天文播客

這裡沒有張惠妹的歌「站在高崗上」提到的綠波海茫茫，在這裡只有黃土茫茫，而且缺氧。

由天文所主導之為阿塔卡瑪大型毫米及次毫米波陣列（簡稱”ALMA”）研發的「第一頻段接收機」於2016年被採用，並已於2021年開始接受訊號，聽聽科學家如何努力的刻服惡劣環境，堅持至今。努力工作時，又看到了哪些有趣的動物呢？且聽分曉。

背景音樂由 audionautix.com 提供

數月之後，隨著一座最新太空望遠鏡的發射升空，由天文學家精心設計的觀測計畫也將在離地球150萬公里的太空中開始付諸實踐，到底會發現什麼？仰望星空，令人引頸期待。其中的一份觀測計畫，是來自臺灣中研院天文所博士後研究 Dr. Sascha Zeegers（諸葛沙夏）團隊的提案。

本集節目中，沙夏要告訴我們，她為什麼醉心投入宇宙塵埃這個研究主題、她的期待與展望；不可少的，也聊一下這個大家已經等了20年的韋伯太空望遠鏡，可以用來做什麼。

本集內容為英語。

背景音樂由 audionautix.com 提供

Transcription:

Welcome to the Astronomy Podcast produced by Academia Sinica Institute of Astronomy and Astrophysics

I am show host of today, Lauren Huang. And, we are having our postdoc fellow Dr. Sascha Zeegers here with us. Hi, Sascha, we know that a space telescope is going to be launched into the space later this year, and, you're one of those who got the observation time to use it. Would you please explain for us what is this telescope aiming to do?

Thank you Lauren.

So the James Webb Telescope, which we also call JWST or Webb for short, will be the largest telescope that we ever send into Space. The whole telescope will be roughly as large as a tennis court. The mirror is 6.5 m in diameter. This telescope will be launched in October of this year. Because it is such a big telescope with very sensitive instruments it can observe things we have never been able to see before. We may be able to observe the atmospheres of exoplanets, look inside clouds of gas and dust and observe how stars are born. We can also look at the youngest, most far away galaxies in the universe and learn a lot more about the history of the universe.

Is it going to replace HST?

So I guess the answer to that is yes and no. We often compare this telescope to the Hubble space telescope, but the two telescopes are actually quite different. JWST is an infrared telescope, so it looks at the universe at a longer or redder wavelength. Hubble is more optimized at the wavelength where our eyes can see and the ultraviolet. This longer wavelength enables JWST to look inside molecular clouds to see how stars are born and it can explore the early universe and the youngest galaxies further. Hubble is still an amazing telescope though and to make our observations more complete over the spectrum we also requested time to observe with Hubble.

How long will this JWST telescope fly…?

We are usually cautious to say what the lifespan of the telescope will be, since we don't exactly know. Things may go wrong, although very often space telescopes operate far longer than expected. Hubble has been flying for around 30 years already.

We think that JWST should be able to operate for some time between 5.5 to 10 years and perhaps longer. It is certainly shorter than Hubble, since the mission is limited by the supply of hydrazine fuel needed to maintain the spacecraft’s orbit. It will also operate much further from Earth (1.5 million km), so unlike what was done with Hubble, we can't just go to the telescope and fix things which are not working properly. That is why people have done long and extensive tests on JWST from Earth.

How many people from Taiwan are involved in the proposals that that got the selected time of this round so there are three proposals from people in Taiwan that got accepted so one of them is someone from another university so not from our institute from ASIAA. But within ASIAA we have two people who are the principal investigator of a project so there are two different projects. And the project I work on and I'm the principal investigator of, there are two other people also working at ASIAA, Jointy Marshall and Ciska Kemper who are also involved in this project. It's called co-investigators.

So, you're leading the team? I'm reading the team yeah.

I heard some people said that the competition for this JWST time is quite fierce, do you think so?

I think so yeah. It was quite fierce. It was also because there is this big anticipation we've been looking forward to doing science with this telescope for maybe two decades already. Also the expectations are super high. So now this is the first time people could submit their projects and everyone wants their project to be accepted of course. So the telescope is "over-subscribed" and there are different types of projects related to the amount of time you request to observe -- so there are small proposals, medium and large proposals. And in my category, which is a medium proposal, the oversubscription was about five to one -- so only one out of five submitted proposals would get selected.

WOW! congratulations!

Thank you

So what was the immediate thought when you learned that you've won? Was it like -- I know it's coming to me! Or you more like -- ahh! winning a lottery!!!

So what happens is that you know roughly when the day comes that they announce it. But still when they send out all the emails with the yeah accepted and rejected proposals it's still a surprise so here in Taiwan we're a bit ahead in in the day compared to the us of course so they send it at the for them normal time in the in in the morning but for me came here at midnight so i saw this email and then it's it's it's like it's yeah unbelievable when you open that email and they say your proposal is accepted. So. yeah. It's not like winning the lottery because the odds are much higher of course, but it does feel like winning the lottery yeah. It was fantastic. And then you think oh wow okay so now really this project is going to happen, so we have to arrange lots of things. Yeah, so the immediate thought is: wow!

So now tell us about your research! What in this cosmic dust is fascinating you in the first place? and by now what are you studying?

I will use JWST to observe cosmic dust. This is dust produced in the atmospheres of old stars. The stellar wind then injects it in space, the interstellar medium. The fascinating thing about cosmic dust is that you can find it everywhere in the universe, even in the most far away Galaxies. It is also very important, because a lot of processes in the universe happen thanks to this dust. The most important reason to study it, is because we and everything around us is made of this star dust. So if we want to study life in the universe, we need to study the properties of stardust.

That's fantastic! Sascha, can you recall at what age you first time learned about "we are all made of dust"?

