The Supermassive Podcast - 50: BONUS - Dust, stars and alien streetlights

Episode Date: March 13, 2024

What is cosmic dust? Could we reignite a dying Sun with a nuclear weapon? How do we know what galaxies stars are in, and can the JWST see streetlights on alien worlds? If you have a question for the Supermassive team, send them 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. 

Hello and welcome to another bonus episode of the Supermassive podcast from the Royal Astronomical Society. With me, science journalist Izzy Clark, astrophysicist Dr Becky Smethurst and the society's deputy director Dr Robert Massey. This is the place where we dive into the Supermassive mailbox even more to tide you all over between normal episodes and we answer some more of your questions um but before we get into the questions we have to do a shout out to my johansson who has emailed us to say hi guys i would just like to thank you for awakening my childhood love or obsession with space i work as a doctor and realized how much i missed physics and space so now i'm taking a part-time class that is basically how space works for people who know a little but not super much in my free time at a university shout out to Linnaeus

University much love from Sweden how nice is that so good that's so nice I'm so glad we could help in rekindling that passion are we influencers I think we're influencers. The look of concern on Becky's face right there. Okay, so Becky, can you help with this question from Mike in Oregon? They say, the bicep experiment was fooled by dust. Tired light is caused by dust. The dimming and brightening of Betelgeuse is thought to have been due to dust. There's so much dust everywhere, but what is the dust that is so ubiquitous in the cosmos? Love the podcast, Mike in Oregon.

Well, I like to say that dust is supernova poop, Mike. I feel like it is the best description of what it is. That is not where I, that's really just not where I was expecting this to go, but I love it. Carry on. It's the best description. I don't know what else to call it

because that's literally what it is, right? It heavier elements things like carbon nitrogen oxygen that are produced by stars as like they put off dying right they've run out of hydrogen so they scramble and they're like oh let's convert the helium let's convert the carbon and then when they do eventually die and go supernova or nova just fizzling out like they spread those elements back out into the universe and then they clump together and they form like grains of dust that are like you know like micrometers across right they're pretty small but there's still enough of it that it does block our view sometimes and so there's sort of like many, like almost like layers of dust. We have solar system dust. We then have Milky Way dust. You have dust in galaxies themselves that sometimes block our views of like the centres.

And so when you do look out into the universe, you have to take that into account all the time. So for example, like one of the most cited astronomy papers ever is a map of dust across the sky and the amount it affects light coming in in that specific direction because you always have to correct your data by that amount and that's why it's the most cited paper because everybody has to use it um schlegel hotel shout out schlegel hotel um and it's funny that you know so many people have had to make careers out of studying dust like that so that we can you, we want to understand dust itself because actually dust can act as a catalyst for star formation. So it's sort of like a shortcut for making what we call molecular hydrogen.

So H2, like O2, you know, like two hydrogen atoms bonded together. And that's what you need to make stars. And it's a bit of a shortcut for that. And it also blocks like cosmic rays and UV light that can then break apart those molecular hydrogens. So it also keeps them stuck together in the first place. It's about 1% of the mass of the entire galaxy, right? It's not, that's more than the black hole, right?

It's not the super massive black hole at the center, right? It's not an insignificant amount. But what I love is, yeah, people have made whole careers of studying it. Like Brian May, for example, his PhD thesis was about, you you know the solar system dust that no one else cares about are we gonna have to add dust to the list aren't we for like future episodes yeah it's gonna have to happen okay uh robert david chris gore has this question he says hi team first i love the pod and i adore the year in space book. It's glorious.

Avid watcher of Dr. B's YouTube channel too and recently finished a brief history of black holes. I mean, all the plugs. Thank you so much. Thanks. So my burning question, having watched the Marvels on Disney Plus last night is, Captain Marvel uses her power to reignite a dying sun.

Is it actually possible or is a dying sun simply going to expire no matter what? All the best, Dave. Thanks for that, Dave. Massive plug there. I think reigniting the sun or any sun for that matter would make us absolutely godlike. I mean, firstly, firstly. Yeah, it's Captain Marvel.

Exactly. Unless everything we know about stars is wrong wrong there's no way that our sun for example is suddenly going to shut down shut down even because it's got lots of fuel uh you know plenty of gravitational energy driving that reaction in the center generating energy from fusing hydrogen to helium there's lots of hydrogen left so there's no reason to believe it was suddenly shut down but if it did there's pretty much nothing we could do about it um you see these films like sunshine and so on but the idea of even delivering the most powerful nuclear weapon we have into the heart of the sun would be nowhere near and well it would be impossible to get it there and that would be nowhere near enough energy to change it but i did

come across looking around this i thought this is one of those crazy questions and sure enough it turns out people have thought about how you could do things like prolong the sun's life so or to change it and one idea is to take a passing star which is obviously a trivial exercise move it near the sun stir up the outer layers of the sun to drive more hydrogen into the center to fire up the reaction again so you know nice and easy i guess the sort of thing the marvels could manage um that it could also prolong the life of the sun by breaking it or removing mass to make it more like a red dwarf which has the minor side effect of making it a lot cooler as well so we'd have to simultaneously move the earth closer so a few little things to get in place to manipulate this stuff um or even make a ring of red dwarfs somehow you know this is all bonkers stuff. And I have to say that either sadly or fortunately,

