outcome and you're there for the for the game. You're there for the for those exciting moments. And, and you don't know how the whole thing is going to turn out. And we're right now today in mid 2023. We are in this moment and I love it. So thank you, Pamela. 

Pamela Gay [00:27:35] And thank you. And thank you to everyone out in our audience who makes this show possible through your patronage over at Patreon.com. And all of you get ad free episodes as a benefit. We we can't thank all of you during our episodes, but this week I would like to thank under a level, Gerhard Schweitzer or Schwarzer. I'm sorry. David Emmy Zang zero chill astrocytes. Paul F, Andrew Stephenson, Alex rain, Paul L Hayden, Sam Brooks and his mom, Bart. Flaherty, Brian. Kelby, Stephen. Coffee, Philip. Walker, Nate Detwiler, Benjamin Carrier, the air major, the lonely sand person, planetary. Louie. Zealand semansky, Sammy Raskin, John Drake, Gabriel Gelfand, Dean Glenn McDavid, Nyla Sean Matz, Benjamin Davies, ninja neck, Jason caduceus, Robert. Hundley. Kim. Barron, Paul. Esposito, Bob. Ezgi, Arthur. Latz. Hall, Ron. Thorson, Jordan. Turner, Hal. McKinney. Zebra. Lark, Bruno. Lutz, Jimmy. Berger, Ron. Rubin, McCarthy, Ian. Abdullah. Abdullah. Just MacDonald and Lee Harbaugh. And thank you all for tolerating my mispronunciation of your names week after week. 

Fraser Cain [00:29:06] Thanks, everyone, and we'll see you next week. 

Pamela Gay [00:29:08] Bové. Astronomy cast is a joint product of the Universe Today and the Planetary Science Institute. Astronomy cast is released under a Creative Commons Attribution license. So love it, share it, and remix it, but please credit it to our hosts, Fraser Cain and Doctor Pamela Gay. You can get more information on today's show topic on our website. Astronomy. Cars.com. This episode was brought to you. Thanks to our generous patrons on Patreon. If you want to help keep the show going, please consider joining our community at Patreon.com Slash Astronomy Cast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomy Cast. 

After the cosmic microwave background radiation was released, the Universe returned to darkness, cloaked in this clouds of primordial hydrogen and helium. Gravity pulled these vast clouds into the first stars, and then the first galaxies. This is Cosmic Dawn, and JWST will help us probe this mysterious time.

(This is an automatically generated transcript)

Fraser Cain [00:00:49] It's  Astronomy Cast episode 683 cosmic Dawn. Welcome to Astronomy Cast, a weekly facts based journey through the cosmos where we help you understand not only what we know, but how we know what we know. I'm Fraser Cain, I'm the publisher of Universe Today. With me is Doctor Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmic Quest. Hey, Pam. How are you doing? 

Pamela Gay [00:02:15] I am doing well. We we are continuing to put out new episodes of our Escape Velocity Space news podcast. So if you want news instead of blasting permanent, you can really listen to it all the time. Glory that is Astronomy Cast. We have a little tiny news show that is out there that I would love you to subscribe to. And it's just exciting to be building new things. 

Fraser Cain [00:02:41] That's that's great. After the cosmic microwave background radiation was released, the universe returned to darkness cloaked in the clouds of primordial hydrogen and helium. Gravity pulled these vast clouds into the first stars and then the first galaxies. This is the cosmic dawn. And t will help us probe this mysterious time in the universe. All right, Pamela, cosmic dawn, put cosmic Dawn in perspective for people, like, talk about the earliest eras of the universe, put them in order. Okay. Of time so that we can figure out where cosmic Dawn fits in. 

Pamela Gay [00:03:19] So we have the much talked about first three minutes way over here off the edge of the screen, during which everything that is and ever will be sprung into existence out of a single point, depending on which theories you follow and the forces separated and clue syntheses happened. And the end of this three minutes, we were left with a universe that consisted of hydrogen, helium, and trace amounts of lithium, beryllium. And it was exceedingly hot, hot to the point that all of the atoms were completely ionized, and it was entirely dense, to the point that a photon trying to go through the universe would pretty much instantaneously get absorbed and readmitted in a new direction. So the universe was hot and opaque and ionized, but it expanded and cooled and expanded and cooled and expanded and cooled until about 400,000 years after that Big bang, it reached the point where it was finally cool enough and not dense enough that the atomic nuclei were able to go electrons, you are mine! And the universe settled out into being a neutral gas, and the photons were like, we're free and they took off. And we are currently able to see the photons that were released 13.8 billion years ago, hitting our eyeballs from all directions. They're not actually visible to our eyeballs hitting our microwave detectors, which we used to see them from all directions, and we could go anywhere in the universe and we'd be able to see that sphere. It would look different of light that was emitted in all directions simultaneously. At that point. 

Fraser Cain [00:05:15] The analogy that I always that feels really comfortable for me is when you go outside and you look up on a sort of a misty night, or if there's like some high atmospheric clouds and you can see this ring around the moon. Yeah. And that ring and if you move, you walk 20m to the side. You still see a ring around the moon. And the ring that you're seeing literally at every moment is a brand new ring that is generated by the light coming from the moon, refracting through ice crystals and making their way down to your eyeballs. And it is different photons every time. And it's different. Ice crystals every time. Same moon, but different, different different photons coming from the moon and different ice crystals that the light is passing through. And yet you're constantly seeing this ring around the moon as if it was always there. But it is being. And so the cosmic microwave background is the same thing you are. You're looking the space. You are seeing the birth cry of the universe, but it's a completely different region of space that's a little bit farther away. Every second that goes by, one new part of space is releasing its photons at you and you're seeing them. And so you're always seeing this same time in the universe, even though it's a different place in the universe, because it's farther away. 

Pamela Gay [00:06:36] Yeah. And and we could go on for episode after episode after episode just talking about the cosmic microwave background. But that is not why we are here today. It is awesome. All hail! The amazing science that comes from the CMB. Yeah. 

Fraser Cain [00:06:51] Then. And like this. This is always a risk when we talk about the CMB is because we could just rabbit hole. It's unintentionally. It's been two hours talking about CMB. 

Pamela Gay [00:07:00] But we are not going. 

Fraser Cain [00:07:01] To we're not going to focus. We we we are professionals. We picked a topic. We're going to get to it. So so here it is. You had reached the CMB and the dangerous rut that is the CMB, but you made it through what came next. 

Pamela Gay [00:07:19] The problem is, what comes next is the dark ages of the universe, which is this period of time of which we know almost nothing because it was dark. The Dark Ages is that period of time where the universe's gases were neutral, hanging out, being a giant cloud, essentially, with a few places that were slightly more dense and few others that were slightly less dense and dark matter. And luckily, there was enough structure in this cloud of material that was the entirety of our universe, that the places that had a little more stuff sucked in. Even more stuff with gravity, in the places that had a little less stuff sat there going, hi, I can hold on to nothing. And they got emptier. And the result of all of this was probably just a few hundred, maybe even just a couple hundred million years after the universe came into existence, the very first stars were able to collapse and the ultraviolet light in particular, that was given off by hot, bright, young, massive stars was able to start re ionizing all of the material that makes up the universe. And there were also supermassive black holes forming and being fed by material falling into them. And that was also giving off ultraviolet light. And so we have this moment where the universe goes from dark, except for the leftover bits of the cosmic microwave background to a universe that begins to have pockets of structure and starts its way on the journey to becoming what we see today. 

Fraser Cain [00:09:15] And another analogy I bet a bunch of these analogies that I've worked out, I've I've, you know, workshopped over decades. Have you ever, like, stood at the top of a mountain and watched fog rolling through an area? Yeah. And and you can see when the fog hits an obstacle, like a Statue of Liberty or a an island, you get this, this clear spot that there's no fog in at all, and yet there's fog all around. And so if you're standing in that clear spot, you look around and the air would be perfectly clear. And then you see this wall of fog. But from above we can see the this gap opened up in the fog. And so imagine that, that those first stars that are forming in this giant fog of material of hydrogen, helium, this cooled down enough to form stars, but is still everywhere blocking all the light. But you get these pockets and the radiation that ultraviolet radiation coming from the stars is blasting open these pockets, and every now and then two pockets merge in. Two stars can see each other for the first time. You're like, oh, you're over there. Hi. That's great. Is that cosmic Dawn? Well, when does it become cosmic? Because again, this is an episode we've done first stars in the universe. We could rabbit hole again. Yeah, but I want to make this this distinction. When does cosmic Dawn start? 

Pamela Gay [00:10:42] And cosmic Dawn is really when you go from. Individual little bubbles to the universe is opening up. So think of it as as sunrise is when the day begins. Cosmic dawn is when the transparency begins. And so there is this magical moment that we're starting to hone in on. It looks like it occurred somewhere between 200 million years and 500 million years after the Big Bang. Where? The the density of the the neutral gas between galaxies between clusters of galaxies had become diffuse enough that you can say the universe was transparent. Our universe is never, ever going to be truly transparent. 

Fraser Cain [00:11:40] We can. 

Pamela Gay [00:11:42] We can, we can totally look out. And we still see. We call it the Lyman Alpha forest, these clouds of neutral gas between us and distant systems. So these kind of have to pick a moment where it's like empty enough. 

Fraser Cain [00:11:57] So we've got this time where I guess those first stars are starting to peep out of the dense fog, but they're still large blobs of this fog, even to this day, are out there in the universe, but they're becoming less and less dense over time. And so why is the cosmic dawn so difficult to observe? You would think that these incredibly bright stars out there would be obvious. 

Pamela Gay [00:12:28] So we have three problems. One is all the stuff that wasn't transparent yet. So? So. There's still clouds out there, so trying to find the stuff is difficult. Then there's the whole. It's giving off light from the beginning of the universe that has all been shifted into the infrared, where until very recently we didn't have the capacity to really look directly. And even though we now have the capacity to look directly, there's this problem known as they're really, really tiny and faint. So even with austere, which can see the right colors, we need to use gravitational lensing to start to magnify the light from these objects. So first you have to have g t to see the correct color. Then you need a galaxy cluster to gravitationally lensed things. And then, of course, you have to figure out how to, like, make the gravitationally lensed thing make sense because it's distorted. 

Fraser Cain [00:13:41] Yeah. I mean, even if you have a star that is 100,000 times more massive than the sun and it's putting out a ludicrous amount of radiation. Yeah, it is nothing compared to a quasar, and we can just barely find quasars at 12 billion light years travel time. You know, like, yeah, just a couple of billion years after the Big Bang. Hubble would need gravitational lensing to see quasars that are less than a billion years old in most cases. Yeah, and so even a ludicrously bright star is not bright. Considering the distances involved. 

Pamela Gay [00:14:27] And this is where we're lucky, because what we're actually looking for isn't so much individual stars. Although, I mean, if we could do that, that would be amazing. We would love to do that. 

Fraser Cain [00:14:40] Just please. 

Pamela Gay [00:14:41] Yes, more of that. But what we're looking for is these new baby galaxies that have clusters of star formation costars luckily like to form in groups. And they also have, like I said, these active black holes in their center. So we're we're still working to piece together. And and this is something I love seeing how science changes. And we're getting old enough that we have seen science change. It's it's we're starting to realize it's not just the stars. It's also the supermassive black holes and their accretion disks that are blowing bubbles in the early universe that are helping make things transparent. 

Fraser Cain [00:15:29] Right. And so if you were to like, say, you were to like, look in your telescope and look and go, oh, I see cosmic Dawn. Look at that cosmic dawn. That is so much cosmic dawn going on over there. What would you be seeing? 

Pamela Gay [00:15:46] I would be seeing mostly if theory is right and and here we have to put a huge question mark. I would be mostly seeing small galaxies that look rather like dead lightning bugs on a windshield in the Texas summer, and they are rich in splatters of bright blue star formation. I would also see larger galaxies that structurally look somehow remarkably like galaxies we have today, like our own galaxy, like the Andromeda galaxy in structure. But again, they're populated by massive young stars. And the reason I had to put so many caveats on this is J ust here's updating our understanding of this so fast that part of me is worried by the time this episode is edited and goes live in seven days, some of what we say will already be outdated. 

Fraser Cain [00:16:47] Okay, so just as an example of this, like you remember, there was these did these discoveries of these galaxies that were impossibly large too early in the universe. So a week ago I, a simulation called Renaissance overturned that and said, actually, those galaxies fit perfectly well within various models of of the early universe formation. And you're like, okay, yeah, that makes sense, right? Like we need a better models. And then this this week we got new evidence that, in fact, those galaxies might be even more massive than astronomers originally thought. And that's like, that's like a month, a month's research into this goes galaxies found. They're too massive. Oh, no. Actually, those fit the theories. Oh, no, those galaxies were more massive than we thought. Yeah, you're exactly right. The research is coming so fast and furious. We. It feels like I research. We could barely keep up with it. Let's talk about observing. Cause you don't. Because you sort of went into this a bit that you need some kind of gravitational lens with s t to take a crack at that. So what what are the sort of the physics involved here? Or I guess the, the trigonometry involved? What's going to be happening for you to be able to see some cosmic a little bit of cosmic dawn in your. 

