The next great eclipse is upon us, with viewers across North America witnessing the moon passing in front of the Sun. It’s an amazing experience, but also an opportunity to do science. Let’s talk about what we can learn from this momentous event.

(This is an automatically generated transcript)

Fraser Cain [00:01:04] Astronomy Cast episodes 715. How to watch a total solar eclipse and do some science. Welcome to Astronomy Cast for 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. IPam, how are you doing? 

Pamela Gay [00:01:26] I am doing much better than last week, and I would like to say to everyone who stuck through it. Thank you. While we were trying to record that episode, everything on my screen was flashing red and I have to give a special thanks and a special shout out to Richard Drumm, our editor for hiding most of the chaos that was returning and to our patrons who allow us to pay him. It turns out that our local fiber trunk was in the process of being sliced through while we were recording the episode, and about ten minutes after we were done with like, fighting the internet gods to keep things going. All internet was lost for about 24 hours. Local construction. The message we got from our provider was fabulous. It was a third party doing construction sliced through the fiber trunk. Oh, we don’t know when it will be fixed. It was the most passive aggressive. Wonderful. And thank you all for your patience. Thank you, Rich, so much. And patrons, you’re the ones that allow us to keep going and have as close to excellent as we can get. When I’m distracted by red flashing lights as possible episodes when all the red lights are flashing. Thank you, thank you, all of you. 

Fraser Cain [00:02:49] Yeah, any episode would have been twice as long with us troubleshooting live during the episode. Is it you? Is it me? Is it the YouTube? No. YouTube? Yeah, yeah. It turns out your fiber connection was being degraded in real time while we were attempting to do the episode. I’m amazed we got through it as much as you did, because, yeah, you sent me a text message maybe 15 minutes after we closed, like, well, we’re all offline, and it was a disaster, so. I’m amazed. 

Pamela Gay [00:03:23] So thank you, everyone. 

Fraser Cain [00:03:25] All right. The next great eclipse is upon us, with viewers across North America witnessing the moon passing in front of the sun. It’s an amazing experience, but also an opportunity to do some science. Let’s talk about what we can learn from this momentous event, and how to maximize your chance of getting it in your eyeballs. All right, Pamela, you are a veteran eclipse hunter. How many total solar eclipses have you witnessed in all of your years of chasing after eclipses? 

Pamela Gay [00:03:58] Zero. 

Fraser Cain [00:03:58] Zero. 

Pamela Gay [00:04:00] The running joke is you want to be anywhere but near me. 

Fraser Cain [00:04:04] That’s my plan this year. 

Pamela Gay [00:04:06] Yeah, yeah. So the two of us were both vaguely together for 2017. I was I on the floor of the stadium in Carbondale. And you were out in the observing field in Carbondale? Yep. And I had a slightly bigger than the sun sized cloud go in front of the sun just at totality, and you got to see totality. 

Fraser Cain [00:04:30] I but I got maybe five seconds of totality right at the. 

Pamela Gay [00:04:35] You’re still seeing it. 

Fraser Cain [00:04:37] I guess I have. 

Pamela Gay [00:04:37] Not yet saw Corona. I have never seen Corona. 

Fraser Cain [00:04:40] Yeah, I guess I. I’m going to still say that I saw zero. Oh, but but but you. But you’ve tried a few times now. So yeah. Each time you get to that. Yeah. All right. And so I think this, this is going to cast a long shadow, pardon the pun, over our recommendation. So, so we’re going to get into the science with this. But but first I think it’s really important for us to just give general advice about about how to maximize your chances of getting the best experience for the total solar eclipse, if you’re going to be in the eclipse, and I’m like 30 million people in North America live under the path, just live. You step outside, look up, you will see the eclipse. And then there’s all the people that are coming from elsewhere, like me, like you, to try and get under the eclipse path. So first step one, let’s just talk about safety because it’s absolutely critical. 

Pamela Gay [00:05:38] Yes, I a lot of people have a lot of misinformation. If you’re going to try and use welding glass, it has to be 14 or higher. So the myth that you can just use a welding visor is, is like on Rotten Tomatoes where they’re like, there is a grain of truth in there somewhere, but it’s not true. Right. It’s it’s much more a case of you have to have level 14 or higher. The best thing to do is to not try and get yourself welding glasses. They’re heavy, they’re thick. They cost a whole lot of money. Instead, get yourself a pair of ISO certified eclipse glasses. 

Fraser Cain [00:06:21] So the, the, the American Astronomical Society has a page where they describe vendors. You can buy them on Amazon. Still you’re looking for the ISO certified. 

Pamela Gay [00:06:34] Yes. 

Fraser Cain [00:06:35] Look, you know, I mean, I know it’s really tricky to buy stuff on Amazon, especially last minute. There’s a lot of people are going to try and sell stuff. People are freaking out about fakes. I wouldn’t be that concerned with it. And there’s some tests that you can do when you get the glasses that you can just double check to make sure that they are good enough. So how do you do that? 

Pamela Gay [00:06:55] So. It’s AI unless it’s ISO certified. I can’t say where I might get sued that you can see if it’s safe or not, because at home no one has the stuff to see if it’s ISO certified. What you can do is is the basic make sure it doesn’t have any pinholes in it. Yeah. Make sure that it doesn’t have any scratches. And holding your glasses up to a very bright light is a good step one. Yeah. Step two is to hold them up to the sun and not have them plastered up against your eyes, but sort of like, okay, does that look entirely dark? Because I’m looking at it. Yeah. Yeah, it’s tricky story, but the main goal is you shouldn’t be able to see any bright light through your glasses. 

Fraser Cain [00:07:47] Exactly. And anecdotally in the chat, I’ve seen that Walmart has plenty of them. And I think that’s a good way to go because if this late in the game now, if you’re going to try to go to Amazon then yeah you might get a pair. That’s not great. But if you just go to Walmart or whatever, and as long it says ISO certified, that is the that’s the code word that you’re looking for. That will mean that these glasses are the right level of darkening for you to be able to see it. Target. 

Pamela Gay [00:08:15] Rainbow Symphony Online is where I would go, actually. You can still get them from Rainbow Symphony and their stuff’s ISO certified. 

Fraser Cain [00:08:21] Okay, yeah. So ISO certified. That’s really looking for from any of these places. Just it should have written on it ISO certified and then you’re good to go. All right. So that’s the safety thing. But there’s more nuance to this because you can look at the sun and in fact you get the best experience when you do look at the sun. But but there is a timing thing. So explain when it’s unsafe to look at the sun and when is it safe to look at the sun? 

Pamela Gay [00:08:48] The only time it is safe to look at the sun without an eclipse viewer, or using a safe solar viewer of some sort is during totality. There are apps that you can get that will play a sound when the moon completely blocks out that main disk of the sun, and there, it will make a sound when the moon starts to leave that main disk of the sun. And it’s only during that few minutes or less period of time, depending on where you’re located, under the path of totality. Yeah. Where you can take your glasses off. Yeah. And you really do want to take your glasses. 

Fraser Cain [00:09:30] You totally do. And this is the key. Yeah. So you want to make sure that you are definitely in the path of totality, and you’re watching with your glasses, and you’re going to see this little final sliver diamond right at the very edge of the sun. And then when that goes away, when you pretty much can’t see the sun anymore with your glasses, then you can take your glasses off, and you should be able to see the sun in the corona. And then. And the trickier part is when that sun is going to return. Because then on the flip side, you get that little diamond appear again on the sun. And so as you said, if you got some timer, that’s great. But it’s like the second you start to see a brightening, put the glasses back. 

Pamela Gay [00:10:08] It’s over. 

Fraser Cain [00:10:09] Yeah. It’s over. 

Pamela Gay [00:10:11] And the thing to think about is looking at the solar corona during totality. That’s like the same amount of light as a full moon. It’s not even as bright as a full moon. That’s an exaggeration. But it’s safe to look at the full moon. It’s safe to look at the solar corona. Yeah. The rest of the time, there were cases after 2017 of people who managed to burn the crescent sun into the retina. You don’t want to burn the crescent sun into your retina. That’s just the wrong kind of scarring to get on purpose. 

Fraser Cain [00:10:46] And don’t mess with binoculars or telescopes unless you’ve got proper safety equipment. Yeah, like I, I can’t even like I wouldn’t even in the middle of totality. I wouldn’t look at them at the sun. Now, with binoculars, even though it’s safe, it’s going to be unsafe in a in a heartbeat. And the second there’s a little bit of sunlight, it’s burning your retinas. So I wouldn’t even take I would not take the risk. 

Pamela Gay [00:11:14] One thing that is safe to do, as long as you have glass lenses, because otherwise you’re going to melt your telescope. And that’s a very expensive thing to do by accident, is you can project the sun onto a wall under a board. Yeah. Or. 

Fraser Cain [00:11:29] So with camera, whatever you want to do. 

Pamela Gay [00:11:31] Yeah, yeah. So I, if I have the opportunity, will be projecting the sun through binoculars on a tripod, and that’s a perfectly safe way. And there’s even easier ways to do this. You can simply have something that you have punched a hole in with a three ring punch and use that to project the sun. And one of the coolest things I learned about is disco balls are very good at reflecting light, but they aren’t dangerous about reflecting light. And so you can just get a disco ball out there, have it scatter images of the sun in all directions, and every one of those little square pieces of mirror is going to give you a perfect projection of the sun. 

Fraser Cain [00:12:17] Yeah. All right. We’re going to talk about how to maximize your experience in a second, but it’s time for another break. 

Pamela Gay [00:12:24] This show is sponsored by BetterHelp. Time is one of the most valuable things each of us have in this modern economy. Many of us, myself included, feel the need to hustle to finish one job and start the next. It sometimes feels like the only me time I have is what I steal from myself. Each night as I read just one more chapter a few too many times, finding time that is meant for me. Too many of us leave ourselves out when planning our day. And this is where BetterHelp comes in. Working with their counselors, you can work to define what is important to you and how to make it a priority. Therapy can help you find what matters to you so you can do more of it. If you have been thinking about starting therapy, give BetterHelp a try. Early in the pandemic, hearing an ad like this on another podcast got me to give it a try, and I learned coping mechanisms I need it. BetterHelp is entirely online, designed to be flexible, and you can switch therapists at any time. To get started, just fill out an online questionnaire. That’s it. They’ll match you and get you started. Learn to make time. For what? Makes you happy with BetterHelp. Visit betterhelp.com/astronomy today to get 10% off your first month. That’s BetterHelp. Help slash astronomy. 

Fraser Cain [00:14:01] And we’re back. All right, we got the safety warnings out of the way. So let’s talk about how you maximize your chance to not be Pamela. 

Pamela Gay [00:14:11] Well, I mean, the best thing you can do is position yourself next to a highway near the path or under the path, and be prepared with maps and with a full tank of gas. And look at the weather models the night before and plan a run for it. Now this eclipse is quite polite, so you will have the ability to get up and say, I’m going to make a break for it and decide which way to go. 

Fraser Cain [00:14:42] Yep. 

Pamela Gay [00:14:43] It enters, Mexico. The eclipse starts at 1107 Pacific in Mexico, here in Saint Louis, where we’re about the midpoint in the United States, maxes out at 2 p.m.. We’re at 99%. I’ll be down in Carbondale, where it’s 100% at 1:59 p.m., and it leaves into Canada at 3:33 p.m.. And I have to admit, I was not able to find the times that it was going through Canada because everyone is like, yeah, don’t go there. The weather. 

Fraser Cain [00:15:14] Is terrible. I’m a Canadian. I’m not going to Canada, now. And so I think there’s this sort of state, the strategic plan that you have to think about. So, so a few days in advance, you have to look at those weather forecasts and say, yeah, what regions are expected to have sunny skies and then you’ve got to choose to go to one of those, like if it’s where you are, great, you did it, you won. But otherwise you’re going to have to go. It looks like it’s going to be sunny 100km north for me or 100km south for me. And so you’re going to have to plan to be there. And, and as you said be close to a highway. But there’s going to be a lot of traffic congestion. And so being away from a highway is also good if you can just take back the. 

Pamela Gay [00:16:01] Rural. 

Fraser Cain [00:16:02] Routes. Yeah. If you can’t rural routes to get where you need to go then then that might be the the path to go as well, because the highways could just be chock a block and you’re stuck in it. You know, people ask me like, well, I want to, you know, what’s the right place to see it? What’s the what’s the best situation and scenery and like, it doesn’t matter. None of that matters if all that matters is that you can see the sun from where you are, and you could be the dense forest. And you find a little spot, an opening in the in the trees you can see the sun, you can be in the plains, whatever. I would avoid places where a lot of people are expecting to go, because you’re not going to be able to get out and you’re not going to be able to stay mobile. 

Pamela Gay [00:16:45] The coolest story I’ve heard from anyone so far is, a fellow who in rural Illinois was like, I’m going to go up to my. They build these towers that you can hunt deer from. It’s a thing. Deer stands. So he went up into his deer stand in rural Illinois. He’s the only one for miles. There were trees around. And of course there were deer because they feed deer from deer stands. And he said, all the deer in the herd came and lay down and pretended like, well, I mean, they didn’t pretend for them. It was real, right? It was time to settle down. And there’s actually now subprojects out there for observing animals and submitting data, because researchers are still trying to figure out what of all of these stories that people tell are real or imagined and what is actually happening. 

Fraser Cain [00:17:40] So the the analogy that I always use is think of don’t think of this like a picnic. Don’t think of this like you’re going to go someplace you can sit down. You can bring your friends, you family, you can sit around, think of this like a heist that you are considering your escape routes you are considering, you know, keep the car running and and you’re going to have a bunch of ideas, like, if we have to go north and we’re going to go here, and if we have to go south, that we’re going to go over there. And even on the day, a few hours, the clouds are coming in. But you know that there’s clear skies 100km north. You got to drive. And then even in the moment, minutes before you’re looking at the various clouds, and this is the thing that you couldn’t do. That’s the thing that I couldn’t do. But we had friends that did. They got in their cars and they even in some cases they ran to get out from under a cloud because because, you know, it’s just you. 

Pamela Gay [00:18:33] Can see the clouds coming across the field and you can run. Yeah. Standing in front of the cloud, it’s ridiculous. Yes. It’s a big. 

Fraser Cain [00:18:41] Dodge that cloud. If if there’s just a bunch of fluffy clouds around in all directions, then yeah, you’re going to have to move. And so you’re going to need to replace a field, rural streets, places where you can move and not get hit by car. And so think about your safety, but also think about how to get to a place where you are going to get clear skies because it’s two minutes and then it’s done, and then you just then you can take as long as you need to get home again in horrible traffic. 

Pamela Gay [00:19:08] Yeah. Yeah. Can I recommend pausing, picking up food, eating some of the food, and then just being prepared to treat this like the longest munchie car ride ever. On your way home? 

Fraser Cain [00:19:24] Yeah, exactly. Now, what about cameras? Because a lot of people ask, you know, I talked to a bunch of people, and they’re, like, telling me this is their first time, but they’re also going to bring in their camera gear and they’re going to try and capture the eclipse. What do you think about taking pictures of eclipse? 

Pamela Gay [00:19:37] So there is software that you can get for jailbroken cameras that will control the exposure times for you. You set up your camera, you get it going with the software and it just goes and does its own thing. Now, if you’re in a situation where you can have your jailbroken camera that you are utterly ignoring like it is dead to you during totality, that’s fine. Yeah. Do not be messing with your exposures. Do not be touching your camera. Do not be looking through your viewfinder. None of this is is a good use of that seconds to minutes that you have in the shadow of the sun. 

Fraser Cain [00:20:18] Unless you’ve seen multiple it. Unless you’re bored of watching total solar eclipses with your own eyeballs, then consider trying to take a picture of it. Or if you’re a pro. But it is. It is one of the most complicated astrophotography shots to do because you’re going from full sunlight. Yeah, to no sunlight. 

