The Supermassive Podcast - 46: Q&A - Spice Girls, Black Holes, and Ice-Cream in Space

Episode Date: October 27, 2023

It's been a while, so Izzie, Dr Becky and Robert dive into The Supermassive Mailbox for a Q&A Special. How is the mass of a star determined? Does JWST have fuel to come back? And is it possible for Voyager 1 or 2 to switch their cameras back on? Here's the link for space-related jobs that Becky mentioned: https://jobregister.aas.org/ Got a question for the team? Email it to [e-mail] or find us on Instagram, @SupermassivePod. The Supermassive Podcast is a Boffin Media Production for the Royal Astronomical Society. The producers are Izzie Clarke and Richard Hollingham. 

To measure the mass of a star, you need two stars. Well, Voyager 1 is 24 billion kilometres away. And I feel like they must mean the royal we there. Our honest listeners from 1859. Hello and welcome to the Supermassive podcast from the Royal Astronomical Society with me, science journalist Izzy Clark and astrophysicist Dr. Becky Smethurst. Yeah, it's been a while since we did one of these Is, so who's ready for a good old Q&A episode? And well, if you've clicked play on this podcast, you've got no choice because this is absolutely

what we're doing. But if you're new to the podcast, we ask everyone to send in their questions to the Supermassive mailbox. And asked becky and robert the deputy director of the royal astronomical society as many of your questions as possible but we always start with some space trivia so to the both of you what's your favorite space related myth that we've now proven incorrect oh i like this one incorrect so um my favorite myth is that although we've now proven incorrect anyway is that you cannot see the great wall of china from space i'm so sorry to tell you oh so many people are gonna be so upset by this i know i know i know i mean this myth it's so fascinating it has roots like well before even like the space race you know in sort of like the 60s like there was a letter

that a reverend william stukely wrote in 1754 and in that letter he says that the great wall of china is so big that you could see it from the moon which is crazy to think like you know even back then they were thinking of things like this that obviously was debunked by apollo 12 astronaut the lunar module pilot alan bean who said no you definitely can't see that from the moon but you also can't see the Great Wall of China with the naked eye from the International Space Station either so there's lots of Chinese astronauts that have confirmed that you know our favorite commander Chris Hatfield also famously commented that he couldn't see it but apparently with a digital

camera and a zoom lens it is somewhat possible if you know exactly where to look on the surface of the earth you can then just pick out uh this sort of like structure like that is winding through the countryside that is the great wall of china yeah big caveat there though just gotta get a camera and a special lens and find it at the right point at the right time yeah okay robert what about you well i was thinking about ancient ones and And one of them was that, obviously, before we understood as much about the universe around us, the prevailing idea was that there wasn't a vacuum in space. And this comes from Aristotle, so right back in the 4th century BCE. And he suggested, not unreasonably, that there was this idea of nature of boring a vacuum.

And, of course, if you do experiments on Earth, it's really hard to create vacuums. And, you know, you have to use, even today, obviously, high-powered pumps and so on to achieve that. However, you know, the extension then was, well, that couldn't be the case in space. And it's funny, it's sort of true in a sense that everywhere in space has at least a few particles around, even the space between clusters of galaxies, the voids. They're really incredibly empty, but there's still a few things in them. But it is much closer to a vacuum than anything we could create on Earth. And the idea had basically disappeared by the 18th century. But there are some really great stories about this.

So Serrano de Bergerac wrote an idea of floating there in the 17th century. And then the self-describing eccentric physicist Charles Morton, who suggested that birds migrated there for the winter. So they weren't going down to Africa or up to the arctic they were going to the moon oh well there you go can i just also give a shout out to all of the listeners from the east midlands because the word aristotle is my favorite word said in the east midlands not to give an accent aristotle it's just beautiful nice okay so let's crack on with the question so robert let's start with this fun one from natalia hearns on instagram she says would chocolate ice cream taste the same if i were

to eat it on another planet it's it definitely appeals to me now natalia i think we've got to try it out but the answer is we don't quite know. We don't quite know yet. And the reason is, you know, we haven't really had an asteroid sun on the planet. They went to the moon, of course, and they were apparently the freeze dried ice cream didn't actually go with them. They mostly subsisted on things like biscuits. But the general description of people say in orbit around the Earth is because the microgravity because, you know, you're basically weightless. They feel like they've got a head cold a lot of the time and tastes tend to be a bit duller. So my thought on this is that we need to ramp up the chocolate content a lot to make it taste