That's a hard question. I don't know. A lot of people they've watched this program… "the Cosmos"! so yeah there is this. But i think if you're in Europe you don't really know about that program. I grew up in Europe. But there is this program the Cosmos and the first edition of that was by Carl Sagan, in 80s, and he in his his program he said "we're all made of stardust" so yeah that's like the the thing that people cite the most. But i think my realization came much later when i heard when i learned that stars produce elements, and then i was like okay, so everything is produced by stars. And later on I learned about that stars produced dust and that that dust is the stuff that gets injected into our solar system and finally created everything that's around us. So I think it's a more of a gradual realization than like… Around the age of 11, 12 years old, then i learned that stars produced elements. And i was like, wow, okay, so everything comes from stars. But yeah the realization that there is dust floating around in space, that claim, I learned about that much later.

So yeah, dust from the interstellar medium gives us the starting conditions for solar systems, so if you want to understand how our own solar system formed, we need to know the properties of this cosmic dust, and what the starting point, starting conditions for our solar system were. The dust from the interstellar medium gives us the starting conditions of solar systems. If we want to understand our own solar system and how it is formed, we need to know what the properties of this cosmic dust are!

So this is what I am interested in.

i want to find out what happens to the dust in space so when it floats between the stars because there it gets bombarded by radiation and particles that change the dust. And at the moment we don't really know why dust survives this environment at all and how it ends up in planets eventually. So we need to study the properties of the of these dust particles, so for instance, whether they are crystalline or whether they are completely amorphous, or what the chemical composition is, and how large these grains are.

With JWST we will look at stars in the Galaxy and observe how part of the light from the stars gets absorbed by dust along the line of sight before it reaches us. Every type of dust has its own particular pattern in which it absorbs the light and from that we can derive what kind of dust we are looking at.

Yeah so the reason I'm fascinated by it is that we're all made of stardust. And we really have so many questions yet to answer to get to the point of how did everything especially also the earth form and life started.

So this is going to answer the big question about origin.

Yeah it will be one part of the answer in the origin and the life cycle of stars in the universe.

Will you count this one one of your greatest achievements when maybe looking back in 10 years of time from now? Do you think?

JWST has the precision to answer many of our questions. It will be the first time we can look at the universe in this precise way and we have been anticipating it for years. I am sure that whatever we may find, it will be very exciting and that I will look back on the achievements of the team with a lot of joy.

Right! How this is going to affect the astronomers of Taiwan do you think or uh how they affect the next generation scientists of Taiwan?

So yeah i hope that we can involve more people in this type of research and that it will give the research about cosmic dust a big boost especially here in Taiwan because we have people working on that within this institute but also all over Taiwan and for yeah for infrared astronomy in Taiwan this will be great so the infrared astronomers that are looking at this specific wavelength will benefit from this research but also anyone else that uses dust models in their research will benefit from from this research project so hopefully it will also raise many questions and new projects and new things for people to work on also for students in Taiwan so yeah it's a it's an exciting time for people here

Wonderful! Lastly, what results of your observation are we expecting? and when?

we can make predictions of what we may find and what it means of course for instance if we find dust particles that are crystalline they may be recently produced by stars and if they are small they may be shattered and perhaps the dust is different in different environments so the composition changes slightly on which way we look. And perhaps not a yeah and perhaps the there will be surprises something that we really really didn't expect. Because yeah we are studying the dust in this environment of the galaxy for the very very first time. so yeah we always have to be prepared for something completely unexpected which is difficult um yeah it will take some time before we get results because first the telescope needs to be launched, then it needs to be moved into position, and then there is a phase where they will test the instruments very carefully, and after that time so that's about six months after the launch, then observations are starting to take place, but we are observing quite a large number of stars, so these observations they will trickle in in like they will come in slowly off in the course of a year. um and then we need time to study the results or the observations and reduce the data so this whole process easily takes up two or three years.

Right. Very well! so good luck with the observation time!

Thank you.

We look forward to your exciting new results!

I think there will be lot lots of news coming out from James Webb around that time from many projects!

Yes! Nice work! See you next time!

"地球並不孤單，地球／太陽也不只我們這一組。"這情境，現代人都一清二楚，並不稀奇，但哲學家伊比鳩魯和鄧牧，早分別在西元前3百年和中國的元代都已想到過了，那可算是真厲害。至於，製作出一台望遠鏡來放眼向太空瞭望看看，那就比較更近代一點，已經是第17世紀的事了。

中研院天文所的 Dr. Gilles Otten 幫大家整理這段太陽系外行星從哲學走到科學之路。並解說為什麼非要用望遠鏡直接地看到單一行星不可，理由何在？到底有多難呢？目前為止有哪些技術困難已克服？最大的光學望遠鏡現在蓋到哪兒了？何時能啟用？聽說臺灣也有幫忙貢獻，是嗎？

本集內容為英語。

In this episode, Dr. Otten very briefly summarized how people thought about the issue of "planets around other stars" since millenniums ago.

Also, he will tell us, who firstly coined the word "exoplanet"? Is it easy or hard to discover exoplanets?

What are the challenges needed to be solved in order to photograph exoplanets?

What technical terms like Diffraction limit, Adaptive Optics and Coronagraph actually mean?

What are the current status of the biggest telescopes? Does Taiwan play a role?

Transcribe:

Welcome to Astronomy Podcast produced by Academia Sinica Institute of Astronomy and Astrophysics, or A-S-I-A-A, "ASIA A", a shorten name. Today’s show host: Lauren Huang. We are having Dr. Gilles Otten with us. Gilles is working for ASIAA, in Taiwan, helps building one of the world’s biggest telescope, and today he will tell us about Direct imaging exoplanet around another star. Hi, Gilles, thank you for coming in the middle of a pandemic.

Thank you.

Well, let's start the show! First question, since a long time ago people have thought about planets around other stars. Indeed a long, interesting history about discovering. Important questions we asked and always still want to ask. Gilles, how about… a summarization?

