The Supermassive Podcast - 14: A Star Is Born

Episode Date: February 26, 2021

This month, Izzie and Dr Becky are shining a light on the first stars in the Universe. When did they form? And could any still exist today? Plus, they explore the life of Cecelia Payne Gaposchkin, the astrophysicist who discovered the structure of stars, and Dr Robert Massey joins them to discuss the latest NASA rover on Mars.  With special thanks to Dr Emma Chapman from Imperial College London, author of First Light, and Donovan Moore, author of What Stars Are Made Of: The Life of Cecilia Payne-Gaposchkin. The Supermassive Podcast is a Boffin Media Production by Izzie Clarke and Richard Hollingham. 

We can only calculate an age, but, you know, individual stars in our own milky way. With the first stars, you don't have galaxies, you've got nothing. This is a very empty, warring universe. Could the death of a first star have created something like the first supermassive black hole? Hello and welcome to the Supermassive podcast from the Royal Astronomical Society, with me, science journalist Izzy Clark, and with astrophysicist Dr Becky Smethurst. Last month, we discussed the Big Bang. So it only felt right that this month we explore the first stars in our universe.

And thank you for the suggestion, Mark France on Twitter, that if we're talking about first stars, then we should do an entire episode on the true first star, Miss Kylie Minogue. I do think that's probably something for another time. Right, look, Mark, we've got enough debate in the scientific community without adding who is the first superstar into the mix, all right? So I don't think that episode is ever going to happen.

But as always, we're joined by Dr. Robert Massey, the Deputy Director of the Royal Astronomical Society. Yes, we are going to be talking about the first stars, but we're also going to be talking about Mars later. And I know that you've been Mars gazing from your own home. And I think it's quite amazing that, you know, we're here on Earth. You can look up and you can see Mars. And not only that, but the idea that we've now got two active rovers and a lander on Mars. I just think it's incredible.

It is, isn't it? I mean, Mars is such a well-explored planet. And, you know, obviously there's so much more to find as well. But the fact we've had rovers driving on it for now 24 years. The first one was Sojourner connected to the Pathfinder mission right back in 1997. You had the amazing Spirit and Opportunity that landed in 2004. And Opportunity ran for 14 years, drove a total of about 40 kilometers around the planet.

Curiosity got there in 2011 and has been doing extraordinary stuff, doing things like looking at what appeared to be dried up riverbeds. And now we've got Perseverance. And I think anybody who saw the footage of the landing must have been seriously impressed. I mean, the way that the parachute comes out, the first time all this stuff has been built, the heat shield falls off and it kicks up dust as it lands nicely. It reminds me a bit of the Apollo footage where you see all the moon dust being kicked around.

So it really made it feel as though it was this planet that humans could visit, albeit that may be a long way off. But you look and you think, yeah, this is a place we can stroll around. You can imagine picking up rocks in that in that red desert and you're right it's great to be able to see it in the sky still as well it's a lot fainter than it was last autumn but it is still there and it's not a hard thing to take pictures of and i think that's what resonated with me so much was that yeah okay we've been going to mars now for 20 odd years and i think that's why the images that it sent back they looked really alien yet at the same time so familiar in an odd way and I think it is just

because we've been going for so long now and it's funny how a lot of people took for granted that you know Perseverance Percy would just land and it wasn't a given right so cheers for that Robert we'll be catching up with you later in the show for some more stargazing and some more Mars chat as well. So let's get to it. After the Big Bang, we have lots of hydrogen and helium excitedly bumping about the universe. And over time, everything expands and it calms down a little bit and we sink into what we call the cosmic dark ages.

That's around 400,000 years after the Big Bang. So when did the first stars form? It was a question that I put to Dr Emma Chapman from Imperial College London. We think around 180 million years after the Big Bang, this gas starts to come together in big enough clumps that we ignite fusion. And so when this happens, you suddenly get a twinkly light in the sky, then you get another twinkly light and another twinkly light. And this is why I love this field, because it's such a beautiful idea. The idea that the universe just lights up all over at the same time-ish, one by one, I think it's incredible. And so yes, we think this happens around, let's say 200 million years after the Big Bang.