even more chocolatey. And I'm, you know, if there are some, say, ESA or NASA experiments going on, I'm more than happy to help sample this. I mean, I imagine my co-presenters would say much the same thing as well i will do it for science exactly maybe we can all take a different flavor like oh bagsy strawberry i'm doing bagsy pistachio we're all happy okay um becky we've had a few questions about mass so can you help um so first up curious stargazer asks how is the mass of a star determined and then danger the one who knocks then asks how do astronomers and astrophysicists calculate the observed mass of a galaxy so how does it work are they the same process they're not the same but they are linked slightly so for stars

to measure the mass of a star you need two stars you actually need stars in a binary pair so orbiting each other now they're very common so fairly easy to find and so this was done fairly easily when people once people you know could observe them to high enough accuracy and to work out essentially first of all the total mass of the two stars orbiting around each other you need to know two things you need to know the separation between the two stars and the time that it takes them to orbit each other. So obviously you need some pretty detailed observations to be able to get at those numbers. But once you do, the total mass is pretty simple. It's just the distance between them cubed or divided by the period, the time it takes, squared. And that's just from like, you know, Newton's laws

of orbits and stuff like that. And then to get the individual masses of the two stars, you measure how far each star is from the centre of mass, like the point that they each orbit around in between them. And you plug that into more of Newton's equations. And then you can get the mass of each individual star in the binary system. And then from the light we receive from stars, we know that stars have certain types, and those certain types are the same masses. So once you've calculated the mass for that certain type, you have the mass of all of those types of stars that you then observe. You don't have to do this again even for lone stars as well. Now once you've got the mass of stars, you then know how the brightness of the stars relates to its

mass. And that's very handy when you then observe a galaxy of lots and lots and lots of stars. So what you do is you measure the brightness, the overall brightness of a galaxy, and you assume the same spread of the types of masses of stars that we see in the Milky Way has also formed in that galaxy and then you could estimate from the brightness how massive it is in stars and we call that the mass to light ratio as well and it's something that is very common. There's lots of arguments about whether that does change in different galaxies like we assume it's the same spread of stars in the Milky Way but is that a good assumption? Probably not at the highest redshifts that we're seeing with JWST at the

minute either and that's where a lot of the arguments are coming in. But it is very interesting to think that mass is never directly observed. It's not a directly observed property, right? It's calculated or it's inferred from something else. And this is particularly frustrating for astronomers and astrophysicists because simulations, when you simulate stuff in, you know, the universe or galaxy formation or whatever in a computer you work in terms of mass but then in observations we work in terms of brightness luminosity and so if you want to compare the two there's always got to be someone who converts what they're working in either the observers have to convert into mass

based on you know the sort of inferences you can do, or the simulators have to be like, right, I've got this much mass here. How bright would this be if it was to give out light? You always have to do some conversion there. And it is particularly frustrating. Yeah, yeah, okay, fair enough. And Robert, Kyle P. 1986 has a spaceflight question.

And it's one I think everyone wants to know. Is it possible for Voyager 1 or 2 to switch their cameras back on? Kyle, great question. Sadly not, I think. I mean, they are incredible, both missions. They launched right back in 1977 and they've been working really well ever since. They essentially used 1960s technology and they've travelled to all well ever since. They essentially used 1960s technology and they've travelled to all the outer planets between them.

So Jupiter, Saturn, Uranus and Neptune and then explored the space around the sun. They're now the most distant objects that have left the solar system and there's only a handful of space probes that have done that. One of the most famous images at the end of the mission, I think it was Voyager 2, was to turn the camera back towards the solar system for the last time I think it was Voyager 2, was to turn the camera back towards the solar system for the last time. So it was well beyond the planets. And it detected, you know,

respectively, all the outer gas giants. So everything from Jupiter to Neptune, and then Earth, Mars and Venus and Pluto was way too faint. And even though it was still called a planet back then, and Mercury was too close to the sun. But that's a unique image from the outside of the solar system. So if you wonder what it looks like, that's the best representation we've got. And it was a series of frames, so it had to do fairly long exposures on each one and then sort of make a mosaic of them. But it's a great image. But the reason we can't do it is they generate their electricity through something called a radioisotope thermoelectric generator. And what that means is that you have radioactive plutonium, which generates heat. And that then is used to generate electrical current.