Pamela Gay [00:18:12] Yeah. James t relativity meets trigonometry I think is definitely the right way to look at this. So we have g t with its giant mirror out there, and it will take an image of a massive, galaxy cluster. This is an object that has thousands and thousands of galaxies in it, a bunch of dark matter. And. If you have the the galaxy cluster and behind it you have light from a distant galaxy. Some about light is trying to shine straight towards us. Some of that light is trying to shine somewhere else in the universe, but it's going to get bent towards us by that gravity. And because these galaxy clusters don't have a smooth distribution, they're not a perfect lens. They're more like a carnival lens. All of these bent towards us, light images that weren't meant to come our way are going to be completely distorted, stretched out, turned into basically streamers of galaxy. Like someone put the galaxy in Silly Putty and stretched it around the edge of a plate. But the thing is, it's not going to be just like one planet's worth of light that gets bent our direction. It is a vast quantity of light that we never would have gotten to see that that is acting like a massive telescope funneling light. So we have j ust being a light bucket. We have the galaxy cluster being a light funnel. And all in all, we're able to start seeing things from 300, 600 million years after the Big Bang that appear in these images, as bright as the galaxies in that galaxy cluster. 

Fraser Cain [00:20:24] So what is cosmic like? If we could observe cosmic dawn with data to see, what does that tell us about the universe? 

Pamela Gay [00:20:32] Well, what's interesting is we're starting to hone in on it. Now, the problem that we're having is we have to look at a galaxy cluster, identify the gravitational lens in the galaxy cluster, and then measure where that gravitationally lensed object is. We have found objects that clearly still have the clouds of material around them. We have also found objects that are free and clear that are only a couple hundred million years apart. So the light ionized the universe very quickly. And so what we know is the universe goes from that island of clearness in the fog that is surrounded by blue with different density, getting shocked by the bubbling out UV light surrounding it to everything is just transparent with random clouds. 

Fraser Cain [00:21:29] And I mean, I guess there are all these dynamics. You know, the age old question did the stars form first or did the supermassive black hole form first? Did they form together? Was it did these galaxies assemble together into larger structures? In what order? How do we get such massive galaxies so early on in the universe? 

Pamela Gay [00:21:55] And supernovae? 

Fraser Cain [00:21:56] What role did dark matter play in funneling and channeling the the structure of these galaxies? When? What could help account for the, the crisis in cosmology, like the difference in measurements between the early universe and that's a different, you know, for sure. But the and we've done a different, you know, another round. 

Pamela Gay [00:22:19] Yeah. Yeah. 

Fraser Cain [00:22:20] But like just to see like was there some process going on that was already present that helped account for that change in measurements. So there's I mean there's just there's so many questions get answered when you see the or you finally have a full picture. Like like we. Can't see the first third or we have it until now, really seeing the first third of the universe's evolution. 

Pamela Gay [00:22:45] Yeah. And what I'm loving is we go from this idea of you have something hot with UV light creating a bubble around it. Well, if you just wait one star at a time to make bubbles, you're going to end up with a bunch of ionized things that look like a cluster of grapes, which is fine, but not entirely effective. And so they're looking at things like supernova explosions are able to basically pop holes out of the disks of galaxies that allow light out. You have jets that are able to pop holes. And so you have all of these different things working together. And so it's blowing bubbles and poking holes and blowing bubbles. And it's so much more chaotic and dynamic than these simple pictures we wanted to be true. And the idea that it's either primarily stars or black holes know both. The universe always says both and and I love that about the universe. 

Fraser Cain [00:24:03] So the universe is a game of Wordle? 

Pamela Gay [00:24:07] Yes. 

Fraser Cain [00:24:08] And we have this. We have the first character cosmic. We background radiation. We understand that. But the kind of starting point. Yeah. And then we have the last like four letters. 

Pamela Gay [00:24:22] Yes. 

Fraser Cain [00:24:24] From like quasars through till the modern universe. We're missing two those first two. 

Pamela Gay [00:24:32] And we've tried all the vowels. So. Right, right. We're stuck knowing it's a consonant and. 

Fraser Cain [00:24:39] T is helping us work out character number three. Yeah. And we probably and we'll give hint some character number two, the cosmic dawn. There was, you know, there was this other set of giant observatories that were planned. Of course, everyone's familiar with luvoir and hatchbacks, but there was a an x ray telescope called Lynx, and then there was origins. And origins was going to be a beefed up version of T that would be in the 12 meter range. Yeah. And would it be capable of directly and would have farther infrared, more like Spitzer beefed up to mega T size. And it would be the machine that would directly observe those first stars forming a cosmic dawn. And it's been shelved. 

Pamela Gay [00:25:27] Yeah, everything keeps getting shelved. 

Fraser Cain [00:25:30] Yeah, yeah. 

Pamela Gay [00:25:31] That's another show that's much more depressing that we're not doing this year. Maybe next year. 

Fraser Cain [00:25:35] Yeah. So, half. Can we do that? Can we do an episode about the missions? That being that this missions that have been canceled that make us sad? I feel like that that does meet your criteria because they didn't fly. And so now we can talk about how they make it sad. Yeah, I think it's reality. We should totally do that. All right. Thank you. Panel. 

Pamela Gay [00:25:59] Thank you, Fraser, and thank you to everyone out there who is part of our Patreon community. You allow this show to to happen this week. I would like to thank Aaron Zegras, Michael Regan, Omar Del Rivera, Scott Briggs, Dan Mendes, Benjamin Mueller, Janelle, Jay, Alex Alexander, J, Alex Anderson, Peter Frodo, tannin, Bo Jim McGinn, Kenneth Ryan, Matt Rucker, Dean McDaniel, Mark Steven Rusnak, and Michelle Cullen share some Mark H. Whittock, Philip, Grand father Abraham Cottrell, Bruce. Amazon, Dwight. Elk, James, Roger and and Esau. Thank you all so much. 

Fraser Cain [00:26:52] Thanks, everyone. We'll see you next week. 
Pamela Gay [00:26:54] Bye. Astronomy Cast is a joint product of Universe Today and the Planetary Science Institute. Astronomy cast is released under a Creative Commons Attribution license. So love it, share it, and remix it, but please credit it to our hosts, Fraser Cain and Doctor Pamela Gay. You can get more information on today's show topic on our website. Astronomy. Cars.com. This episode was brought to you. Thanks to our generous patrons on Patreon. If you want to help keep the show going, please consider joining our community at Patreon.com Slash Astronomy Cast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomy Cast.

It’s been over 20 years since astronomers first discovered that the expansion of the Universe is accelerating thanks to dark energy. And in these decades, astronomers still don’t have much evidence for what could be causing the increased expansion rate. Maybe there’s something else going on to explain it.

Show Notes | Transcript

Escape Velocity Space News (CosmoQuest)

PODCAST: Ep. 4: The Search for Dark Matter (Astronomy Cast)

PODCAST: Ep. 11: A Universe of Dark Energy (Astronomy Cast)

The Dark Energy Survey

The Nancy Grace Roman Space Telescope (NASA JPL)

South Pole Telescope (University of Chicago)

Physical Review Letters (APS)

Hot new early dark energy: Towards a unified dark sector of neutrinos, dark energy and dark matter (Physics Letters B)

Casimir Self-Interaction Energy Density of Quantum Electrodynamic Fields (Physical Review Letters)

Dark matter (CERN)

Dark Energy (Hubblesite)

Doppler Shift (Swinburne University)

Equation of state (cosmology) (Wikipedia)

Hubble's Exciting Universe: Measuring the Universe's Expansion Rate (Hubblesite)

Planck (ESA)

WMAP- Content of the Universe (NASA)

Supernovae Were Discovered in all These Galaxies (Universe Today)

What are Cepheid Variables? (Universe Today)

Carnegie Supernova Project II: The Slowest Rising Type Ia Supernova LSQ14fmg and Clues to the Origin of Super-Chandrasekhar/03fg-like Events (The Astrophysical Journal)

Research team discovers unique supernova explosion (Phys.org)

Planck and the cosmic microwave background (ESA)

Hydrogen Epoch of Reionization Array (HERA)

FOLLOW-UP: What is the 'zero-point energy' (or 'vacuum energy') in quantum physics? Is it really possible that we could harness this energy? (Scientific American)

First principle (Wikipedia)

WMAP Inflation Theory (NASA)

Could a Dark Energy Phase Change Relieve the Hubble Tension? (Universe Today)

Michael S. Turner (University of Chicago)

What is the Casimir effect? (Scientific American)

The Nobel Prize

The Higgs boson (CERN)

Particle Fever (2013) (IMdB)

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Transcriptions provided by GMR Transcription Services

Fraser Cain:                 Astronomy Cast Episode 669, Challenges to Dark Energy. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos where we help you understand not only what we know but how we know what we know. I'm Fraser Cain, the publisher of Universe Today. With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmo Quest. Hey, Pamela, how you doing?

Dr. Pamela Gay:         I am doing well. The third episode of our new TV show aired Saturday and we got it to the station 90 minutes before it was due, due to computer crashes, because computers know.

Fraser Cain:                 Yeah.

Dr. Pamela Gay:         But if you haven't checked it out yet, it's Escape Velocity Space News. It airs on Now Media and I am gonna be putting together a podcast version and loading that up later today.

Fraser Cain:                 Congratulations, that's amazing. It's been over 20 years since astronomers first discovered that the expansion of the universe is accelerating thanks to dark energy. And in these decades, astronomers still don't have much evidence for what could be causing the increased expansion rate. Maybe there's something else going on to explain it.

                                    If you go back into the archive of Astronomy Cast shows, one of the first episodes that we did was Dark Matter and then after that was Dark Energy, like within the teens anyway and we've brought it up a couple of times since them, but I had been expecting in the 15 years that we've been doing this show that we would have something more to say on the matter. But to be honest, not much has been figured out, apart from some really interesting new surveys, like the Dark Energy Survey Telescope, the development and eventual launch of the Nancy Grace Roman Telescope. We still have no idea what this is.

Dr. Pamela Gay:         One of the things that actually caught me by surprise is I was expecting to spend today talking about the new results from the Dark Energy Survey and the South Pole Telescope, and there are actually two really cool papers that have both come out in Phys Rev Letters in the past couple of months that are both clearly the, hi, we're theorists, we have predictions, there are only two of us on this paper, please give us the Nobel Prize when our predictions prove true.

Fraser Cain:                 Right.

Dr. Pamela Gay:         And so, we may be getting to the point that theorists are starting to figure out how to get a handle on things, and they're finding answers that may also help confine dark matter, which is kinda cool.

Fraser Cain:                 Well, that's great. So, then, I guess, what is the evidence for dark energy?

Dr. Pamela Gay:         Basically it comes down to when you measure the distance to a supernova and you measure the rate at which that galaxy is moving away from us using doppler shifts. We find that the universe is actually accelerating over time, which is not something that was in anyone's predictions but it was in the math in the form of a constant to the equations of state for the universe. When Einstein originally came up with these equations there was an integration factor, when you integrate you have to add a constant, and he assumed that the constant would have a value that caused the universe to be static.

A few years later, Hubble came along, found the universe is expanding. Now we have a constant that makes sense for that. But it turns out that if you have a universe that is accelerating apart, that is a value for the equations of state, and so now what we're finding is, in order to explain the geometry of our universe, which is flat, flat, flat, very flat, and an accelerating universe, you have to have 70% of the universe made of something that isn't observable matter, that's about 4-1/2 percent of the universe, that isn't dark matter that gets observed through gravitational lensing, gets observed through rotation curves of galaxies, gets observed through the motions of galaxies and clusters, that's 27-ish percent and instead you have dark energy.

Fraser Cain:                 So, this measurement really relies on how good the measurements to those type 1A supernovae are.

Dr. Pamela Gay:         Yes. And it also comes down to, once we realized, okay, so we have from the Planck Observatory the flat geometry and then you combine it with everything else and you look at the mass density of the universe, the only way to explain the mass density of the universe is to have this extra stuff as well. So, you can get to dark energy from a couple of different ways but to get at the value that we're seeing, yes, that came very clearly from the 1998 observations that the universe is accelerating with time and its expansion.

Fraser Cain:                 And we did some coverage on a new database that came out a couple of months ago, where astronomers had gone through and like recalibrated, normalized all the data for about 1,000 total type 1A supernova measurements and if anything, have gotten even more accurate.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 You overlap the Cepheid variables with type 1A supernovae, the distance ladder is beautiful, the error bars are ever shrinking and the amount of dark energy in the universe is zeroing in on this. They're really nailing this number.

Dr. Pamela Gay:         And one of the wild things about this is we keep trying to find an excuse that maybe further back in the universe these kinds of supernovas, due to the change in the chemistry, would have different properties, and we do keep observationally finding random exceptions. There was a super cool type 1A supernova that went off while inside of another star, which is one way to blow up a white dwarf.

Fraser Cain:                 You can imagine that would pollute the results a little bit.

Dr. Pamela Gay:         Right. But these one-offs that we're finding are super cool but they are one-offs. The vast majority of the type 1A supernovae are just boring white dwarfs that ate more than they could hold without changing states.

Fraser Cain:                 Right. And so I guess one possibility is that the type 1A supernovae aren't the standard candles that astronomers had always believed but the evidence is continuing to build that yes, indeed, they are.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 Except for these ones where one star blows up from inside another star.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 Right.