So it takes some time. But in the grand scheme of things, that's not really much. So what is driving those, the twinkly lights to begin, I suppose? After the Big Bang, you've got this web of dark matter all over the universe. And it really does just look like a web, which has a really strong gravitational pull. So over these 200 million years, it gathers more and more hydrogen, and you eventually get this fusion. It's the same kind of process as form stars in our galaxy, is that you get gravitational attraction and these stars come together. But I suppose now you've already got the galaxies, whereas with first stars you don't have galaxies you've got

nothing this is a very empty boring universe and so you really just get these these first stars flashing to life now we used to think that they were alone but actually only in the last five ten years have we had good enough simulations to realize that actually we think these stars formed with siblings so in binaries in we've even got systems that have got 100 of these first stars in, but crucially they're not galaxies. That's so interesting. Do we know why they would form sort of with siblings in these pairs or is there even more than say, you know, two?

Would there be like a group? Yeah, definitely. So we really do think there are groups of these first stars it's a really good term to call them actually instead of a galaxy it's a group of stars and what's happening is that when you have a gas cloud that collapses it forms what's called an accretion disk so that's just a disk of matter and what happens is that matter slowly falls towards the center and you can imagine it kind of like as a vinyl record, a needle point on a vinyl record, slowly spinning round to the centre. That's

exactly what's happening with this gas cloud. We've got atoms of hydrogen slowly making their way to the middle. And within that accretion disk, we've basically got kind of local whirlpools of turbulence. And so what happens is the disk fragments. And so while you've got this really massive first star, we're talking maybe 100 solar masses, even larger, right at the centre, around it, we can get smaller sibling stars forming. Wow. And I'm glad that you mentioned that because I'd like to talk about their appearance. What did these first stars look like in terms of what was their makeup? How big were they? Do we have that information? Yeah, we do.

So that's what's so fascinating about these stars is that they aren't just kind of an early edition of the sun. They're actually an almost possibly completely extinct species. They're completely different. You cannot form them in the modern universe anymore. And that's because by definition, these first stars are made entirely of hydrogen and helium, maybe a smidgen of lithium, because that's what constituted the early universe. That's all there was in terms of normal matter. And so when these stars formed, they just had hydrogen and helium in them now what that means is that they cannot cool down as efficiently so when you've got metals what we call heavier elements and helium we call

them metals because we're astrophysicists and we round up the periodic table when you don't have metals stuff can't cool down as much and so it can't shrink as much And so these first stars were very massive. They were 100 times-ish the mass of the sun, but probably only a few times the radius. So they're quite a lot denser. They're very, very hot. So they probably have been whitish, bluish. So they're very different. But these first stars were responsible for everything that's come after because in these fusion engines right at the centre they are forming these heavier metals that when these first stars die and they die very quickly then they spread all of their metals across the universe and they kind of pollute the universe so suddenly you've got metals everywhere so these are very very early editions

of stars that you just can't find anymore. You certainly can't make them anymore. Yeah, so it is quite literally like live fast, die young. So absolutely. How do we categorise these first stars compared to, you know, stars that we have today? Yeah, well, I've been using the term metal free a lot, because I think it just invokes what they're all about. But we also call these stars population population three and that falls into a category system that we use for all the stars around us so we started with our sun it's really close it's really easy to look at and so we called that population one nice young star and then when we started to see older stars with less metals in we called those population two and And then around the 70s,

80s, somebody was sitting in their office and went, hang on a minute, if we go a little further back and we have stars that have no metals in, ah, let's call them population three. And so it's a bit of a weird turnaround of what you would expect them to be called, but it just reflects the history of our understanding of stars. I know this might sound like a ridiculous question, but is there any chance that first stars could still exist today? Yes. So I can categorically say yes there. And it's a really exciting answer. And this is because we've mentioned a few times that these first stars are really massive and they died young. But we also mentioned that there are some sibling stars and these sibling stars form at much lower mass and when you have a lower mass star it lives a lot longer

so our solar mass star is our sun that lasts around nine billion years if you have a star about 80 percent the mass of the sun that could could live 13 billion years. So that could be hanging around our local neighbourhood, our local Milky Way now. And there are lots of scientists, astrophysicists looking for them right now. And we call these guys stellar archaeologists. I love that. I absolutely love that. It's pretty cool because when I was a kid, I wanted to be an Egyptologist, I wanted to be an archaeologist. And then I switched to all this physics and astrophysics and I've still managed to make it about archaeology

and digging up these stars. And so they're looking for them right now. And the way they're looking for them is by looking for the light that these stars emit and seeing how many metals, how much metals these stars have in them. Because when you have metals in a star, they basically form gaps in the spectra, in the light that's coming from these stars.