depending on your perspective, I think there's pretty much no prospect of us being able to do any of those things. That was all starting to sound a little bit like the Mistborn trilogy by Brandon Sanderson. For anybody who's read that out there, they'll know what I'm talking about. Okay, Becky, can you answer this question

from Brian Smithson? They they say greetings from rainy south carolina my question is how do we know what galaxy a given star is in couldn't it be in front of or behind a galaxy of interest love the show thanks for your time yeah i mean behind a galaxy of interest is very unlikely because if we think about individual stars compared to the brightness of an entire galaxy um you know of billions of stars we're never going to spot a single star unless it's like lensed so people might remember uran dell the most distant star ever spotted that was spotted by the whole space telescope and it's since been looked at by jdbst as well um that was like lensed magnified by sort of the curvature of space by gravity itself so that we could actually see it and from the light that we get from it we know

that it's an individual star and not a collection of stars. In terms of stars in the foreground I mean galaxies are mostly so far away that we can't resolve individual stars so if you see a single point source of light that is so incredibly bright that it's probably going to saturate your detector because if you're trying to expose an image to detect a very faint distant galaxy then you're going to probably saturate your detector with a much brighter star that's quite nearby and so you that's why you do get those big spikes on things like you know like the Hubble ultra deep field i feel like that's an image that people are quite familiar with you have a few stars in there that are very very bright and have these spikes on them where the light has sort of bled into nearby pixels because it was so bright um in the pixel that it was detected in that's usually how

we can tell obviously with jdbrst that's changing a little bit because now it can resolve individual stars in some nearby galaxies but still like from from the light that we detect from them you can you can tell that they're stars in our own galaxy necessarily and not you know part of a collection much further away again redshift usually is what gives it away yeah well on the theme of jwst we have this question from rory goodbody so robert can you help with this he says hi from Dublin I've really been enjoying your podcast after finding it a few months ago and have gone through the whole back catalogue as a somewhat yeah I mean good good work that's amazing as a somewhat

lapsed astronomer having been a member of Astronomy Ireland as a child I got back into astronomy last year when my then five-year-old was interested in seeing things in space. My question is about recent rumours about JWST purportedly detecting city lights on Proxima Centauri b. You know what? The internet has a lot to answer for. It does. Which of course turned out to be false.

Yes. Turned out to be. It never was true true it was always false firstly could jwst ever hope to detect such lights on any planet and determine that they're artificial rather than reflected light from the nearby star and if so how would we go about making contact with the little green men over four light years away yeah i hadn't heard about this until congratulations thank you rory yeah i missed that yes people were like can you debunk it and i was like no that'd be an enormous waste of my time exactly yeah yeah it's like i mean yeah anyway i think it's confused there was um the discovery of aurorae so northern and southern lights on a

brown dwarf and i think it spiraled out from that so brandon was an object intermediate between a star and a planet but yes there are no are no detections of lights on planets around other stars at this point. It's an interesting one in the sense that what you'd be saying is, assuming this civilisation, you'd like to think they're much more advanced than us. They're still doing light pollution, which is slightly depressing, but there we go. But essentially, it's impossible forwst to see those lights and there are several reasons um one would be that if they're anything like the lights we have on earth you know they're emitting invisible wavelengths like modern leds then jwst wouldn't be well

placed to detect them because of where it operates in the mid-infrared but mainly because that even the nearest stars so far away those lights lights would be fantastically faint. And JWST can't even see Earth-sized planets directly, really, unless there's something that I've missed about it. You know, they're simply too faint and too small and typically too close to their stars. Now, some next-generation telescopes coming on stream, like the ELT, that's one of the things they might be able to do for the nearest stars. But JWST can't. It's just not quite big enough now the other part of the question what would we do to make contact with the little green men well I think it's funny there are lots of discussions about this about whether we should contact aliens if we actually hear from them or detect them and all of the ethical considerations about what that means but assuming we wanted to I guess there are various things we

could do like send radio signals and also devise light signals of our own to to see whether they might detect those and then expect that it's going to be an eight-year reply time which is a lot better probably than most of the if there are alien civilizations out there and that's very debatable but if there are then we'd typically be looking at hundreds or even thousands of years for reply so eight years we could probably live with but lots of ethics to think about around that about whether we should advertise our presence in the universe more than we're doing already through you know through older tv transmissions and routine radio transmissions anyway very interesting all right well thanks everyone and keep the questions coming you can email podcast at ras.ac.uk.

And we're also on Instagram. It's at supermassivepod. We'll be back next time with an episode all about interstellar objects. These strange visitors that pass through our solar system. Clearly, it didn't come from our solar system. It came from another one. And we're like, oh, hello.

And then they disappear. And we're like, oh, bye. I know, Izzy, you're very excited. I can't wait. I'm really, really excited for this one. And I'm sure many of you out there have questions. So make sure to send them in,

as Izzy said. But until next time, everybody, happy stargazing.