Dr. Pamela Gay:         And so, I mean it's just like saying most human adults are between five foot and six foot, yes, there are people who are only three foot and there are people who are only seven foot, but the vast majority of us are between five and six foot. So, yeah, it's averages.

Fraser Cain:                 So, then, let's talk about some of the largescale surveys that have been developed to try to get to the heart of dark energy. Not necessarily explain it, I guess, but at least to confirm it, map it, try and nail down its parameters.

Dr. Pamela Gay:         So, the big one with the obvious name is the Dark Energy Survey, which was done from down in Chile where they observed with extreme sensitivity vast swaths of the sky with the goal of looking to see how the structure of the universe evolved with time. So, the idea here is, we know that the universe started out as pretty much smooth distribution of particles. It wasn't even anything more fancy than particles initially, with slight over and under densities that were created by soundwaves moving through the early universe.

                                    That mostly smooth distribution that we can measure in the cosmic microwave background, then had to collapse down into galaxies, stars at the smallest scales, but then clusters of galaxies, walls of galaxies, super clusters at the largest scale and it does that over time. And we have models that basically say okay, here is the CMB, here is the modern universe, let's fill in in between and the Dark Energy Survey was designed to get at the more recent few billion years.

                                    The next survey that is super exciting to look at is HERA, which is being done in the radio, looking at the redshifted 20-centimeter line of cold hydrogen, that the detectors for this, they're looking at wavelengths of light that instead of being just 20 centimeters are instead many, many feet, so, longer than us. And in these longer wavelengths we are able to start seeing how cold hydrogen was distributed in the early universe, start piecing together how cold gas clumped and then got re-ionized in the era of re-ionization.

                                    And between these different surveys, we're working our way through measuring what was the structure over time so that we can better confine our models and say, okay, was the amount of dark energy constant over time. Was there some sort of a phase transition? Was there a kick somewhere? And these are the kinds of questions that folks are trying to answer, is what observables can dark energy give us that will help us confine our theories?

Fraser Cain:                 And so, in addition to the type 1A supernovae measurements, they're able to now look at these galaxy clusters and then on top of that they're looking at the concentrations of these regions of hydrogen gas. And so, you've got like three independent lines of observation that theoretically should allow you to map out the amount of dark energy.

Dr. Pamela Gay:         Yes.

Fraser Cain:                 And is the assumption that they're gonna find it? Like I know the Dark Energy Survey is still partway through its survey. You didn't even mention the Nancy Grace Roman, it's gonna be launching in 2025, and –.

Dr. Pamela Gay:         Well, you don't count your satellites until they're orbiting.

Fraser Cain:                 Fine, fine, okay. Pamela, put your hands over your ears. Audience, the Nancy Grace Roman, one of its main jobs is going to be to characterize dark energy, doing kinda the same thing that the Dark Energy Survey is but from space. So, this is classic, right. Like if you don't have an easy answer then you build more instruments, more observatories. You keep trying to characterize the nature of the problem, building hypotheses, testing them against your observations, removing bad ideas one after the other and hopefully trying to pin down the final thing. So, we may never know what's causing dark energy but we'll have it measured to Six Sigma accuracy.

Dr. Pamela Gay:         Well, and the other side of it is the particle physics side. So, we know that dark energy, whether it's a force, an energy, a field theory, whatever it is, puts into every cubic meter of space basically a proton-ish worth of energy. And so, how do you explain that energy existing? And by better understanding the quantum mechanic side of the universe, the particle physics, the vacuum energy, are sterile neutrinos actually a thing or not, this is another way of coming at the fullness of the universe by looking at the smallest factors inside of it.

Fraser Cain:                 All right. So, I guess, you found a few papers that have been proposing some alternative explanations that would explain the observations but not necessarily be new energy that's being injected into every cubic meter of the universe, which I guess sounds satisfying. Like the fact that energy is appearing out of nowhere, that's unnerving, so what are they proposing?

Dr. Pamela Gay:         So, the first paper in here, I have to look at my notes, the first paper came out from Martin Sloth and Florian Niedermann, where they're looking at new early dark energy. And the idea here is our universe has undergone phased transitions in terms of the energy of the entire universe. So, the first massive phased change occurred in the first fractions of a second, where we essentially went from every basically molecule sized bit of the universe expanding out via inflation, which we also don't know what is, to be about the size of the observable universe according to some ways of looking at it.

                                    And this massive, fairly instantaneous epic of inflation may have only been one of two phased transitions or there could have been a later phased transition that, if there testable ideas are right, leads through first principles to having a cosmological constant of 72, which is within error bars of what we see for the modern universe, and fixes the discrepancy we see with the old universe.

Fraser Cain:                 And so, sorry, so like, the idea of inflation –.

Dr. Pamela Gay:         Yes.

Fraser Cain:                 Happening in just the first fraction of the Big Bang was developed I think back in the '70s –.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 To help explain a lot of the problems with the Big Bang. Like the Big Bang beautifully explains the universe as we see it today, but there are these flaws in the theory. How can vastly separated parts of the universe be similar temperature, there's a bunch of these ideas. And so, one of the theories is that, in fact, there was this period of rapid inflation that carried everything away from each other really quickly and then it settled down.

                                    So, I think baked into modern cosmology is already this idea, as you say a phased changed, a dramatic change in the expansion rate of the universe. So, it doesn't seem that surprising that there could then have been others later on.

Dr. Pamela Gay:         Right.

Fraser Cain:                 So, when would have this other, they're calling it, what, early, what are they calling it, early –?

Dr. Pamela Gay:         They're calling it new, early dark energy.

Fraser Cain:                 Dark energy. Right, okay.

Dr. Pamela Gay:         So, NEDE is the abbreviation.

Fraser Cain:                 New early dark energy, right. And so when would this have occurred in the timeline of the universe?

Dr. Pamela Gay:         This still would have occurred during what they refer to as the dark times prior to the release of the cosmic microwave background. And it fits in with the way – Michael Turner, who is a prominent cosmologist, now professor emeritus from the University of Chicago, he says there's basically these three unknown pillars of cosmology, inflation, dark energy which he actually named, dark matter. And so, this looks at that early period, makes some solid predictions for temperature details that we should be able to see with enhanced continuing to look at the cosmic microwave background, which tells us everything apparently.

                                    But it also makes some finite predictions for what kinds of neutrinos should be out there, and what kinds of specific particles we can expect to find, thus, also perhaps explaining dark matter. So, we have one coherent theory spelled out in a letter-sized research article making concrete predictions. It seems good and just needs tested now but it's not the only one out there.

Fraser Cain:                 All right. Well, let's talk about the other one, then.

Dr. Pamela Gay:         So, the other one is by Alexander, and I'm going to mispronounce this and I am sorry, this appears to be a Ukrainian last name, Tkatchenko, and the other one is Dmitry Federov. And they look at the vacuum energy of the universe, and vacuum energy is something we know is real because of the Casimir effect, which is just one of the best named effects in particle physics. The dude's name was Casimir but it just sounds cool to say.

                                    And what the Casimir effect says is if you take two plates that are capable of conducting electrons and you put them extremely close together but you're not actually running charge through them and they're not being exposed to any fields, nothing should happen I a vacuum. But the reality is, if you put these two plates just a couple nanometers apart within a vacuum, they will either attract or repel due to the constant creation and destruction of virtual particles that are in their creation and destruction, creating a field. So, if you have a proton spring into existence as a virtual particle between these two plates, that proton has a field and it creates the effect.

Fraser Cain:                 Right.

Dr. Pamela Gay:         And we see this.

Fraser Cain:                 Right. And if I understand, like the Casimir effect, because the gap is so small the virtual particles of only certain sizes can pop into existence outside or as a field.

Dr. Pamela Gay:         Right.

Fraser Cain:                 Outside the plates and then they are pushing inward, there is essentially a field on the outside and not so much field on the inside and it's pushing on these plates. And once you move the plates farther and farther apart, now there's room for the fields to appear both in between the plates and outside the plates.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 And then that force goes away. And it sort of shows you the presence of this vacuum energy that is everywhere. And it's been beautifully measured, so no one argues with the existence of vacuum energy. The assumption, though, is that this energy cancels out, goes away very quickly and doesn't provide any ongoing force to the universe.

Dr. Pamela Gay:         And that's one school of thought. Another school of thought is, no, it's totally providing dark energy-like forces, but when they do all the maths, they have consistently come up with an amount that is too large by a factor of 10 to the 120 for the theories that I like the best and that are among the prominent theories. And the best case for getting it down has, until this paper as far as I know, been 10 to the 30th. And when you're off by somewhere between 10 to the 30 and 10 to the 120, it really doesn't matter.

Fraser Cain:                 That's a lot. Yeah.

Dr. Pamela Gay:         It's a lot. And this is where these two researchers, Tkatchenko and Fedorov, they said, well, okay, what if the vacuum energy has a polarizability, that the particles can actually have alignments that affect what can and can't come into existence and annihilate. And they make again solid predictions that should be testable if we go looking with new technology that we don't currently have laying around.

And it's just one of those nice, simple, elegant ideas of we know stuff can be polarized. We know particles can be aligned. What if just the universe as a whole has this polarizability characteristic to it that we just hadn't been including? And again, with this research, it makes set predictions on what to go look for. It looks at the particles that are out there and says, okay, here is what to see in particular physics and I don't know which team I'm rooting for more. I like the polarizability one.

Fraser Cain:                 Why choose?

Dr. Pamela Gay:         Well, I mean that's – it's two theory papers making predictions. Both of them have only two authors. Both papers are clearly gearing up for a Nobel Prize. It's always good to cheer for people but I guess I'll cheer for both.

Fraser Cain:                 Yeah. When you think about the winning Nobel Prizes, many of them start this way.

Dr. Pamela Gay:         Yes.

Fraser Cain:                 That a theorist puts together a paper and says there should be a particle called the Higgs boson, right, and then 30 years later experimenters are finally able to find it, and this is the same thing. So, I mean I guess if dark energy makes you uncomfortable already –.

Dr. Pamela Gay:         This doesn't help.

Fraser Cain:                 Buckle up. Yeah.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 You still got another 30 to 50 years of searching and scanning and trying theories to try and narrow in on an answer to it.

Dr. Pamela Gay:         And if you want to get a feel for what it's like within the field of particle physics to watch people so clearly chasing Nobel Prizes, watch the moving Particle Fever, it is very delightful. It shows the good, the bad and the ugly of scientists being scientists, and just the joy that comes from people getting to see their dreams come true through instrumentation.

Fraser Cain:                 I will check that out.

Dr. Pamela Gay:         It's really cool.

Fraser Cain:                 Yeah, that's awesome. All right. Well, thanks, Pamela. I hope within the lifetime of Astronomy Cast we will do the show we finally know what dark energy is. After we do the show where we say we finally know what dark matter is, we will do both those shows. This is my promise to all of you.

Dr. Pamela Gay:         And this is where it's just sort of like we can hope, and when that finally happens is that when we retire?

Fraser Cain:                 No, no.

Dr. Pamela Gay:         Okay.

Fraser Cain:                 Because there will be there will be a hundred new mysteries that are even –.

Dr. Pamela Gay:         We keep going until we die.

Fraser Cain:                 Yeah, there will be a hundred new mysteries that are even more complicated and more troubling, so, no, that's how this whole process works. All right, Pamela, thanks a lot.

Dr. Pamela Gay:         Thank you. And thank you to all the patrons out there. I don't actually have a thing of names, I just discovered, to pull out because it's the very beginning of the month and the list hasn't been generated yet but I do want to say thank you to all of you. We have been reading the names of just a subset of you on air, it's one of the perks associated with the different levels but we love all of you, whether you're a $1.00 a month contributor or a $100.00 a month contributor. You allow us, through our ongoing efforts, year after year to allow us to pay our humans and keep the show going, and occasionally replace cables from my camera when they die. So, thank you.

Fraser Cain:                 I will take this opportunity then to sort of mention a trend, a disturbing trend that you who are a fan of educational content should be aware of and that is artificial intelligence generated content.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 That more and more websites are moving to this model of getting ChatGPT and other artificial intelligence to generate en masse the material and this trend is going to accelerate.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 And it's just another career that is gonna be –.

Dr. Pamela Gay:         Go away.

Fraser Cain:                 Go away, sunsetted. The career of the science communicator and that's because it's way cheaper to let a large language model generate explainer content. And hopefully, Pamela and I have value and place in this society as more and more of this content shifts into being generated by enormous databases. I know it sounds shocking and surprising but this is where it's all gonna go and it's gonna happen startlingly fast. So.

Dr. Pamela Gay:         We have had people write in and say, hey, why don't you switch over to using ChatGPT to generate your scripts.

Fraser Cain:                 Right.

Dr. Pamela Gay:         It's already people are suggesting it.

Fraser Cain:                 Yeah, yeah.

Dr. Pamela Gay:         And we won't do that.

Fraser Cain:                 Yeah. I will get ChatGPT to recommend ideas but I won't –. See, here's the key, there are no scripts, that's the trick.

Dr. Pamela Gay:         Right, right.