And so if you can find a star that doesn't have gaps, then that means that it doesn't contain metals and that it is a first star. So they're doing this right now. They're digging away. We've not found one yet, but we have found one that has so few metals in that we actually think it's a first descendant. So a second star, if you will. So we're really, really close. I've got a lot of hope for this field, but it is hard. There's a lot of stars in the Milky Way. They've basically got to go through them one by one. They basically got to go through them one by one. I think they're going to be there for some time.

That was Dr Emma Chapman from Imperial College London. And if you want to find out more about the first stars, Emma has just written an amazing book. It's called First Light, and it's all about switching on stars at the dawn of time. So, Becky, I love this idea that astronomers are trying to, you know, Becky, I love this idea that astronomers are trying to, you know, dust away those heavy metals and see if there's a first star lurking in our universe. But do we know what the oldest star in our universe is? Well, yes, kind of. And then also no at the same time.

Right. So there's two things at play here. Right. So the first one is how we actually even calculate star ages and then the second is that you know what are the stars we can actually calculate an age for because we can only calculate an age for you know individual stars in our own milky way you know we can't resolve individual stars in other galaxies or even on the other side of the milky way that are very distant from the sun so we can only find the oldest star near to us in our sort of own solar neighborhood if you will and we do know which one that is it's the one emma was just talking about actually it's the second generation star that's about 200 light years away or so and it's called hd140283 and it's been dubbed yeah well it's been dubbed the Methuselah star as well because it is so old I think that's a reference from the bible I think but how do astronomers actually you know

study them and calculate the ages of these stars yeah so I mean we obviously observe them across all different wavelengths and get as much data we can about them so that we can essentially model what age they are so we need to know a few things you need to know the luminosity of the star so for that you need how bright it appears to you and then you need the distance to that star as well so you can then get what it's luminosity it's like actual brightness and because brighter stars obviously are much younger fainter stars are the more long-lived stars so if you can get the luminosity you know a lot about it then also you need what we call the spectrum of the star as well you need to split that light

into all of its component colors and wavelengths sort of like the fingerprint of what elements are actually in the star you know is it made of pure hydrogen and helium or has it got some of the heavier elements like oxygen and nitrogen and carbon and things like that then what we can do is model what light we expect to get from stars of different ages containing different materials as well. And then essentially we can say, okay, well, when we've observed a star, what's the best fit model we have for describing that? And therefore, what's the age of that model that describes it?

And so that's how we get the ages. So for Methuselah example, we do that and we get 14.46 billion years old. Hang on. But with an error. And this is the key thing, an error of 0.8 billion years. And I think I know what you were going to say there. Go on, Izzy. Yeah, because we say that our universe is younger than that.

What is it? 13.8 billion years old. Yeah, 13.8 billion years as opposed to 14.46. Yeah. So this is why people get very, very excited about this star because like, is it older than the universe itself? And it's like, well, no, of course it's not. Because first of all, like you have this big error on the estimate of the age of the star of almost a billion years either side. So it could be as low as 13.7 or it could be as high as 15.3 billion years, right?

Because there's just this huge error that comes from the fact that our models aren't perfect, right? There's always going to be some error in the models that we're not perfectly modeling what light we expect to get from stars, etc. Second of all, the estimates on our age of the universe as well are all over the place, right? One method says it's 13 and a half billion years old.