Sure. So there are a lot of written examples of philosophers who have wondered about the existence of planets around other stars. So, for instance, in the third century BC there was a Greek philosopher named Epicurus （伊比鳩魯）who thought there would be an unlimited amount of worlds and even in the 13th century there were philosophers such as the Chinese philosopher Deng Mu (鄧牧) who said it would be unreasonable to assume that there are no other worlds beyond our own. So this is uh…, it sounds almost like science fiction if you look back at it. And some of these philosophers even speculated about life on other planets. But now in the present day with the modern science we can of course form more structured questions than they ever could, like: is the role, the position of our earth unique or eventually we can probably answer this ultimate question whether there's life on other planets using scientific methods, which of course these philosophers never had.

Right, when did modern astronomers start responding to all of these questions and, what did they do?

So only after the first telescopes were invented in the early 17th century things really started to become more scientific. So just -I think- a few years or maybe even in the year after they invented the telescope Galileo Galilei discovered the first moons orbiting Jupiter and seeing this miniature solar system almost orbiting as if it was a tiny solar system like our own. It kind of validated the earlier philosophical comments. So yeah when you realize the earth and its moon are not really in a unique situation, you can really believe that all stars could have planets on their own and of course it didn't stop people from philosophizing, even scientists they can philosophize, but through the invention of this first telescope the first steps were made to this modern astronomy and the eventual discovery of exoplanets only 30 years ago.

So, who invented this word “exoplanet”? Which word do you use in the place where you're from? Is it easy or hard to discover exoplanets?

Yeah so i looked a bit into the history of the exoplanets and how long have people been searching for exoplanets. And even though i think already in the 19th century people were trying to discover extra-solar planets but they would call it a planet around another star or a potential companion and in the end none of these discoveries turned out to be a real exoplanet. But the earliest reference that i could find is from 1943 where a team of astronomers in the US under the director Peter van de Kamp said that they discovered a planet around a star 61 Cygni because they had seen wobbles in the motion of this star. And their team has made many such claims of many exoplanets and maybe they even invented the word or first mentioned the word in a scientific paper. But in the 1970s all of these claims were proven to be just a measurement mistake, a systematic error. But yeah where i'm from in the Netherlands, we use a similar word as exoplanet “exoplaneet” but there's also an other word that people use buitenaardse planeet which means extraterrestrial planet. So after the 70s only in the late 80s the first reasonably convincing discoveries were made of exoplanets. But people were still skeptical in the late 80s and the beginning of the 90s. Until 1992, then there was a discovery by (Aleksander) Wolszczan and (Dale) Frail of a planet around a dead star so-called pulsar with a planet, and the field of extra-solar planet research it really kicked off just after 1995 when they discovered a Jupiter-sized planet around a sun-like star by the team (Michel) Mayor and (Didier) Queloz and since then many thousands of exoplanets have been discovered using various different methods: the radial velocity method, the planetary transit technique, and microlensing, for instance. And up to 2004, exoplanets had only been discovered with these indirect methods, and mostly they discovered planets very close to their stars. So only in 2004, they were able to discover the first exoplanet directly in an orbit around a “Brown Dwarf”. And a brown dwarf, it's such a small star that it doesn't even have nuclear fusion. So because it was so difficult to see it around the regular star the first objects they found directly image planets around was a brown dwarf. And since then only a few dozen exoplanets have been directly imaged, so it's quite challenging.

What challenges needed to be solved in order to photograph exoplanets?

So there are multiple challenges when it comes to directly imaging exoplanets and that's also one of the reasons why it took so long after the first discovery before they they could photograph one directly. The first challenge is that you need to separate the starlight physically from the planet light, so they are seen as two distinct objects instead of just one blurred together object. And then secondly you need to correct the turbulence of earth's atmosphere that would otherwise distort your images when you're observing using ground-based telescopes. And thirdly, you need to suppress the starlight because your starlight can very easily overwhelm the light that you can get from the planet. So it would be ideal if you could somehow switch off the star so you can only get the light from the planet. But yeah we have some we have to use some clever optical tricks to do this. And lastly when you have removed your star light you still need to clean up your images by using all kinds of software techniques to get rid of this last remaining starlight and really reveal the planet.

What is your research interest?

So i did my PhD on coronagraphs which is exactly the method you suppress starlight with. I'm interested in all kinds of instrumental approaches to help support the discovery and the detection of these extrasolar planets.

Very interesting! Any technical terms we need to know before going into further details? …diffraction limits? “adaptive optics”?

yeah so, here for instance, to separate the starlight from planet light, we have to deal with the physical limits of an optical system, and this is called the “diffraction limit”. So the diffraction limit is the smallest angular scale that we can see with any optical system whether it's your eyes or a telescope and for the biggest telescopes we have right now if you're looking at the nearest stars this diffraction limit can easily be the same angular size as the size that we see; well the size of the planetary system that we see. So if you want to reduce the size of this diffraction limit we have to build even bigger telescopes, even bigger than the like the 10-meter-wide telescopes that we're building nowadays. Now the other thing the to correct this turbulence of the earth's atmosphere and the twinkling of the stars that you see at night. We use something called an “adaptive optic” system and it consists out of three components. First of all, a deformable mirror, secondly a wavefront sensor, and thirdly, a control system like an advanced computer, and together these three components they very rapidly measure the distortion that the earth's atmosphere -the turbulence in the earth's atmosphere- induces in our stars and in our planet image and then it uses a deformable mirror like a very thin mirror with all kinds of fingers on the back to [push on] and the mirror can therefore assume any shape and then they can correct the shape of the light a thousand times per second and only with this correction we can reach the diffraction limit from the ground. But now this actually almost routinely occurs in the major telescopes around the world and these telescopes can actually obtain sharper images than even the Hubble Space Telescope. So yeah and to cover these coronagraphs -- these starlight-suppressing devices that i mentioned that i worked on in the past, so they are there to reduce the amount of starlight at the location of the planet, so if we are looking for earth-like planets around a star like our sun then we need to be able to overcome a contrast difference of 10 billion to one. And the most intuitive form of a coronagraph it's called a Lyot coronagraph which is almost like sticking your arm out and putting your thumb on the star to be able to see the planet! And lastly, as i already said, astronomers use a lot of software techniques and a lot of the progress in the last 10 years has been made in that area. So a lot of new discoveries of planets, even around stars that we knew already had planets, they come from these better software techniques and the easiest way to do this with a computer would be to take two images: one of a star that you think might have a planet, and another picture of another star nearby which might not have a planet. And if you subtract the two images then you're left with mostly the planetlight. So that's a very basic approach. So these four techniques simply explained, they are the basis of many of these discoveries.