Pamela Gay [00:20:42] And so people are pulling filters off. 

Fraser Cain [00:20:44] Yeah. The exposure requirements are different that you have to put any filters on top of it. And after removing a change exposures, all of that and all of this time as you’re fussing with your camera, with your back to the sun, you are not experiencing the solar eclipse and you have to do the solar eclipse. And so and so my recommendation is like, unless you’ve seen a bunch of these and you know what you’re doing and you’re an experienced astrophotographer, don’t even bother bringing the camera. You cannot capture the magic in your soul that you experience from seeing the eclipse. And you will just ruin your experience by attempting to fast with your gear. Don’t do it. It’s a it’s a newbie trap. All right, so people are watching it, but they want to take their enthusiasm to the next level. How can they participate in some science while this is happening? 

Pamela Gay [00:21:40] So the projects that you can still get involved in. Aren’t all that exciting. If you’re dreaming of recreating, general activity observations or something. Those projects, those people. So we have the modern Eddington experiment. We have Project Kate. They have been doing practice observations for months so that it will be muscle memory during the eclipse. So there are citizen science projects out there that are observation based, looking at the sun, fancy equipment. They are amazing. I can’t wait to see their results for you. Dear humans watching this right now, the kinds of things that we have available for you are the globe which does globe at night, and a variety of other science projects. They have a project where they’re asking people to measure the temperature change from before the partial phase starts all the way through the partial phase, through totality and out, and also measuring the percent cloud cover. And they’re trying to better understand the correlation between clouds temperature and, phase of the eclipse that is being experienced, to make sense of all of these stories about totality, had some clouds go away. There are a lot of stories people have, not me. I’m not one of those people. There are a lot of stories other people have about how that occurs, and they’re trying to get to the science of that. There is also projects to understand what exactly happens with the wildlife. So here we have the soundscapes project, Google Eclipse soundscapes. You can still get involved in a variety of different roles. They have people both observing what’s going on around them, putting up, audio recorders to actually measure both comparison data 24 hours or more ahead of time and afterwards. And then during the eclipse, seeing when things get twilight colored, what happens at midday? How are these animals responding? I’m really excited about the soundscape project. This is an extremely well done project that also allows people who are differently abled to fully be involved in the project in a variety of different ways, which we don’t see very often. 

Fraser Cain [00:24:01] Yeah, it’s really cool. And so. We’ll put some links in the show notes for people to be able to to access some of these projects. And so not just to the science actually NASA now is doing some science as well. So on a chase plane I know, I know, it’s so amazing. They’re going to they’re going to and they’re going to send a rocket. They can do sounding rocket. 

Pamela Gay [00:24:26] I’m much more excited about the chase planes because when you’re in the path of totality, there is just something cool about looking up, seeing the Jets go by, and knowing those chase planes are literally working to keep their butts in the shadow of the sun, measuring what’s going on with our atmosphere throughout the entirety of totality. There’s also all sorts of weather balloon projects that are going on. So our atmosphere responds to the sun, responds to the solar energy, it responds to the magnetic field of the sun. And all of these different things are getting shadowed to different amounts. Yeah. Where there are people who are going to be out there looking at changes in radio signal, changes in how our ionosphere is working, there’s actually a ham radio project that is, collaborating with all these other NASA projects to see how far they can bounce radio signals through the ionosphere during totality. Essentially, this is the one free chance we get to look at the middle layers of the solar corona. See how the magnetic energy is getting transformed into heat by looking at how these layers of the corona that we otherwise never get to see are changing and moving. We get to see the electron density flowing through that magnetic field. All of this is stuff normally hidden from us entirely by that bright disk of the sun. 

Fraser Cain [00:26:01] Yeah, yeah. So the these chase planes, I mean, it’s it’s crazy. I mean, the eclipse shadow’s moving so fast, you don’t realize, but it is moving at well over 1000km/h. And so you still only get a little extra time of totality as you’re flying in the, in the chase plane, but it’s enough to just do more new double or triple the science. And there’s some weird stuff that happens during eclipses, like temperature changes, cloud changes that happen. And what’s great is that it’s this way to introduce this one variable. You make this, everything is the same. It’s the middle of the day time. You know what the normal weather conditions are. You know the normal climate conditions are. And you remove the sun right from each one of these places along the entire eclipse path. And this just informs scientists an enormous amount. There’s a there’s a weird tendency for clouds, for light clouds to disappear. Yeah. As the eclipse is beginning. 

Pamela Gay [00:27:00] And it’s finally getting understood. 

Fraser Cain [00:27:03] Slowly and hopefully they’re going to understand. Yeah, yeah. So there’s you’d think after hundreds of eclipses that people have been able to see over hundreds of years. 

Pamela Gay [00:27:16] And this is one of the things the, the ability to get high quality equipment and high quality weather in the same place is statistically like it just does not happen the way you would expect. Eddington back in 1919 was super lucky with taking the images he did and seeing as many stars near the edge of the sun as he did allow and confirmation of general relativity. Now he was able to confirm that near the edge of the sun there is a, bending of the light of about 1.75 arc seconds. We know that the amount that the light is bent should decrease in a well-understood way. As you go further and further from the edge of the sun. Those numbers still haven’t been fully confirmed. Like we trust them. We believe them, but they aren’t confirmed, and folks have been trying to confirm them since those original measurements. And they’re going to try again this year to confirm. 

Fraser Cain [00:28:27] What Eddington saw. 

Pamela Gay [00:28:29] This this function of distance with the modern Eddington experiment. And I read a paper on all the things that have plagued past measurements, from perfect weather and not enough stars to enough stars and imperfect weather. It’s just a cursed experiment. 

Fraser Cain [00:28:47] Yep, yep. It’s really interesting. Well, I think on this note. Good luck. Everybody getting a chance to see the eclipse. Those of you who aren’t gonna be able to travel to it, you will be able to watch versions of it online, I’m sure. 

Pamela Gay [00:29:02] And partial eclipse for everyone in North America. 

Fraser Cain [00:29:05] And right. But remember, 99% is is. Nope. You know, if you can if you could see 99%, you could see 100%. So don’t. It’s 99% is unacceptable. 

Pamela Gay [00:29:18] And there’s research showing that this actually causes brain chemistry things to happen. Wow. And there’s ongoing research. This this is as close to the overview effect as you get while all over the planet. 

Fraser Cain [00:29:31] That’s awesome. 

Pamela Gay [00:29:31] So go experience it. Feel all the endorphins I have never felt. 

Fraser Cain [00:29:36] You know. Oh, this is it. This is your year. 

Pamela Gay [00:29:39] And I have rain forecast. 

Fraser Cain [00:29:41] Oh, I’ll do you. Oh, I haven’t even even dared look at my long range forecast. I was just going to freak me out in Texas. 

Pamela Gay [00:29:48] Yeah, I know, I’m attached to a sound board on the floor of the Carbondale Stadium again, so. 

Fraser Cain [00:29:53] Yeah. 

Pamela Gay [00:29:54] Yeah. 

Fraser Cain [00:29:55] All right. Well, Pamela, thank you so much. Good luck. And we’ll talk in a couple of weeks after we both experience our versions of this amazing adventure. 

Pamela Gay [00:30:04] And and thank you to all the patrons who make this and everything else we do possible. We thank the $10 and up folks at the end of our episode. You are are I shall mispronounce your names category of donors and you make all the difference. All of you, even even the folks who throw $1 at us once a year. Maybe it makes all the difference. We appreciate you so much this week I would like to thank by name, which I will mispronounce, time Lord IRA, Robert Handel, Paula Esposito, Michael Hartford, just me and the cat, will Hamilton, Jeff McDonald, Lee ha, born Katie Byrne, Conrad Holling, Thomas Gazeta. Jarvis, Earl. Tosh, Nana. Kimmy Mike. Hazy, Bob. Crail, Greg. Wilde. John. Baptiste. Lamont. Ney, Noah. Albertson, Cody. Rose, Michael. Purcell, Sterling. Gray, Adam W, Simeon. Thompson, Mark. Schneider, Michael. Chandler. Astor, Bob. Galactic president, superstar MC scopes a lot. I love that one. And John Theys, thank you all so very much for everything you do. 

Fraser Cain [00:31:23] All right. Thanks everyone. We’ll see you next week. No, in two weeks. 

Pamela Gay [00:31:26] Two weeks, two weeks. 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 Gang. 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. 

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Fraser Cain: Astronomy Cast episode 703: The Solar Max of Doom? Maybe. 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 Cosmoquest. Hey, Pamela. How are you doing?

Dr Pamela Gay: I am doing well. I am excited that we’re actually taking two weeks off because of Christmas Day and New Year’s Day following on Mondays, and I apologize to the audience that we won’t be with you, but my house is about to get very clean.

Fraser: Oh, good. Yeah, and my forest is about to get very clean. We were talking about this beforehand that you know we have different ways of utilizing our free time, and for me, I am going to just continue the defense against the deer who clearly were in the garden while I was gone.

Pamela: I need to harden the defenses against the four-legged things that get into our walls and have recently gotten out of the walls into the house.

Fraser: Okay. Solar cycle 25 is shaping up to be a doozy with plenty of flares and coronal mass ejections blasting off the Sun as the solar activity continues to rise. How are things shaping up? So how is solar cycle 25 matching your expectations?

Pamela: It is actually… so leading up to it, there were predictions that it was either going to be weaker than the last one which was pretty weak or it was going to be a whole lot stronger than the last one. And it turns out in reality it is stronger than the last one, and it’s looking kind of normal, but we are in a new and interesting place with this particular so solar cycle. So 11 years ago – so we’re talking 2012 – there weren’t that many CanSats. Like it wasn’t a thing, yet. People weren’t doing small sats. Starlink didn’t exist until 2019, and so this is the first solar max since we started trying to fill low earth orbit.

Fraser: Right, and so we’re learning quickly what impact… so, well, I guess like what influence does the Sun have on low earth orbit, on the Sun, on its atmosphere, on the ionosphere?

Pamela: Yeah. So to back all the way up because I don’t think we’ve explained what solar max is in episodes and years and years and episodes.

Fraser: Okay.

Pamela: So our Sun has a magnetic field – a very powerful one that influences the entire solar system, and it periodically inverts north to south / south to north in how its magnetic field is set up. And in the middle of this process, all chaos breaks loose. Magnetic field lines puncture through the surface all over the place creating visible sunspots. And periodically, these magnetic field loops, which are literally loops filled with plasma, snap and send material our way. And there are other things that happen as well – coronal mass ejections – and all of this activity that sends high energy particles streaming towards Earth very rapidly are most likely to occur during solar maximum. And when this wave of charged particles, this front of charged particles, hits our atmosphere, it imparts energy onto the atmosphere causing it to expand out and increase the altitude at which satellites experience significant amounts of drag. It also causes amazing aurora, so there’s this “I want to see the aurora”. There’s also these charged particles being incident on the moon and on Mars allow us to do really cool science experiments. When we have wussy solar max, we don’t get as good a data. So we’re in this sad position of for the not terrestrial science we want big solar max; for the aurora that are just amazing to see, we want big solar max; but unless you want the Kessler Syndrome, you probably don’t want it for low earth orbit.

Fraser: Right, so if you want to see beautiful auroras, you want solar max.

Pamela: Yeah.

Fraser: If you want to learn some important new things about the Sun at its extreme, you want a powerful solar max; but if you care at all about your nation’s infrastructure, your satellite systems then you probably don’t want solar max, and unfortunately, we don’t really have any kind of control over this. So when did – and you know I mentioned in my introduction that we’re in solar cycle 25…

Pamela: Yeah.

Fraser: So how long does this process take? How long is a cycle?

Pamela: So to go from one flip to all the way through – so north ends up as south, south ends up as north – takes 11 years. To do all the way back to north is the north pole of the Sun is realigned back to where it started is 22 years. So we we have the complete cycle is 22 years, but everyone talks about the 11-year solar cycle because maximum to maximum, minimum to minimum, is really what has the greatest influence on the Earth. And for the longest time it was really all we could observe because we’re just looking at the sunspots, and we didn’t have the capacity to measure the magnetic field alignment of the Sun in the 1600s when they started observing sunspots.

Fraser: Right right right. And so like we get this solar max every 11 years, but the solar max is whether the Sun is configured with the poles flipped, so sometimes the north pole is at the top, and then other times I guess the magnetic poles flip, and that takes 11 years each time. And so we get a solar maximum every 11 years, but the full configuration – and then we get the solar minimum in the in-between times.

Pamela: Right. Right.

Fraser: Yeah. And so I guess, you know, you mentioned sort of – you provided like a laundry list of things that can happen, so let’s kind of like break these down one by one here. So what… if you were to sort of describe… you know you described like the puffiness of the atmosphere, you described the amount of auroras, you described like the the effect of the magnetosphere…

Pamela: Yeah.

Fraser: …the effect on satellites and the ground-based electrical infrastructure. So what are the different… like when this… what does… what is the Sun doing that is then causing an effect on Earth?

Pamela: So during solar flares and coronal mass ejections, the sun is releasing a plume – for lack of a better word – of high energy particles. One of the reasons we like to put solar observers out at the Lagrange Point between the Earth and the Sun is we first see the light of these events. And if it’s on the edge of the Sun, we know we are completely safe. If one of these things happens, and it’s pointed our way, we need to know, first of all, is it really pointed our way or is it going to miss us because it’s just slightly the angles wrong? And two, just how fast are all those particles moving? And since a satellite between us and the Sun can go, “Okay, light moving at the speed of light reached me at this time; it will reach Earth at this time. Okay, so the particles associated with that light reached me a few minutes… a few hours later; therefore, I now know how fast these particles are coming.” And we can start to put the power grid that is facing towards the Sun for that part of the planet that’s going to get hit into safe mode; we can start putting satellites into safe mode.

Fraser: Does anybody really do that, though?

Pamela: Yeah, they actually do.

Fraser: Okay, okay.

Pamela: Yeah, there’s alerts that go out, and with the power grid this is particularly important because we often, especially in the summer and the coldest parts of winter, will run the U.S. power grid – and the Canadians are guilty of this, too – very close to maximum capacity. And wires can only carry so much electricity, and they heat up, they sag, and they will eventually break if you overload them. Now there’s the power that’s in the power lines because it is getting put into the power lines by the power grid; now, if you walk up to any old wire anywhere, and you shake a magnet next to it – changing the magnetic field – you can generate an electric field. It is far more effective to couple this with a bicycle, but when you see these machines that are using bicycles to produce electricity, it’s because there’s moving magnets next to wires, and you’re effectively moving the magnets to generate the electricity. When charged particles, which are essentially little tiny magnets, interact with the Earth’s magnetic field, which is also essentially electric field… it’s all the same thing, folks… all of these movements generate their own magnetic field like you standing there shaking a magnet but at a much larger scale. And this will generate additional power in the power lines, and Quebec experienced this in the 80s and took out a large swath of the American Northeast and the Canadian Southeast. Do you refer to it as the Canadian Southeast?

Fraser: No, we refer to it as Quebec.

Pamela: Okay. [laughter]

Fraser: Yeah, I mean everything’s south in Canada. Like we all live along the border so…

Pamela: All right. Fair.

Fraser: …very few people live anywhere else, so there’s the like… you guys call it the Pacific Northwest. and we just call it the West.

Pamela: Right.

Fraser: So this idea that you’ve got your electrical cables, and you are hitting it with a very powerful magnet, essentially charged particles delivered by the Sun…

Pamela: Yes, a moving magnet.

