The Supermassive Podcast - 55: BONUS - Galaxy Spin and Saving Herstmonceux Observatory

Episode Date: August 21, 2024

Does an instantaneous star map exist? Where are the perfect spheres in space? How did Venus get so close to the Sun? It's a bonus episode from The Supermassive team.  Sign the petition and support Herstmonceux Observatory here... https://www.change.org/p/save-the-observatory-science-centre-herstmonceux

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. Yeah, this is the place where we dive into the Supermassive mailbox and answer all of your questions. Now, a few episodes episodes ago we asked you to share the interesting places that you were listening to the podcast and this all started with someone who shared that they were listening to the supermassive podcast in the dentist chair to help them calm down well we've had an email from mark waters and he has sent us a photo whilst driving down the side of a mountain in north canterbury new zealand

i try not to make any sudden loud noises in case twitches and rolled off the side of the road gosh what a what a multitasker yeah exactly you know driving listening to a podcast taking a photo so disclaimer if anyone else is listening at the side of a mountain please park up before before doing any photos to send it to us yeah yes exactly and actually before we get onto the questions there's an observatory in the uk that needs our help so robert can you tell us what's going on for our friends at herstmonceau observatory yeah yeah absolutely yeah so you'll recall um that we visited it last year and did a night a really nice episode there it's absolutely a fantastic place so this is the site the royal

greenwich observatory moved to for about 35 years at the end of the second world war until until 1990 and it has these fantastic historic telescopes there so the problem they have is that the science center on the site the observatory science center their lease is coming to an end in 2026. So they're looking for a new home. And that's a huge shame because they're brilliant experts there. And it's an incredibly special place. So not only would we like them to be able to stay, but we're also worried about what that would mean for the historic telescopes on site,

the observatory buildings there too, which have been lavishly restored. There's lots of lottery money went into it. It's a really really really beautiful place uh and also making sure they've still got proper public access and then alongside that is the slightly less publicly accessible but really important stuff the geophysical facilities like there's a satellite laser ranging station there which is doing great science well as it implies measuring the positions of satellites and if you go there you see this laser beam going up into the sky it looks very very James Bond-ish, but that's what it's doing.

So what we're doing at the RAS, we're writing to the executive director of Barda College, part of Queen's University Canada, because they own the site. And we're quite keen to meet with them to talk about it. But for anybody listening, if you're concerned about this and you agree with what they're saying, I mean, have a think about it, obviously. There's a petition we can sign,

and I guess we can put a link to that in the show notes so you can look at that and see what it's about and if you browse news articles there's quite a lot of news media coverage of it as well yeah absolutely i'll make sure that the petition is in the show notes so if everyone could go and sign that that would be really amazing much as much as we can get onto this to try and keep it where it is in its historical site the better so thank you to anyone who goes to assign it i couldn't believe it when when robert first told us about this because it's such an incredible site and it does loads for astronomy in the local community for all ages as well i think it's things like that that it's so important to maintain that history it is and it's also it's also really rare i mean the things there aren't very many examples like this in the UK.

You know, there's a limited number of historic telescopes. There's some in Cambridge and so on, but not very many with public access, not very many at all across the country. You know, there's little domes run by amateur astronomy societies and so on. But, you know, it'd be a terrible, terrible shame if that access wasn't there and if the telescopes weren't kept and the site wasn't, know this incredibly special site isn't preserved and kept for us all yeah absolutely okay let's move on to the questions becky basil bb has been in touch and he says hi there huge thanks for the mahoosive podcast i learned so much and enjoy the banter my question is to do with the distance to observable objects especially those that are a very very long way away what we see when we look up is temporally distorted because of the speed of light and an object's distance has anyone made a star map that shows where everything is right now if light was instantaneous i know that would be very difficult because of gravitational lensing and we might not

have enough data to work out which direction everything is traveling in i hope this is not a silly question thanks again i look forward to hearing your future episodes so there's a couple of things here like i know you mentioned star map basil but i think also in terms of like very distant objects like galaxies where this would have like the biggest impact on it i think you're talking about something that's known as co-moving distance so because light takes time to travel to us at like 300 000 kilometers a second or so we see distant galaxies as they were billions of years ago and where they were back then as well but we can't actually correct for sort of you know their their apparent distance they appear to be at to the real

distance that they should be at to the real distance that they should be at now if we take into account the expansion of the universe that's happened in the intervening time right that's what we call the co-moving distance and we could make a map of galaxies like that and correct all of their positions and take into account the expansion but it's so dependent on the model that you have for the universe and the expansion rate that you get from that model or the expansion rate that you measure in another way. And as we've talked about before on this podcast, there's the famous crisis in cosmology at the minute

or the Hubble tension when no one can really agree on a rate of expansion because all the measurements tell you different things. So if we do make a map of the universe, we tend to just leave them in their sort of apparent observed positions essentially as the stars in our own milky way we're seeing them as they were and where they were a few hundred thousand hundred thousand years ago and gaia is doing this it is making a map of the positions and also recording the velocities of all of those stars as well so we do have sort of like a moving map of the milky way now which you could correct

for like okay so they've moved since then a few 10 000 years or so but i don't think there's any scientific reason that you would necessarily want to do that so i don't think anyone's made that map right because scientific reason why you would do it everything's sort of moving in roughly the same direction in the galaxy anyway there are some local effects of stuff going in different slightly different directions and drifting apart from each other but it wouldn't be that big that you would probably notice a difference if you were going to make a map of like the entire milky way so that's why no one's really done it you could it could possibly be quite a

cool data visualization, but also would you notice the difference like with the human eye? I don't know. All right. Thanks, Vicky. And Robert, can you help with this question from Stephen Bryant in Sydney? He says, hi all, love the podcast. I was surprised to hear that there are no perfect spheres in one of your recent episodes, not even in black holes. Does this tell us something fundamental about our universe? Well, as you might expect, Stephen, I'm going to say that's a great question, which means I'm thinking about it quite hard. And pretty much every system has imperfections in it.