Right, so what are the current status of the biggest telescopes?

Yeah, so of course we want to build bigger telescopes, not just to be able to gather more light so we can see fainter objects, but for direct imaging of exoplanets we really need the bigger telescopes to be able to resolve planets close to the stars. So to be able to say that there actually are two objects next to each other not just one big merged blob. Yes. And currently there are about three extremely large telescopes under development in the world. So, “extremely large” means it's like the next generation, about three to four times as big as the current record holder. And these three telescopes are called the “Giant Magellan Telescope”, “the 30 Meter Telescope” which both are about 25 to 30 meters. And then the third one is called “the Extremely Large Telescope” which will become 39 meters in diameter. And for two of these telescopes they're actually already building, they're building them. So in the coming five to ten years you will start to see more images of them being constructed and around 2025 2026 we should be able to use them. And Taiwan plays an important role in this 39 meter wide Extremely Large Telescope. So there's an instrument in development it's called METIS and it will do this direct imaging of exoplanets. So, which… I mean it will not only discover new planets but it will also be able to do a detailed characterization of the atmospheres of these planets. And even for the nearest stars this instrument and telescope are sensitive enough to discover Earth-like planets. Taiwan contributes both to the mechanical part of this instrument and also in the scientific build-up and Taiwan will sit in the front row when the first scientific results come in on these planets.

Really cool! Look forward to more news of your progress. Hopefully soon we will find a whole new world of better things waiting ahead. See you next time.

背景音樂由 audionautix.com 提供

唐朝詩人李白在「將進酒」中豪氣高歌：「黃河之水天上來」，敢問詩仙是否知道，天外之水都從何處來？

缺水令人愁，積水令人憂，水資源是民生大事，不僅如此，水還是科學家已知能用來判斷遙遠星球有無可能孕造出生命的重要指標，本集歡迎大家一起來多多認識：我們的水！

多年來用地面及太空望遠鏡詳細追蹤「星際水之旅」的天文學家 Daniel Harsono （漢字姓名：何英宏 ） ，在本集中為我們談「水」話題。

究極探討水在星際空間中不同條件下的不同分布量，科學一點一滴取得進展，從天文的光譜觀測獲知化學成分豐度，綜合天文物理的已知，目前所得的最新結論是，行星形成的過程可能很快。

最近Daniel 難能可貴的申請到競爭激烈的「韋伯太空望遠鏡」的觀測時間，到底他想用太空望遠鏡觀測什麼呢？他覺得那東西很重要的理由有哪些？請聽他的分享。

本集節目為英語。

逐字稿：

Welcome to Astronomy Podcast produced by Academia Sinica Institute of Astronomy and Astrophysics, I am Lauren Huang ~ So happy to have Dr. Daniel Harsono here with us today. Daniel is one of the guys who were awarded James Web Space Telescope time, or, the other way to put it, the time allows you to make observation using this very powerful space telescope, acronym JWST. A telescope people have been waiting for for 20 years. Totally, three projects submitted from Taiwan got the green light, and Daniel leads one of them. After graduated from the UCLA in America, Daniel moved to Netherlands and obtained master and PhD degrees from the Leiden University. Hi Daniel, is it right that Leiden is a world leading school especially famous for its astronomy department?

Very famous in terms of history(s), yes. Yes a lot of famous astronomers are from Leiden, but they have very famous law faculty and also physics department.

Right, we are going to talk about, again, the JWST telescope. Last time we interviewed Sascha Ziggers about the same topic, would you please tell us again what is this telescope aims to do?

So JWST is James Webb Space Telescope it is the next generation optical or infrared of after Hubble Space Telescope. So Hubble Space Telescopes maps the sky in the optical domain that's the same wavelength that human eyes can see but the James Webb Space Telescope will focus mostly in the infrared so that's the regions where human eyes cannot see and by moving to the infrared you can see cooler objects so much younger and much more distant than what Hubble can see. So with the James Webb Space Telescope, for example, you can study more of the first stars and the very distant universe and then also because James Webb is very sensitive you can try to see the dust features that are present in the infrared.

Right. By the way, which subjects were you best at? Math? Physics? Chemistry?

I think from my background it was mostly mathematics so yes it was mostly mathematics

And that helps a lot in doing astronomical research?

For astronomy what the interest me the most was black holes and neutron stars so that was the reason why i went to UCLA but in the end I did not study them. But yes! Math is helped a lot but i think in the end i was much better at doing programming rather than pure mathematics.

You've won the JWST observation time at the first cycle right? are you doing a "mapping" related project?

Yeah that's correct. Our proposal is to map so-called jet launching region. This is the region where young protostars try to release a lot of its energy so when a young star born a lot of material is ejected from the young star and this is in form of a jet or an outlaw and previous instruments have difficulties in mapping this hot region near the young star where the material is launched so ALMA does not actually gives you a really full picture of the jet launching region. So this is where uh JWST will try to solve that problem.

Why do you think your proposal got selected? can you guess?