Fraser: Yes, charged particles delivered by the Sun, and you’re getting these, and you know the most famous example of this, of course, is the Carrington Event back in the 1800s where telegraph poles caught on fire because you had too much charge moving through these wires. It wasn’t prepared for that at all. And so, you know they had no insulationm and so these things caught on fire, and as you said in Quebec in various times you get the situation where the wires run through, the transformers blow, the power grid goes down, everything is interconnected…

Pamela: Yeah.

Fraser: …and so it’s a very bad day especially during the Canadian winter during an ice storm when this happened, so it was a very very bad day in Canada. And just a hint of what’s possible. The other thing is really interesting, and we actually had this – the most powerful solar flare in recent, during this cycle, just happened on Friday, the Friday before we’re recording this. And it caused a radio blackout on the hemisphere of Earth, in certain wavelengths, that are pointed at. And so this is devastating for Air Traffic Control Systems, things like that, they had trouble communicating with airplanes; people weren’t able to send radio transmissions; they had to wait a couple hours before they could resume radio transmissions, and often during the most powerful flares, this is a thing that happens.

Pamela: It’s really wild because we we don’t talk about the radio blackouts. Back when Hurricane Maria was taking out Puerto Rico a number of years ago, there was a radio blackout associated with solar activity, and so, well, most of us are actually connected through wires to one another, not everyone. So the Carrington Event was in 1859, and yeah, there were telegraph systems that worked just fine for hours with no actual battery power going into them; just the solar power was causing this to happen. And there’s amazing transcripts of telegraph operators being like, “Okay, take your battery off. All right. This is working better.” Absolutely amazing.

Fraser: Yeah.

Pamela: There was another storm in 1872 that caused fires, and there were actually aurora seen in Bombay and Khartoum, which are rather…

Fraser: That’s south.

Pamela: Yeah. Yeah, and then in 1921, we had more things that caused fires, this time in New York City, and it was associated with the trains more. So we know that in recent history at least three times in 60-some-odd years, there were massive, debilitating storms, and we’ve just been lucky in the modern era.

Fraser: And it’s also interesting like astronomers have seen flares even more powerful than the ones that triggered the Carrington Event just not headed towards us, so they’ve watched them pointed, you know, the Sun’s gun went off in a different direction than where the Earth was, but if it had hit us, it would have been devastating. And the thing that I always find so interesting is that there are these tree ring effects that have been found where very powerful solar storms have hit the Earth, and it caused a sort of cascade of I think carbon-14 to be released into the atmosphere, and it was drawn up in trees, and they were able to see these. There was like…

Pamela: Yeah.

Fraser: …six of these events over the last like 2,000 years, and the craziest part is that the Carrington Event doesn’t even register. So there are six events – maybe more – that are vastly more destructive, more damaging than the Carrington Event that have happened within a couple of millennium. So, you know, we talked about this specific cycle leading up to this, and we know all the interesting things the Sun can do. What was the expectation of astronomers that for what was going to happen this cycle?

Pamela: So we do run computer models. We don’t have as much data as we’d like since STEREO A and B aren’t both currently working to give us data on other parts of the Sun. That was one of the glories of having STEREO A and B is we got a fuller picture of the entire sphere of the Sun. But going into it based on sunspot numbers, based on activity levels ,based on all the things that we can measure, compared to past behaviors, it’s basically meteorology of the Sun, folks. It’s not an exact science. There were two different models. One said that we would have a lower solar max, so less activity; the other said we’d have significantly more. And at this point, what we know from past behavior is the rate at which the number of sunspots increases from basically zero at solar min to whatever the peak is going to be any given cycle – the rate at which that goes up tells you how quickly solar max is coming – latest data shows we’re about a year out right now – and it also indicates to an inexact degree what that entire curve is going to look like. And it looks like we’re probably going to peak at a fairly average peak. So last year was significantly below normal; this year’s looking like it’s going to be kind of average a year from now. But there is very little relationship between how big the coronal mass ejections, how big the flares are, and solar max. What matters is the bigger the solar max, the more events there are, and the higher the probability of one hitting us rather than empty space.

Fraser: And it’s interesting. I don’t know if you’re looking at the graph of the number of solar flares that have happened, and so in 2021, there was a couple of small flares. In 2022, there were about 25 powerful flares, and then in 2023, there have been almost 50.

Pamela: Yeah.

Fraser: So, it just keeps growing.

Pamela: I have to admit I had a long, hard discussion with my bank account last week because this solar max is looking like it’s going to be really cool, and the time to see it is going to be either next fall – so fall 2024 around equinox – or March 2025 around equinox. Aurora are always best around equinox. You can see them the entire winter long; that’s just when they’re typically best, so increasing statistics and wanting some daylight wherever I go. Nut the best places to go for aurora trips are super expensive.

Fraser: Iceland.

Pamela: I’m apparently going to wait another 11 years.

Fraser: Right. Yeah, I might go to Iceland this fall.

Pamela: Did you see the pictures from – I think it was two nights ago?

Fraser: No.

Pamela: There are amazing… so the Blue Lagoon Resort, which is north and west of the city of Grindavik which is near where this brand new eruption went… The Blue Lagoon Resort with its natural springs does aurora watches, and while the resort is completely closed pending volcanic eruption, there’s still cameras. And they have pictures that I saw posted of aurora and baby volcano, and it was super exciting. I want to see aurora and baby volcano.

Fraser: Yeah, yeah. So I’m just comparing the cycle 24, and so it peaked at about 40 solar flares. So we haven’t hit solar maximum, yet, but we’re already 10 flares more than the peak of Cycle 24, so I would say it came on pretty fast and has grown quite strongly and so could very well be… when you look at… like it took four years building up to the solar max, as you say, we have one more year. And so if these things continue, then there should be another flare. Now, for those of us who aren’t worried about infrastructure, like what this really means is this is your chance to see an aurora.

Pamela: Go. Go look. Go.

Fraser: Yeah. Yeah, and you know, every time we talk about this like, find some kind of aurora alert app; no, we don’t have any recommendations. I’m sorry. Put it on your phone. Get it to tell you when there’s activity in your area, and this year, it could be pretty far south. There were some auroras that were seen in northern Arizona; there were auroras that were seen, you know, in France. So as this solar activity builds and as you get more and more of these powerful solar storms, then your chances of seeing aurora get better and better. Find a place that you’ve got a nice view to the north where you’ve got good dark skies, set up your Aurora alert, and then when the aurora alert comes in, go for it! Go to your spot, and maybe you’ll see something… and maybe you won’t. But you know, I always say you miss 100% of the auroras that you don’t try to see.

Pamela: And there are amazing, amazing destinations in Alaska, in all of the Scandinavian countries, in Iceland. Choose the ancillary activities you want, whether it be a spa, horseback riding, or just a private glass-covered igloo to spend the night under blankets looking at the stars. There is an adventure for you out there waiting to happen. Maybe this time, maybe in 11 years. It depends on your bank account.

Fraser: Yeah, so I mean, if people want the low-cost version, and you live somewhere in mid latitudes…

Pamela: Yeah.

Fraser: You know like a person like me… I live in Canada obviously, but I’m in southern Canada; it’s not great. But northern U.S., the middle of Europe, Japan, South Australia.

Pamela: Yeah, the app is just fine for you. I’ve seen amazing aurora from New Hampshire, absolutely amazing from New Hampshire.

Fraser: And the greatest aurora that I ever saw was from this process.

Pamela: I was scared of aurora growing up. Did you see aurora growing up?

Fraser: Oh, yeah. Yeah, quite a bit.

Pamela: I didn’t know what they were, and they looked like the ghosts from the old Warner Brothers cartoons coming up from the horizon. So tell your children what aurora are, people. Tell your children. This is the lesson.

Fraser: Right. Yeah. Well, and they’re very different, and so like I’ve seen ones which are these green sheets, I’ve seen ones that were like red stripe that just runs across the entire sky like a seam in the sky, kind of bizarre. But yeah, and then I think if you have a little more money, this is it. This is your, you know, next year, you’re going to want to go to Norway, to Iceland, to Alaska, to northern Canada, southern Argentina, Tasmania… I’m trying to think of places where you can go. Antarctica…

Pamela: Patagonia.

Fraser: This is your chance. Yeah. Yeah, Patagonia. And it should be good, but you know, I mean I think this is like the lesson that we’ve really learned is you have to just go. Like you still haven’t seen true totality of an eclipse, yet.

Pamela: No, because I keep getting rained on. I keep trying! I do keep trying.

Fraser: Yeah, yeah, and so like you’re gonna try again in April.

Pamela: Yes.

Fraser: You know… round four for Pamela, round two for me. And so you’ve just gotta like… there’s no guarantees…

Pamela: Right.

Fraser: …in this world…

Pamela: Right.

Fraser: …when it comes to astronomical events, and yet, if it plays out, then wow, is it amazing.

Pamela: Yeah.

Fraser: And so, like, you never really know, but when you look at how fast this solar activity is coming on, how high it’s already reached…

Pamela: Yeah.

Fraser: …a year away from solar max… it does feel like it’s going to be a very good year.

Pamela: Yeah. Oh, okay, so I want to go. I’m clearly going to be waiting, but just remember, folks, do pay attention to space weather, and we’re about to learn things we never knew about how Starlinks react, about how CanSats react. And the scary thing before we go… I just want to make sure everyone knows is when that atmosphere gets bigger, it’s creating new drag on spacecraft, and the amount of drag they experience is is related to the direction of motion, the shape of the spacecraft, in the direction, and that shape of the spacecraft in the direction of motion adds a chaos factor that we don’t always know how to calculate. So when these flares hit the planet, everything’s orbit changes in a somewhat unpredictable way, and as we’re filling up low earth orbit with more and more and more stuff, collisions are getting more likely. At some point this is going to cause a collision, so it’s all fun and games until somebody’s spacecraft hits somebody else’s spacecraft.

Fraser: Yes.

Pamela: So enjoy it while you can and realize what is fun and games to us and our cameras is also devastating to satellite operators.

Fraser: So there was a paper that came out, and we reported on it on Universe Today. I haven’t seen anybody else report on this, yet.

Pamela: The FAA report?

Fraser: No no no. About… that essentially, we are putting more charged particles into the atmosphere.

Pamela: Oh, yeah.

Fraser: And so we are creating our own version of the ionosphere, and when we reach millions of satellites with billions of pieces of space junk, it will overwhelm the Earth’s natural ionosphere with unpredictable results, and so just when you thought there was, like, you know, that we’ve found all places that we could… all the environments that we could affect… turns out, we might cause damage to the magnetosphere of Earth with all of our satellites.

Pamela: Oh, dear.

Fraser: Isn’t that great? Yeah. Yeah.

Pamela: Happy holidays, everyone.

Fraser: Happy holidays, everybody.

Pamela: Hey, today is solstice or tomorrow is solstice?

Fraser: Tomorrow.

Pamela: Tomorrow. So Happy Solstice and Merry Perihelion in early January.

Fraser: All right. Thanks, Pamela.

Pamela: Okay, thank you, Fraser, and thank you to everyone out there who helps us through Patreon. This week I would like to thank The Big Squish Squash, Justin Proctor, Cooper, Georgi Ivanov, Benjamin Müller, Don Mundis, Eran Segev, Peter, Philip Grand, James Rodger, Sam Brooks and his Mom, Camy Raissian, Sean Martz, Nate Detwiler, Dean, Kimberly Rieck, Disasterina, Jeff Willson, Tim Gerrish, Paul D Disney, Janelle, Michelle Cullen, Benjamin Davies, Gabriel Gauffin, Dwight Illk, Phillip Walker, Brian Kilby, Jordan Turner, Bob Zatzke, Sydnie Walker, David Bogaty, Maxim Levet, Justin S, Ruben McCarthy, Arthur Latz-Hall, Paul Esposito, Jason Kardokus, Ron Thorrsen – we only have two episodes in December; I’m sorry – Robert Hundl, Daniel Donaldson, Timelord Iroh, Frank Stuart, Kristian Golding, Geoff MacDonald, Leigh Harborne, Nicholas Cunningham, Cody Nitschke, Conrad Haling, and Slug. Thank you, everyone.

Fraser: Thanks, everyone, and we’ll see you next year.

Pamela: Buh bye.

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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.

In 2017, astronomers detected the gravitational waves and electromagnetic radiation from colliding neutron stars. This had been long theorized as one of the causes of a certain type of gamma-ray burst. By studying the event and its afterglow, astronomers have learned a tremendous amount about the formation of the heaviest elements in the Universe.

(This is an automatically generated transcript)

Fraser Cain [00:00:49] Astronomy cast. Episode 681 kilonova. Welcome to Astronomy Cast for 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 Doctor Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmic Quest. Pamela, are you doing? 

Pamela Gay [00:01:10] I am doing well. I am having the meteor shower full moon sads, though this this weekend there was theoretically going to be an outburst of ETA Aquarius. And there was a full moon. Yeah, instead. Yeah, I have the full moon sads. 

Fraser Cain [00:01:30] Yeah. How do we destroy the moon? How do we make this happen? I think that’s it’s important. At some point, Vantablack. 

Pamela Gay [00:01:40] Can we just. Vantablack. Just paint. 

Fraser Cain [00:01:42] The moon? 

Pamela Gay [00:01:43] Just paint the moon black? Yeah, it’s super heated, to be fair. So all the infrared astronomers would hate us. But like us optical folks, we’d still have tides. We’d still have all the physics that we need that the moon supports Vantablack. 

Fraser Cain [00:01:58] Okay, there we go. So. So before we destroy the moon, let’s just paint it black. And that will, that will and that. That way people who like tides and stuff will still be all right. Okay. Good call. In 2017, astronomers detected the gravitational waves and electromagnetic radiation from colliding neutron stars. This had been long theorized as one of the causes of a certain type of gamma ray burst. By studying the event and its afterglow. Astronomers have learned a tremendous amount about the formation of the heaviest elements in the universe. What we’ve I think we’ve talked about this before. From my perspective, the announcement and discovery of the kilonova was the best kept secret, known by about 5000 people in the field of astronomy. And like when you hear about conspiracy theories and you’re like, you know, two people can’t can only keep a secret, one of them’s dead. I was caught completely flat footed by the announcement of the kilonova. And it is my job to sense the scuttlebutt of what’s going on. You knew in advance this was coming, right? 

Pamela Gay [00:03:11] I knew parts of it in advance. But the fullness of how? Basically 1 in 3 active research astronomers globally were involved in this discovery, the the sheer number and the fact that it was detected over gamma rays and optical and particle science. The fullness of the discovery was one of those things where I was like, that was bigger than I thought. 

Fraser Cain [00:03:46] Every particle physicists. 

Pamela Gay [00:03:47] Think. 

Fraser Cain [00:03:47] Yeah, all these particle physicists, all of the people working in the gravitational wave astronomy. And then every astronomer associated with every major observatory, both on land and in space. 

Pamela Gay [00:04:00] Yeah. 

Fraser Cain [00:04:00] Part of these observations and part of the science paper, I’ve never seen a science paper with so many names associated with it. And those are just like the primary people from each working group, not to mention all of the other people who were involved in detecting it. Analyzing it. Yeah. It was hats off to the astronomy community for for working on this and I guess like. I guess the conspiracies are all real then. Clip that and. 

Pamela Gay [00:04:32] All right, so that was the. 

Fraser Cain [00:04:34] So what was the killer talk about the the event. What happened. 

Pamela Gay [00:04:38] So so back in 2017, there were two neutron stars, two remnants of massive stars, but not so massive that they became black holes. These these two neutron stars, I they had been spiraling towards each other, giving off gravitational waves over time. And a that release of energy in the form of gravitational waves that causes them to spiral in towards each other. And one fateful August day, the signals of this merger occurring reached our world. And literally, I can’t say, shook it, but I can say warped it. 

Fraser Cain [00:05:20] Stretched it and compressed it. 