Another says it's 14 and a half billion years old. And they've also got huge errors on them too. So this star is not older than the universe, right? It's that we don't know things accurately enough to actually say what the exact age of this star. accurately enough to actually say what the exact age of this star. Our models of both the light that stars give out and our models of the entire universe to get at the universe's age are not accurate enough. And so this is, I'm going to say it now,

and I'm going to say it once, the Methuselah star is not older than the universe, but it is one of the oldest stars that we know of. Okay, we've got that clarified, cool. We know that these stars were massive they were really hot and that just makes me think that their deaths must have been really impressive as well so could the death of a first star have created something like the first black holes the first super massive black holes so perhaps maybe not the first black holes because there's some ideas that maybe primordial black holes are formed sort of from

the soup of material after the big bang these are really really tiny black holes that just come from these tiny little quantum fluctuations grouping you know bits of material together and they could still be around technically but they would be the first sort of massive black holes you know they're around about the size of stars maybe even up to you know a hundred times the mass of the sun so some people think that these first stars were so massive that they could have skipped supernova entirely and just directly collapsed down into a black hole and just gone what i've disappeared into a black hole see ya yeah and then also the once that's happened people think well could these actually be the sort of the seeds which over billions of years did grow into supermassive black holes you know that we

now find in the centers of galaxies right so perhaps not the first supermassive black holes but perhaps they were the sort of you know the things that became supermassive black holes eventually it's sort of you can't talk about the first stars without the first black holes. Or at least I can't. It's something that we often take for granted, that stars are mostly made up of hydrogen and helium. But this was only discovered in the early 20th century. Before that, people thought that stars were made of silicon and iron, you know, similar to what you would find in the Earth's crust. Now, the astrophysicist behind this discovery that stars were made of hydrogen was Cecilia Payne Kaposchkin. And to find out more,

we're joined by Donovan Moore, who has written a book about her life. Hi, Donovan. Now, why don't you start with just saying, who was Cecilia Payne Kaposchkin? Hi, Jonathan. Now, why don't you start with just saying, who was Cecilia Payne Kaposhkin? Right, Becky. Well, the short answer to that is Cecilia Payne is the most famous astronomer you've never heard of. She made one of the most fundamental discoveries in all of science. But she was told she was wrong by the very man who, four years after her discovery, proved that she was correct. So what do we know about Cecilia? Like, where was she from?

You know, what was she studying? How did she get to make such a huge fundamental discovery? Right. Well, for centuries, astronomers had been looking up through telescopes, if you will, to determine the composition of stars, what stars are made of. It turns out that they were looking the wrong way. Cecilia actually did what all those astronomers were trying to do by looking down. She was looking at spectrograms, which are glass plates etched by starlight.

She did this when she first arrived at the Harvard Observatory in 1925. Now, the reason she could do this was physics, and here's why. Before Harvard, she was a student at Cambridge University in the early 1920s, and it was a time when physics was being applied to all kinds of other disciplines. Ernest Rutherford was applying physics to chemistry, and Niels Bohr was applying physics to the quantum theory. Albert Einstein was applying physics to mathematics. So along comes Cecilia Payne, and she learned physics at the knee of Ernest Rutherford at Cambridge. So she was then able to apply physics to astronomy, thereby becoming one of the very first astrophysicists. So she knew that when enough heat and pressure are applied to an

element, the electrons will jump to another orbit. Some will even flee altogether, producing an ion of that same element. So she could see that a few hydrogen atoms in the spectrograms were producing incredibly strong lines in the glass, meaning there's a lot of hydrogen there. So she used her physics training to figure it out. She understood that hydrogen ions were responsible. It was still hydrogen, but it was just in an ionized state. And in fact, her research was showing that hydrogen was a million times more prevalent in stars than the men of science had assumed. And I do mean men, most scientists at the time were men. But she must have crossed over with a lot of the women who were made computers at the Harvard Observatory, right, to look through so much astronomical data.

Yes. There were four main computers at the Harvard Observatory. But, Becky, that's all they did. All they did was catalog stars. They didn't try to understand what they were composed of. Now, in fairness to them, it wasn't their job, but they also did not have the training in physics that Cecilia had. So that when she came along, she took those, then there were hundreds of thousands of these glass plates. She was able to look at them and understand what those lines were telling her. It's like the Harvard computers. It's like they built a library with thousands and thousands of books, but they never read any of them.