Fraser Cain:                 So, how could we have a script if there are no scripts? Smart. Anyway. So, if the work that we're doing, like if the loss of science communicators at the mainstream media was already troubling to you, now they're coming for all science communicators. So, if supporting the work that we do is important to you to make sure that we can keep doing the show, paying the people on the team, keeping the servers running, all of that, join our Patreon.

Dr. Pamela Gay:         Thank you.

Fraser Cain:                 Patreon.com/astronomycast. Thanks, everyone, and we'll see you next week.

Dr. Pamela Gay:         Bye-bye.

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Astronomers have made extremely accurate measurements of the expansion rate of the Universe and come up with different results. And the error bars for the observations don’t overlap, so there’s something strange going on. What’s the answer and how can the Crisis in Cosmology be resolved?

Show Notes | Transcript

See Comet ZTF (C/2022 E3) Dash Between Big and Little Dippers (Sky & Telescope)

Comet Hale-Bopp (NASA JPL)

Comet Hyakutake (NASA JPL)

Comet NEOWISE, the best comet of 2020 (EarthSky)

Comet McNaught over the Pacific Ocean (ESO)

Hubble Tension Headache: Clashing Measurements Make the Universe's Expansion a Lingering Mystery (Scientific American)

Hubble telescope refines universe expansion rate mystery (Space.com)

Megaparsec (Swinburne University)

Messier 87 (NASA)

Andromeda galaxy: All you need to know (EarthSky)

Ask Ethan: Is there a better way to measure cosmic time? (BigThink)

Type Ia Supernova (Swinburne University)

How do astronomers measure the brightness of something? (Astrobites)

Luminosity (Swinburne University)

Standard Candle (Swinburne University)

What are Cepheid Variables? (Universe Today)

Gravitational Lensing (Hubblesite)

Dr. Adam Riess (Space Telescope Science Institute)

Astronomical deep-sky photometry and spectroscopy (BBC Sky at Night)

Gaia (ESA)

Baryon Acoustic Oscillations (NASA)

COBE (NASA)

Planck (ESA)

LAMBDA - ΛCDM Model of Cosmology (NASA)

Astronomers Grapple with JWST's Discovery of Early Galaxies (Scientific American)

How Did Inflation Happen — and Why Do We Care? (Space.com)

The Big Bang (NASA)

IMPROVING MEASUREMENTS OF THE COSMIC EXPANSION WITH GRAVITATIONAL WAVES (LIGO)

Cosmic Inflation Theory Faces Challenges (Scientific American)

Sloan Digital Sky Survey

The Dark Energy Survey

JWST (NASA)

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Transcriptions provided by GMR Transcription Services

Fraser Cain:                 AstronomyCast, Episode 668, “The Crisis in Cosmology.” Welcome to AstronomyCast, your weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, the publisher of Universe Today. With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey, Pamela, how you doing?

Dr. Pamela Gay:         I am doing well. How are you doing?

Fraser Cain:                 Doing great. Yeah, nothing to report.

Dr. Pamela Gay:         That, I think, in 2023, is really the best any of us could ever ask for.

Fraser Cain:                 Yeah, the weather is fine, the snow is gone, I’m getting out and doing a bunch of hikes and stuff in the nature, even though it’s wintertime, but still, garden’s coming along.

Dr. Pamela Gay:         Dang.

Fraser Cain:                 I saw the comet last night. It sucks, but…

Dr. Pamela Gay:         Oh well.

Fraser Cain:                 Yeah, it’s gotten quite diffuse at this point, so although it’s bigger and brighter, it’s also more of just a cloud.

Dr. Pamela Gay:         It’s spread out, so the light from any given place – its surface brightness is really low.

Fraser Cain:                 That’s right, so you really don’t get that nice, little, tight nucleus with the tail, you just get this – what looks like a little cloud in the sky. But still, it’s easy to find. It’s so easy to find because it was right beside Ursa Minor, right beside the Little Dipper, and then, it’s moving towards Cassiopeia. So, if you have never seen a comet – you can’t see it with your eyes, but you can see it in a pair of binoculars or a small telescope. It’s easy to find, and that’s nice, as opposed to one where it’s in a fairly difficult constellation to discover. But unfortunately, completely inaccessible now to the folks in the Southern Hemisphere, so this one is just for the folks in the north. So, if you haven’t already –

Dr. Pamela Gay:         Who do not have cloud like the Midwestern folks in the north.

Fraser Cain:                 Right, yeah. It’s gonna peak in just a couple of days from now, so now is your chance, and then it’s just gonna get – but it mostly sucks. I always compare comets to Hale-Bopp and Hyakutake, and people are even like, “Oh, didn’t you like Comet NEOWISE?” I’m like, no.

Dr. Pamela Gay:         No.

Fraser Cain:                 No, it sucked. I could see it with my eyes. That does not a good comet… That is necessary – sufficient but not necessary? Anyway, just barely being able to see a comet with the unaided eye does not – you do not declare victory in the comet world. No, you want the one that is gigantic –

Dr. Pamela Gay:         The tail.

Fraser Cain:                 The tail spans multiple handspans across the sky, that you can see it even in light-polluted skies. That’s a comet, and everything else the universe is sending our way right now is mediocre, and I reject them. So, no, NEOWISE sucked, McNaught sucked, this one sucks. We demand better. I will wait, but I’ve been patient for too long. Come on, comet!

Dr. Pamela Gay:         I…I can’t argue with that. All of that is true. It’s all true.

Fraser Cain:                 Yeah. For people who are like, “Oh yeah, Comet NEOWISE was fine,” no, it wasn’t! It wasn’t, and you’re settling. You deserve better. I deserve better. We deserve better comets. The universe can provide it; it’s done it in the past. It’s time to put up or shut up. All right.

Dr. Pamela Gay:         Yeah…

Fraser Cain:                 Astronomers have made extremely accurate measurements of the expansion rate of the universe and come up with different results, and the error bars of the observations don’t overlap, so there’s something strange going on. What’s the answer, and how can the crisis in cosmology be resolved? So, what is the crisis in cosmology?

Dr. Pamela Gay:         So, some people call it the Crisis, some people call it the Hubble Tension. A lot of us just put “WTF?” and call it a day. So, what’s happening is before the supernova teams did such an amazing job of measuring the present expansion rate of the universe, we were like, “Nah, the universe is expanding somewhere between 50 kilometers per second per megaparsec to 100 kilometers per second per megaparsec,” and I had so many profs that were like, “Just use 100. It makes the numbers easier.” It was pleasing.

Fraser Cain:                 Right. Just so people understand this idea, that you take a megaparsec of space, which is about 33 million lightyears of space, and when you think about that, that is the distance between us and faraway galaxies, like Andromeda’s really close. We’re talking about galaxies that are 30 million lightyears away, like M87 is kind of in that – when you think about the supernova image. Every second that goes by, those objects are now 100 kilometers farther apart, or 50 kilometers farther apart.

Dr. Pamela Gay:         And it is a function of how far something is away from you, so the further something is away, the faster it appears to be moving away from you. A lot of people use a raisin bread analogy on this because the raisins stay the same size as the bread dough expands, so two raisins that start really close together will end up a little further apart, two raisins that are really far apart initially will end up seriously far apart by the time that bread is done rising.

Fraser Cain:                 And why is knowing the expansion rate of the universe important?

Dr. Pamela Gay:         It’s one of those things that allows us to put together all the rest of our cosmological ideas of how you go from our universe being a single point to expanding out, to forming hydrogen and helium, trace amounts of lithium and beryllium, to – the whole story is tied up, and it slowed down or it sped up, and understanding what rate we’re going now, since there’s no accelerator pedal that we know about, what we see has to be defined by the physics of our universe, and we can start to define all that physics of the universe if we know this one number that refuses to be measured.

Fraser Cain:                 I apologize, I was off by a factor of 10 there, so, sorry, and you should have caught me – it’s surprising you didn’t – but a megaparsec is 3.3 million lightyears, not 33, so Andromeda, roughly, is in that ballpark range. So, apologies.

Dr. Pamela Gay:         Yes. The way I think about it is someone in Andromeda looking back at us would be seeing Neanderthals.

Fraser Cain:                 Right, but astronomers don’t think in lightyears, they think in megaparsecs, so if I get off by a factor of 10, that’s fine by you because you don’t even think about it, so apologies in –

Dr. Pamela Gay:         It’s true.

Fraser Cain:                 Yeah, the general public thinks in lightyears while astronomers only think in parsecs and megaparsecs, but yeah, so, apologize, let’s continue. So, why – you were discussing why knowing the expansion rate of the universe is important.

Dr. Pamela Gay:         It basically just gives us this reference point that we can work all the other maths back from.

Fraser Cain:                 So, how long the universe has been around for?

Dr. Pamela Gay:         How long the universe has been around for, basically –

Fraser Cain:                 What will happen in the future…?

Dr. Pamela Gay:         The one that gets me is by understanding the current expansion rate, we can actually figure how fast the universe went from being a mostly smooth distribution of gases to forming galaxies, to forming galaxy clusters. The rate at which we formed large-scale structure, at a certain level, hinges on how fast our universe is expanding. It’s everything.

Fraser Cain:                 Right. And so, in the olden days, we used to get “How old is the universe?” and people would say, “Well, it’s kind of somewhere between 10 and 20 billion years old,” and that’s that range of measurement. If you get 50 kilometers per second per megaparsec, you get one age of the universe because you just measure how long the universe is expanding, but if you get 100, you get a different one, and they are very different, and knowing that is important. So, how do astronomers measure the expansion rate of the universe at the close and at the far?

Dr. Pamela Gay:         So, there are two totally different suites of mechanisms. The “local time” way of doing it is we look for supernovae, which give off a set amount of light if they’re Type 1A supernovae – explode a white dwarf star, and you get essentially the same explosion over and over and over again, with errors that we’ve discussed in other episodes.

Measure how bright that explosion appears, measure how fast the galaxy the supernova is in is moving, and this tells you the distance using measured brightness and known luminosity, and it tells you the expansion rate by looking at the Doppler shifting. So, we’re literally measuring how much the colors of the different bands of atomic lines have been shifted by the galaxy’s motion, and that gets us a velocity.

Fraser Cain:                 Right. And so, we have all of these standard candles, from the Cepheid variables, to the supernova, to – I saw a list. There must have been 30 potential standard candles overlapping, going from – some of which are very well known, others of which are poorly known, but you go from local measurements using parallax that overlaps with Cepheid variables that overlaps with Type 1A supernova, and you just get this really beautiful, smooth measurement, and what number did we get from the local methods of measuring the expansion rate of the universe?

Dr. Pamela Gay:         So, we’re getting around 70 kilometers per second per megaparsec, and this is using not just supernovae, but as you point out, there’s a bunch of other methods. So, folks are looking at red giants, they’re looking at planetary nebulae, they are looking even at the distant gravitationally lensed galaxies that we’re able to see multiple versions of using crazy geometry when we can see the galaxies’ lenses do the same thing at different times. All these methods are giving us definitely over 70, and narrowing in on 74, so it seems pretty constant.

Fraser Cain:                 Right, and the error bars are really tightening up. The quality of the observations is exquisite. I talk to a lot of astronomers, and they talk about how good of a job they’ve done with those observations, and they just gush.

Dr. Pamela Gay:         The SHOES survey by Adam Reiss – they’re quoting an error of 1.3%, and they are basically going from the nearby Cepheids that they have taken some of the most precise photometry of that anyone has ever taken, then using Gaia parallax data, and then working all the way out. How often does anything in astronomy get done with that level of accuracy? We know this. The local value is basically 74 kilometers per second per megaparsec.

Fraser Cain:                 Right. And so, let’s go the other end of the range because there is another group of measurements that are taken not locally.

Dr. Pamela Gay:         Right, and this is where things are squirrely. In the cosmic microwave background, we see these baryonic oscillations, these soundwaves that move through the early universe, causing slight over- and underdensities, and we can map so beautifully this distribution with our theoretical models, and by combining our understanding of, okay, the universe had this much regular matter, this much dark matter, this much – putting all of these base understandings that we come at from the theory, combining our average temperature information that we got from COBE and other missions, putting it all together, it gets us in the 60s, 68, generally.

Fraser Cain:                 But the most accurate version of this was the Planck satellite from the European Space Agency.

Dr. Pamela Gay:         Right, and this is where it’s important to note the Planck data was used to get at that distribution of baryonic oscillations, and that was used in combination with a mean temperature that they were, in a lot of the papers, referring back to COBE data. So, Planck got us, very specifically, deviations about the mean, and we just fed all the data together in the context of what’s called lambda cold dark matter.

This is a theoretical framework that says that our universe is not just expanding, but it’s accelerating as it expands, that the dark matter, the stuff that we’re not really sure what it is, that may be related to neutrinos in some way – whatever it is, it wasn’t moving extremely fast early in the universe, so that’s where the “cold” part comes in. So, we have lambda, the dark energy, and cold dark matter, two things we have very poor understanding of. When you combine those with the data, it gets you, again, roughly 60 kilometers per second per megaparsec with error bars that don’t overlap.

Fraser Cain:                 Right, and this is the key. So, you look at the local neighborhood and you get a measurement that’s in the low 70s with very tight error bars, you look at the early universe, you get 68 with very tight error bars. Both are exquisite observations, both are trying to tell you the same thing, and they disagree with one another, and this, at the heart, is the crisis in cosmology.