Pamela Gay [00:05:22] Yeah, yeah. So? So as these two stars, reached the point of of merging together, becoming a black hole, they released a massive amount of energy in the form of gravitational waves that were detected by LIGO. Virgo, these gravitational wave detectors on our planet, as the planet literally getting stretched and compressed in a damped harmonic oscillation. 

Fraser Cain [00:05:50] Yeah. 

Pamela Gay [00:05:52] It also released a whole lot of neutrons. Neutrinos, because there was a vast creation of what are called are process elements will return to that in a bit. So we had particles getting here and at the same time the, the, the first photonic signal of this was a very short blast of gamma rays that were then followed by an optical afterglow. And when I say a short burst of gamma rays, I mean it was less than two seconds. 

Fraser Cain [00:06:29] Okay, so give us kind of a timeline from, from the detection of the different classes of, of waves. 

Pamela Gay [00:06:40] So what’s what’s wild here is they had to piece together after the fact that that all of these things were, were tied together. So there was the almost simultaneous measurement of the gravitational waves and the gamma rays. So the first thing that happens as these stars merge is, is the flash of light and the release of gravitational energy. After this, you have these slower moving particles. Particles can’t move at the speed of light. And you also have coming afterwards the residual glow of things going on around where the merger took place. So this is the kind of event that stretched out over time, both in arrival of the information and also in being able to follow it evolve over time. 

Fraser Cain [00:07:36] The thing that I find just absolutely amazing was not only did we get this, this multi-modal detection of these two of mean gravitational waves and electromagnetic radiation, but we got like the first definitive proof that gravity moves at the speed of light. 

Pamela Gay [00:07:53] Yes. 

Fraser Cain [00:07:53] Right. Like big question. Astronomy solved. 

Pamela Gay [00:07:57] Yes. This is something that we’ve been struggling as a profession to prove for a long period of time, and we’ve gone to great mathematical and geometric ends to try and say, well, the light from this quasar was gravitationally bent in a way that indicates as Jupiter was moving, and it’s never enough proof. But when you get the gravitational waves and you get the gamma rays getting here within our ability to detect at the same time. 

Fraser Cain [00:08:26] Well, and not even just at the same time, like the gravitational waves come from the last few milliseconds of the neutron stars orbiting around each other before they actually collide. That’s when you get the gravitational waves, and then moments after you get the electromagnetic radiation from their collision in the explosion. And so, you know, if the waves and the electromagnetic rays came at exactly the same time, then in fact, they wouldn’t be moving at the same speed. But because you got the the waves, then the light, it lines up perfectly. And when you think that these this light was moving hundreds of millions of light years to get to us with that level of precision. They move the same speed. 

Pamela Gay [00:09:09] It. It was one of those truly amazing. All of the clocks were actually in sync kind of discoveries. 

Fraser Cain [00:09:18] All right, we’re gonna talk about this some more, but it is time for another break. 

Pamela Gay [00:09:23] This show is sponsored by BetterHelp. We hear all the time that it takes a village to raise a child. What folks forget to remind us is it takes a community to support an adult. I hope each of you have your own tribe, your found family, your own place where you can just go out and hang out even if it’s over a gaming server. The other thing they don’t tell you is we can all get burnt out trying to support those around us. It’s easy to get stretched thin trying to support others through all the job, money, relationship and health issues that are part of adulting. And sometimes we need to turn somewhere other than to our friend group for help. Sometimes we need someone who is outside and has that outside perspective and an arsenal of skills and tools. We don’t have to help us level up in life. This is where BetterHelp can be there for you. They’re licensed therapists, can give you tools to set boundaries or know how to better support others while supporting yourself. Whatever you need, they will help you find it, and you can switch between therapists until you find the one that is the right match for you. It’s all online and they can work with your schedule, so you never need to miss a raid or shop late to ADHD session. Find more balance with BetterHelp. Visit betterhelp.com/astronomy today to get 10% off your first month. That’s BetterHelp. H e lp.com/astronomy. 

Fraser Cain [00:11:03] And we’re back. So let’s talk about this mystery of gamma ray bursts and how this helps explain what those one class of them are. 

Pamela Gay [00:11:15] So. So we started discovering gamma ray bursts back in the early days of the Cold War, when there had been a nuclear test ban treaty passed that said, basically, you shall not test nuclear weapons in the air or in outer space, and to monitor whether or not that was actually happening. We launched satellites sensitive to the kinds of gamma ray light that come out during nuclear explosions, which also have our process elements. Just we’re going to still come back to that. Now, unfortunately, it turned out that for the first time ever, we discovered once above the atmosphere that there are natural sources of gamma rays. And the early detectors were not good enough to nail down what direction gamma rays were coming from. So there was a bit of, oh dear, what’s going on? That luckily, we quickly realized that gamma rays appeared to be coming from all directions on the sky in different durations. And over the years, with satellite after satellite after satellite, we’ve built up this understanding that there are essentially two broad categories of gamma ray bursts those that can last many seconds to many minutes. These are your long gamma ray bursts. And then there are the short gamma ray bursts that appear to actually break into two different groups. These are the ones that are two seconds or less. 

Fraser Cain [00:12:53] Right. 

Pamela Gay [00:12:54] Now. But the long ones, we we blame those on hyper nova. Astronomers shouldn’t name. Things were really, really bad. 

Fraser Cain [00:13:02] Well. Are you are you kidding me? That’s the best name. Like Nova ultra Nova. Nova? Yes, please. More of that. So supernova is fine, like I. I think they nailed it. Supernova? They they got a good name out the door. They’re hyper nova. That’s just that’s just taking a win and then taking a victory lap. So I 100% agree with you when I think about the poorly named cosmological objects out there. Hyper nova. No way. 

Pamela Gay [00:13:35] It’s just this feels like. How do you torture your undergrads? We have classical nova, cataclysmic variables. Nova nova, recurrent nova, hyper nova, kilonova, supernova. And then we just have letters to stuff. 

Fraser Cain [00:13:51] Yeah. 

Pamela Gay [00:13:52] You’re good with this. 

Fraser Cain [00:13:53] Okay? Are you kidding me? Yeah. Hyper nova. Yes, yes, I’m fine with that. Not only am I fine with that, I think it is one of the best named objects in all of astronomy. 

Pamela Gay [00:14:05] All right. Anyways, so there are hyper novae which produce prolonged gamma ray bursts. And there’s two general theories about what’s going on here. In one case, you have a, massive star going supernova and its mass attacks, a nearby companion that is probably a neutron star. And as it falls on to the neutron star, this creates massive jets of gamma rays. That’s one possible idea. The other possible idea is that this is simply a special kind of fast, rotating, massive star that is capable of generating these jets all on its own. Whichever scenario it is, these create massive optical after glows that we’ve been able to see since the 90s, and they’re long enough that we have time to catch them in the gamma rays, spin something around to look at them in X-rays, and zero in on where they are in the sky very successfully. These things, easy to observe in the grand scheme of hard to observe objects. 

Fraser Cain [00:15:17] Because they’re just so bright. 

Pamela Gay [00:15:19] Exactly. Yeah. Then the other, not a kilonova gamma ray burst is it? Looks like some of the sources that cause fast radio bursts also cause bursts of gamma ray radiation. And these can be things like highly magnetic neutron stars that are called magnetars, rearranging their magnetic field and releasing massive, short lived bursts of energy. One of these occurred back in December of 2004. It was bright enough that it passed through the sides of telescopes in between the two of these kinds of objects. This is where are two neutron. Stars coming together to produce heavy elements exist. 

Fraser Cain [00:16:06] All right, hit us. What exactly is going on as these two neutron stars come together? 

Pamela Gay [00:16:16] So the glorious thing about it is these stars get, to a certain degree, completely shredded as they coalesce. And and the totally disrupted neutrons there, they’re flung out during that catastrophic explosion of a merger and they hit the surrounding material. And if you take your friendly everyday atom and you bombard it with neutrons fast enough, it doesn’t have a chance to undergo what’s called inverse beta decay. This is where your typical everyday neutron is like. I don’t like to exist by myself. You take a neutron, you put it on a shelf. It’s like. 

Fraser Cain [00:17:02] No, do you come back five minutes later and it’s gone? 

Pamela Gay [00:17:05] Exactly. It decays into an electron and a proton. Now, if you take an atom and you bombard it fast enough with all of these neutrons, they build up, they build up, they build up, and then they switch identities. And when they do, suddenly the core of this atom goes from being your random everyday low on the periodic table atom to something crazy like Einstein M and and so this rapid release of neutrons that a salt and make themselves part of the nuclei of heavy elements in the surrounding materials allows us to get even heavier elements. And this is one of the only ways to do it. And what I love is this. This is a story that builds up over the entire lifetime over these stars. Because massive stars have massive solar winds, they blast material in all directions around them and that material hanging out around them. That’s where these heavy elements get to form. And it’s just a cool story. 

Fraser Cain [00:18:13] Yeah. So you’ve got this. I mean, just think about the forces involved that you’re taking a neutron star, one of the densest objects in the universe, and you’re turning it into a neutron slurry. Yeah. As these neutron stars are coming together because of the tremendous forces involved, and then the neutrons are crashing into other neutrons, and there’s so much energy compacted in a small space that they’re just getting assembled into larger, heavier elements like gold. And this is one of them. This was one of the most incredible things. They saw Earths worth of gold in the explosion. 

Pamela Gay [00:18:54] And prior to confirming the reality of these things, like they’d been predicted in the late 90s, that this should be a thing that happens out there somewhere. But when I was in grad school, I’m old. I was in grad school in the 90s and early 2000. We were taught that these heavy elements came from massive stars exploding as supernova. Add your letters and numbers after it. And and this whole idea of combining neutron stars, it wasn’t something that was just regularly taught. And now we know that the reason supernova modelers were having so much trouble in the 90s reproducing the matter we see in the universe is supernova aren’t to blame. It’s it’s these neutron stars coming together. And it’s just a really cool way that science pretty much overnight was like, yeah, and we were wrong. And right now we know now. 

Fraser Cain [00:19:57] But we can’t blame all the gold on kilonova. What can we know? 

Pamela Gay [00:20:01] So there is. 

Fraser Cain [00:20:02] Still our process going on in some of the most heavy stars. And that is also contributing to the heavier elements. 

Pamela Gay [00:20:09] It’s the overall production ratios where we have to start saying, okay, so let’s look around the solar system, let’s add up how much carbon we have, let’s add up how much iron we have, let’s add up how much technical we have. And when we make this abundance curve of of how much exists of each atomic isotope in our solar system, then we start doing the okay, so what what supernovae do you have to have go off to cause this to happen? And so you say this kind of supernova is going to produce this ratio of ingredients. This is going to produce this ratio of ingredients. And to reproduce what we see, you have to have these kilonova out there that are dedicated super heavy atom producers. And and so it’s just you need different kinds of factories producing different ratios that all together add up to the solar system we’re in. 

Fraser Cain [00:21:12] Right. Right. And so now that we know about this, what role do we think that a kilonova had on the formation of the solar system and the and the gold in our wedding rings and, and electronics and things like that. 

Pamela Gay [00:21:30] Well, it starts to tell us that these have been happening for a long time, and they had to exist for us to be here. I have to admit, I feel like this is one of those moments where you have read a key paper that I missed that said, exactly how many kilonova what went into our solar system. 

Fraser Cain [00:21:50] So there was a kilonova. So astronomers were able to essentially estimate that the kilonova went off about a within a thousand, no thousand light years of us closer, about 100 million years before the solar system formed and delivered a tremendous amount of heavier elements into the solar system. So something within our galactic corner neighborhood in recent history, before the solar system formed. And the thing is really interesting is, is how these might be. Some of, you know, we always talk about like, what it takes to start star formation in some nebula. And now it appears that there might very well be that you could have these, these kilonova go off a seed, heavier elements, and also kickstart the process of collapse in the stellar nebula. And so at least one, probably multiple kilonova went into the formation of our solar system and gave us the heavier elements that we have all around us. And we probably wouldn’t have life on Earth in the way that we understand it without those events. So they’re, you know, they’re doom, but they’re also help with the formation of life. 

Pamela Gay [00:23:08] And that’s a really cool story. One of the earliest examples that we had of what we thought might be a neutron neutron star merger was back in 2013. And the reason that they were able to say, yes, we think this is a neutron star, a neutron star merger is it occurred in a system that didn’t have significant star formation. It was old, it was elliptical. It was consistent with a old stellar population that would have fully evolved neutron stars in it. Now, if there was a neutron star, a neutron star merger within a thousand light years of the the cloud of material that we formed out of that gives you this amazing image of how old stars and unused material were mixing in the Milky Way. And makes me question. Could it have been like that kilonova or other related events from that super old population that triggered our molecular clouds collapse? And. 

Fraser Cain [00:24:15] Right. 

Pamela Gay [00:24:16] It’s it’s a multi-generational story. 

Fraser Cain [00:24:18] So there’s a couple of of recent tweaks on top of this. One is I know if you saw the story that that researchers were able to calculate that the kilonova was a perfectly spherical explosion. Yeah, that was really interesting because you would expect like they’re coming in, as I said, the neutrons are turning into this kind of slurry as they’re orbiting on this plane. And you’d expect it to be the explosion to kind of match the collision. But in fact, the the explosion was perfectly spherical. 

Pamela Gay [00:24:47] And they figured that out by looking at the black body radiation, which would have had a different distribution of life if if there had been red shifting and blue shifting and going on. But no, it was just spherical. And and what’s cool, though, is there was a slurry of material. And as some of it went out, that optical afterglow we were seeing was from some of the remainders coming back in. So you have this completely symmetric explosion, and then you have the material falling back in doing the disk thing and self-destructing as an optical afterglow on the newly formed black hole’s event horizon. 

Fraser Cain [00:25:31] Now, from what I understand, there’s only been like just like maybe two more kilonova. Yeah. So, yeah, we’re at the very beginning of this science. And a big part of that is that LIGO is has been offline for the last couple of years, but it’s coming back online in just a few months from now with its next iteration. 

Pamela Gay [00:25:54] And with the next iteration, we’re going to have greater sensitivity. We’re going to have. I had the chance to hopefully be sensitive to more and more of these kinds of objects, and in combination with things like the Zwicky Transient Factory, with Swift and Fermi still being healthy up in orbit. And hopefully Alice’s tea. Alice’s tea. We need to return while LIGO is still running on the next run. Or launch start return. This has nothing to do with that. 

Fraser Cain [00:26:26] Yeah. But yeah, yeah, yeah. I mean, we have this incredible opportunity to do observations of an extreme event that helped deliver the essential, heavier elements into the universe. And we are months away from the next iteration of like, like, like originally they detected, like, 1 or 2 events. Yeah. Then they did an upgraded version and they were detecting one a week. And now we’ve got the new version coming out in just a few months. That should crank that up even to the next level. Several gravitational wave events a week. 

Pamela Gay [00:27:07] Yeah. Yeah. The the most optimistic I’ve seen is there are hopes of maybe one a day getting noticed. Yeah. So those are the most optimistic. Yeah. I choose to be an optimist. 

Fraser Cain [00:27:22] Yeah. And hopefully a new class. Yeah. Of of objects like neutron stars colliding with white dwarfs. Like maybe other parts of these gamma ray bursts that are. There’s still some controversy can go away once we do more and more of these observations. So, so stay tuned. It’s going to be an exciting year, I think. Well, thank you, Pablo. 