And the problem is that the plutonium decays over time. So the level of radioactivity goes down. And that means the power drops as well by a few watts a year. And you get to the point as you are now where there's only enough power for a few of the residual instruments. And of course, the radio transmitter to send the results back to Earth. Otherwise, there's no point running the instruments. So they use things like particle detectors, cosmic ray detectors to

find out what's going on in the space outside the solar system. They're officially in interstellar space, in the space between the stars. And that's the priority now. And we can still pick up data from them incredibly. Well, Voyager 1 is 24 billion kilometers away, and Voyager 2 is 20 billion kilometers away. So these are our 20 billion kilometers away so these are our detectors in interstellar space and they should keep going I think the prediction is for at least another few years probably into the 2030s. And if we could though just humor me here if we could turn the cameras back on what would Voyager see? Well I think it would I mean it's six times as far well Voyager 2 is five times as far away Voyager 1 is six times as far away as Neptune now. So I think what they would see is just the sun would still be really bright. It's still, you have to go a very long way before it looks like another background stars further than, you know, we will might be able to pick up the planets around it, some of the outer ones anyway, but they'd be much closer in than they were during that famous photo. So

and then of course, you know, you could turn the camera, I guess, to the other stars and so on, and they would look much the same as they do on Earth. But we would have this, I guess it would be looking back at its origin and seeing the planets have in an ever shrinking positions around the sun. Yeah, I kind of almost wish they'd done it like a few times so you could almost get like a time lapse of the solar system shrinking god we need a high car and what were you thinking and becky boaz wisner asks what is this cosmic web i hear about every so often is that something to do with galaxy clusters?

Yeah, so the cosmic web is essentially the structure of the universe that we can see. So it's formed by galaxies and galaxy clusters. And you really do see this pop out when we make like 3D maps of the universe. So you record not just the positions of galaxies on the sky, but also their distance away. And then you sort of like can plot that out and make this 3D distribution of where you find them all. And you find this like sponge-like structure that emerges, almost like, you know, if you could make a spider web in sort of like, you know, like three dimensions rather than flat, right? And so you've got galaxies all along these thin filaments, and then where they intersect, yeah, you do have these big galaxy clusters, but also you have these huge voids in between all these filaments as well. So that's

why we say that it really does look like a web. And this comes from the fact that in the very early days of the universe, you had this process called inflation, which essentially imprinted these areas of higher and lower density amounts of hydrogen and dark matter as well so that where there was more hydrogen more galaxies formed and where there was less hydrogen less galaxies formed and as the universe is expanded that sort of must exacerbated that some more to end up with this sort of these concentrations along the filaments than these big voids as well what makes me laugh though with cosmic web is that everyone now with the popularity of the James Webb Space Telescope, they think that it's somehow related as well like web, but that was just his last name,

W-E-double-B and not cosmic web as in like a spider web. Must clarify, must clarify. Okay. must clarify must clarify okay so i'd like to take a little break from the astronomy questions because now we're going to give some careers advice oh cool which is a little different from us but a couple of questions came into our mailbox that i really wanted us to talk about so first up evermore 28 thought their question which i hope is in a taylor swift reference i'm pretty sure it is i should have clarified but i think we can assume that it is and she thought that question... Which I hope is a Taylor Swift reference. I'm pretty sure it is. I should have clarified, but I think we can assume that it is.

She thought their question might be stupid, but I really don't think it is. So Evermore28 asks, any advice for students in their first year of physics at university? Becky, do you want to start first? Yeah, I think there's gonna be a lot of students listening or even parents of students or whatever.