Dr. Pamela Gay:         Correct.

Fraser Cain:                 So, this is the crisis in cosmology, so what’s the answer?

Dr. Pamela Gay:         Well, this is where I personally am a bit excited, and I don’t know how many people are with me on this one because I wasn’t at the meeting, but at the American Astronomical Society meeting, there was a lot of discussion about how JWST images of gravitationally lensed early galaxies appear to be showing from two different studies that have both made it through peer review that there were already well-formed galaxies 350 million years after the Big Bang, and that’s early.

There is other work that is being done that is still going through peer review that is showing there may have already been galaxies – massive ones – at 200 million years after the Big Bang. So, with galaxies forming this early in the history of the universe, it tells us that that model we have, lambda cold dark matter, is off somewhere because while we thought there would be a couple, a few massive galaxies early on, those baryonic oscillations didn’t lead us to believe there would be as many as we are now finding.

And so, we have to figure out a new way to get from mostly smooth universe with the cosmic microwave background to galaxies forming in bigger and probably larger numbers than we anticipated to our present structure, and folks are putting out ideas like maybe there was a bit of leftover inflation, maybe the value of dark energy hasn’t been constant, and all of these different ideas – I don’t think we can really throw anything out yet, and I am the first person to want to throw out ideas.

Fraser Cain:                 Right. So, the challenge here is that you’ve got – the most obvious possibility is that one or both measurements is incorrect –

Dr. Pamela Gay:         Yes.

Fraser Cain:                 – which is what would be everybody’s first instinct, that someone’s wrong, that one of these measurements is incorrect. But, because of this dichotomy, both measurements have been scrutinized and scrutinized, and teams have gone back, and all they’re doing is narrowing the error bars. They’re not finding a large discrepancy. So, that’s the one that is most likely, and yet, that seems to be less and less of the case, and so, you’re left with the universe –

Dr. Pamela Gay:         New physics.

Fraser Cain:                 New physics, right, that our understanding of Einstein, our understanding of what those acoustic oscillations should be in the cosmic microwave background, is wrong.

Dr. Pamela Gay:         And this is where I’m not gonna lay blame on anybody. Relativity seems to work so far, it doesn’t seem to be the problem, but our understanding of the distribution of kinds of matter, the way different forces interplayed, whatever the heck inflation might be – we have no idea what inflation might be – it is somewhere in this physics of how we get from the Big Bang to now that we are missing something, and it’s kind of awesome.

We don’t get a whole lot of surprises anymore, it feels like, some days. We’ve found all the particles in a standard model. We didn’t find any of the particles from supersymmetry. This gives us something new to chase, and the fact that even the folks using gravitational waves to measure distances – they’re still getting the same local universe numbers.

Fraser Cain:                 And that’s harder to get wrong.

Dr. Pamela Gay:         Yeah!

Fraser Cain:                 I know I’ve talked to some people working in gravitational wave observatories, and I’ve had this conversation, and effectively, the more precise, the more powerful these gravitational wave observatories get, the farther they’re able to see out into the universe. You can rely on their measurements, so it’s another layer of observation, but one that’s very trustworthy, and it only goes so far. It doesn’t take you all the way up to the end of the universe, but maybe some future observation will.

So then, new physics – so, maybe we don’t understand how the early cosmic microwave background worked, maybe we don’t understand how Cepheid variables work, maybe we don’t understand all these different pieces, but there have been a few hints. Maybe Type 1A supernovae aren’t the standard candles that we thought they were.

Dr. Pamela Gay:         And this is where there are so many different things that are getting us that local 73-ish that, yeah, I’m happy saying there are discrepancies from one Type 1A supernova to another in weirdo special cases. We’ve got to talk about some of those. If the white dwarf ends up inside of another star, that explosion’s gonna be a bit different, and that happens, but it really seems like there is something about how you get from there – cosmic microwave background – to here – gravitational waves, Cepheids, planetary nebulae, supernovae, all these other mechanisms. There’s something in the science that we have yet to uncover.

Fraser Cain:                 And then, another possibility is if the rate of expansion of the universe changed. So, perhaps there was a – the model that I’ve heard is this idea of late inflation.

Dr. Pamela Gay:         Yeah, that’s the one I was looking at as well, where whatever it was that caused us to initially blow up, there’s a little bit of that left over that caused another kick, but we don’t understand what’s going on there.

Fraser Cain:                 Right, right. And so, if you had an expansion rate of 74 early on – or, sorry, 68 early on, and then it slowed down, you could get the one that’s today, and that’s even taking into account dark energy. I’m sure people are like, “What about dark energy?” That’s layered on top of this. That’s accounted for. And so, you would have this almost – instead of the universe smoothly applying the accelerator on the gas, it was like putting the accelerator a little harder, and then pulling the foot off the pedal a little bit, and then putting it on harder again, and who knows what kind of shenanigans it got up to in the intervening period? So, what is the way forward at this point? What is the way out of the crisis in cosmology?

Dr. Pamela Gay:         We need to basically do a survey of just what was the distribution of galaxies and galaxy clusters in the early universe. We have done a beautiful job, first with the Sloan Digital Sky Survey, doing a volume around our galaxy. Then, with the Dark Energy Survey, we have pushed out even farther in some areas of the sky. With JWST, we’re going to be able to continue pushing the survey of structure size further and further out, watching how the universe goes from being Swiss cheese with giant holes in it to being Swiss cheese with smaller and smaller holes in it –

Fraser Cain:                 Right.

Dr. Pamela Gay:         – and by measuring how that large-scale structure changes over time, that will start to put a different form of constraint on our models. We need to be out there, counting early galaxies.

Fraser Cain:                 Right, and so, you’ve got this structure of the cosmic microwave background radiation, and the hot spots and cold spots should map to equivalent clusters and distributions of galaxies, and so, you’ll know that this transition from the farthest that you can see to more recent is smooth –

Dr. Pamela Gay:         Yes.

Fraser Cain:                 – and then, that will tell you, and you can keep moving forward at that point, but that’s a much harder observation. Weird as it sounds, the galaxies are much dimmer and harder to spot and map out than the cosmic microwave background radiation, which is everywhere in all directions.

Dr. Pamela Gay:         Yeah. More telescopes.

Fraser Cain:                 Yeah. And then, the other side of that is going farther with gravitational waves, and hopefully, you’ll get to this point where the two overlap, where the gravitational waves reach the cosmic microwave background, or shortly after.

Dr. Pamela Gay:         That is technology that someone maybe someday will fund, and we’re at that frustrating point where the next big discovery beyond what we can do with the new, massive radio telescopes that have started to catch star formation at earlier periods, and what we can do with JWST – it’s gonna take multiple nations getting together to build these 30-, 80-, however-many-meter telescopes that are being discussed to be able to look back.

Fraser Cain:                 All right, place your bets. It’s the close observations are wrong, the CMB observations are wrong, or there’s new physics.

Dr. Pamela Gay:         New physics.

Fraser Cain:                 Really? That’s the most exciting outcome possibility, is new physics, so if that’s true, that would be wonderful.

Dr. Pamela Gay:         Or at least a new understanding of that cold dark matter temperature.

Fraser Cain:                 It would be huge thing, like there was a revision to relativity that nobody saw coming.

Dr. Pamela Gay:         So, again, I’m not sure saying a revision to relativity is the right way to say it because I think that what we’re looking at is something coming out of the realm of particle physics, and particle physics and relatively do not talk to one another, and I really think it’s going to be something about how particles interact in different regimes, and whatever the heck this dark energy is that’s gonna be what gets us to the solution to this discrepancy.

Fraser Cain:                 I think this “crisis” makes it sound like a bad thing, but you talk to astronomers, and they couldn’t be more excited. They’re so happy to not understand something, what was considered to be this bedrock idea, because the problem is bedrock is you get this ossification. Suddenly, you have this space that has opened up, where the solution is in there somewhere, and a lot of interesting ideas and theories, and a lot of brainstorming, and a lot of intellectual power gets to be put onto this problem, and they love it. They love it. So, I feel said that the term “crisis” – because you get a lot of pseudoscientists sort of rolling their eyes at scientists at this thing.

Dr. Pamela Gay:         I like “the Hubble Tension.”

Fraser Cain:                 “Hubble Tension” – yeah, but “Crisis in Cosmology” is a better name, so I’d rather reel them in with “the Crisis in Cosmology,” and then help people understand that, in fact, astronomers couldn’t be more excited and happy to have this opportunity. All right, Pamela, thank you so much.

Dr. Pamela Gay:         Thank you, Fraser, and thank you to everyone out there who makes this show possible through your patronage at Patreon.com/AstronomyCast. This week, I would like to thank Camy Raissian, Gabriel Gauffin, Benjamin Davies, Steven Coffey, john öiseth, Arcticfox, Dean, Corinne Dmitruk, Bart Flaherty, The Lonely Sand Person, John Drake, Nate Detwiler, Lew Zealand, Brian Kilby, Naila, The Air Major, Ron Thorrsen, Arthur Latz-Hall, Leigh Harborne, Jason Kardokus, Robert Hundl, Kim Barron, Paul Esposito, Ruben McCarthy, Bob Zatzke, Jordan Turner, Timelord Iroh, Daniel Donaldson, Frank Stuart, Ian Abdilla, and Geoff MacDonald. Thank you all so much for making everything we do possible.

Fraser Cain:                 Thanks, everyone, we’ll see you next week.

Dr. Pamela Gay:         Bye-bye.

Voiceover:                   AstronomyCast is a joint product of Universe Today and the Planetary Science Institute. AstronomyCast is released under a Creative Commons attribution license, so love it, share it, and remix it, but please credit it to our hosts, Fraser Cain and Dr. Pamela Gay. You can get more information on today’s show topic on our website, AstronomyCast.com.

This episode was brought to you thanks to our generous patrons on Patreon. If you want to help keep this show going, please consider joining our community at Patreon.com/AstronomyCast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been AstronomyCast.

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Astronomers came together in January to present their newest research, and not surprisingly, the Winter AAS meeting was heavy on news from JWST. What were some of the new results that were announced?

Show Notes | Transcript

Escape Velocity Space News (CosmoQuest)

NowMedia TV

NowMedia Channel (YouTube)

Roku

First Science Results from JWST (Space Telescope Science Institute)

241st AAS Meeting (American Astronomical Society)

First Images Shared From Webb Telescope Reveal Unseen Universe (ESA Webb)

VIDEO: AAS 241 Press Conference: Building Systems in Our Local Universe (AAS Press Office)

VIDEO: AAS 241 Press Conference: Eyes on Galaxies with JWST (AAS Press Office)

NASA’s Webb Reveals Cosmic Cliffs, Glittering Landscape of Star Birth (NASA)

Close-up of "Proplyds" in the Orion Nebula (Hubblesite)

Herbig-Haro Object (Swinburne University)

Carina Nebula Jets (NIRCam Narrowband Filters) (ESA Webb)

JWST Sees Furious Star Formation in a Stellar Nursery (Universe Today)

The Pillars of Creation (NASA)

NASA’s Webb Takes Star-Filled Portrait of Pillars of Creation (NASA)

The Initial Mass Function (The Center for Astrophysics | Harvard & Smithsonian)

Pleiades – or 7 Sisters – known around the world (EarthSky)

Webb Reveals Shells of Dust Surrounding Brilliant Binary Star System (Webb Telescope)

NASA’s Webb Uncovers New Details in Pandora’s Cluster (NASA)

NASA’s Webb Delivers Deepest Infrared Image of Universe Yet (NASA)

Astronomers Grapple with JWST's Discovery of Early Galaxies (Scientific American)

Two Remarkably Luminous Galaxy Candidates at z ≈ 10–12 Revealed by JWST (The Astrophysical Journal Letters)

Early Results from GLASS-JWST. III. Galaxy Candidates at z ∼9–15* (The Astrophysical Journal Letters)

Gravitational Lensing (Hubblesite)

LAMBDA - ΛCDM Model of Cosmology (NASA)

NASA’s Webb Telescope Reveals Links Between Galaxies Near and Far (NASA)

Coelacanth (Smithsonian Ocean)

NASA’s Webb Confirms Its First Exoplanet (Webb Telescope)

NASA’s Webb Reveals an Exoplanet Atmosphere as Never Seen Before (NASA)

New Webb Image Reveals Dusty Disk Like Never Seen Before (NASA)

The Late Heavy Bombardment: A Violent Assault on Young Earth (Space.com)

NASA’s Webb Catches Fiery Hourglass as New Star Forms (NASA)

VIDEO: The Science of the L1527 "Butterfly" with Dr. Karl Stapelfeldt (Weekly Space Hangout)

NASA’s Webb Captures Dying Star’s Final ‘Performance’ in Fine Detail (NASA)

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Transcriptions provided by GMR Transcription Services

[Intro Music]

Fraser Cain:                 AstronomyCast Episode 667: JWST First Science Results. Welcome to AstronomyCast, your weekly facts-based journey through the cosmos, where we help you understand not only what we know but how we know what we know. I’m Fraser Cain. I’m the publisher of Universe Today. With me is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey Pamela, how you doing?

Dr. Pamela Gay:         I am doing well. I had a super exciting thing happen on Saturday.