Pamela Gay [00:27:42] Thank you. And thank you so much to everyone out there in our audience who supports us through Patreon. We we could not do this without you. You allow us to have editors that make us sound good and get everything posted up on the internets so you can download us if you would like us to. If you would like to help us support these people, please consider joining our Patreon and this will also get you ad free versions of the show. This week I would like to specifically thank Berry Gowan, Jordan Young, Steven Wright, Nano Phillips, Andrew Plasterer, Venture Trust Charlie, Brian Cagle, David Trog, Buzz Pass act, Les Howard, Laura Carlson, Robert Plasma, Jack. Mudge, Joe Holstein, Richard Drum, Greg Davis, Frank. Tippin, Gordon. Davis, Alexis. Adam and these Brown, William Andrews. Gold, Roland. Warmer, Dom, Jeff Collins, and Kellyanne and David Parker. Thank you so much, all of you out there. 

Fraser Cain [00:28:42] Thanks, everyone, and we’ll see you next week. 

Pamela Gay [00:28:44] Bye 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.

Last week we talked about rogue stars. This week we’re going to take things up a notch and talk about an even more extreme event. Rogue black holes. Astronomers recently discovered a supermassive black hole on an escape trajectory, leaving newly forming stars in its wake. It’s wonderful, terrible, nightmare fuel.

(This is an automatically generated transcript)

Fraser Cain [00:01:50] Astronomy Cast Episode 680 Rogue Black Holes. Welcome to Astronomy Cast, her 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, 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 [00:02:10] I am doing well. How are you doing? 

Fraser Cain [00:02:13] I’m doing really well. Like, I, you know, like, I know we talk about the weather a lot. This channel. Like, maybe this should just be the weather podcast weather cast, but. But spring arrived. Finally. Finally. And with a with a roar. So we had records broken all across British Columbia because we had such a warm spring day. 

Pamela Gay [00:02:35] I learned last week that asparagus is capable of growing four feet in one week. 

Fraser Cain [00:02:42] I got a plate of Fergus. I love asparagus and and it’s like easy to grow and it’s perennial. And yeah, I gotta get that going on. 

Pamela Gay [00:02:50] It’s a multi-year dedication to it. And this was supposed to be the first year we could harvest it, and it was just coming up above the ground at the beginning of the week. And it rained all week. And I went outside with scissors ready to harvest. And the staff was like. 

Fraser Cain [00:03:06] You still, you could still harvest. You just cut the top and then it’ll throw more up and then you cut those up. 

Pamela Gay [00:03:11] That’s what I did. 

Fraser Cain [00:03:12] Going. Yeah. Yeah. Last week we talked about rogue stars. This week we’re going to take things up a notch and talk about an even more extreme event rogue black holes. Astronomers recently discovered a supermassive black hole on an escape trajectory, leaving newly forming stars in its wake. It’s a wonderful, terrible nightmare. Fuel, right. So last week we talked about rogue stars and how they are, you know, they adorably fly out of the galaxy on escape velocities thanks to close encounters with rogue black holes. But black holes themselves, yes, can be ejected and probably are often ejected. 

Pamela Gay [00:03:52] So the thing about rogue black holes is, is the definition for rogue black holes incorporates so much more than rogue stars with with rogue black holes, it’s any black hole that doesn’t have a companion. And and there’s thinking that there could be a 100 million rogue black holes just randomly making their way through the Milky Way. And that is awesome. 

Fraser Cain [00:04:16] So, I mean, is just a black hole a rogue black hole? 

Pamela Gay [00:04:19] If a black hole has a companion, a disc, something that it can feed upon so that it is not alone in this universe, it is not a rogue black hole, but a black hole by itself, minding its own business, not eating anything, or that has been ejected out of a galaxy just to confuse things. Those are rogue black holes. 

Fraser Cain [00:04:44] Right? But like, does that mean like a star is a rogue star? No. 

Pamela Gay [00:04:47] No, because we can see a star line. 

Fraser Cain [00:04:51] So. So if we can’t see it, then suddenly it’s gone rogue. I guess that. Yes. 

Pamela Gay [00:04:58] Yeah. 

Fraser Cain [00:04:58] Right. All right. Okay. You know, I think that tracks fine. So so I guess what. But it really is. It does seem to be approaching that all black holes are rogue black holes, which is. Which is fine. 

Pamela Gay [00:05:10] I think such a star is not rogue. It has not gone rogue. It has gone evil. But it is not sure, sure. 

Fraser Cain [00:05:17] But like Cygnus X-1 has not gone rogue because it has a companion and we can see it. But it’s is rare. 

Pamela Gay [00:05:23] It is capable of maintaining relationships. They just aren’t healthy ladies. 

Fraser Cain [00:05:28] And as soon as it’s finished destroying its companion, it has gone rogue. Yeah. All right. Fine. I, I, I will accept your expanded terminology of what is a rogue object, which in this case is just any black hole. 

Pamela Gay [00:05:45] That isn’t. 

Fraser Cain [00:05:46] It isn’t tied down. But is it tied down? Yeah, exactly. Yeah. That’s fine. All right. Fine. So let’s talk about the ones that are drifting within the galaxy. 

Pamela Gay [00:05:56] So one of the early thoughts of what dark matter might be is just rogue black holes and, neutron stars that we couldn’t see called white dwarfs. And so researchers set up two different long term observational programs, Ogle and Macho. One was pointed towards the center of our Milky Way galaxy, looking at all the stars in the bulge and looking for them to brighten and fade away as something passed in front of them and gravitationally magnified their light. The other one was pointed out, looking at the Large Magellanic Cloud, and was looking for the exact same thing, and the thought was if there are sufficient stellar remnants. Out there to be dark matter. We would, within a short period of time, be able to see all of them. And we did not. But over the years they have firmly seen one seven solar mass black hole that over a long period of time, gradually passed in front of a background star and said, hi, I am here with its gravity, right? And that that is our. Our prototype for rogue black holes in the Milky Way. 

Fraser Cain [00:07:18] And I mean, this is the same technique that astronomers have used to discover planets. They watch as a star moves in front of a background star, and the star flares up in a way that that has an almost like a double flare. And you can see the distortions not only of the gravity of the star, but the distortions from the planet itself, and they identify the planet. The downside of that is that you don’t get a second shot at it. Like once. 

Pamela Gay [00:07:43] This very. 

Fraser Cain [00:07:43] True. Once in a lifetime situation lines up. You get to see it for a couple of hours and then it’s gone. And so they they just like, stared at the entire galaxy hoping to see any of these alignments. And they saw one. 

Pamela Gay [00:07:59] Yes. 

Fraser Cain [00:08:00] And so dark matter, though, being 90% of the matter in the universe, you’d think you’d see more. 

Pamela Gay [00:08:08] Well, this just means the dark matter is not predominantly made of stellar remnants. It is stuff that we now define through its distribution of particles that don’t like to interact, that do not interact with the electromagnetic spectrum that may be sterile neutrinos and other similar particles. Yeah. So tiny bit of dark matter, red black holes, most of dark matter stuff. 

Fraser Cain [00:08:38] Particularly stuff. 

Pamela Gay [00:08:39] Particle stuff. 

Fraser Cain [00:08:41] They haven’t ruled them out. They just have ruled them out at a certain sizes. Right? From what I understand, they can either be a thousand times the mass of the sun, or they could be the mass of an asteroid, but you can’t have them in between because of these surveys that have ruled out the in-between stuff. And so the really, you know, the intermediate mass black holes, they’re not going to line up enough so they could still be out there while the teeny tiny ones, they’re not going to cause enough of a distortion that you’re going to be able to detect it. 

Pamela Gay [00:09:07] And and this is where there, there is still the potential that a noticeable amount of dark matter is going to be made of. These missing intermediate black holes is going to be made up of, microscopic black holes. Primordial black holes haven’t evaporated away, but. The more we see distant galaxies getting distorted by all of the intervening clouds of dark matter, the more evidence we have that the dominant part of dark matter, which is going to turn out to be a whole family of different things, working together to break our brains. 

Fraser Cain [00:09:49] Yes. 

Pamela Gay [00:09:49] It’s it’s going to be particles. 

Fraser Cain [00:09:51] Yeah. And just to put a pin in that like. Yeah, allow me to predict the future. Well, when people go like it turns out dark matter was. And then you list out these ten things, right? That it was it was neutrinos and gas and black holes and a kind of particle that we didn’t know about before, and a different kind of particle that we didn’t know before, and another different kind of particle that we didn’t know before. And we did nursing gravity at the largest distances. So yes. And yeah. All right. So we’ve talked about just like roaming black holes, ones that are just just gently drifting cosmos causing havoc in their wake. But what about ones that are on like regular stellar mass black holes? Can they get on an escape trajectory? 

Pamela Gay [00:10:43] Yeah. 

Fraser Cain [00:10:43] Like stars. 

Pamela Gay [00:10:45] Totally. And and again, it’s it’s going to come from that same sort of multi-object interaction. And it’s, it’s now starting to look like there, there are many systems out there that have multiple, massive objects in binary systems. And all they need to do is find a third friend to send somebody off flying where we’re seeing gravitational waves from black hole, black hole mergers. Now, if instead of having two that are merging, you have a third one come in. And there’s lots of multi star systems out there that’s now unstable. And so something’s going to get thrown away and can escape. And it’s not necessarily just going to happen with stellar mass black holes. Do we want to go there. Do we want to go to the paper. 

Fraser Cain [00:11:43] Night. Which one. The but supermassive not. Yeah. So so one thing I want to talk about like just regular you know we talked about this last week. We talked about how you can have. They can have a close encounter with a supermassive black hole. They can be part of a binary star system. We talked about how one star can detonate as a supernova and the other star can be thrown out. But yes, but could one of could one explode and then the other one. It’s been turned into a black hole. 

Pamela Gay [00:12:11] So the the. The idea that you can have a system where both stars become black holes and they fling themselves apart, they aren’t going to have a sufficient difference in mass for conservation of momentum to make one of them a high velocity star. Part of the magic of the rock stars we talked about last week is you have high mass black hole, neutron star, really dense object. It’s going away in one direction. And then the other lightweight thing is like, shoot. So imagine that you decide you’re going to put a. Heavy weight ball. I’m cricket a cricket ball on your pool table. And you hit your cricket ball with that little white normal cue ball from pool. It’s going to move a little bit, and the other star is going to come flying back at you. And and so that’s how we get rogue high velocity stars. Now if you just have two black holes, they’re going to wander apart from each other. But they’re going to still have that more normal 45km per second. But one might end up going the wrong direction. So it’ll still seem to be moving at a faster velocity. But it’s not as exciting because we can’t see them until they decide to try and kill us, in which case we won’t see them until they encounter the Oort Cloud. And that’s always. 

Fraser Cain [00:13:42] Fun right now. UMass together. Croquet, cricket and pool bear, I think. 

Pamela Gay [00:13:47] Yes, yes I did. 

Fraser Cain [00:13:49] Okay. But, but, you know, I remember when we talked about the different kinds of supernovae, there’s one called the pair instability. Yeah. Supernova, which is the largest stars where they just explode completely. So could you have, say, one star with a merely 20 times the mass of the sun and then another one with 100 times the mass of the sun orbiting one another, and then 100 mass. One goes first and now it’s apparent stability. Supernova was just gone. And now that other star is now thrown out, and then it later decides to go off as a supernova. 

Pamela Gay [00:14:25] So I’m trying to figure out how that mass would get flown out preferentially in one direction, so that the other star with. 

Fraser Cain [00:14:36] One star just disappears, right? Yeah, the 100 100 solar mass star just vaporizes. No remnant left behind. 

Pamela Gay [00:14:44] Right. 

Fraser Cain [00:14:44] And the other one, the 20 solar mass star, is now. 

Pamela Gay [00:14:47] Hanging out, going at the velocity it was going before. 

Fraser Cain [00:14:51] But wouldn’t it be? It was in an orbiting around the the center of mass of 100 mass star. And so now it’s just careening off like regular stars. Right. They’re they’re busting around each other. One now is no longer exists. The other one is thrown out like a like a slingshot, but it’s still the kind of star that’s going to go supernova in the future. And so it’s heading out on an on an escape trajectory, and then it explodes as a supernova. And now you’ve got a black hole. 

Pamela Gay [00:15:17] So. So the explosion is going to carry away the angular momentum of star one because boom star 2nd May have. Well, now it will have a change in its velocity, but it’s not going to be huge because you don’t have enough angular momentum to fling it off. Right. Unless you do something to the other star. 

Fraser Cain [00:15:44] Well, one star is no longer there once it disappears. 

Pamela Gay [00:15:47] But but it’s it’s the case of you have a ball on a string, and when you let go, yes, it flies off, but it’s it’s not getting terribly huge amount of velocity. Whereas with the rogue star’s situation, you have one object in motion in one direction and the other, that it’s that extra component that you get right, that gives it the extra kick. 

Fraser Cain [00:16:16] Got it. Yeah, yeah, yeah. It’s just like it’s it’s not enough angular momentum tied into the interaction that when it lets go it’s it’s a more serene escape. Right. Right. So this idea that of a rogue black hole. Because people ask me this question all the time, they’re like, oh, if a rogue black hole came into the solar system, so play that out for me. What would happen if a rogue black hole made its way through the solar system? What would happen? 

Pamela Gay [00:16:42] So it all depends on the crossing time. So it turns out that if a black hole goes through our system super, super fast, everything’s going to go, wait, I’m being pulled. Oh, I’m not being pulled on anymore. Right. And so things get jiggled around and that could be truly catastrophic. But it doesn’t necessarily have to be. Where it really sucks is if it’s coming along and it’s approaching from behind, and it’s just going a few kilometers per second faster than us through the galaxy, and it meanders slowly through the system. And as it meanders slowly through the system, it’s able to pick up everything within the system and cause them to enter orbit around it and potentially eat everything as it goes, depending on how much friction it creates. 

Fraser Cain [00:17:39] Right or cause through body interactions, it causes things to do. Things crash into other things than those things being squished out added to the accretion disk. So? So the distance, like how close does it get to the sun and how? Slowly. Does it make this journey. 

Pamela Gay [00:17:56] Exactly. 

Fraser Cain [00:17:57] Right? Yeah, but. But what I love is that we don’t see any examples of it in the in the solar system has been here for 4.5 billion years. And so everything like we do not look like the kind of place that a black hole passed nearby at any point in the last almost 5 billion years. 

Pamela Gay [00:18:16] So so the thing to think about is we cannot historically tell the difference between a large star passing near solar system and a black hole passing near our solar system. What we can say is, to the best of our understanding, there hasn’t been a high mass object that passed through our solar system, but we do think that there has been some sort of gravitational disruption that has flung large amounts of comets in at various points. So we could have taken a glancing blow, and we wouldn’t have the capacity to tell the difference between a glancing blow from a black hole and a glancing blow from a star. And that’s one of the most wonderfully weird parts of science, is you can have a whole variety of different things, different masses, different speeds that have the exact same effect on our solar system. We just know nothing destroyed us, which is good. 

Fraser Cain [00:19:24] All right. We’ve been waiting. Let’s talk about it. Let’s talk about these. So we’ve talked about just regular old black holes. The common variety black holes. But supermassive black holes can go rogue, too. Yeah, a star. A black hole with millions or even billions of times the mass of the sun can be on a escape trajectory. Yeah, causing mayhem in its wake. 

Pamela Gay [00:19:51] And. And what I love is we have periodically found, galaxies that don’t appear to have a supermassive black hole in their core. And that makes no sense by any of the dynamics we know. And we now may know why. There was a paper posted to archive several months ago that you discovered in the original passing. 

Fraser Cain [00:20:14] Yeah, I reported it three months ago. Yeah. And now everybody’s. Yeah. I’m not bitter. 