So I think it's not talked about enough that the jump from school to university is very very hard it's a completely different way of learning material you're not being taught one-on-one by teachers anymore it's almost like off you go listen to a lecture and then carry on your learning yourself and it's it's very it's very hard to get used to that difference as well that you're sort of left alone to your own devices it doesn't feel like there's anyone almost supervising you anymore through your learning and so it is a big change and I know I really struggled with that in my first year as well so everyone if you are struggling with that that's totally normal yeah and just give it time I totally I agree with that I had similar experiences yeah

I think your first year really is the year to make mistakes um university uh academic I hope necessarily anything else but yeah I think by doing so you learn what your weaknesses are and you learn what you don't know well enough yet and so you can then work on those going forward because I mean I don't know if this is true in other countries but in the UK your first year doesn't necessarily count your final grade so it is the year to you know make those mistakes and figure out what you don't know and then also use your lecturer's office hours to the max right if you don't understand something go to them that is literally their job and they are there to answer all of your questions i literally couldn't agree with this like more so i if i look back at my first year i felt so shocked by that jump of level um and you know some of the stuff that you have access to my

school i'd never really done proper labs at school and suddenly to go to university and i felt that everyone knew how to take measurements of certain things and I just I didn't I hadn't had experience of that before so I I used lab technicians a lot and my lecturers if they'd set the task and then the lab technician was running an experiment I was always going to them to ask for help because I just need I needed it and I don't think I wish I'd done that more because I definitely sat in that feeling of thinking, oh gosh, I should just know this. And it's okay sometimes if you don't,

that's what your professors and your technicians are there to help you with. It's okay to ask for help. Yeah, I feel like you get to university with this sense of like, oh, I have to impress. And we're there like, we've let you in because we want to teach you this stuff. We don't expect you to know it where they're like we've let you in because you know we want to teach you this stuff we don't expect you to know it all already the fact that

you don't know it is why you're here and yeah like I in my first year of university didn't get that and I did the very British thing of like I don't want to be an inconvenience to anyone you know like oh sorry sorry sorry sorry but can I ask this you know one question but like that is why your teachers are there they are experts in this so you know get as much knowledge from them as you can and make sure that yeah you you know starting lectures writing a list of like i didn't understand this i didn't understand that that's not failing on your part that's just like in this very quick hour quick file we've had lecture i didn't have enough time to take it in so yeah speak to as many people as you can i'm gonna i'm gonna violently

agree with the two of you on this i think yeah i absolutely wished i'd made more use of my lecturers at university i think i think interestingly for me i think it was the mature students who knew to do that more because i guess they thought well i'm gonna go and ask you know those days were not days of high fees but still you know i'm putting myself through this for three or four years so i've got to go and ask i think it's absolutely the right thing to do yeah get your money's worth you know that's what you're paying for you're paying for your lecturer's office yeah and one thing I would also say which I wish I had done more in first year and I think that would have changed my first few years of university was just really take time to read over my notes from lectures more regularly don't wait for exam season just keep that knowledge

ticking over um because i was a crammer i will not be afraid to say that and i wish i'd done things differently because later and later on i got into better revision habits or working habits and i then suddenly started to really enjoy things because I'd basically making more time to double check that I knew what had just happened in the hours that I just had. Because some of it's really complicated and you're not going to get it in that first hour or half hour or whatever time you've got. But also usually it's like, OK, remember all the stuff we did in the two previous lectures that I'm assuming now that you know off the like like the back of your hand now because you know that we can we can then dive into this and if you don't you're so lost so yeah reading just reminding yourself before every lecture is what you've done and supposedly learned the past two yeah it's really helpful okay and then similarly anna l on instagram says i have a business background but love space.

Is there a place for me in the space industry? Robert, can you help with this one? Yeah, absolutely. Yes, Anna L, you know, and go in there and get a job there. Because frankly, everything I hear from these companies or these conversations is that there's a big skill shortage and they need people across the board. Because when you talk about the space sector more generally, you're considering a lot of private companies. Of course, they need people with a whole range of skills. And to give you an idea of the scale of it, the latest report on this, I think it came out in the summer or the spring, is that there are nearly 50,000 people directly employed in the space

sector in the UK and maybe another 130,000 across the companies supplying it. So it's a lot of people and there's still growth. It's one of those areas that's quite successful and the companies are growing despite even things like COVID and the other headwinds we've got going on. So I would say, no, go and talk to those space companies. And frankly, I think it's up to them as well to think about people that are changing career too, because there's a whole wealth of talent. I mean, we're all going to be working into our late 60s. So, you know, it should be absolutely the right thing to do to change career. And something as exciting as the space sector is a really good place. Yeah, I don't know about like the space sector as a whole, but I can give people a resource for specifically like astronomy or like space mission jobs.