Fraser Cain:                 What happened?

Dr. Pamela Gay:         The very first episode of Escape Velocity Space News aired on NowMedia television. Our new TV show has gone out to the masses, and we’re gonna be releasing the podcast and YouTube versions this week. So, I’m hoping everyone will go check it out.

Fraser Cain:                 Well, that’s exciting! If you want to watch it on the television, where do you have to live?

Dr. Pamela Gay:         So, I can’t keep track of all of the cities they have coverage in. I know that they’re in Houston, I wanna say San Antonio, Atlanta, Mexico City, and there are other cities. But if you go to nowmedia.tv, you can find out all the cities, –

Fraser Cain:                 Mm-hmm.

Dr. Pamela Gay:         – and they also go out on Roku and of course, on their own website.

Fraser Cain:                 That’s cool. So, if you have a Roku, you can subscribe to the Now –

Dr. Pamela Gay:         Yep.

Fraser Cain:                 – television channel, and then you can watch. Or you can just watch it on YouTube.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 Right. It’s funny, but like what is a television show in this modern age?

Dr. Pamela Gay:         Well, it’s so weird, ‘cause it’s Patreon-funded. When did TV start to be Patreon-funded? But –

Fraser Cain:                 Mm-hmm.

Dr. Pamela Gay:         – this is where we live, people.

Fraser Cain:                 Yeah. Yeah, exactly. Astronomists came together in January to present their newest research. And not surprisingly, the Winter AAS meeting was heavy on news from the James Webb Space Telescope. What were some of the new results that were announced? Now, you didn’t attend this AAS, did you? You don’t normally do.

Dr. Pamela Gay:         Remotely.

Fraser Cain:                 Yeah.

Dr. Pamela Gay:         COVID is still bad enough that going to a 100-person event last weekend was like the limits, and I still –

Fraser Cain:                 It’s scary!

Dr. Pamela Gay:         – was exposed to COVID, but –

Fraser Cain:                 Yeah.

Dr. Pamela Gay:         – same room, different time blocks.

Fraser Cain:                 Right.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 But you didn’t get it?

Dr. Pamela Gay:         No.

Fraser Cain:                 Good. Yeah. It’s funny. So, the last time we were together was at the Winter meeting of the AAS in Honolulu in –

Dr. Pamela Gay:         Yes.

Fraser Cain:                 – 2020, and this was about a month and a half, two months into the beginnings of the pandemic. And I think we even had this very conversation.

Dr. Pamela Gay:         Yes.

Fraser Cain:                 But this is probably the last time that we’re gonna be traveling for a while. And true enough, I haven’t been on an airplane since. So, –

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 – 2020, 2021, is it three years now I haven’t been on an airplane?

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 But I’m ready. I’m ready. I’m almost ready to get back on an airplane and start to travel again. But I’ve been busy with the forest. So, I guess what were the big… I guess we’re just gonna dive into this. Let’s talk about this. As I mentioned in my introduction, right? It was JWST news. Why was it so heavy on news from Webb?

Dr. Pamela Gay:         Well, it was that sweet spot where folks started getting their data about six months ago. And six months is kind of the minimum amount of time needed for a well-funded research team, especially if there’s a Summer in there, to go from data in hand to analyzed result that’s ready to be presented, and in some cases, published.

Fraser Cain:                 And so, a lot of the time, from up to this point, the news that we’ve been seeing has been someone from NASA has gone, “Here’s a cool picture!” And posting it on the NASA website with the bare minimum description, or some researchers, or there’s been stuff that’s been publicly available that people are pouring over, because some of the stuff is in open access. But a lot of it is proprietary research, –

Dr. Pamela Gay:         Yep.

Fraser Cain:                 – they’ve booked time on the telescope, they got their data. Only they got it, –

Dr. Pamela Gay:         Mm-hmm.

Fraser Cain:                 – and now they’ve had up to six months to analyze it, process it, and they were able to start explaining it to their cohorts at the American Astronomical Society meeting.

Dr. Pamela Gay:         Yes. And the results that came out spanned everything from star formation in a whole variety of star-forming regions to remarkable observations of some of the earliest-detected galaxies in the universe. And it’s hard to even figure out where to start, because really, the science spans the entire gamut of the profession, basically. There were even a couple of planets.

Fraser Cain:                 Right. So, I mean, were there any large themes?

Dr. Pamela Gay:         I think there were two big themes. One was star formation observed with JWST, and the other one was these early galaxies, and do they / don’t they break our understanding of how our universe formed and evolved.

Fraser Cain:                 All right. Well, let’s go into star formation then.

Dr. Pamela Gay:         Yes. So, back in July, we got that amazing – they named it, “Cosmic Cliffs Image”  –

Fraser Cain:                 Mm-hmm.

Dr. Pamela Gay:         – of the Carina Nebula, and the set of filters that they turned into that beautiful color image included filters that light couldn’t pass through. So, you have this yellow wall with the blue nebulosity above it. Now, when they instead only look at some of the filters, they’re able to see through that yellow wall to all the star formation that’s going on within. The Carina Nebula is known to be a remarkable star-forming region. There have been papers from Hubble coming out detailing solar system proplyds.

These are the cocoon-y formations where a star is just starting to light up in the core. There have been objects called, “Herbig-Haro” objects that are protostars that as material flows into them, some of it gets ejected then through jets in the Axis of Rotation. There’s been a whole variety of these different, young, active stars detected in the past, but the detections have always been, “We kinda, sorta think we’re seeing this, but we’re not really sure.” Well, when JWST hit the scene, it not only was able to go, “Yes, all of those are real, Herbig-Haro, Herbig-Haro, Young Star, Young Star,” –

Fraser Cain:                 Mm-hmm.

Dr. Pamela Gay:         – identifying all of them. It was able to also identify additional new objects, additional new jets. And the jets in particular are what we’re interested in, because as a molecular cloud like the one that led to all this star formation in Carina, as it fragments and collapses into individual stars, the biggest fragments collapse down fastest. Gravity does that. Biggest stars form first, you get these jets coming out.

Those jets then smush the other fragments around them, thus triggering more and more star formation. Hollowing out nebula over time. This is a stellar feedback mechanism. And well, once you turn off that yellow wall by going to longer wavelengths, you can see the stellar formation and the stellar feedback in action. And Carina was just one example of this. Hubble famously observed the pillars of creation, and that image has been used in just about everything since then.

Fraser Cain:                 Yeah.

Dr. Pamela Gay:         Well, JWST got their own version of that image that we saw last Fall. And yet again, we’re seeing more of this star formation, identifying the details. And this is starting to allow us to get at something I think we’re gonna start hearing more and more about again. And this is what’s called the “Initial Mass Function,” which is the distribution of sizes that stars form in out of different collapsing and fragmenting molecular clouds.

And by looking at all these different systems that have different contents, different masses, and seeing how stars of different masses form in different numbers, it starts to allow us to get down to the population statistics of these regions in ways we couldn’t when we couldn’t look through the gas. So, yay for x-ray vision that’s actually infrared vision.

Fraser Cain:                 And I think that release was the perfect example of this first initial showoff of a really great picture, but with not a lot of science going –

Dr. Pamela Gay:         Right.

Fraser Cain:                 – on.

Dr. Pamela Gay:         There was no science.

Fraser Cain:                 They were like, “Here…” Well, there was SOME, I mean. But here is the Carina Nebula. Look at these cool cosmic cliffs. And these –

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 – described some of the features, right? You know what you’ve got this. When you think about that picture, you’re seeing the combined stellar wind of all of the stars that have already mostly formed and blown out their neighborhood.

Dr. Pamela Gay:         Right.

Fraser Cain:                 And it’s like this combined wind that they’re creating that is continuing to pile up and blow away this material off into space, and eventually, the whole area will be cleared. We’ll feel a lot more like say, the Pleiades. But –

Dr. Pamela Gay:         Yes.

Fraser Cain:                 – for now, you’ve got the parts that are in Nebula and out of Nebula, and then you got to see a few little knots and regions and stuff. But this time around, now they’ve gone back through and they’ve measured things, and they’re saying like, “Here’s a star, and there’s a star, and here’s the jet.” And then, they’re measuring the amounts and quantities, and they’re also looking at the kinds of chemicals that are piling up. And so, you get this detailed analysis of six months of the astronomers doing their job on what was a beautiful picture. And in many cases, this is probably some of your phone wallpaper right now. But we got the analysis of that picture, –

Dr. Pamela Gay:         Yes.

Fraser Cain:                 – and that for astronomers is really interesting, because no star-forming region has been imaged at this level. And I think like with Hubble, I mean, we have images of Carina Nebula taken by Hubble, and we have images –

Dr. Pamela Gay:         Yes.

Fraser Cain:                 – from the Eagle Nebula. But Hubble has some infrared capability. And so, Webb was able to give far more resolution, and also peer through a lot of the gas and dust that’s obscured to Hubble to see even more features. And so, they’re looking at many new objects that had never been seen before, as well as being able to confirm the objects that Hubble had already seen. So yeah, it’s just amazing research. And that is, I think, just the perfect example of a gorgeous picture, –

Dr. Pamela Gay:         Yes.

Fraser Cain:                 – and now the follow-along science, which is just as interesting to astronomers. And hopefully, to the public.

Dr. Pamela Gay:         And with both of these systems, it’s really a matter of looking at the forest, where we’re seeing the entire region of star formation going on. But there were also opportunities where it was able to focus in on not just individual trees, but their leaves, you might say, to carry that analogy far too far.

Fraser Cain:                 Yeah.

Dr. Pamela Gay:         And this is where they have this tremendous image of Wolf-Rayet 140, which is a binary system with a Wolf-Rayet star. It’s about 10 solar masses, and a companion that is an O-type star about 30 solar masses. And these two systems go around each other every 7.9 years. And when they do, it compresses out a shell of material. And so, we’re able to see these individual shells that are getting compressed together through orbital mechanics and gravity playing together as this young star is settling down into its very short life.

It's these kinds of details that JWST is going to allow us to hopefully start to understand some of the more complex interactions that just haven’t made sense to us as we’d like. We’re seeing the same thing happening with planetary nebula, and other forming stars, and there’s just where do you want to go next?

Fraser Cain:                 Yeah. All right. So, the next big theme was on the cosmology side. The large-scale –

Dr. Pamela Gay:         Yes.

Fraser Cain:                 – structures in the universe. The things that are most distant.

Dr. Pamela Gay:         And at the AAS meeting, the research that we had to look at the published results are based on two different fields that contain galaxy clusters that we’re using to basically fast track us to being able to see the earliest objects in the universe in as little telescope time as possible. These two fields included an Abell cluster, a SMACS cluster. And these two systems, their mass allowed us to see magnified and enhanced amounts of light from galaxies we now have confirmation are 350 and 450 million years after the Big Bang is when we’re seeing them.

Fraser Cain:                 Yeah.

Dr. Pamela Gay:         And they were already formed, and they’re extremely bright. There’s two different competing research teams that published on these. One was led by Rohan Naidu from MIT, and the other one was led by Marco Castellano of the Astronomical Observatory of Rome. And so, when you have two different teams, both conforming the same lookback time for these two systems, that tells us that yes, JWST is seeing things that long ago. And we also see evidence – still needs to be conformed, still needs to go through peer review – potentially of bright galaxies that we’re seeing them as they appear just 200 million years after –

Fraser Cain:                 Wow!

Dr. Pamela Gay:         – the Big Bang. Yeah.

Fraser Cain:                 And that’s within the capacity probably through gravitational lensing though. It’s gonna take…

Dr. Pamela Gay:         Exactly.

Fraser Cain:                 Yeah. And I think one of the things that’s quite surprising is how well-formed these galaxies are. I know with one piece of research, they saw fairly mature-looking spiral galaxies just –

Dr. Pamela Gay:         Yes.

Fraser Cain:                 – like maybe a billion years after the Big Bang. Galaxies that would look identical to what we have today.

Dr. Pamela Gay:         And this is one of the things that the high resolution that JWST is capable of acquiring data at is allowing us to see that there were already not just brighter-than-we-expected galaxies, but bigger-than-we-expected galaxies, and more maturely-formed galaxies. And this is causing a rash of two different kinds of papers. One is saying, “Cosmology is wrong! We don’t –

Fraser Cain:                 Yeah.

Dr. Pamela Gay:         – understand it! JWST overthrows cosmology!”

Fraser Cain:                 I don’t think that cosmologists are making that claim. I think you have some people who are alternative theorists who have been pushing that diatribe for decades now, and are looking for any little crack in observations to push that narrative.

Dr. Pamela Gay:         So, the narrative –

Fraser Cain:                 No.

Dr. Pamela Gay:         – is related the structures of Lambda Cold Dark Matter, where the question is can we understand the ability of Dark Matter, which we don’t fully understand, that is moving fairly slowly – that’s the cold part – to quickly form massive structures. So, on one hand, we have the folks that have been doing some fairly sophisticated computer modeling saying, “Yeah, you can’t get things that big that fast.” Now, on the other hand, you have the star formation people going, “Wait! Wait! Early universe! We don’t understand the first stars.”