Pamela Gay [00:20:21] Thank you. And and this particular paper, what happened was researchers, first noticed that there was this fairly dwarf ish galaxy that resembled dead bugs on a windshield. And they looked at it, and there was a stripe coming off of it. Just this, like straight line filament of light coming off of the dwarf galaxy. And we see stuff like that out there. Galaxies have jets, galaxies, all sorts of different stuff happens. But when you have a jet, it’s just like a, water fountain. The water starts out tightly collimated and then widens out as it moves away from the source. A galaxy has a jet. It starts out tightly collimated and then widens out as it moves away from the galaxy. But this this stripe that they saw in their Hubble images turned out that it started out wide and got tighter and tighter as it moved away. So they had some time coming up on CAK. They used that time to look at the system, and they looked at the galaxy, they looked at the system, and it turned out that the stripe, the line was baby stars, and they had the same general age as as that dwarf galaxy. And so you have a dwarf galaxy and a line of stars, same age, same redshift. What can cause that? And so they got to imaging and they got to thinking and they got to thinking and they got to imaging. And what they realized is, well, when you end up with these dead bug shaped dwarf galaxies, it’s usually because mergers have taken place and the physics of three galaxies coming together, having all three supermassive black holes begin interacting could lead to two supermassive black holes going in one direction, one supermassive black hole going in the other direction, and that runaway singleton colliding through the intergalactic media was able to trigger star formation as it went. So basically, it’s going along. And as it’s going, it’s going come together gas come together, guys. 

Fraser Cain [00:22:49] Right. 

Pamela Gay [00:22:50] And this gas coming together is forming stars. And then over time they drift apart. 

Fraser Cain [00:22:55] And we always talk about that, that you need some some trigger to begin star formation. And we talk about it like a supernova shockwave maybe the gravitational fact of a nearby star. But in this case, a supermassive black hole was passing nearby and causing ripples of gas and dust to come together and cause over densities and begin this process of star formation in its wake. 

Pamela Gay [00:23:20] And and at the furthest and tightest, pulled together part of this line, they’re seeing unusual emission. That’s just enough different from everything else that it seems to be consistent with that supermassive black hole. And in the other direction, they see hints of what appear to be shocks in the intergalactic medium not enough to trigger star formation, but something indicating something in this way past. And left its mark. So now we have. Dead, bug shaped galaxy with no supermassive black hole and. Three rogue supermassive black holes, two flying together, one by itself, passing between the galaxies. And this raises the interesting idea that at any moment, a supermassive black hole could emerge from the darkness and begin interacting with with the space around our galaxy or any other galaxy. And it might not be easy to see, but it would sure be cool if it happened. 

Fraser Cain [00:24:33] Would you need that three body interaction? I mean, is there any way you can get a like a two body interaction with a supermassive black hole and less massive black hole? 

Pamela Gay [00:24:44] In that situation, they’re just going to merge, right? It’s you have to have that unstable third system to fling something away. 

Fraser Cain [00:24:52] But when you think about even the history of the of our local group, we’ve got the supermassive black hole, the heart of the Milky Way, the one in Andromeda. There’s probably supermassive black holes in several of the dwarf galaxies around us. 

Pamela Gay [00:25:03] Yeah. 

Fraser Cain [00:25:04] Triangulum doesn’t have one. Which way back to that? You know who knows. 

Pamela Gay [00:25:09] Everything that happens there? Yes. 

Fraser Cain [00:25:11] And so you can imagine two dwarf galaxies merging together there. Supermassive black holes haven’t merged yet. That combination reaches the center of the Milky Way and Andromeda, and. 

Pamela Gay [00:25:23] Then it can get flung. 

Fraser Cain [00:25:24] Yeah, and then one gets thrown out. Yeah. Yeah. And in those big galaxy clusters, the one seen early on in the universe, you’re seeing. Like just so much material coming together in these gigantic galaxy clusters. I mean, there aren’t many of them out there. There. There are dozens, maybe, that astronomers can see of the ones that are truly into the billion stellar mass black hole range. Right? And those are just the ludicrous, the forces involved in the kind of mayhem that’s going on in those places. 

Pamela Gay [00:25:59] The thing that this gets me thinking about is, for decades, it seems like every other American Astronomical Society meeting they’re announcing a new shredded dwarf. Galaxies star stream falling into the Milky Way has been discovered. And there is a chance that the majority of those stellar streams were, once upon a time, a dwarf galaxy associated with a intermediate mass black hole, a baby supermassive black hole. And so now those masses are somewhere. Somewhere. 

Fraser Cain [00:26:38] Yeah. Over there. Somewhere. 

Pamela Gay [00:26:40] Yeah. 

Fraser Cain [00:26:41] Could be here. Could be there, you know. All right, well, on that note, thank you mama. 

Pamela Gay [00:26:46] Thank you, Fraser. And thank you so much to our audience out there. You are making this show possible by supporting us through patreon.com slash astronomy cast. And if you aren’t a supporter and you want ad free versions of our show, consider joining our Patreon. This week I would like to thank Tim Baron, Paul Esposito, Bob Czapski, Arthur Lots Hall, Ron Thorson, Karen, careen, dump truck, Philip Walker, Hal McKinney, Bruno Latz, Jimmy. Bergeron, Jean-Baptiste. Le Martin. Ng. Timelord. IRA, Daniel. Donaldson, Frank. Stewart, Wil. Hamilton. Christiane. Golding, Michael. Pro toda Galactic president. Super. Oh, my, I this one doesn’t even fit on my screen. Galactic president scooper star mix scoops a lot. I love that name. 

Fraser Cain [00:27:42] It’s amazing. 

Pamela Gay [00:27:44] And shine phase. Thank you all so much for letting us pay the folks that make us look good. 

Fraser Cain [00:27:52] Thanks for all. We’ll see you next week. 

Pamela Gay [00:27:54] Bye 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.

Most stars in the Milky Way are trapped in here with us, doomed to orbit around and around and around. But a few have found a way out, an escape into the freedom of intergalactic space. How do stars reach escape velocity, never to return?

(This is an automatically generated transcript)

Fraser Cain [00:01:19] Astronomy cast. Episode 679 Hyper Velocity Stars. Welcome to Astronomy Cast your weekly facts space journey to 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 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 [00:01:40] I am doing well. Although if you hear any sniffling, it’s because this is the worst pollen year of several years. All the trees are far too happy and far too fertile. 

Fraser Cain [00:01:53] Yeah, like my annual reminder. If there’s anything wrong with you right now, it’s because of spring. It’s allergies. 

Pamela Gay [00:02:02] Yeah. 

Fraser Cain [00:02:02] You can like. Like maybe if you not. If you live in the southern hemisphere and you’re moving towards winter. But whenever trees do their thing for you in your neighborhood, that is like. Are you feeling a little tired? It’s allergies. Are you feeling a little, out of it? Allergies, cold? Allergies. It’s it’s all allergies. Blame everything on allergies. 

Pamela Gay [00:02:29] But I’m hearing that for those who don’t have the cloudy, pollen filled skies that I have, there are northern lights right now under CNE. 

Fraser Cain [00:02:40] So we tried. So it was like really cloudy. And I’m like, oh, we’re doomed. But Cali like showed me a picture of the aurora activity here. And it’s just like off the charts. Yeah, yeah. And so but it was cloudy. I’m like, okay, so went to bed and then I woke up around two in the morning and it was clear skies. And I went and I stood at the window and I looked out to the north and I could see the green aurora glow. Wow. Far away. And I waited for like ten minutes and nothing really interesting happened and I went, now I’m going back to bed. 

Pamela Gay [00:03:07] So that’s fair. 

Fraser Cain [00:03:09] Yeah, yeah. So so in theory, it’s, this is it. This is our time. But hopefully the weather’s supposed to improve later on this this week, so we’ll get some more shots at it. 

Pamela Gay [00:03:18] And as we get closer and closer to solar Max, everyone needs to install their Aurora alerts on their phone because we’re going to get more and more opportunities. 

Fraser Cain [00:03:28] Don’t ask us for recommendations. We have no idea what’s a good piece of software install. So most stars in the Milky Way are trapped in here with us, doomed to orbit around and around and around. But a few have found a way out and escape into the freedom of intergalactic space. How do stars reaches keep velocity never to return? I think about like, the Watchmen. You know that classic line? I’m not. I’m not trapped in here with you. You’re trapped in here with me. So. High profile city stars. What’s going on? 

Pamela Gay [00:04:03] So basically, there are stars out there that are going 50km per second. 100km per second. More than that, in some cases faster around the galaxy than the stars around them. They have been accelerated in a variety of different ways. And some of them, actually end up looking like comets because of the combination of mass loss and motion and. I don’t know where to start. There’s so much awesomeness to look at. Myra, maybe. Is Myra a good place to start? 

Fraser Cain [00:04:38] Well, maybe. I mean, it’s not it’s not leaving, but it’s definitely moving fast. So. Yeah. So then I guess, like, just in general, what are the motions? What’s a normal motion of a star in the Milky Way? 

Pamela Gay [00:04:52] So. So this is where it gets tricky. It’s it’s you look at what is the average motion of all of the stars in a given area. And the high velocity ones are the ones that are going 50 to 100km per second faster than the average where they are. And so the velocity changes depending on where you are. And there’s a lot of complication. So basically these are the ones that are just going significantly faster than the things around them. But in the case of some of the most quickly moving ones, there are actually moving 10% to 30% the speed of light, right? 

Fraser Cain [00:05:27] So like like when we think about, say, the solar system, Earth is going 30km per second around the sun and is in orbit. And the closer you get to the sun, the faster you go. The farther you get from the sun, the slower you go. It doesn’t work that way. In the Milky Way, though, everything is roughly moving at the same speed in the hundreds of kilometers per second range. 30. 

Pamela Gay [00:05:49] 20, 50. Yeah, you get regional differences because you’ll have like this open clusters moving together, that group of things is moving together. And and so this is where you get the really cool dynamics that you can start to see. One of my favorite things about open clusters, which is not where we were going with Myra. We will return to Myra. 

Fraser Cain [00:06:11] Yeah. We’ll get we’ll get back to that. 

Pamela Gay [00:06:14] So with open clusters in particular, you have these groups of stars that formed together out of the same collapsing molecular cloud and star systems. When they’re small and compact. I end up having lots of multi star interactions. And wherever you get three stars interacting, you can often get one star getting flung away. And so when we find these hyper velocity stars, quite often you can figure out what is their three dimensional motion through the galaxy and work backwards hmhm and be like, oh, that open cluster got rid of you for. 

Fraser Cain [00:06:55] Each K dejected. Yeah, so so what is the method that astronomers use to measure the speed of stars? 

Pamela Gay [00:07:02] We look at two different things. One is what’s called proper motion. This is how the stars appear to be moving relative to one another in the plane of the sky. This is the kind of thing that Gaia was designed to do, like no other telescope has been able to do previously. We see most stars over the course of human lifetime won’t really appear to move relative to the background galaxies at all. But there are few stars out there that pretty much year to year we can see their slight motion as they simply flow through the galaxy. 

Fraser Cain [00:07:43] So they just like taking a picture of the sky and then seeing how that stars position changes from the previous year. 

Pamela Gay [00:07:50] Exactly. And one of the easiest ways to measure this is if you’re looking at out of the plane of the galaxy, you can see distant galaxies, quasars, bright, other things that are so far away that we can’t perceive their motion. So we can use those as signposts to measure other objects moving against. And, yeah. So there’s things like Barnard’s Star that we just look at. And with Bernard Star, we see it moving in the sky rather quickly because it’s rather close. So it’s that thing of when you’re driving down the highway, you don’t see the mountains really moving that much past your window. But there’s mile markers. They zip past because they’re nearby and the relative motions seem magnified. They’re not actually magnified. It’s just our perception changes. But yeah, there are stars out there. And the reason I brought up mirror. Can we go back to mirror? Are we ready for mirror? 

Fraser Cain [00:08:45] Yeah. I just wanted, like, if you’re about to say, you know, here’s how fast mirror’s moving. And then I was going to say, well, how do we know? Well, now we can just refer to the proper motion Doppler effect. 

Pamela Gay [00:08:55] So there is another half to it. So I guess I will get to the other half of it. And the other half of it is we can take spectra of stars and we can measure what wavelength does the hydrogen alpha line appear at what wavelength does the calcium doublet appear at what wavelength does all these different molecules? When we look at their wavelengths, they form a fingerprint that can get slid back and forth from red to blue. The spacing between the individual lines stays exactly the same. But what color? We see those lines that can change when an object is moving towards us. Those lines all get shifted towards the blue. When something is moving away from us, all those lines get shifted to the red. And so we measure the the motion in and out of the plane of the sky using spectra. We use. We measure the motion in the plane of the sky using proper motion. We do trigonometry, and thanks to trigonometry, we can figure out the three dimensional motion of these objects. 

Fraser Cain [00:10:05] Right? Right. All right. Let’s talk about mirror. Why? Why are you so obsessed about mirror? What’s this about? 

Pamela Gay [00:10:11] Because. Because so? So this is a star. It’s. It’s not totally weird. It’s going 130km per second, relative to what’s around it. But it is shedding its outer atmosphere as it goes. It’s a, asymptotic red giant branch star. It is a kind of variable star. It is working its way towards becoming a planetary nebula. Except instead of being nice and polite and sitting still and puffing the material around it, it is hauling itself through the galaxy, leaving a train of material behind it. And because we have the capacity to use things like the Galaxy satellite to look at that stream of material left behind, we can actually start to do things like what was the chemistry of the material it gave off 300 years ago. What was the chemistry of the material? It gave off 200 years ago. And so we can see the chemical evolution of the debris cloud left behind by this shooting star. And in addition to that, it’s shocking the interstellar media. So it’s basically plowing into the material in front of it. So we have this really cool kinematic picture because you have a fast it’s not outgassing. That’s the wrong word, but that’s the closest analogy to things you might be familiar with. We have we have a star flying through the galaxy, shedding material, crashing into material, and we can see all of this going on, and we can see the star with our own eyes and with our own eyes. It’s fairly boring. It’s it’s changing in brightness and all that, and it’s cool. But when you look at that little red point of light, it’s at the end of a three degree long stream of material, which means that that little star has six moon widths behind it of material trailed across the sky. 

Fraser Cain [00:12:12] That’s amazing. So like in instead of the star just sitting there and puffing out its outer layers and you sort of measure it like tree rings, it is hurtling through the cosmos. And so you can see, you can just measure it based on history. That’s that’s pretty crazy. Yeah. Mirror, mirror is amazing. And it’s I mean, it’s it’s a type of variable star, like. Yeah, it is the quintessential the because there are, there are mirror type variable stars. Right. That is the that is the OG. 

Pamela Gay [00:12:45] Yeah. It Omicron study is its fancy name. Everyone calls it mirror the wonderful. That’s what my remains. Yeah. And I love that being Canadian. You say it differently than me mirror in America. Yeah. It’s it’s. Yeah. 

Fraser Cain [00:12:58] I don’t know if that’s Canadian. Could just be West Coast, I don’t know. Oh. All right. But that is nothing. That is, that is peanuts compared to what stars can do. So let’s. 

Pamela Gay [00:13:12] Yeah. 

Fraser Cain [00:13:12] Go faster. 

Pamela Gay [00:13:15] So, so like I was saying, some of these stars, the the hyper velocity stars instead of just the high velocity stars, these things are getting to 10 to 30% the speed of light. Wow. And and these are stars that in general have gone through a very rough history. They they were probably part of a binary system and they got too close, we think in general to the supermassive black hole in the center of our galaxy and the two stars in the binary, plus the supermassive black hole in the center of our galaxy. That’s a three body problem. And one of the stars, basically the supermassive black hole said, no more galaxy for you. And when you get a star that’s moving 10 to 30% the speed of light, it’s not going to get held on to by our galaxy. It is going to leave and keep going. And. 