She came along and figured it out. And these glass plates were like, they were almost like jigsaw puzzle pieces. And she was the one who was able to fit them together. I find that fascinating because for us you know it's so i don't want to say obvious but i guess it is that we would take physics take astronomy apply that together but that wasn't really happening at the time and as you say until she came along with the knowledge that she had learned at cambridge and applied that to these glass plates to understand these stars. Right. Her results did not go down well, as you were alluding to. Astronomers back then believed

in Arthur Eddington's concept of the uniformity of nature. That is, they believed that stars, as you said earlier, were composed of the same elements as Earth. Her analysis showed that that long-held belief was false, and that was just too much for the men of science at the time. They just could not wrap their minds around the fact that this young graduate student, young woman graduate student, was able to make such a fundamental discovery. So she was told she was wrong. And so you know what she did? She wrote in her thesis, Stellar Atmospheres, that her results were almost certainly not real. Almost certainly. So David Dvorkin, who's the curator at the Smithsonian in Washington, he observed that she was very clever. She used words that satisfied the doubters,

observed that she was very clever. She used words that satisfied the doubters, but made clear that it was her, Cecilia Payne, who, right or wrong, first made this discovery. So when did this become accepted theory in the scientific community? Like, was it straight after, you know, Henry Norris Russell actually published his paper on it? Or was it, you know, a couple of years afterwards? Did Cecilia Payne Kaposchkin actually live to see this become accepted theory? Yes, she did. It was, what Russell did, he was the head of the Princeton Observatory and kind of the dean of American astronomers, if you will. And he showed by using a different method that she was correct, but he buried that observation on page 79 of his report. So he really, at the time, got the credit for the discovery. She lived until she was 79, and she was born in 1900. So she did live to see her discovery

recognized. But it was really, it was almost 40 years after her discovery that astronomer Otto Struve, he wrote that stellar atmospheres, her thesis, was, quote, undoubtedly the most brilliant PhD thesis ever written in astronomy. She was a relentless pursuer of understanding and really didn't let little things like nonsense, as she said, get in the way. So she did ultimately prevail. It was a long slog, though. She was paid very poorly. She taught astronomy courses at Harvard, but her name was not listed in the course catalog. And Shapley once told her why that was happening. He said to her that Abbott Lawrence Lowell, the president of Harvard, had told Shapley that Miss Payne shall never have a position in the university as long as he was alive.

Not because she wasn't qualified. She was eminently qualified. He said that because she was a woman. But she hung in there. And in 1956, when Donald Menzel became the head of the Harvard Observatory, the first thing he did was he paid her better. But the second thing he did was appoint her as the first woman professor at Harvard. And that was really the crowning point in her life. And it's just amazing to hear as well. You know, you think about it, you said she just persevered. And if it wasn't for her perseverance, you can't

help but wonder whether people like myself working in astronomy today would even still be allowed to, you know, so I tip my hat to her and I thank her very much because I am very happy with what I do. So thank you so much, Donovan, for talking us through her really quite extraordinary life. That was Donovan Moore, author of the book, What Stars Are Made Of. Moore, author of the book What Stars Are Made Of. This is the Supermassive podcast from the Royal Astronomical Society with me, astrophysicist Dr. Becky Smethurst and with science journalist Izzy Clarke. This month we're shining a light on the first stars and Becky, Robert, I know we said we were going to do book club this month but we'll do it next time because it's not

every month but you land a rover on mars during a pandemic as well yeah double tick so i mean have you guys been as addicted to the footage as i've been about seeing this i know we mentioned it a little bit earlier but 100 yeah like i watched the live stream of it landing I was on I was on TV like commenting on the landing for the live stream and I knew I wasn't supposed to make noise and yet I still let out a little like when they announced touchdown but yeah I mean watching you know the team get so excited about it seeing the images come through seeing that video of the parachute and this amazing little jet pack that lowered it down to the surface actually working is incredible hearing the sound of mars for the first time i know they landed on quite a calm day so the wind probably

wasn't that strong but like all of this stuff just it's just been this almost like bombardment of like here's a really cool thing here's a of like, here's a really cool thing. Here's a really cool thing. Here's a really cool thing. And the funny thing is, I know that the coolest things are yet to come. The actual science that they're going to discover from this mission, because they're looking for signs of life where they've landed. And I just can't wait to see what they find. Yeah. So, Robert, can you help cover the basics?