The American Astronomical Society keeps a list of like current jobs that are being advertised. So it's called the AAS, American Astronomical Society Job Register. If you Google that, you should be able to find it. There's obviously jobs that are like hiring professors at universities and postdocs and everything like that. But then if you scroll to the bottom, there's support roles as well. And that could be anything from like they need software developers to develop the tools for a mission or, you know, lab technicians or business support or you know find whatever it might be so if you are thinking about doing something like

that check that out that's not the space industry as a whole like private space companies obviously that would be having something you would have to you know keep an eye on yourself but in terms of space agencies and mission support and universities that kind of thing that's a good place to look for those kind of roles yeah we'll put that link actually in the episode notes for anyone that wants to have a little peek at that. Okay, so let's ease back into the astronomy questions and Really Tiny Ant has a question about the sun. Robert, so he says,

does the sun's gravity affect and lens its own light? Well, that's a great question, tiny and it made me feel like i had a really tiny head when i tried to think through it so um i was thinking about this and at the extreme end black holes sort of certainly do you know absolutely warp the light around the environment uh that's where you get these crazy looking discs around them and we can't see them as they are because of that effect but and stars obviously have a much weaker gravitational field but but there must still be an effect at some level now whether it's detectable i was just thinking about this but what you can definitely do and it was the

proof of gravitational lensing or one of the proofs of uh einstein's general theory of relativity the classic one was that during a total solar eclipse the positions of stars, so in the sky next to the sun, shift slightly. So the effect definitely happens from the sun. What it does to the sun's appearance, I can't imagine there's anything very significant, but it's a really curious one. And another thing I thought about with this was that if you, there are wacky ideas to use the sun as a gravitational lens or use the sun as a telescope. And there was a space engineer wrote a report for NASA, Jeffrey Landis, back in 2017, and proposed taking a spacecraft 550 billion kilometers away. So think about how far the Voyager missions are. Even

Voyager 1 is 24 billion kilometers. It's a huge distance away from the sun. And that would be the place where the sun's gravitational lens would come to a focus and then the idea was you could use the sun as a telescope oh wow okay um and then becky we can you help with this question about web and that is web double b jwst um from saham so saham says hello super massive podcast team i hope you're all doing well i'm an avid listener of your podcast and an even longer listener to izzy clark's work since her time at naked scientist wow that is that's back in 2017 i was listening to the latest episode on uranus and i heard dr becky smethurst mentioned the netflix documentary about jwst unknown cosmic time machine amazing suggestion i I watched it. It

was fantastic. I almost got teary when they were revealing the first pictures from Webb. I was so excited to see Dr. Smethurst appear for a brief few seconds. So was I. I didn't know I was in it. And I was like, oh, how do you not know that you were in a documentary? Sorry. It was they used a clip from social media of like a reaction to those first images. I was like watching images that i was like watching it i was like where there's me okay um okay so back on track um my question to you guys is regarding jwst webb is orbiting the sun from the second lagrangian point l2 and the mission

is supposed to last a decade what happens after that does Does Webb have fuel to come back? Does it become a space junk? Or is there going to be a retrieval mission? Webb is powered by solar panels, but is that just enough to keep the mission alive and maintain the orbit? Why can't a mission like that keep going continuously, considering sunlight will still be there for many years to come? Amazing work again, keep it up. Thank you. Oh, wow wow that was a lot of questions we are gonna get so the thing is about web is that the electronics on board so the instruments you know all the communication back with earth yes that is all powered by solar and the solar panels but moving and pointing the telescope at the different targets you're having to move the whole spacecraft

to do that that is done with fuel sort of like the reaction motors so you just like poof off a little bit the side it'll move another way kind of thing yeah iron man you know style yeah out of the palms and when jwst was launched the launch from ESA was so beautifully done and so accurate to what we needed it to be. We didn't actually need to use a lot of that fuel that was on board to do any course corrections to get it to L2. It was a few, but nowhere near as much as was like contingency for, right? So it was a huge success that. And so that was why the science mission, you know, originally people said, oh, five years science mission. Now it's sort of going to be more like maybe even 20, if we're lucky, you know, not just 10. So that was great. Now, the thing is about JWST is that it's not