Fraser Cain [00:14:21] Like those numbers like 30,000 to 100,000km per second. That’s how fast these stars are going. That is fast. Yeah. And I think escape velocity of the Milky Way is something like a little over a thousand 1500, I think, kilometers per second. So we’re well beyond that. Yes. Now, you mentioned a possible source of this is getting too close to the supermassive black hole. 

Pamela Gay [00:14:48] That that is believed to be one of the sources of difficulty for these poor objects, right? Our belief, that this is the case comes from looking at the chemistry of a bunch of these systems. We we know of, over a thousand now, thanks to a variety of different, surveys, which which ten years ago, we thought there were only a thousand out there. Now we know of over a thousand. So it apparently is something that happens fairly regularly. Stars get accelerated. So. So there’s. Known populations of stars that get in close to the center of our galaxy, they have a given chemical signature. When you see things with that chemical signature on a high velocity escape orbit that traces back to the center of the galaxy, it’s a pretty good bet that that was a star that formed in the center, lived in the center, and was ejected from the center. 

Fraser Cain [00:15:49] But that’s not the only way that these stars can probably get this level of an escape velocity. 

Pamela Gay [00:15:55] Now that’s the so there’s a variety of different ways. Like I said. So there’s the standard three-body problem. There is we also think that some supernovae where you have a close in companion and the star that goes boom, that through a variety of different effects, ranging from conservation of angular momentum to just the general shockwave of the explosion. You were sending that companion away at a high velocity, right? 

Fraser Cain [00:16:30] So you I mean, you’ve got these two stars whirling around each other. Yes. And then one of them ceases to be. 

Pamela Gay [00:16:37] Yes. 

Fraser Cain [00:16:37] And the other star is now hurled into space. It has that same velocity that it was going around that other star, but now it no longer has the the gravitational anchor. It’s being thrown like a sling. 

Pamela Gay [00:16:52] And and what’s really cool is we see both the kinds of stars that get formed during supernovae moving at high velocities, and the kinds of things you would expect to be the companion, in the case of a supernova. So there are probably cases where you have both stars ending their their coexistence as they leave behind a now empty nebula of material. And I just kind of love that visualization. This is the ultimate stellar divorce. No one gets to keep the house and, off they go. 

Fraser Cain [00:17:31] And it’s kind of a grim analogy though, right. Because I’m. 

Pamela Gay [00:17:34] Sorry. Vaporizes well, one might turn into a neutron star while the other one flies away. 

Fraser Cain [00:17:42] Sure. But even that would be a bit of a gravitational pull. 

Pamela Gay [00:17:45] Would be a bad day. Yeah. Would be a bad day. 

Fraser Cain [00:17:48] Yeah. 

Pamela Gay [00:17:49] Yeah. It’s the kinematics of of all the different things that can happen is, is endless in its variety. 

Fraser Cain [00:18:00] All right. What is the other way that we can get these hyper velocity stars. 

Pamela Gay [00:18:04] So, so we also see stars that have been evicted from many things in the outskirts of our galaxy. So these are the situations, where. You have globular clusters with multi star interactions. You have dwarf galaxies that have merged together and things get flung out. And in a lot of cases you’ll see these stars that are on highly elliptical orbits moving at not quite escape velocity. They still appear in many cases, but not all cases to be stuck to us. And these are again systems where due to mergers, due to close passes, due to high densities of stars, you end up with that three body system or more. More body systems can have. 

Fraser Cain [00:18:57] More body. 

Pamela Gay [00:18:58] And something just got ejected. What’s really cool is, well, they don’t end up on these massive, sweeping orbits. When we look at the dynamics of globular clusters over time, they actually seem to beat like a heart. Heart? Yeah, that’s the right word. Beat like a heart as, basically the kinds of orbits that exist in them heat things up and then they settle back down, heat things back up, and then our back down. Kinematics is amazing. 

Fraser Cain [00:19:27] So but I mean, these kinds of stellar interactions, they can come from almost anywhere. You can have a star floating around inside a globular cluster. It gets into some kind of through body interaction and it gets the boot. You can have a young star cluster because I know that astronomers have recently seen that as well. They’ve seen stars coming. And the story that sort of helped trigger this was it was assumed that these hyper velocity stars were mostly coming from the supermassive black hole at the heart of the Milky Way, but there was a few fairly recently found that are nowhere near the black hole. And so, yeah, had to have come from some other source. I mean, I guess it could be another black hole, a small one. 

Pamela Gay [00:20:13] Well, yeah. So this is this is where there is a really interesting story that came out last week, maybe two weeks ago. Time has no meaning of a dwarf galaxy that was spotted with, for lack of a better term, a proboscis of forming stars coming off of it. And this long, narrow train of stars didn’t look like your standard jet formed stars. Because instead of being highly collimated, tightly held together close to the system, and then falling apart, the further away it got, like water coming out of a fountain, it was. The stars were more scattered near the galaxy and then got tighter and tighter focused. The further out and after follow up observations and modeling and looking closely, what is thought to happen is three dwarf galaxies or more came together. And at one point you had three supermassive black holes in the center of this dwarf galaxy. One black hole got flung in one direction, whereas it went through the intergalactic media. It triggered star formation, and the other two went in the other direction and triggered shockwaves, but not star formation. And so this is the full scale version of what we see happening at stellar scales, with globular clusters, with with open clusters, with any high density area of stars. We used to think stars couldn’t collide. We used to think it wasn’t common for stars to gravitationally grab onto each other. It turns out all those things we thought weren’t happening. Totally happening, totally happening. 

Fraser Cain [00:21:58] So there are also. So I guess black holes are a type of star. And that and that story about how about the black hole on escape trajectory? I love that, I love that idea that it’s maintaining. It’s like building a trail of star formation in its wake. Yeah. And you kind of wonder like what impact that has had on other galaxies. This is a common thing. Yeah. So the other thing is you can get high velocity pulsars. 

Pamela Gay [00:22:24] Yep. Yeah. So. So these are where you have that system of a binary, a binary system where one of the stars goes supernova and the neutron star. All pulsars are neutron stars. Not all neutron stars are pulsars, right? 

Fraser Cain [00:22:41] I guess you have high velocity neutron stars, right? 

Pamela Gay [00:22:44] Including pulsars. Yeah, exactly. And and so what’s really cool about high velocity pulsars is you have yet another way to get at their velocity. And that’s from the pulsing of their spinning. You can actually start to get the dynamics of where you have binary systems. It doesn’t help with the high velocity, but with binary systems of systems of planets, you can see in the the changes in their velocity over time that there’s an orbit going on. Back to the high velocity part. I’m easily distracted today, apparently. This this is what we were talking about earlier, where you have a supernova and and when it goes, you have an asymmetric blast, and and star goes and one way stellar remnant goes in other way, and you end up with this massive supernova remnant left behind. And it’s in trying to understand these non spherical stellar explosions that we’ve started to piece together. Well let’s go looking for the central star. Oh I can’t find the central star. Let it go. Yeah yeah. So expand your view. And often they find these runaway pulsars that again you trace back their their motion and you can follow them back to where they originated. 

Fraser Cain [00:24:09] That’s amazing that you’ve you’ve got this star and for some reason, like maybe it’s got a binary companion, some instability in the shape of the star, some, you know, it’s not perfectly symmetrical. 

Pamela Gay [00:24:21] And the disc. 

Fraser Cain [00:24:22] Explodes where one side explodes harder than the other side, that it experiences a thrust. Yeah. And so it’s turned into a little rocket in a way. It goes off into space and and. Yeah. So you’ve got this situation, you’ve got this, this beautiful supernova remnant nebula, like the Crab Nebula or something. But like, you look at this end of the Crab Nebula, you find the pulsar. But there are these, these remnants, if you look at the center and it’s gone. And like, one possibility is that star just exploded and disappeared, but they’re finding them receding away from the scenario. And one of the things that I really like about this is that we can use gravity in theory, we can use gravitational waves in the future, larger observatories to measure these, the formation of these hyper velocity stars as they’re forming, because it’ll be an instability. 

Pamela Gay [00:25:18] What I really love is the basic physics behind this is super simple. You have all the mass tied together and and if the cloud is going to go away asymmetrically, the, the momentum has to go somewhere. Right? And so this is purely a conservation of momentum problem. It’s a really complicated conservation of well conservation of energy and momentum problem. it’s just cool. 

Fraser Cain [00:25:46] Space is scary. 

Pamela Gay [00:25:47] Oh yeah. And awesome. 

Fraser Cain [00:25:49] Well sure. But I mean awesome in this sometimes in scary way too. Like in the, in the sort of the full meaning of the word. Awesome. Yeah. All right. Thanks, Pamela. 

Pamela Gay [00:26:00] Thank you, Fraser, and thank you to all of the folks out there in our audience who are keeping this show going by being part of our Patreon community. Those of you who join our Patreon get to get all of our episodes, advertisement free. So, this week I would like to thank planetary, Alex, rain, Karthik, Becca, trauma and Steven. Kathy, Andrew Stephenson, cameo rotation, Sean Matz, Gabriel Galvin, Glenn McDavid, Nat detweiler, Szymanski, Sam Brooks and his mom Bart Flaherty, the air Major Benjamin Carrier, Brian Kelby, Benjamin Davies, Arctic Fox, Lou Zealand, the lonely sand person, new LA dean, John Drake, Jordan Turner, Reuben McCarthy, Ian Abdullah, Jeff McDonald, Lee Ha born Andre Lev, soul Zero, chill Wanderer and 101 Felix Good Astro sets. Simon Parton, Papa Foxtrot and Christian Golding. Thank you all so very much. 

Fraser Cain [00:27:05] Thanks, everyone, and we’ll see you next week for bye. 

Pamela Gay [00:27:13] 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. 

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)

Back to Top

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.

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.

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The Sun is a third-generation star, polluted with the metals from long-dead stars. Astronomers have also discovered second-generation stars, with very low metallicity. But theories suggest there must be a first generation, with stars made from only pure hydrogen and helium. Can we ever find them?

Show Notes | Transcript

This episode is sponsored by BetterHelp. Give online therapy a try at betterhelp.com/ASTRONOMY and get on your way to being your best self.

NASA Artemis (NASA)

JWST (NASA)

DART (JHUAPL)

Chinese space station epitome of aerospace workers’ wisdom: designer (CGTN)

InSight Mission – NASA’s InSight Mars Lander (NASA)

Overview | Sun (NASA)

Stars – Stellar Populations (Astronomy Online)

What is stellar magnitude? (EarthSky)

Population I (Swinburne University)

Population II (Swinburne University)

Population III (Swinburne University)

What is a globular cluster? (EarthSky)

Two planets around Kapteyn’s star: a cold and a temperate super-Earth orbiting the nearest halo red dwarf (MNRAS Letters)

Pair-Instability Supernovae: What might they look like? (Astrobites)

Gamma radiation (ARPANSA)

Hydrostatic Equilibrium (Swinburne University)

Positron (Swinburne University)

Potential First Traces of the Universe’s Earliest Stars (NOIRLab)

Quasar (Swinburne University)

Gravitational Lensing (Hubblesite)

PDF: First Stars and First Light: The Epoch of Reionization (NSF)

What is the Cosmic Microwave Background? (Universe Today)

New insight of AGC 198691 (Leoncino) galaxy with MEGARA at the GTC (MNRAS)

Elemental Abundances (Center for Astrophysics)

Hubble Space Telescope

American Astronomical Society

241st AAS Meeting (AAS)

Supermassive Black Hole (Swinburne University)

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Transcriptions provided by GMR Transcription Services

Fraser Cain:              Astronomy Cast, Episode 664: The First Stars.

Fraser Cain:                 Welcome to Astronomy Cast, 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. My name is 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 are you doing?

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

Fraser Cain:                 Good, good. So, we did a wrap-up of the space news in 2022 and – while 2022 like many years sucked – for space it was the best, right? We had Artemis, we had the James Webb space telescope, we had DART, we had the Chinese space station, we had so many amazing things come together. It feels like it was probably one of the best years in space in my career. So, it’s amazing. It was an amazing year and I don’t see as many exciting things coming up for 2023, but who knows?

Dr. Pamela Gay:         That is true. See I’m still mourning InSight. The InSight mission was my favorite little Mars sitter/lander.

Fraser Cain:                 But it lasted twice its lifetime.

Dr. Pamela Gay:         It did. And so I guess I’m still mourning. I’m still mourning the little lander that tried so hard.

Fraser Cain:                 Well, what more could you have asked for it, right?

Dr. Pamela Gay:         A giant earthquake.

Fraser Cain:                 It should have lasted for four times as long? Ten times as long? They can’t all be opportunity.

Dr. Pamela Gay:         I know. I know.

Fraser Cain:                 Right. All right. The sun is a third-generation star polluted with the metals from long-dead suns. Astronomers have also discovered second-generation stars with very low metallicity. But theories suggest there must be a first generation with stars made from only pure hydrogen and helium. Can we ever find them? So, first, please explain the generation numbering scheme for stars because it’s ridiculous.

Dr. Pamela Gay:         Okay.

Fraser Cain:                 We have a pop I star?

Dr. Pamela Gay:         Yeah. Astronomers –

Fraser Cain:                 And there are pop II stars?

Dr. Pamela Gay:         Astronomers shouldn’t be allowed to name things or set the directions of calibrations. So, just like astronomers screwed up in terms of calling the brightest stars magnitude zero – meaning faint stars are magnitude 20 – we decided that our current population is number I. We’re number I.

Fraser Cain:                 Right because we’re the first star that we ever discovered.

Dr. Pamela Gay:         Well, yeah, we are the first star we ever discovered sort of I guess. You fell asleep the first night and then you found all the rest of them?

Fraser Cain:                 Yeah.

Dr. Pamela Gay:         But anyways, so the generation of stars older than us – that doesn’t have as many metals – can’t probably form planets the same way. Those are population II and as illogical as it can possibly be, the first generation of stars the universe ever formed is population III.

Fraser Cain:                 Right. So, it makes sense. The first star that we ever discovered, they’re population I. The second stars that we ever discovered; those are population II. And then we’re hoping someday we’ll find the third stars – the type of stars – which will be population III, still theorized. Okay. So, that is the – and then how do you define them? As an astronomer, when do you take a star and put it into the pop I bucket and put it into the pop II bucket, and the theoretical pop III bucket?

Dr. Pamela Gay:         So, pop III means these stars are primordial ingredients. They are made of the exact same stuff that was produced in the Big Bang – hydrogen, helium, maybe a trace amount of lithium and beryllium – definitely a trace amount of lithium and beryllium. But then pop I are all the stars like our sun that are being formed currently. These are things that are two to three percent of atoms heavier than hydrogen and helium and the stuff in between is the population II.

So, once you start getting to the point – and I’m sure this is gonna get redefined as the formation of planets plays a larger and larger role – but pretty much once you start getting to the point that you’re not seeing planets forming, that’s where you have population II stars.

Fraser Cain:                 Although I’m sure someone’s found planets are on pop II stars or will shortly?

Dr. Pamela Gay:         The issue is population II stars these are objects that are generally less than a percent of heavier atoms. And if you don’t have heavier atoms, you can’t form planets. So, one of the amazing things is globular clusters out there. These are population II stars orbiting our galaxy. They don’t have planets so far and we have looked as hard as we can possibly look at things that far away and they’re just not showing up.

Fraser Cain:                 So, there’s one known type II star that has a planet?

Dr. Pamela Gay:         Are we sure, sure?

Fraser Cain:                 Well, it’s called Kapteyn’s Star. It’s a M1 red sub dwarf and the metallicity is about 14% of the sun, which classifies it in the type II star.

Dr. Pamela Gay:         How do you always find these exceptions?