Like, who's launched this lander? What are they hoping to explore? Yeah, so the lander is a NASA mission and it follows on from Curiosity, which did so well using a similar technique, what Becky describes as the jetpack, which I think is a good name. They call it Skycrane,

which sounds pretty crazy really, doesn't it? But it works. And when you see the footage of that working, that's gobsmacking in its own right. But the idea is it's exploring a crater where we think, a Jezero crater, where we think there was a lake bed there about three and a half to four billion years ago, because a lot of planetary scientists think that Mars went through a wet period when there was a lot more water on the surface. And of course, if you had water there for hundreds of millions of years,

perhaps liquid water, it's just possible that life developed there. And it's certainly a really important thing to test. So the mission aims to look pretty much for fossilized signs of that. I mean, I guess it's, you still have in the back of your mind, you think, will they find actual life there today? Probably not. But you know, it's always there in the back of your mind. And places like this on Earth, there are small fossils that can be detected. So they're looking for similar things. And they will collect samples. The idea the idea is that you know there might be a vehicle that can go there later to get those samples and return to the earth and the best thing well it's not necessarily the best thing but the most fun thing i think is this helicopter they've got with

it as well so the mars helicopter ingenuity will fly for the first time on mars it's just brilliant isn't it you know if you could imagine this kind of even if it's only a test thing flying a few meters above the ground and going a short way away from the rover isn't that fantastic you know we'll see this footage of this thing it's like like taking a drone to mars it's so so cool and i love the fact that people have nicknamed perseverance percy and then the helicopter is called ingenuity so they've nicknamed that ginny and i'm like right that's two weasleys on on mars right and so this mission that they're going to so that perseverance is going to collect some rock samples and leave them for another mission to collect and return to earth and like the uk is like super heavily involved in that

aren't they and i really desperately i don't know if that mission has a name yet robert you might know but i desperately want to call it rendezvous and then we can call it ron that would be just perfect as a cultural reference but yeah i don't know if it's got a name either it's all part of the exo mars program and all of these things are supposed to at someone's specified point in the future lead to humans going there as well but But I do think to myself, if you found evidence of fossils, we wouldn't want people going there, would we, really? Because imagine that, how would you keep it sterile? How would you prevent bringing those things to Earth? I know we've talked about that kind of thing before,

but it just seems it would be such a huge discovery. We'd want to be ultra careful in how we preserve it. I've had a lot of scientists talking about this. Mars is essentially like the most exciting lab and experiment that we've got at the moment. So there's an idea that we need to find out as much as we can before we go around stomping on it in case, you know, we cause any, I don't want to say problems, but, you know that that's a genuine concern isn't it? I do you know very much I mean how can it not be you know imagine if you just go along how can you sterilize the spacesuit if you've got a person inside it you know the you even if you're

in the spacesuit there's no way really that you can do that to the kind of level that you'd I think be happy with it so I suspect that if you wanted to be really good about this we'd have to as much as possible rule out any extent or even fossilize life on mars before we were happy stomping around there i mean you can clearly do that on the moon we know the moon is lifeless but an environment like mars i mean just would you really want to take terrestrial bacteria there to mess things up i don't think we would and i think well whatever the aspirations of elon musk and people we should we should be really careful about this stuff. Well, until we get those answers,

I guess we'll just have to look at all those lovely photos and images and videos that it's sending back. Oh, life is hard. But back to this month's topic, as always, we've had lots of questions in, so thank you for everyone that sent them in. Zelith on Twitter asks, do we have a name for the

first star we expect to have existed? Was it called Keith or something? I'm gonna say yes it was yes it was the first star was called Keith. Next question. It has been decreed. But okay I'll get on to some serious questions. So Robert a lot of people have asked this one which is would these first stars have their own planets and Alexander von Wernherr also asked did they also by chance have a habitable zone or was the universe too wild back then yeah I mean it seems very unlikely that the first the very first stars would have had the materials around for planet building, because you need those heavier elements that astronomers, as we've said, confusingly refer to as metals, but you need the heavier stuff. And if you've only got mostly hydrogen, mostly helium, it's quite hard to build a planet from just those things, because we think that even planets like Jupiter and Saturn, big gas giants, have a rocky nucleus in the center. So it's probably unlikely that they have first planets. It would be a great science fiction thing, wouldn't it?