at L2. We talk about it being like physically at that specific point and staying at that point. What it actually does is orbit L2, this sort of stable point in the Earth-Sun system. And so again, it needs a little bit of fuel to keep it in orbit around L2. So it's orbiting the Sun, yes, but as it orbits the Sun, it's also doing this little loop around L2. So it's orbiting the sun, yes, but as it orbits the sun, it's also doing this little loop around L2. So you can imagine it just sort of like a little spiral sort of bouncing along kind of thing. So when it runs out of fuel, A will no longer be able to point to any specific targets that we want to and actually do science, but B, it will also drift out of its stable orbit around L2 where we can keep it, you know, shielded from the sun's light

with its big tennis court sized sun shield. At that point, you know, it could just find a stable orbit around the sun and just happily, you know, carry on for millions of years just orbiting the sun. Or it could go into orbital decay as well. It really just depends sort of like what the conditions are at the time, in which case over a very, very, very, very, very, very long time, it would eventually spiral into the sun as the orbit decayed. So it would technically be space junk. Space junk is, you know, stuff in space that doesn't work anymore, that doesn't, you know, we can't communicate with or do anything with.

So yeah, it will just be space junk. I doubt there'll be any form of retrieval mission the cost to bring it back I don't think would be worth it necessarily and similarly people also ask you know could we refuel JWST as well but there was no sort of um plan plans to do that so there was nothing put in to be able to access the fuel tank to be able to refill it people are like oh why why why and it's because you really need to just completely seal the the sort of spacecraft bit that houses all of the telescopes incredibly delicate instruments you don't want to leave a hole in that even for fuel okay all right then um and robert so this next

question has come from a shared email account it's come from graham and sharon o'donnell so one of them has emailed to say hello hope you're doing well since i discovered this podcast two years ago i have never missed an episode thank you for the great work oh i really appreciate that okay my question is we observed the carrington event in 1859 during which we could see auroras as far south as Hawaii. And I feel like they must mean the royal we there. Otherwise they are the oldest people in existence. Our oldest listeners from 1859.

Wow. So the question is, have we watched a similar phenomenon? I can never say the phenomenon. Phenomenon. This is going to finish me. Have we watched a similar phenomenon? I can never say the phenomenon. Do-do-do-do-do. This is going to finish me. Oh, okay.

Sorry. Oh, no. Sorry, I just can't get back together now. Similar thing. Okay, anyway. Have we watched a similar event happen on other planets that have auroras like jupiter and saturn during which their aurora spread to distances far beyond their poles yeah that's a brilliant question um graham and sharon and another one where i had to go and do

some research so the thing about the aurora on jupiter and saturn they're really spectacular they're quite big and bright and they really stand out in the ultraviolet with images from hubble and so on um and they're complicated so they are a result of both interactions with the solar wind the stream of particles in the sun and events you get in that interacting with their magnetic fields and also with the uh to some extent with the interaction between the planets and their respective moons. And it turns out also that Saturn might be driving Aurori from its own atmosphere. There's a paper out on that quite recently too. So I asked around, I actually asked Lee Fletcher and Henrik Melling, who have both been involved with the podcast in the past. They're experts on the giant planets and they study this. And they pushed me towards

a paper by James O'Donoghue, who also did some stuff with the RAS actually a while ago. He has a great YouTube channel as well with loads of cool animations. Oh, fantastic. His animation of the planet's rotation and their different speeds is incredible. So check out James' stuff. And he's at JAXA, so he's at the Japanese Space Agency, and he led a team that found a heat wave pulsing out from the poles on Jupiter associated with the aurora. So it looks as though in some way, at least, yes, when there's a big amount of solar activity,

they do get driven down towards the equator like on Earth. But even when that's not happening, it's worth bearing in mind that the aurora on Jupiter, the northern lights on Jupiter and the southern lights on Jupiter are tens of thousands of kilometers across so they're bigger than the earth so irrespective of whether they go with the whole planet they're huge it makes me feel like a tiny ant yeah we're all there we're all tiny ants okay i'm becky michael trampas says hi izzy becky robert and all you other superstars at the Supermassive podcast. Hi. I was watching Becky's recent YouTube video on the size of stars and their possible upper limit. Insert shameless plug for Becky's YouTube channel here. You're welcome.