And that's really a result of the fact that there are massively a complexity of things. So, you know, you think of the solar system, right? You've got the sun in the middle the planets going around it we imagine i guess our first visualization or it or i thought of that as children is that the sun's circuit or a sphere and the planets are all moving around in perfect circles and of course that's far from the truth and they're all nudging each other and you know the force of gravity the way in which planets and stars forms means that they're going and the way they are means that they're going to be a bit irregular and those things change over time as well and it tells us i guess that what it tells us physics works because we're able to usually describe why

they're like that and that means that the inevitable result is they're not going to be they're going to have imperfections they won't be perfect spheres ever i was thinking about examples of this and if you're looking for some deep concept then there is this idea there's this cosmologist max tegmark and it's quite controversial but his idea is that maths is an integral part of the universe and that obviously has some kind of perfection in it but other people argue that's really not a fair thing to consider because there's an infinite number of mathematical solutions you know do these things actually exist in a meaningful sense as well so i think the answer to your question is it tells us certainly something fundamental about physics and the way the universe works that you know you're not going to get

perfection or perfect symmetry in any system that you look at okay if you i love that have you ever heard this phrase i don't know i don't know where i heard this but like if you you want perfection become a mathematician if you want imperfection become a physicist and yeah i've heard a ruder version of that which i won't relate in case there's children listening and then i feel like there's one for engineering as well right that it's just like if you just want it to just work and not question it then go into engineering that's so good okay and becky beta monkeys on instagram has a question about galaxies and i for listeners i'd just very much recommend

going to their Instagram account because it's full of like quite fun comics. They ask, how do you measure the spin of a galaxy? So to measure how fast a galaxy is spinning, you need to measure how fast the stars in it are moving. And thankfully, the light that we get from stars has a sort of fingerprint to it that we can use to trace those

speeds. So the molecules in the atmospheres of stars, things like, you know, like carbon and oxygen, things like that, they absorb very specific wavelengths of light. They steal away very specific colors of light, giving us this like gap in the rainbow or the spectrum of light that we get from from stars and those gaps appear in a very specific pattern so we can spot that pattern when we look at stars and galaxies and then we can tell if that pattern has been shifted because of a doppler shift because something is moving so remember as we've talked about doppler shift before right where you hear like the the pitch of a siren changing as it races past you like an ambulance siren or something because the wave gets squashed as it comes towards you and it gets stretched out as it moves away from you when light gets squashed it gets bluer shifted to

shorter wavelengths it goes bluer and when light gets stretched out it goes redder and shifted to longer wavelengths and so those gaps shift as well right now? Now for galaxies, there is like an overall shift, a Doppler shift, what we call a red shift, thanks to the expansion of the universe. So the universe is expanding, it makes the galaxy look like it's moving away from us and so that all the light gets red shifted a certain amount. But as you look at the galaxy,

one side of it is moving towards you and one side is moving away from you and those effects of the expansion of the universe and then the galaxy moving sort of add together and so if you look from one side of the galaxy to another at that sort of pattern of gaps in the the rainbow of light you see that it there's just an ever so slight difference from one side of the galaxy to the other which you can translate to okay that side of the galaxy is moving away the side's moving towards and at what speed as well right you can translate it into the speed that stars are moving at or how fast the galaxy is spinning right and i mean just

to put a ballpark figure on it it tends to be somewhere from like 100 to 200 kilometers a second in terms of how fast the stars are moving that's about 200 000 to 400 000 miles an hour so uh yes a car can do that right but it's fun to think that we're technically moving at that speed now right because the earth orbits the sun the sun is orbiting the center of the milky way as the milky way spins at around about 200 kilometers a second yes and i think i can hear all of our listeners going i'm so insignificant cool just like okay and robert going back to our latest episode on venus david connerty asks how did venus end up so close to the sun in its orbit this is sort of more about how it formed and the type of

planets you find forming in different places around the sun and two well we don't have enormous samples of this but for other stars as well so why the terrestrial rocky planets are all close to the sun and the gas and ice giants are further out and the temperature is one of the key factors so closer in you don't have the the planets didn't have the ability to hold on to hydrogen and helium to build up atmospheres in the same way that jupiter and saturn and slightly different way the ice giants uranus and neptune did so the rocky planets grew through accreting debris and end up with big rocky bodies you know with molten cores inside and a relatively i mean although venus's atmosphere is pretty thick a relatively thin atmosphere compared with their size now one idea caveating that is that jupiter migrated towards the sun early in its history

towards its present location having formed further out and that might have then or probably would have then actually disrupted the whole solar system including the orbits of venus and the earth a bit so their orbits might have changed shape even if they stayed in roughly the same place so i think that you know the message from this is there was a lot of chaos in the early solar system it wouldn't have been a very stable place at all but the main reason that you've got that different category of planets is just to how close they were to the sun when they formed and that is the distinguishing factor how hot it is what kind of materials are available to make planets in different places thanks robert and thank you to everyone who has sent in a question please do keep them

coming we love reading them uh you can email podcast at ras.ac.uk and we're also on instagram at supermassivepod we'll be back next time with an episode about mercury but until then everybody happy stargazing