I think I'll try to speculate here but what we're trying to do with the project is that we have a lot of data from ALMA from HST also follow-ups high spectral resolution spectra in the optical and near infrared where we know all the molecules that are present in that region and what JWST can do is the mapping so we can try to see where those molecules are located. So now we just know that what the line profile or how that the emission is looks like in terms of velocity space does it go fast or slow. In addition, by mapping it you know where it is but especially from the center, so then you know where it is fast whether it's close to the center or it's actually fast further away. So it's the mapping is from the IFU instrument so the NIRSPEC (it is the name of the instrument) has an IFU, an Integral Field Unit um yeah so by in that case what you get is spatially and spectrally resolved data so you get the spectral cube so you know your xy and spatially resolved down to 0.1 arc seconds so that's roughly 14 au or so. But then you also have the third component which is the velocity so you can you have the full data set.

All right! So that will help us understand the region much better.

Yep, right.

I know you are also involved in that water review recently published by Leiden university right, so can you tell us about the "Water Journey" story that group of astronomers were working on?

Yeah um so the Herschel (Telescope) this uh the Water Review is based on the previous far infrared space telescope which is the Herschel Space Observatory, it is no longer active. Um so what Herschel can do is that it can it was targeting a lot of the water emissions -- the spectra of the fingerprint of water -- that is actually in space. The main aim of the program uh the Herschel Program that's called WISH so Water and Star forming regions with Herschel, to map and to detect water emission from early stages of star formation down to the later stage of planet the late stage of star and planet formation so what you want to know is how water is being transported from the molecular cloud where stars are born down to the region where the planets are actually being formed so with Herschel it is the only way that can probe this really cold water emission that you cannot do from the ground. So we need another telescope like Herschel in order to do this better, and there's no other plan for the next Herschel in the near future. So the Water Review tells you a lot of the improvement over the last time that we know how the water is being transported during star and planet formation.

Unfortunately the biggest surprise was that water is not very abundant than previously thought.

Oh? it is not?

Right, the previous infrared telescope that was Spitzer (Telescope). Spitzer probe not the water – well -- it probes the water emission from the very inner regions of the planet forming disks and it also probed the ice features so dust grains have ices on them and spitzer revealed that water is the most abundant in the ice in the solid form that is consistent with the theory. In that case then when this a lot of water ice is being transported to the inner regions it should be supplemented onto the gas phase and we should see a lot of it in the emission with Herschel… that was not the case…

So a lot of the water emission that we see from Herschel is in the outflow, so in the “jet” that we try to map now with JWST fore example. Right. To understand where it's actually coming from… so Herschel is a single dish and you cannot map anything with a single dish instrument except uh for the PACS instrument which gives you different water excitation. So except the Herschel has a number of instruments that can cover the cold water so that's where the water that is being sublimated through energetic photons so that's different water than the inner hot water so there are different water reservoirs in star light information that you tried you have to try to cover them all so there's the jets and outflows and then the inner hot that's where the water gas, water has been sublimated from the ice grains, and also the cold water that is being released onto the gas phase by cosmic rays and energetic photons. So those parts that are not in the outflows are actually lower than expected than before. So what we think is that, the consensus from the water review: it seems that planet formation actually happens very quickly and the way to decrease the amount of water vapor so it doesn't emit is to lock them up in larger dust grains or in very early uh planetesimal (small planetoids like vesta) so this is the origin where the planets are actually forming from.

So the water review discussed that of how the water transported from the molecular cloud, to planet forming regions. It discusses whether or not the water fraction is the same for the earth so trying to understand how old is the water for example so by looking at the spins of water because water has spin states between ortho and para so that's complicated for spectra but the the ortho and para spins is related to the temperature with when it was solidified onto the dust grain and that seems to be consistent with the solar system so it's it also shows that the water on the earth forms very very early before the star is actually important so that's uh one part of the wish program that tries to tackle how early the water is actually formed and then the last part is the complicated story of oxygen right the oxygen is uh it's an element that is crucial for life on earth that we know it um the major carrier of oxygen is of course water in terms of astrochemistry so in terms of chemistry in space but then the crucial component is that we don't know where the oxygen goes so this is called the "unidentified oxygen carriers" so if you sum up all the oxygen carriers it's not exactly the same as what you think the ratios should be but i don't work in this so i don't know the details as much so yes that's one part of the other story that water review has.

Are these two projects related uh in terms of your research interest?

yeah i think the what my research centers is uh is trying to understand how star sun star planet formation goes in terms of their chemical composition and also how to rebuild the physics from those chemical abundances a lot of the oxygen actually is also is known on earth so from the metals and from the oxygen from the soil for example so you can see the oxidation state of the different minerals on earth and you can trace this back to the meteorites and that those meteorites actually tells you what what the physical conditions uh in the past when the planet earth was actually forming and this is one way to connect astronomy and our astrochemistry in general with planetary science and geochemistry. Trying to connect how the earth was born from all these uh different composition that you see in astronomical observations. I don't work directly for the life signatures component but of course water is part of that and only a small part of the chain of our complex life but indeed my collaborators are much more uh much more knowledgeable about this area than i am of course in terms of complex organics that's their main focus. So a lot of complex organics now is seen with ALMA, for example, and you saw them already in the past in the ices. So these complex organics to deform on the dust grains for the most part especially for the oxygen carriers. So yeah it is related.

What is the change that you think your result is going to bring to the non-astronomers? maybe not immediately, but if in 50 years?

um yeah that's a very good questions and i think we will have better understanding of how the earth was actually formed. And also the crucial items how did life actually start on earth. Whether this complex organics and all this complexity chemical compounds are actually set in the early stages of star formations so a lot of the chemistry already happened before the star was actually born, or a lot of processes actually occurred during the planet formation, or it's actually when after the earth was born and then somehow meteorite the asteroids bring it to here, so, we don't know. So i hope that my research can actually contribute the piece to that story by placing the different elements and molecules and see where actually where and when the complexity happens

Right, so, in our wildest imagination, the world with or without your science, is there going to be a difference? what do you think?