You know, living in a much smaller universe and what that would be like. But probably there weren't any planets around for that to be possible. And as for the Goldilocks zone, well, hot stars do theoretically have a Goldilocks zone because it's just the point to where you're far enough away that you can have liquid water.

But the problem is that they probably didn't live that long. And so very unlikely that you'd have a chance for life to develop, even if you had planets there. So it's not really a great place to go and visit and certainly not to set up home. I mean, you could have had something like a, I guess, like a failed star, like almost like a brown dwarf or something, you know, that's like halfway between a planet and a star.

They call them planimos, don't they? Which is like, it's not quite gotten big enough for nuclear fusion. So perhaps maybe like a binary system where one of them failed, and so it's still orbiting it. So would you technically class it as a planet? Probably not. It's a good question, isn't it? I'm just thinking about how many, and I don't know the answer. This is exactly the kind of thing that people like Emma know more about, but it's how many low mass stars were there in the universe? Because part of it is about the reason you get these very large stars forming, right,

is because you haven't got those metals around. So does that mean that more stars tend to be very, very big? You need more material there to begin with. And so you form fewer ones. I don't know. It's a really good question. But I suppose that would be a nice science fiction story as well, living on something which is a failed star,

if it's just small enough for that to be possible. I'll get writing. They have a fortune, Izzy. Yeah, here I come. And Becky Paul Winston asks, of fortune is he yeah here i come and becky paul winston asks the first stars condensed from hydrogen helium and a little lithium they lit up once the right temperature and pressure were achieved what elements were produced in those earliest fusion reactions was it more helium and lithium or were higher elements formed too so we think that the same fusion reactions that are happening like in stars today

would also have been happening in the earlier stars too. So, you know, the helium that's being made through hydrogen fusion, yeah, like during most of a star's lifetime when it's on something we call sort of the main sequence, you know, when it's just sort of, you know, just happily living its life. But at the end of like normal star's life that we see you know right now when they start to run out of fuel and they start sort of pulsing because sort of gravity wins for a minute crushing inwards and then it gets hot enough to start the next round of fusion sort of next step in the periodic table and then it pushes it outwards again against gravity that kind of

cycle is when like lithium berylliumium, and then also carbon, nitrogen, and oxygen start forming as well. And you start burning those elements. And so in most stars that we see today, those two processes are separate, right? One kicks off after the other one finishes. So when hydrogen to helium burning is finished, you start burning the next heaviest things, right? And then those elements are then ejected. And then, you know, you have iron and carbon being made in supernovas and stuff like that. And that's sort of the pollution that Emma was talking about previously.

But these hypothetical population three stars that we, you know, think were hundreds of times more massive than the sun and way bigger than, you know, any star that we currently see that's sort of the most massive star that we know of now. There are some people that say that the hydrogen burning into helium wasn't actually enough to resist gravity pulling them inwards because they were so massive. Like it didn't give you enough energy. So they didn't just do hydrogen burning. They also did this fusing of carbon and nitrogen and oxygen at the same time. So they had to have both of them to resist the pull of gravity pulling inwards to give you

enough energy pushing outwards to keep the star stable that's just one idea obviously but it's interesting to think about the fact that both of those processes could happen at the same time and that the first stars you know weren't just making a truckload more helium and then in a supernova making the heavier elements but actually making the heavier elements in their normal, let's call it day-to-day life of a star. Amazing. Well, I hope that clears that up for you, Paul. And if anyone else wants to send in questions for a future episode, then email podcast at ras.ac.uk or tweet at Royal Astro Sock and we'll take a look.