So, the argument is actually coming down to were the first stars so much brighter, and was there initial mass function, to bring that phrase back again, was their initial mass function so different from what we’re used to seeing in the modern universe that it was possible to have exceedingly bright, 10 times brighter than expected galaxies within those first few hundred million years, or is there something in our understanding of how the early universe like molecular clouds fragmented and collapsed? Which of those two things –

Fraser Cain:                 Mm-hmm.

Dr. Pamela Gay:         – or both is where the struggle is? My personal feeling is that we don’t have a good understanding of the initial mass function of the early universe because you only had Hydrogen and Helium. And we know that the initial mass function is strongly related to the melodicity of stars. So, I’m leaning that the majority of the problem is going to be on stars were just brighter back then, and we’re still understanding that.

Fraser Cain:                 One of the observations that I really enjoyed from this round of press releases was the imaging of objects that looked like green pea galaxies. And these were a finding by a team of – was it Galaxy Zoo? Anyway…

Dr. Pamela Gay:         It was Galaxy Zoo. Yeah.

Fraser Cain:                 Yeah. Found these weird galaxies that are green pea galaxies. And so, they’re mashed together. And you’re seeing the light coming, the collective light from all of the ionized gas in the galaxy. There’s so much ionized gas in the galaxy that it’s just glowing in the ultraviolet, and it appeared green in the images. It’s not that it’s actually green. And JWST was able to find examples of these galaxies early, early on in the universe. And although the wavelengths were pushed into –

Dr. Pamela Gay:         Shifted.

Fraser Cain:                 – the infrared, –

Dr. Pamela Gay:         Right.

Fraser Cain:                 – by all means, they matched these green pea galaxies. And so, what’s exciting about that is you get this connection. You got these things that are very close at hand, and are relatively easy to study, and you’ve got a confirmation that these things are very similar to the things that we saw at the beginning of the universe. And so, you can study the ones that are nearby.

They’re easy to get your hands on, and know that you’re looking at something that is kind of primordial. It’s like people pulling up a coelacanth from the bottom of the ocean, this primordial fish, and knowing that this thing has been around for this long. You can study an alligator, or a crocodile, and know that a version of this has been around for hundreds of millions of years. And I really enjoyed that story, and sort of what the implications were.

Dr. Pamela Gay:         I’m really enjoying the fact that as we’re able to see better and better in the infrared, we’re able to see that the expansion of the universe has just taken things that are familiar in the ultraviolet, in the modern universe, and shifted them. So, in the Middle Ages, they were optical-colored. Hubble showed them to us.

And now, we’re seeing the exact same objects from early in the universe that are shifted all the way into the infrared, and this confirms to us that while so many things have completely changed, the melodicity content of the universe, the number of heavy atoms, essentially, the basic physics of how things turn on, how they form, what they look like is the same at every single epic, except for maybe that very first epic, ‘cause there was only hydrogen and helium.

Fraser Cain:                 Now, did we get any planetary news?

Dr. Pamela Gay:         There was. So, JWST was able to confirm a test source. It had been seen as two rough transits. Previously, it was seen again by JWST, and with JWST’s abilities, they were like, “Yes, this is a planet.” And there was another world that originally, they thought maybe this isn’t a planet, because there was a double eclipse. And the thinking initially was that it was a sun-like star, and a Jupiter-like planet, and with that size of a planet, you shouldn’t be seeing both kinds of dips.

Fraser Cain:                 Mm-hmm.

Dr. Pamela Gay:         But then, they redid some of the star’s physics, and they were able to figure out, “No, wait. This is an object that the star is actually significantly bigger, significantly hotter, and yes, that is also a planet.” So, we’re at the finding planets, we are at the – they are starting to look at atmospheres, they’re still in the stages of eliminating stuff that they don’t see, but getting down to the stuff we’re interested in, like Carbon Dioxide is going to take a bit longer, just because it’s harder to observe, it’s deeper down in the atmospheres.

Fraser Cain:                 And there was another image. And this isn’t exactly planets. I guess it kind of is. But it was a picture taken by JWST of this fairly famous, newly-forming planetary system called AU Microscopii. And the star system is fairly new. And it’s relatively close, and it’s seen edge-on. But what was cool was you got a chance to see the coronagraph from JWST in operation. And so, it was blocking out the light from the star, and you could see the protoplanetary disc surrounding it.

And astronomers have already found multiple planets in this disc. And so, you’re seeing the left-over planetesimals that are all crashing into each other, and creating this rubble area around the star that is probably still causing mayhem. So, we think back to the early age of the solar system with the late heavy bombardment period, you’ve got that rough period that these planets are going through right now in this nearby star system. And it’s an amazing picture, just to see the star is gone, and then –

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 – the fainter objects around it are revealed. So, very cool.

Dr. Pamela Gay:         And my favorite star – and I have to look at its license plate every time – it’s a star in Taurus L1527. And this is one that you interviewed the scientists who worked on it over on the weekly space hangout. And it’s a fan-like structure coming out from this little, tiny, dark line of a disc in the center that has a young star in the very center. And the light coming out in cones just like a flashlight beam into a dust storm allows you to see all the structure of the gas around this young solar system. And I just love the ability that we’re finding with JWST to make out the fine structure.

Fraser Cain:                 Mm-hmm.

Dr. Pamela Gay:         A bunch of new work on the southern ring nebula is showing very similar, “Okay, let’s turn on just this one neuroband filter. Okay, so we see the hot gas in the center. Now, let’s turn on this other filter. Okay, now we see all of this filigreed ring structure including planetary nebula formed through the basically exhalation of the atmosphere of a star into the surrounding space, and in the outskirts of this, you start to see faint, individual rings from when the material was getting blasted off of this young, white Dwarf.

Fraser Cain:                 Very cool. All right. We’re gonna have to wait another six months for the next big AAS meeting, and then I’m sure we will see another, probably even more comprehensive list of stories coming out of JWST. Thanks, Pamela!

Dr. Pamela Gay:         Thank you so much! And thank you to all of our audience members who support us through patreon.com/astronomycast. This week, I would like to thank by name, Michelle Cullen, Dean McDaniel, Scott Briggs, J. AlexAnderson, Micheal Regan, Benjamin Carryer, Matt Rucker, Peter, Abraham Cottrill, Schercm, Jim McGihon, Frode… he gave me pronunciations that include a character. I don’t know what it means.

Fraser Cain:                 That’s not helpful!

Dr. Pamela Gay:         Okay. Frode, I’m gonna figure this out. Frode Tennebo, Philip Grand, Mark Steven Rasnake, Anitusar, Brent Kreinop, Father Prax, Dwight Illk, Bruce Amazeen, Gfour184, Dustin A Ruoff, Planetar, Alex Raine, Glenn McDavid, Andrew Stephenson, Paul L Hayden, James Rodger, Sean Martz, Cemanski, The Mysterious Mark, Karthik Venkatramen, Sam Brooks and his Mom. Thank you all so much, and thank you to all of you who are putting in pronunciation guides, and if you’re a human whose name I continue to mispronounce, I’ll look up that letter that was deeply mysterious. Thank you.

Fraser Cain:                 All right. We’ll see you next week!

Dr. Pamela Gay:         Buh-bye! AstronomyCast is a joint product of Universe Today and the Planetary Science Institute. AstronomyCast is released under a creative commons attribution license. So, love it, share it, and remix it. But please, credit it to our hosts, Frasier Cain and Dr. Pamela Gay. You can get more information on today’s show topic on our website, AstronomyCast.com. This episode was brought to you thanks to our generous patrons on Patreon.

If you want to help keep this show going, please consider joining our community at patreon.com/astronomycast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox, and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up! This has been AstronomyCast!

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The Cosmic Microwave Background Radiation tells us so much about the Universe. After that era, the Universe went dark. Then, as gas pulled together into the first stars and eventually galaxies, light returned, beginning the Age of Reionization.

Show Notes | Transcript

241st AAS Meeting (AAS)

JWST (NASA)

Hubble Space Telescope

What is the Cosmic Microwave Background? (Universe Today)

Epoch of Reionisation (MWA Telescope)

What Is the Big Bang? (NASA Space Place)

What are photons? (Live Science)

How the Cosmic Dark Ages Snuffed Out All Light (Quanta Magazine)

Energy Levels of Electrons (SDSS)

Ionization (Energy Education)

Population III stars: The Universe’s ultimate reclusive pop stars (KIPAC)

Dwarf Galaxy (ESA/Hubble)

The Pillars of Creation (NASA)

Spitzer Space Telescope views cosmic bubbles in infrared (BBC Sky at Night)

Messier 42 (The Orion Nebula) (NASA)

Quasar (ESA/Hubble)

What is ‘red shift’? (ESA)

What is Gravitational Lensing? (CFHTLens)

Quasars, the Lyman Alpha Forest, and the Reionization of the Universe (Astrobites)

Lyman-alpha_line (ChemEurope)

Astrophysical Classics: Neutral Hydrogen in the Universe, Part 2 (Astrobites)

Peter Gunn (TV Series 1958–1961) (IMdB)

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Transcriptions provided by GMR Transcription Services

Fraser: AstronomyCast, Episode 665, “The Age of Reionization.” Welcome to AstronomyCast, your weekly facts-based journey through the cosmos, where we help you to understand not only what we know, but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmo Quest. Hey, Pamela, how you doing?

Dr. Gay: I’m doing well. Right now, the American Astronomical Society meeting is taking place in Seattle, and I was watching the beginning of a press conference earlier before we went live, and there is so much JWST science that’s going to come out this week. It’s tasty, awesome goodness.

Fraser: Yeah. I got up early, got as much of my news organized and out of the way because I just needed to be prepared for the ongoing tidal wave –

Dr. Gay: Onslaught?

Fraser: The onslaught of news, and normally, when the astronomy panels come out, there’s a few interesting takeaways, but I can go a day without saying, “Okay, that’s really interesting and we should cover that” during the AAS, so I’ll do a couple, but I’m sure this one – each one is gonna be superlative, right? This is gonna be the most of this, and most extreme that, and the first time we’ve ever seen this, and this theory’s been overturned. It’s gonna be a monumental week in astronomy and science, the first time astronomers have got a chance to use JWST, and they are going to run with it.

Dr. Gay: Yeah, and we’re looking at a couple of decades of this, and what I’m also enjoying is there are some hints coming out that it is being considered if they can reboost HST to allow it to keep working for a little bit longer, so we might be looking at this nice era of having good coverage from slightly into the ultraviolet all the way into the far infrared-ish – not too far, because they don’t have a lot of coolant – but it’s a good age for discovery.

Fraser: The cosmic microwave background radiation tells us so much about the universe, but after that era, the universe went dark. Then, as gas pulled together into the first stars and eventually galaxies, light returned, beginning the age of reionization. I’ve always had a really hard time wrapping my mind around those early phases, from the cosmic microwave background, to the dark ages, to the age of reionization. So, can you explain that process for everybody, and I will finally get it into my head?

Dr. Gay: I can try. So, as the story goes, universe formed, there was massive heat and energy, and for the tiniest bit of time, the universe didn’t have any stuff in it, but as it expanded and cooled, expanded and cooled, particles came into existence, and at a point about 370,000 years after the formation of the universe, things cooled enough that all of the previously free-flying electrons were able to find a hydrogen, or helium, or maybe, if they were lucky, a lithium or beryllium atom to glom onto, and this process of the electrons joining in with the atomic nuclei allowed the photons that previously had tried to go somewhere and then gotten absorbed, and tried to go somewhere and gotten absorbed, allowed them to finally just fly free.

And so, this moment of the universe cooling enough that atoms could form and photons could fly free is the moment the cosmic microwave background was formed.

Fraser: So sorry, before we move on, I just wanna sort of put a couple of other notes on that. So, the first thing is if you could stand there when these electrons – sorry, when these photons are first trying to fly around, what would it look like? What color would it be?

Dr. Gay: The best way to think of it that I have is you’re gonna have all the colors, first of all, because this is just continuum radiation, and it’s super hot, so, peaking in the ultraviolet, and at the moment that this occurred, it would be kind of like turning off a neon light or a fluorescent light, where you go from having light coming out, but not getting anywhere, so you’re standing there, and the photons that are lucky enough to have been created right beside your eyeballs go into your eyeballs, but the light itself can’t really get anywhere. It’s trapped in this stuff, so it’s like being inside the neon light.

Fraser: Right. And then, the other thing is – you described it – again, it’s like turning off a neon light, but it wasn’t instantaneous.

Dr. Gay: No.

Fraser: It was a gradual process to go from no light can escape to now, light gets to move for a centimeter, to now, it gets to move for a meter, now, it gets to move for a kilometer, and eventually, it got to move for lightyears.

Dr. Gay: And it’s unclear how fast that process happened. It was something where areas of the universe that had a higher density – well, they also had a higher temperature, and areas that had a lower density had a lower temperature, and those lower-temperature regions were the first to be able to go, “Hi, here’s the cosmic microwave background.”

Now, the thing that always gets me is we talk about how the universe was opaque when all these neutral atoms were formed, but we also say this in the same breath that we say the cosmic microwave background was released, which, clearly, we can see. So, how is it that we’re seeing the cosmic microwave background if we now have an opaque, completely neutral universe? And the answer to that is that for the most part, the cosmic microwave background just passes straight through because of its wavelength, which is a bit confusing.