Fraser Cain:                 Because I have a hunch. Look, okay, look. Here’s my standard operating procedure, right, is that I think all I do is report on surprising new discoveries and new things moving forward and so it just it feels like somewhere there is a headline, “Astronomers find the first planet around a type II star.” Yeah, anyway, and I’m sure they’ll find many more because “Astronomers shocked to discover. Theories overturned.” So, yeah, all right, we’re gonna talk more about the first stars in a second – which we know we don’t know of any. Or do we?

Dr. Pamela Gay:         It’s true. We don’t yet.

Fraser Cain:                 We’ll be back in a second. Oh, wait a second. I may have news for you then. We’ll be back in a second.

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Fraser Cain:                 And we’re back. All right. So, we’ve classified the pop I star, the pop II star. Let’s talk about the pop III. So, these are theoretical. As you say, they are made of the pristine material left over from the Big Bang – pure hydrogen and helium – at the exact constituents left over when the universe had cooled down that these atoms could form. How would they be different from a star like we have today? I’m gonna guess no planets, but then even that like I’m sure at some point somebody’s gonna be like, “We found planets around – We discovered pop III stars and we also discovered a planet” a gas giant, who knows?

Dr. Pamela Gay:         All right.

Fraser Cain:                 Pop III gas giants. Yeah, please continue, but what would they be like?

Dr. Pamela Gay:         All right. So, one of the weirdest things in trying to understand stars is what are the effects that these heavier elements have on the ability of the star to form and radiate heat? And it turns out that if a star is made of pretty much just hydrogen and helium, the light that is forming in its core just radiates out. And because it’s radiating away and not interacting as much with the protons and electrons because the energy levels just aren’t right, the star is able to become much more massive before it starts pushing out its outer layers, and a star that’s more massive – in this case 100 to 200, 300 times the mass of our sun – it’s only going to live for a million-ish years.

So, we’re in this situation where the very first stars formed roughly 100 million years after our universe formed and then they only lived for a million years before they underwent this super-weird form of supernova where the star essentially eats itself from the inside out, and leaves nothing behind except for a spray of light and heavier elements.

Fraser Cain:                 So, you don’t get a black hole. You don’t get a neutron star. You just get the thing detonating completely?

Dr. Pamela Gay:         It’s called a pair-instability supernovae and –

Fraser Cain:                 Can you talk about this? You say it eats itself from the inside out, but what is actually happening with pair instability?

Dr. Pamela Gay:         So, you have – in the core of the star – gamma-ray photons are getting produced. And these extremely high energy gamma ray photos they’re going to be interacting with protons, with electrons – and not as efficiently as if they were metals – and they’re also going to be interacting with each other. And ideally, the rate of energy production is such that the star is in thermodynamical equilibrium. Gravity is pushing inwards, heat and light are pushing outwards.

Again, the light isn’t as effective here because it’s mostly just flying through the atoms. And when these gamma rays interact with each other, they will produce an electron and a positron. This is a particle and an antiparticle that are able to then later interact with each other if they hit each other later and produce more gamma rays but – because of the kinetic energies involved – some of the energy is lost in this process. The lower energy gamma rays are going to lead to a changing situation where the outer layer of the star isn’t being supported as well. The star begins to collapse down.

As the star collapses down, it heats up. More gamma rays are produced. Gamma rays interact with each other because there’s more of them. It’s easier for them to interact. They produce more positrons and electrons. These interact and annihilate and the star is literally eating itself out of having matter and energy through the loss of energy to kinetic energy. It’s wild and what gets me is we think we may have actually been able to see the chemical fingerprint of one of these kinds of supernovae in the light of distant quasars.

Fraser Cain:                 Okay. Well, that was the evidence I was gonna bring up.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 So, then, yeah, yeah. And so I mean we see those pair-instability supernovae. We’ve seen these detonations before but just from heavier stars.

Dr. Pamela Gay:         Right.

Fraser Cain:                 Just stars with other elements like pop II or pop III – pop I, sorry. I got to keep this straight. But the second and third-generation stars but they’re very massive.

Dr. Pamela Gay:         Yes.

Fraser Cain:                 They have exploded as pair-instability supernovae and just completely vaporized themselves – no black hole, no neutron star.

Dr. Pamela Gay:         Right.

Fraser Cain:                 Just kablooey.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 Yeah. Okay. All right. So, they [inaudible]. Now you were starting to make some estimates of their masses – 100 times the mass of the sun, 200 times the mass of the sun. Do we have a sense of how big these things can get?

Dr. Pamela Gay:         This is where you end up with a lot of different people arguing in the literature. There are some folks that are like, “Above 300 solar masses, the energy being produced is going to cause no additional material to be able to fall onto the star. It’s going to be quenched.” There are those that are like, “At 150 solar masses, that’s gonna happen.” There are those who are like, “At 1,000 solar masses, that’s going to happen.”

Fraser Cain:                 Right.

Dr. Pamela Gay:         The safe bet is it’s occurring in the hundreds of solar mass range because – as you pointed out – we do see some massive stars in our modern universe. These are objects that are 150 solar mass to 200 solar mass when they first form and they do have these pair-instability supernovae when they die. So, just how big the very first ones get? We’re looking at hundreds is a safe bet, but exactly how many hundreds we’re not sure.

Fraser Cain:                 And there could be all kinds of weird dynamics that are going on. There could be magnetic field lines, there could be accretion disks, there could be ways to get beyond pushing that material back away from the star and that’s why it’s – I saw a simulation where they thought that maybe you could get into the tens of thousands of times the mass of the sun.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 They’re crazy. And then what is a supernova? They simulate in a supercomputer what a supernova would look like when a 50,000 solar mass star goes through this pair instability process.

Dr. Pamela Gay:         And then that light doesn’t get very far because the early universe was not yet ionized again, re-ionized.

Fraser Cain:                 Right.

Dr. Pamela Gay:         So, all of this is going on behind opaque layers of gas hiding from us.

Fraser Cain:                 Huh. We think about these. Sorry. We think about the cause of microwave background as this like someone came and turned off a switch, but it wasn’t like that.

Dr. Pamela Gay:         No.

Fraser Cain:                 It was this long, slow, gradual process of the clouds lifting over the course of several millions of years. And so could you have had these first-generation stars forming within this fog of the early universe?

Dr. Pamela Gay:         Yes. That’s exactly where they would have been forming and we’re starting – through gravitationally lensed galaxies – to be able to see the age of reionization, to see early galaxies that still have these clouds of neutral gas around them. But the very first generation, the closest we can come to hoping to be able to find them is that there are pockets of gas out there that just somehow got isolated and left alone for the fullness of time and there’s one – AGC198691 – I have to look at its license plate number.

It is one-twentieth of a percent made of atoms heavier than helium and it has one-fortieth the metallicity of our sun, which means that it’s population II stars. But it is so metal-poor that it starts to give us hope that maybe we’ll get lucky and – while there’s not anything in the nearby universe that is pristine material just starting to form stars – maybe we’re going to be able to find some lensed system from the first billion years of the universe that we’re able to start catching the light of those first supernovae.

Fraser Cain:                 So, then I have a two-question. I got to remember to bring up the other thing before we end the show, but anyway – So, first let’s talk about trying to observe them. So, you mentioned that they – even though these stars are ludicrously bright, even though their supernova are brighter probably than any supernova we’ve ever seen – they are cloaked in the fog of the early universe and will be difficult to see both their existence, but also their death.

Dr. Pamela Gay:         Yes.

Fraser Cain:                 So, how could we theoretically see them?

Dr. Pamela Gay:         If they formed in a pristine galaxy that – or a pristine blob of gas that managed to escape the first round of star formation like a blob of cookie dough without chocolate chips that escaped onto the counter. That escaped gas is probably the best hope we have of seeing these things. Now, the other problem that we’re dealing with is – if you go back to some of the earliest episodes of this show – we talked about the missing G dwarf problem, this idea that low-mass stars have the capacity to live longer than our universe has been around. So, the very first lower-mass stars to form should still be out there shining.

And this is where we get ourselves into trouble of just how effective was the mixing and how much metal does it take to start forming lower mass stars? And these are things we’re still trying to figure out. So, on one side, you have people looking for the oldest low-mass stars that were the very first low-mass stars to have ever formed. And on the other side, you have people trying to find pristine pockets of gas in dwarf irregular galaxies, in other forms of dwarf galaxies, that just don’t have anything to increase the mass of stars as they form – increase the metallicity of stars as they form.

Fraser Cain:                 Right, right. Now, you mentioned maybe through lensing.

Dr. Pamela Gay:         Yes.

Fraser Cain:                 So, Hubble never could.

Dr. Pamela Gay:         No.

Fraser Cain:                 But I know that using gravitational lenses in the way that Hubble could see the farthest galaxies, Webb could be able to see the farthest stars.

Dr. Pamela Gay:         And this is where – at the time that we’re recording this – we are about a week and a half away from getting the first deluge of science to come from the JWST at the American Astronomical Society meeting.

Fraser Cain:                 Oh, it’s the JWST meeting. Oh, yeah. I never even thought about that.

Dr. Pamela Gay:         Yeah, yeah.

Fraser Cain:                 You’re right. This is gonna be chock-o-block, isn’t it?

Dr. Pamela Gay:         They’re gonna have a whole lot of early results from JWST being announced and I’m kind of afraid that anything I say – other than JWST was specifically built with finding first stars in mind – is gonna be out of date within weeks of this episode going live.

Fraser Cain:                 Yeah, that’s interesting.

Dr. Pamela Gay:         So, stay tuned.

Fraser Cain:                 We should maybe do in that episode.

Dr. Pamela Gay:         We have it scheduled.

Fraser Cain:                 Oh, it’s already scheduled? Okay.

Dr. Pamela Gay:         Yeah, yeah.

Fraser Cain:                 All right. Yeah, yeah, we’ll do a first science result – first proper science announcements – from JWST. That sounds great. So, what would it take then to build? What kind of instrument could see them directly? Because I know there was a space telescope – the Origins Space Telescope – that was shelved and that was going to be a nine to 12-meter class infrared observatory – essentially a super-duper version of JWST. That was hoped could maybe find evidence of the pop III stars.

Dr. Pamela Gay:         Right. So, what we need is something that is capable of seeing the faintest light from dwarf galaxies that are being gravitationally lensed or from galaxies that aren’t yet fully fledged, fully full of light. This goes back to how do galaxies form? We have this notion today that they form both through the massive collapse of giant pockets of gas, but also through smaller pockets that collapse into dwarf systems and then merge together.

Those dwarf systems that have less mass in them will form stars at a slower rate. Big things form faster, small things form slower. By being able to see dwarf systems that are being gravitationally lensed and are super faint and are in the earliest days of the universe so their light is redshifted into the infrared, we can get back about as far as we can get back.

Fraser Cain:                 Right.

Dr. Pamela Gay:         It’s hard. It’s hard.

Fraser Cain:                 Yeah, yeah. Now when you think about the size of these stars – and we talked about how they don’t seem to form – they probably don’t form black holes, but there’s got to be some kind of link. Could there be some kind of link between these first-generation stars and the supermassive black holes – which are also a mystery – because they don’t seem to be able to form quickly enough to have the mass that they have already in the universe that we see them? Is there some connection between these first-generation stars and these monster black holes?

Dr. Pamela Gay:         At a certain level, yes because you’re, again, at this problem of, “If you have an atom –” Technetium is my own personal enemy because in stellar spectrum, technetium it has electrons bouncing around at all of the interesting, visibly apparent in your standard optical telescope colors of light. So, you’re trying to study whatever – small magnesium hydride was what I was working on – whatever small molecular lines or atomic lines and technetium is there going, “Hi. There are a few atoms of me. We’re gonna dominate everything.”

And what’s happening is – as the energy tries to radiate out from the center of the star – it’s absorbed in by all of these different energy levels of the electrons in the technetium and then re-radiated as the electrons jump between energy levels going back down. So, you have this one-two whammy of a whole lot more electrons involved in the energy levels and a whole lot more energy levels increases the ability to re-radiate that energy and this causes a pressure essentially. So, the light goes out, it gets absorbed into these atoms, and that supports the outer layer of the star. If you don’t have all of these energy levels to absorb in the protons, the protons just fly through.

So, this allows giant stars to form. Well, if you’re in a early galaxy and you have collapsing mass that is able to heat up and much more effectively radiate out energy, you can first of all get bigger that way. And then models that look at adding in turbulence to again allow more mass to get down in there than you could through a nice, calm collapse, this one-two punch of lower metallicity and significant turbulence allows you to start getting at supermassive black holes maybe.

Fraser Cain:                 Right. There’s an interesting experiment you can do talking about turbulence. You can take a bottle of pop – what you may call soda – and you turn it upside down and it glugs out and it’s very slow. But if you give it a spin, then the water pours out because it gets an air hole coming up the middle of this vortex and the thing will just empty in a heartbeat – just boom, completely empty – and so turbulence can have a tremendous effect. So, one idea – if the turbulence models are right and if they do just keep gaining mass forever – is you don’t get the pair-instability supernova. Instead, you just get this direct collapse into a supermassive black hole.

Dr. Pamela Gay:         Yeah, yeah.

Fraser Cain:                 That would be crazy. That’s amazing. Yeah, to think that however many million times the mass of the sun could all collect together into one spot and then just directly turn into a black hole.

Dr. Pamela Gay:         And it all comes down to how big were these slight overdensities and under densities of mass in the early universe?

Fraser Cain:                 Yeah. Wow.

Dr. Pamela Gay:         If we had had a different distribution of overdensities, we might have become a universe of nothing but supermassive black holes.

Fraser Cain:                 Right.

Dr. Pamela Gay:         So, there’s your food for thought for the day.

Fraser Cain:                 I love it. All right. Well, that was fantastic, Pamela. Thank you so much.

Dr. Pamela Gay:         Thank you and thank you to all of our patrons out there. We wouldn’t be here without you and this week I want to thank Brian Cagle, David Everson, Bruno Leitz, Alex Raine, and I’m gonna pause and say we now have an add-free distribution of this show on an RS feed through Patreon.

Fraser Cain:                 Nice.

Dr. Pamela Gay:         That you can only get if you’re a Patreon. So, I’m gonna keep going. We’re thanking Michael Prochoda, Burry Gowen, Stephen Veit, Jordan Young, Jeanette Wink, Kevin Lyle, nanoFlipps, Barre Andre Lysvoli, J.F. Rajotte, Venkatesh Chary, Andrew Poelstra, Brian Cagle, David Troug, Aurora Lipper, David, Gerhard Schwarzer, Buzz Parsec, cacoseraph, Laura Kittleson, Robert Palsma, Jack Mudge, Les Howard, Joe Hollstein, Frank Tippin, Gordon Dewis, Alexis, Adam Annis-Brown, Richard Drumm, William Baker, WandererM101, Zero Chill, Felix Gutt, Androsetz or Astrosetz, William Andrews, Gold –

Roland Warmerdam, Jeff Collins, Simon Parton. Kellianne and David Parker, Jeremy Kerwin, Rob Cuffe, Harald Bardenhagen, Matthew Horstman, Alex Cohen, Phillip Walker, marco iarossi, David Gates, Scott Kohn, Scott Bieber, Justin Proctor, Matthias Heyden, Claudia Mastroianni, Kseniya Panfilenko, Daniel Loosli, Jim Schooler, Gregory Singleton, Disasterina, Cooper, Tim Gerrish, Tim McMackin, Jeff Willson, Paul D Disney, Eran Segev, NinjaNick, Kenneth Ryan. And don’t you love that there’s fewer episodes in January and there’s that many more names at the end of the episode?

Fraser Cain:                 Fantastic. Thank you everyone for supporting the work that we do and we will see all of you next week.

Dr. Pamela Gay:         Bye, bye everyone.

Announcer 2:              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 Dr. Pamela Gay. You can get more information on today’s show topic on our website, AstronomyCast.com.

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