So, Robert, I just wanted to talk to you about something because I know that the Royal Astronomical Society have been talking about stars quite a lot recently, as you guys tend to do. But there was one particularly interesting article in the monthly notices of the Royal Astronomical Society, which was, is it a heart shaped nebula? Is that what I saw? Yes, yeah. Yeah, it's Messier one the also known as the crab nebula which is a reasonably bright object for amateur astronomers and is the remnant of a supernova that happened back in 1054 so actually it's quite well documented too it's interesting to see how this has developed over nearly a thousand years since and a researcher a group led by thomas

martin who's at a university Laval in Quebec, in Canada, and he's created this 3D reconstruction of the nebula. And I'd say we thought about, you know, announcing this one on Valentine's Day, but it's not a very romantic looking heart. It looks rather more anatomical. Yeah. The astronomical blood vessels and so on.

It looks more like it's been shotted on the ground. Yes, sort of more than looking thing. But yeah, what they've done is they've used a spectrometer, measured the speed in which the materials around it are moving, and they create this fantastic image. And then they're hoping to do this kind of thing as well. They've also got, if you go to the link on their website, you can also see a sort of fly through as well.

So it really is a really nice 3D image of something which is very well studied. And amateur astronomers like looking at it because they know they're looking at the supernova remnant. But again, you know, another fantastic piece of work. It also fits in quite nicely with, you know, some of the stuff we'll be doing next month around neutron stars, because there is a pulsar in the middle,

the remnant of the supernova that's still powering all this. Oh, nice. And if you wanted to see this yourself outside at the minute, Robert, where would you look and what would you need to see it? You need, I think, unless you've got a very dark sky and a big pair of binoculars, you need a small telescope. And it also certainly helps to be away from the light city.

I have seen the Crabnear Brewery a good few times, but you need a decent-ish telescope and you need to know where to look. It's in the constellation of Taurus. You'll find it on quite a few maps. It was the first object catalogued by Charles Messier when he was creating his deep sky catalogue, which is basically the brightest nebulae and clusters in the sky. And it's still visible.

You'd be able to see it certainly throughout March and into April while Taurus is above the horizon. Then it becomes visible again in the autumn. Nice. And I guess whilst you're in Taurus, there's something else you can see there at the minute? Yeah, there's a lot going on. I mean, actually, there are two nice events involving Mars this month. Now, it's nothing like as bright as it was back in the autumn when it was dominating the sky, you know, it gets to these bright points, actually, not very often at all. But it's

somewhat fainter, but it's still as bright as a bright star and pretty obvious. And if you look out on the 3rd of March, you'll see it next to the Pleiades cluster. So a nice photogenic opportunity, much as Venus was there last year. And on the 19th of March, it will be near the crescent moon in the sky. So I think in both cases,

it's definitely time to get the smartphones out, get the decent cameras out, take pictures and actually tweet us and tag us in it because we'll happily share that stuff. In the month in general, we're now moving nicely into the spring. So you move away a bit from Orion and Taurus and so on, though they're still there. And you start to see these spring stars too. So we see things like Leo, which is the lion and actually is one of those constellations that genuinely does look a bit like a lion. Most constellations don't look anything like the thing we're supposed to be

depicting. If you really use your imagination, which I guess is what the people who created constellations were doing. But Leo does look a bit like a crouching lion. It's got a mane and its hind legs look as though as they're in this triangle. So you can see that. And between Taurus and Gemini, the twins and Leo, there's a nice object to look for too called the

beehive cluster. And it's one of the best things to pick up with a pair of binoculars. Looks like this delightful kind of jewel box of stars. And I was thinking about the fact that we're still not really allowed to go outside of our locality, although hopefully that'll change. But clusters and things like that are fairly easy to see even in light polluted skies. If you've got a pair of binoculars, all you can do is look out of a flat window a lot of these things you should be able to still see thanks robert and that's it for this month sticking with stars we'll be back next time with a look at pulsars and neutron stars yeah i'm excited for that one and also send us your questions it's at royal astrosoc on twitter or email podcast at ras.ac.uk

and we'll try and cover them in a future episode. Until then everybody though, happy stargazing.