Thank you. It's a given that the bigger a star gets, the shorter its life will be. In one video, you mentioned that we've thus far been unable to find any stars with masses over roughly 150 to 200 solar masses. This made me wonder, if stars get that big, how does that influence their lifetime? Does the lifetime of a star decrease exponentially or linearly in proportion to its mass or something else entirely? And what would that mean for the lifetime of a star of, let's say, 500 solar masses? Thanks for bringing us astronomy with a smile for over three years already. Love from the Netherlands. Oh.

Very nice. So more mass questions, Becky. Yeah. Well, I actually loved this question, Michael, because I got to do a little bit of back of the envelope calculations. Oh, you love a little calculation. I love when i can do that so yes so yes lifetimes are proportional to a star's mass right and that's because the

bigger star you have the faster the star has to convert its hydrogen into helium and use it as fuel to produce enough energy to resist the crush of gravity inwards. So as you add more and more mass, that has to get faster and faster and faster and faster to resist that crush. And there is actually an equation that you can use to work this out. So the lifetime of a star is proportional to one over the mass of the star to the power of 2.5. It's a power law, okay? So if we use the sun at one solar masses, so one times the mass of the sun, and we know that it has a lifetime of roughly 10 billion years, then we can use that as sort of like the constant of proportionality in our little equation, right? And then we can start working out, for example, like Michael said, like a 500 times the mass of

the sun star. But I want to start with, let's say, an O-type star, 500 times the mass of the sun star but I want to start with let's say an O type star which are the sort of heaviest of stars that we see you know up to main times we really see about 100 times the mass of the sun but yeah the biggest we've seen are up to 200. 100 times the mass of sun that lives about 100,000 years okay 200 times the mass of the sun, 17,000 years. 500 times the mass of the sun would only live about 1,700 years. So this is another argument for why maybe we actually don't see stars that big, because they literally don't live very long if they do exist. And so the chances of actually capturing one after stuff has formed, especially when stars tend to form in really big dust clouds as well, that shroud a lot of the visible light from us. You know, that could be one of the reasons.

But then I had some fun with this because I kept going. And we can start to think about some completely hypothetical stars. So a 10,000 times the mass of the sun star, if it existed, would only live for one year. That's how quick it would have to burn its fuel you can keep going though uh one million times the mass of the sun star would only live for five minutes and a 10 million times the mass of the sun star would only live for a minute before it ran out of fuel and i just you know i feel like i did this back of the envelope calculation when i was a student as well when i found out the equation i was just like let's just keep going i haven't had so much joy in so long so thanks for that Michael that was really fun and actually Becky I've got another question for you um before

we get on to some stargazing because we couldn't have a Q&A without a question about black holes of course so Gabriel Judkin asks love the. I was thinking about black hole mergers and got stuck wondering about the exact moment that two singularities become one. Oh my gosh, that's exactly what the Spice Girls were thinking about. We're so on the same wavelength. That's what they're thinking about.

Is it when the event horizons touch or when the center of one of the black holes crosses the event horizon of the other? Or does the event horizon even matter? Yeah, so we class black holes as merging as when the event horizons overlap. So when they're crossed, we say that black holes emerge, because at that point, there's really only one scenario that you can end up with there. And that is that, yeah, okay, mathematically, as we describe it it the two singularities become one in the maths but yeah you've got to remember that a singularity is like a mathematical definition of

what a black hole is we don't know what happens beyond the event horizon so the event horizon is really what we define as a black hole that sort of sphere in space that's completely unknowing that we don't have any information from and don't know what's it's like inside the event horizon so like how if you think about you know if two stars are going to merge when have they officially merged right it's when their atmospheres are overlapping right not when like the centers of the stars are in the same two place they are merged right when they have become one even if it's not a fully spherical shape by that point okay well now if ever i hear the spice girls i'm now just going to think of black hole mergers so two of my favorite things to be fair um okay so robert what can we see in the night sky this