That's difficult to answer um I think the cutting edge that our research is going to bring is to confirm or rather to compare the critical models with observations so not only bringing only observations but also bringing the experimental works to try to confirm whether certain element ratios or some certain isotopes actually consistent with the story that astronomy brings. So this is mostly from the lab experiments such as the one that we're doing in Nan-gang（指位於南港院區的中研院地科所）to see the isotope fractions of different elements to see whether or not there are different reservoirs that are consistent between the astronomy side and planetary science side. We also have models of how the star planet forms for example and hopefully those with the full chemical models to try to explain how early certain elements can be so-cold, can be locked up by this very early planet-forming materials, for example. The only way that certain elements can be excluded from ongoing like from further chemical reactions is to lock them up in larger larger bodies. So this is one of the ways to trace how early planet formation starts and whether or not the formation sequence are consistent with the between the models and the observations.

We focus on the fundamentals and we try to see whether at least a coherent story of how materials actually being transported to earth or any earth-like planets.

You love to do science?

I think science is a way to answer a lot of questions so we have a lot of questions and by doing a lot of scientific uh experiments within astronomy or even in laboratories uh or astronomical observations and lab experiments we can try to answer questions.

That's great.

背景音樂由 audionautix.com 提供

能源及環保問題，是近來最夯的議題，本集中，中央研究院天文所的陳英同博士以三個正在進行的科學研究（太陽能、太空採礦、核融合發電）來介紹，由天文學所衍生出來的科學，如何可以商業應用，以期達到創造能源及減少污染。

背景音樂由Jamendo提供。

逐字稿：

各位好，您現在所收聽的是由中央研究院天文所所製作的節目：天文播客。

我們今天邀請到天文所的陳英同陳博士，來跟我們談一下，簡談如何運用現代的天文學，創造或節省更多的能源，歡迎陳博士。

其實天文學是一個非常古老的科學，物理在最之前也是從天文學開始演進過來。天文學這麽古老的科學如果在現代，由其大家對能源都很關心的當下，能夠提供一些幫助。

我們今天其實在時間有限的條件底下，我們簡談主要三樣東西就好了。

第一個是太陽能，第二個是近幾年非常有趣的一個行業，叫太空採礦，第三個是也非常敏感的發電方式，叫核發電。

我們先講第一個太陽能發電的部份。

太陽能在我們太陽系裡面的能源，以我們的壽命來講是取之不盡、用之不竭。

那它最主要的來源，當然是來自於太陽的輻射，那其實跟等一下要講的核能有很大的關係，只是目前在地球上所用的太陽能，是想辦法收集一些電磁波轉換成能源。

太陽能發展經很長一段時間了，已經你說從最早開始有電，直到做出來的目前商用非常普及的階段，已經經歷了100多年了，最早的應用就是在太空人造衛星的部分。因為太空人造衛星需要一些固定的充電的機制，那太陽能因為在太空中，其實沒有什麼遮蔽物，所以是一個最好的方式。

當然是除了帶上去的核能之外的最好的方式。

那我們先不要講說的很先進的，先講很普級的部份，天文其在這部分的幫助其實蠻大的，其實我們都知道太陽東升西落每天、每個小時、每分鐘都在不一樣的地點，其實你太陽能板如何調整到一個對的位置去接收太陽能，就變成一個很重要的議題。

雖然它需要相對應比較多的成本，可是我們只要投入這些成本之後，我們每一天，只要你是一個固定式，像台灣中南部非常常見的太陽能板，那是固定式的太陽能板，跟移動式的太陽能板的話，每一天接受到的能源，那可能可以差到一倍。

那這部分當然需要更多的就是研究讓整個成本降低之後，不管是製造的材質啊、或者是整個機構後面設計，在天文方面是可以提供很好的幫助。

那第二個部分就是講太空採礦。

那我們都知道目前不管是台灣或者全世界，在用電上面，工業用電其實佔了將近一半的比例，其實是非常非常的高。

那當然有人提到說，工業的污染降低或者能夠提供一些能源，想辦法製造更多能源給工業用，這些都是有種在挖東牆補西牆的概念。

其實太空採礦是做太陽系研究，當初算是意想不到的一個議題，我們後來發現在太陽系裡面有很多小行星存在很多礦物，包含碳、鐵、一些稀土元素，比地球上來講的話，開採相對的簡單不少。

當然有一些技術的限制，因為在太空中，跟我們現在技術比較算是新的技術，是有待開發的部份。但現在其實美國已經存在是3間、4間以上的公司，正在朝這個地方邁進。

為什麼這個太空採礦的項目對於地球上的能源有蠻大的關係度，假如我們能夠把這些重工業移到太空中，那太空中可以用大型太陽能板直接供電，沒什麼遮蔽物、沒有東升西落的問題，所以只要太陽能板不壞掉的話，工業用電上是沒有什麼太大的問題。

我們能夠把這些耗能的移到太空中的話，其實講起來有些弔詭就是對地球污染也減少了，對地球上的耗電也減少了，所以這個目前是歐美，歐洲也有、美國也有新興的公司，都不斷的在投入研究。其中蠻多的成員就是天文學家，一些研究軌道、研究地質的學家在這些公司裡面。

第三個講到的就是核能發電的部分，今天我講的可能跟我們現在目前在商用的核能發電不太一樣。現在最讓大家所詬病的，就是核能發電就是他的核廢料的問題，因為它有放射性，這是一個目前沒有解的一種發電方式。

目前還沒有商用，但是目前大家其實多少有在新聞上聽到就是核融合發電。核融合發電的機制跟太陽系裡面最大的能源發射體：太陽，幾乎是一模一樣的。

核融合發電已經研發很多好幾種，只要給的原料對的話，基本上是不會有放射性的核廢料出現。

但是我們看新聞說什麼國中生、高中生自己在家裡做出一個核融合機構，還有你聽到所有包含中國的研究、歐洲的研究機構，目前都是限制所投入的電遠遠大於發出來的電，雖然核融合成功，但這不叫發電，這是在燒電而已。