Fraser: Oh, okay. So, it was a wavelength of light, kind of reddish. I always describe it like the surface of a red giant star, that that wavelength was the one that could actually make it out further into the universe than other wavelengths, and so, we see – if you red-shift the cosmic microwave background all the way – right now, it’s microwave, but if you red-shift it all the way back to the beginning of the universe, it’s roughly the surface of Betelgeuse.

Dr. Gay: And so, this light is able to – for the most part – make it through, but what’s cool is we’re finally starting to be able to detect the early moments in our universe where the universe still had pockets of neutral gas, and these pockets of neutral gas are actually causing defects – irregularities – in the cosmic microwave background, so we can see the epic of reionization and before it using the irregularities in the cosmic microwave background.

Fraser: And so, this pushed into the dark ages?

Dr. Gay: Yes.

Fraser: And so, why were the dark ages dark?

Dr. Gay: Well, there was nothing giving off light. So, you have two different problems going on. First of all, you have no stars, you have no galaxies, you got nothing, and the other thing is you have a cloud of fairly dense neutral hydrogen and helium, and that’s gonna absorb light that’s coming at it once there is light. So, you start off with the dark ages, as there’s just nothing giving off light. So, then, stars start to form, galaxies start to form, and the first ones forming are having some of their light absorbed, and what’s cool is we’re using this absorption of light as seen in distant quasars to start pinpointing the moment in history that reionization occurred.

Fraser: All right, so, give us the physics description of what ionization is sort of as it relates to star stuff.

Dr. Gay: All right. So, you have your hydrogen nuclei. It has a proton, some number of neutrons, depending on what version of hydrogen it is, and a happy little electron if it’s neutral, and that electron has certain allowed energy levels. These allowed energy levels mean that if a photon hits the electron, only if the photon has the right energy level to allow it to jump between the different levels will that electron move. It can be thought of as if you’re on a stairwell, you’re either on step one or step two, you can’t be on step one and a half unless you have antigravity boots, in which case we’ve broken the analogy.

Now, photons come along, and if they have just the right energy level, that electron that absorbs the photon is going to jump to a higher energy level, and if the photon has a high enough energy, that electron’s just gonna go away. No more electron. And, it’s that process of removing an electron that’s called ionization.

Now, with hydrogen, you only have one electron to get rid of. With helium, you have two to try and get rid of that are in their own little energy levels, and so, you need more energy to get rid of both of them, and as you have more and more complex atoms, you can have something that’s singly ionized – that means you got rid of one of its electrons. You can have something that’s doubly ionized – you’ve gotten rid of two of its electrons. And, if you have a fully ionized iron, it’s had a really bad day.

Fraser: Right, with shell after shell of ionized electrons. So, the point being that the electrons are no longer in place around the nucleus, they are free-flowing – 

Dr. Gay: Yes.

Fraser: – around, and it’s when – and so, that is ionized, and when the electrons pair up with the nucleus to form more, I don’t know, stable atoms, but anyway –

Dr. Gay: Neutral. They’re electrically neutral.

Fraser: Neutral, yeah. Right. And they are no longer ionized.

Dr. Gay: Yes.

Fraser: So, we’ve got these newly forming – we’ve got all this neutral hydrogen that is left over. So, in other words, the universe was ionized. Then, it became unionized because it had cooled down, and you’ve got all this – just a soup of hydrogen –

Dr. Gay: Yes.

Fraser: – neutral hydrogen, where you’ve got hydrogen with its electron, and then, they collapse together in these star-forming processes to form these stars. They heat up, and then they ionize their surroundings.

Dr. Gay: So, this is where it gets super cool. Pop III stars, which we talked about in the last episode – really, really big. And their high-energy photons have an easy time escaping from the core because there’s no heavy elements in the atmosphere of the star to absorb out those high-energy photons and then rerelease them as lower-energy photons. So, we have Population III stars forming. They are giving off ultraviolet and even higher-energy ionizing radiation.

So, we have Population III stars giving off all of this radiation, and this is where dwarf galaxies finally get to do something awesome. Where you have massive galaxies – massive galaxies are gonna have a whole lot of dense, neutral gas around them because more gas to form more galaxy, essentially. The little tiny dwarf galaxies don’t have as much stuff around them, so the stars inside of them are able to give off this ionizing radiation that can escape in much larger amounts.

Fifty percent of the ionizing radiation in a dwarf galaxy is able to escape the dwarf galaxy, and this light is going to ionize a larger and larger bubble, first around each star, then those bubbles will merge, and then around the galaxy, and now you have all these little dwarf galaxies that are just ionizing a Swiss cheese of growing bubbles of no-longer-neutral gas.

Fraser: So, are there some examples of a very similar situation happening in the universe today? I think about the bubbles in the Pillars of Creation. Is that the same kind of thing, where you’ve got this young, hot star that is blowing up this cavity and ionizing the gas around it?

Dr. Gay: It’s a very similar physical process. The science is the science. So, when you have a star-forming system, you have a giant molecular cloud. First of all, you’re not really going to have molecules, other than H2, in the early universe, so you have a giant molecular cloud of all sorts of different gases, and as it collapses down and fragments, these different fragments are going to form stars that are able to blow bubbles around them, including H2 regions, which is the ionized gas around these young stars.

So, you have the same physics, it’s just much more interesting because you’re throwing in molecules that can now emit their own colors of light, allowing us to peer through the gas and dust using radio and infrared telescopes.

Fraser: And so, once again, if you could be there, standing in space a safe distance or maybe an invulnerable distance from the star – we talked about this last week, these gigantic stars at the very edge of what is possible for a star – what would you see?

Dr. Gay: This would be a case of if you were able to fully protect yourself, it would be very much like being underwater, where your headlight – or in a fog cloud, where your headlight allows you to see a certain distance around you, but beyond that, it’s just opaque. So, as you’re near that one just-formed, starting-to-ionize-the-space-around-it star, you have this place where all of the ionizing radiation has been absorbed and done its job, and beyond it, it’s just opaque gas, and you have a wall.

Fraser: Wow! And it would be – the star would have probably – its stellar winds would probably be off the charts, and so, it would have cleared out any additional materials. You’d have this empty space, and then, whatever distance where the edge of the bubble was forming, you would have this reionized gas in this giant sphere around the star, and if you could somehow navigate, you would see them – these blobs of hydrogen with little gaps inside of them where the stars were forming.

Dr. Gay: And what starts to get super cool to imagine is if you’re hanging out in one of these bubbles – and this would require time travel because there weren’t enough heavy atoms to make anything resembling a civilization, so if you time-traveled into one of these bubbles, it would eventually merge with another bubble, so you’d have this window into another area that you could see into that was ionized, and over time, these bubbles would essentially merge with one another, creating a sphere filled with stars, just like when you look at some star-forming regions, you can see that central region – I’m thinking of the Omega Nebula here – that central region that has been cleared out by the star formation and is still surrounded by gas. No dust back then, no dust.

Fraser: So, how long did this period take, do we think?

Dr. Gay: We’re trying to figure this out, and trying to figure this out is a complicated task on two different fronts. So, on front one, we need to be able to figure out the expansion rate of the universe, so we can translate the red shifts, the amount that the different lines being emitted by atoms have been shifted into years, and we also need to observe.

What I can tell you is the galaxies that have quasars in their hearts that we’ve been able to see in the earliest parts of the universe – they’re giving off extremely bright light that, as it travels from that quasar towards us, it’s going to encounter pockets of gas along the way, and these pockets of gas represent areas that are eventually going to become star formation, the material around galaxies between here and there, and some of them represent not-yet-ionized clouds of material.

And when we look at galaxies at Z=6, we’re seeing pockets of this material, but when we’re looking at Z=5 point something, they’ve looked at a variety of these systems, and it appears that already, at that point, the universe was fully ionized, so it was a very fast process.

Fraser: Can you translate that for the non – what is a 5.6 or a 6? Because I know 14 is – sorry, 20, 17 – these new ones that are coming out of JWST, these are 300 million years after the Big Bang.

Dr. Gay: Yeah. So, we’re thinking that all of this occurred between 150 million and 1 billion years ago, and trying to figure out exactly when in there it was done – we know it started around 150 million. We know it was done by 1 billion. Where in between those two that it was done, we’re still figuring out.

Fraser: Right. And I guess the process is uneven, that you’ve got different amounts of gas, different strengths of stars, different sized collections, which were probably linked up to overdensities and underdensities in the cosmic microwave background, and so, different parts collected together, heated up, cleared out sooner than others.

Dr. Gay: Exactly, and like I said, the really cool thing is the dwarf galaxies literally got to shine, and it was the area around the biggest galaxies that, because they had so much more material that they had to ionize, the areas around the biggest galaxies took a little bit longer to clear the way.

Fraser: So, what are our tools to perceive this time?

Dr. Gay: Well, the best tool that we have is gravitationally lensed galaxies that exist back behind galaxy clusters, and those galaxy clusters help magnify the amount of light that we’re able to get, and then, we point our infrared telescopes, like JWST, at those gravitationally lensed galaxies from the beginning of the universe, and we look for quasars, and once we find those quasars, we use them to figure out where in the quasar’s history do we see what kinds of material – well, essentially grabbing out the light. For the collections of gas that are more close by, it’s a Lyman-alpha forest, and then we’re looking back at the stuff that just hasn’t ionized yet.

Fraser: So, we’re seeing the light of the quasar through the gravitational lens –

Dr. Gay: Yes.

Fraser: – because only by harnessing the gravitational attraction of an entire galaxy cluster can you make a telescope powerful enough to be able to see this period.

Dr. Gay: Yes.

Fraser: You’re looking at these gravitationally lensed quasars, and are you seeing them – you’re seeing the light from the quasar go through pockets of gas and dust –

Dr. Gay: Yes.

Fraser: – that are in various states of ionization. You mentioned the Lyman forest. What is that?

Dr. Gay: So, what’s happening is you have – the background quasar is giving off light, where Lyman-alpha is one of the easier-to-spot lines of light. Now, that Lyman-alpha gas that, in the emission lines can allow us to figure out where quasars are. Now, the quasars, in addition to having this entire suite of emission and absorption lines, also have the continuum radiation that they’re giving off.

That continuum radiation, as it travels towards us, is going to have the hydrogen gas, pockets of hydrogen gas, absorb out different colors, depending on where in history they are. So, the light that was absorbed out at 2 billion years after the Big Bang by hydrogen gas is going to be red-shifted to be one color, and that is a Lyman-alpha line that has now been red-shifted into a color we can detect, from the ultraviolet into the reds.

Fraser: Right.

Dr. Gay: From a different age, it’s going to have a different wavelength, so we have the continuum radiation from the quasar that is going to have this forest of what was hydrogen Lyman-alpha absorption lines from an entire suite of different points in history where there were clouds of gas located to absorb the light.

Fraser: So, the light from this quasar is going through multiple gas clouds –

Dr. Gay: Yes.

Fraser: – and you’re seeing the forest with all of these trees.

Dr. Gay: Now, those forests that you’re seeing aren’t the not-yet-ionized gas left over from the Big Bang. That actually gets its own name, which, as someone with dyslexia, I have to be careful with because it’s called the Gunn Peterson trough, and my brain has decided it should be the Peter Gunn trough, which would be far more amusing.

Fraser: Right, right.

Dr. Gay: So, the Gunn Peterson trough is this gap that we can see, a literal trough in the light from the most distant quasars, that is there from the neutral gas that wasn’t ionized in the beginning, and this is what we’re desperately looking for using JWST, so that by finding enough far-away quasars with these Gunn Peterson troughs – while Peter Gunn plays in the background – we are able to say, okay, so we’re seeing these troughs in quasars at these specific points in history, and then we don’t see them anymore. That tells us everything was ionized by this point in history.

Fraser: Very cool. And, as we mentioned in the beginning of the show, be prepared. There’s probably gonna be a bunch of news coming out about the age of reionization just in this week’s American Astronomical Society. So, hopefully, now you will be better able to understand it, like me – I think I get it now, so I think we’re all right.

Dr. Gay: I’m so glad. It’s not easy.

Fraser: All right. Well, thanks, Pamela.

Dr. Gay: Thank you, Fraser, and I need to thank our wonderful patrons who are out there supporting this show. You allow us to pay all of our humans and, where needed, provide them with health benefits, and that is kind of awesome.

This week, I would like to thank by name Burry Gowen, Stephen Veit, Jordan Young, Kevin Lyle, Jeanette Wink, nanoFlipps, Børre Andre Lysvoll, Andrew Poelstra, Venkatesh Chary, Brian Cagle, David Truog, Gerhard Schwarzer, Buzz Parsec, Zero Chill, Laura Kittleson, Robert Palsma, Jack Mudge, Les Howard, Adam Annis-Brown, Joe Hollstein, Frank Tippin, Gordon Dewis, Richard Drumm, Alexis, WandererM101, William Baker, Felix Gutt, Astrosetz, William Andrews, Gold, Roland Warmerdam, Jeff Collins, and Simon Parton. And all of you who join our Patreon will have access to an ad-free version of all of our episodes, so if you’re noticing ads in the episodes, go join Patreon.

Fraser: Do it! Join us! Thanks, everyone, and we’ll see you next week.

Dr. Gay: Bye-bye.

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