much yeah it's it's a really nice uh month november if the weather holds um right now we've got jupiter's really dominant in the night sky around midnight. So what's called opposition, which means it's opposite the sun in the sky. So that means it's visible for the whole night, pretty much at its closest to the Earth. That's actually a couple of days earlier and really high as well if you're in the northern hemisphere. So high and bright in the south. It's also about twice as bright as Sirius, which is the brightest star in the sky. So really, really obvious if you're looking up, you know, that time of night, that's what it is. And it's the biggest planet. So that means if you have even a pair of binoculars and you point them at Jupiter, you can see that it's a disk. You can

see it's got this what's called an oblate spheroid, a sort of bulging shape because it rotates so quickly. You know, we've talked about this in the episode on Jupiter. And it's got these large moons discovered by Galileo going around it. So that's easy to see. And if you get a telescope, then you can see particularly a medium-sized one. You start to see quite a lot more. You see weather systems and dark clouds. And if you're very lucky, the Great Red Spot, which is this giant storm that's been going for possibly four centuries. And as well as that, Uranus, thinking of last month, is at its best this month of the year. Now it's at its absolute best on the 13th of November, when again it's in opposition a little bit to the east of Jupiter in the sky.

But you shouldn't expect too much because it's a long way off and it just looks like a tiny little disk. So don't expect amazing things, but finding it is quite satisfying. And it's cool to still be able to see the blue as well. Exactly. Methane. Yeah, absolutely right. If you have a telescope that's big enough to show it a disc i actually find that even though you can't see anything on it i find that quite exciting so um and then further around over in the evening sky

saturn is still there becky still there they're more or less south at sunset and venus if you're up early in the morning when i was going to say up early actually to be honest with you at the moment is that now when you get out of bed normally yes then venus is really obvious high up in the east and will be for quite a bit longer yet so you'll look up and think what is that thing and it turns out it's venus and apart from that there's some sort of smoothed out or low level meteor activity over november there's the two showers the southern and northern torids that means they appear to come from Taurus and the Leonids as well, which is famous for occasionally having big storms, but we're well away from any of those. And so on their own, they're not particularly spectacular,

but I was just thinking they add up to something. So if you're out looking, you might see a few more shooting stars than usual. And of course, we can never tell you exactly where to look because shooting stars can appear anywhere in the sky. Just enjoy the moment. where to look because shooting stars can appear anywhere in the sky. Just enjoy the moment. And then finally, near Jupiter, two brilliant and beautiful star clusters that start to be visible in the late autumn. And the first one is the Pleiades, which is iconic. And if you've never seen it, well, I imagine a lot of people have seen it probably unknowingly, but you look up this tight cluster of stars together, very visible with the eye, probably I think the brightest one in the whole sky or the most obvious one. And you see six or seven stars with your eye, but there are

actually about 400 stars in there. And a pair of binoculars is perfect for looking at them because it's quite big. So if you get a telescope, you only get a tiny little bit of it. And it's so prominent, it was recorded three and a half thousand years ago on this artifact called the Nebra Sky Disk. So our ancestors were clearly very well aware of it. And then nearby, the other thing that's a nice autumn object is the Hyades Cluster, also a sort of V shape, so less compact but quite big. And again, a pair of binoculars really brings them out.

They're around the star Aldebaran in Taurus. And I think I was ending this thinking to myself, this is like an autumnal sign. So I walked to the station this morning in the autumn with the leaves blowing around and the trees swaying. And for seeing the stars the pleiades and hydes marks that too it's a sign of the seasons changing oh that's lovely okay well i think that's it for this time so we'll be back in a few weeks with another bonus episode we're a bit questioned out so we'll be bringing you the latest space news and then we're going to be ending our journey through the gas giants with an episode all about Neptune.

Yes, I think Neptune's like my second favourite planet after Saturn. Get ready for all of the enthusiasm. Yeah, I'm very excited. Thank you to everyone who sent in questions. We do read all your emails, even if we don't get to answering all the questions in a specific episode we have this growing pile so we will just keep adding to it and pull them for future episodes as well so if you have a burning question for the team email it to podcast.ras.ac.uk you can tweet at royal astrosoc or find us on instagram at

supermassivepod and we'll try and cover all the ones that we can in a future episode. But until next time, everybody, happy stargazing.