未來，在歐洲，將近超過數10個國家投入資源人力，在歐洲的法國目前建立最大的核融合發電，目前預計2025年可以開始進行一些電漿的實驗，可以把核融合限制在一個範圍裡面，然後持續不斷的核融合，這樣我們就可以模擬在地球上有一個小太陽，這個太陽會不斷的發電。

我要強調一下，就是你投入的電，要小於你發出來的電，就是這樣才叫真正的發電。

我們其實蠻期待這件事真的在不久的未來，2025年或者推遲到2030年，都是一個可預期的將來。這些東西其實最基本還是在原始的天文學上可遇見，如恆星怎麼樣發光發熱，我們希望運用這些已知的天文跟物理知識，對於未來一些能源界有一些很大的幫助。

那兩個問題請教，

台灣目前有公司參與太空挖礦嗎？

台灣目前沒有沒有這方面的公司，其實算是近十幾年、十幾年不太可能成本回收的行業，也算是一個新領域。目前我們對於小行星的認知來講，上面的物質的確是滿期待的是非常相近的。技術上的克服，隨著近幾年的太空發射、太空技術的演進，我們覺得是滿可以期待的。

之前看電影，是說到小行星上不容易，必須有一些特別的技術？

對，我的成長過程中，那樣的電影已經是二十幾年前的，在這十幾年來的技術發展非常快速，就這樣這一、兩年內其實就有不少的人造衛星登陸小行星，要採一些物質回來。他們主要的研究的課題是：太陽系的形成機制或者地球的形成，這些研究的經歷，甚至研究的內容都可以對我們太空產業有蠻大的幫助，所以說這十幾二十年來是滿值得期待。

剛提到核融合發電是沒有核廢料的問題？核融合發電已經研究了好幾代、演進了好幾代，其實還沒有真正的成功，在初期的核融合發電的材料的部分，初期部份還是會有核廢料的出現。在大家研究的階段，有研究其它可以替代性的核原料，放進核融合發電場，這樣到最後的產物，是不具有放射性的核廢料產生。這是說為什麼大家都很期待，且將近二、三十個國家都投入人力、投入錢，想辦法把這件事真的做出來。

希望我們未來會越來越好，謝謝陳博士，以上就是本次節目的全部內容，謝謝收聽。

本集的核心問題，不知道你有沒有想過？

怎樣在一片漆黑的宇宙裡確認一個黑黑的東西存在呢？

本集請到中研院天文所助研究員陳建州，簡單解釋一下「怎麼知道那裏有黑洞」的三種辦法。

投入天文研究也講究入場時機，陳建州的物理系是在台灣台大念的，後來去夏威夷，英國，德國，從事一種全地球人都覺得好浪漫的工作：看星星！（＝研究天文），主要領域在星系方面。

目前行情看好的是什麼研究呢？難不成……就是黑洞？

陳老師爽朗分享他的生涯選擇之道

快速瀏覽內容：

• (01:28) - 先講一下，到底什麼是黑洞，他黑的原因是什麼

• (02:31) - 「到黑洞家門口拜訪以求確認他在不在家」…並非不可能，但是……

• (03:07) - 哪一天真的可以到黑洞附近的話，會看到這景象

• (03:21) - 證明那邊是有黑洞的存在的第一種方式是，觀察黑洞附近恆星的繞行軌道

• (04:22) - 但這只能來看銀河系中心的黑洞

• (04:33) - 介紹「重力波」，是第二種辦法

• (05:46) - 第三種辦法是靠黑洞附近的熱氣體

• (06:15) - 黑洞附近看起來會好像一個甜甜圈

• (07:15) - 地球一樣大的望遠鏡…

• (07:26) - 有機會得諾貝爾物理獎，不是夢

• (08:22) - 現在投資是可以的

完整逐字稿放在：https://sites.google.com/asiaa.sinica.edu.tw/podcast/2

背景音樂由 audionautix.com 提供

附註：

想看像星際效應電影裡那個黑洞轉圈圈的動畫嗎？NASA有請專門的人做好了，以超級電腦模擬黑洞的360度gif影片，請參考NASA的網站：https://svs.gsfc.nasa.gov/13326

想更多認識中研院天文所參與黑洞觀測用的是哪些望遠鏡嗎？臺灣對史上首張黑洞影像貢獻了什麼 和 十問格陵蘭 這兩個小網頁可以滿足你的小好奇

TC 聊黑洞，也有英文版：How do you know there is a black hole? 有更多細節和投影片！感謝 TC！

ＸＯ醬我聽過，exomoon是啥？

原來，不只太陽系的行星有衛星，太陽系外的行星也有衛星！

並且更難找，因為非常小！

但滿有可能蘊藏外星生命！

當然得好好找一找。

本集特別邀請全世界第一位"有可能"發現了太陽系外月亮的天文學家 Alex Teachey 博士談談這麼獨特的發現。

Alex 從2020年起在中研院天文所擔任博士後研究，正式英文 title 比其他博士後研究還多出了一個 Distinguished 的字眼，可見他的資歷非常難得。

本集內容講英語

music by audionautix.com

Transcription 逐字稿：

Welcome to the astronomy podcast produced by Academia Sinica Institute of Astronomy and Astrophysics, Episode One. I'm today's show host Lauren Huang. Very happy to invite a "superb" PostDoc Fellow Alex Teachey to tell us about "Discover Exomoons". Hi, Alex! Hello thanks for having me. Did I pronounce your name correctly? um, Alex Teachey, that's right! So Alex, tell us about the work that you do in Academia Sinica.

Yeah so what I do is I work on finding these things called exomoon. And these are moons orbiting Exoplanets. At this point astronomers over the last a few decades have discovered something like a few thousand exoplanet - these are planets orbiting other stars outside of our solar. So that's really been amazing work. But now we're trying to go one step farther and find the Moon of those planets. It's very hard to do, Not very many people working on it, but I feel very fortunate opportunity do this work, because I think it's very exciting looking for these moons.

Why do you care about these exomoons? Yeah I think these moons are potentially really amazing places if you look at the moons in our solar system, of course we have our own moon but there are many other moons in the solar system especially around Jupiter and Saturn and Uranus and Neptune, these are amazing places that, you know, if they orbited the Sun rather than orbiting one of these planets we probably all would have grown up knowing their names. Because they're just as fascinating places as Mercury and Venus, Mars, the planets we're familiar with. At least moons are really gorgeous and very diverse very different from one another. You can just take a look at these pictures of these moons and see how different they are from one another. and maybe I'll tell you a little bit more about those moans but the moons are fascinating and so we think that You know moons in other planetary systems stand to be just as amazing places and just as worthy of discovery in and getting to know them. We think for example that these moons could tell us something about how those planetary system formed, and how they evolved. And, Actually hold a mirror up to our own solar system. Whenever we're looking At these other planetary system, we're really learning more about ourselves as well. Where do we fit in to the Galaxy and what ways are we ordinary and in what ways are we not ordinary. In what ways are we actually maybe quite unusual. This is very much an open question.

How many ways to get moons formed? Yeah but we think there's three main pathways for forming moons. The first way is the way most astronomers think we got our own Moon, And that is through an impact. So what we think happened was that a giant protoplanets maybe the size of Mars slammed into the early Earth this is something 4.5 billion years ago.

This impact occurred and a whole bunch of material was blown off of the surface of the Earth and eventually coalesced and formed our moon Now the second way is through Capture. Sort of a gravitational capture of this Moon. Do you have what is originally a free-floating planet, or small object floating around by itself and then is captured gravitationally by the more massive Planet and then it Becomes a moon we think for example the largest moon of Neptune, it's called Triton. We think that it became a moon in this way that it is captured from the Kuiper Belt. And then finally we see around Jupiter and Saturn for example evidence that these moons formed in disk of material swirling around the planet. Again very early on in its formation very much the way that a solar system is formed what do you have a star in the middle and you have a disk of material in the planets form out of that disc material the same thing seems to happen around planets you have a disc around the plant. The moons are formed out of that material. So that's the three major ways that you get moons.

It seems there's a very interesting possibility that maybe there's life on those exomoons. What do you think we should do about that? Well it is a very exciting possibility we think that even some moons in our own solar system are attractive places to look, in the search for life. The reason that we think that is, for one thing, several of these moons have an abundance of water . In some cases even liquid water underneath and icy surface. So you got a lot of water. Not only that. You also have internal heat we see in several moons of our own solar system. This material spewing from the surface like a volcano or a cryovolcano like a geyser. We see this on for example, IO, and Enceladus and Europa, these moons around Jupiter and Saturn they have internal heat and they have in some cases liquid water. And then we see around another Moon, Titan, orbiting Saturn, the abundance of organic molecules, Carbon-based molecules like methane and ethane, which is sort of suggesting that maybe you've got the building blocks of life. So we've got liquid water, we've got internal heat, we've got the raw materials for life, it looks like some of these certainly could be interesting places to look for life. And so again we think Exomoons maybe just is great places to look for life. Maybe even better places to look for life. It's a long way down the line whether or not we'll actually be able to find life around these moons. But it's certainly an exciting possibility.

How do you look for those moons? Take a picture and what else?

Well we might be able to take pictures, not quite yet, but in the next 10 or 20 years or so, our Imaging might be getting good enough that we can actually See may be indirect evidence of moons through these images. But really What I argue is the Best approach to finding these moons right now is to look for what we called transits. This is when the planet passes in front of the star, from our point of view, so with just the right geometry we're looking at the system Edge on, And so we see the planet pass in front of the star and it blocked out a little bit of the starlight. Now this is 1% or Tenth of a percent or maybe even a Hundreds of a percent of the Starlight, very small amount of Starlight that we're missing

We can in fact measure this and this is the way that we have discovered thousands of planets. So we see planet passing in front of the star, we know that this is a great technique for finding planet . You can imagine it is a planet now has a moon then the planet will pass in front of the store and so will the moon and they will both block out. And so that is the signal that we look for. And it turns out that with this particular kind of data set, we can also see the gravitational influence of these moons on their host planet, they're tugging on the planet gravitationally. And so the planet will wobble and actually the duration of these transit events will change as well. So basically these are three independent signals all in the single dataset. And so it It's really at this point we think the best way of going about finding these moons.

Right! I happen to know that You're the first people who finds the first compelling evidence for moon outside our solar system. Tell us about that! Well it's a controversial claim. Not everyone believes that this Moon is really there . And we're not even entirely convinced it's there. but we do think that the evidence is certainly intriguing and worth the further work. This was a few years ago. We identified Transit. Three transits of this planet called Kepler 1625b. We saw this in Kepler data. Kepler was a phenomenal space-based Telescope mission that has been responsible for so many of these planetary discoveries. We saw three transits to this planet. It looked like maybe there was a moon there. But it wasn't really conclusive it was exciting but not quite enough time so we propose to observe this target again with the Hubble Space Telescope. And we were awarded that time we got something like 40 hours with the Hubble Space Telescope to observe this target and then after we got that day don't we spent about a year working on this data trying to not to see if the moon was there but really Try to disprove that the moon was there. Try to see how many different ways we could come up to say well maybe it's not a moon maybe it's something else. Maybe it's something a little less exotic And you know we spend a lot of time with this and we emerged from this whole process saying well we're not entirely sure it's there but everything is kind of looking convincing that it is there. And so we published this paper and again it's potentially the first transiting exomoon ever found. some people believe it's some people don't stand so that's the way science works. And and we need to take a little more take you know a little more work on this particular system but it was pretty cool it was gratifying experience.

Sounds exciting. Perfect. Great. Well, we learned a lot more about Exomoons today. If there are more news from Alex, we sure will bring him back to the show. So thanks a lot, Alex. Thank you very much, my pleasure.