The Supermassive Podcast - 38: BONUS - More Comets, Less Asteroids

Episode Date: March 10, 2023

Is there a Cosmological Horizon? Can we change a comet's orbit to see more of them? What's the most distant human-made object in space? Izzie, Dr Becky and Robert dive into The Supermassive Mailbox to answer your questions.  Want to support The Supermassive Podcast? Why not buy our book The Year In Space - https://geni.us/jNcrw The Supermassive Podcast is a Boffin Media Production by 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 and astrophysicist Dr Becky Smethurst. Yep, this is the place where we dive into the Supermassive mailbox and take on more of your questions because we can't leave you hanging like we have done with some people. For so long. Okay, so we'll be looking to so robert to get that reference i apologize so robert and becky let's get to it becky jason on twitter wants to know given that the universe is expanding is there an example of a galaxy that was visible and is now not as it has moved over the cosmological horizon if not how long would a vanishing like that typically take uh unfortunately not jason like

you've got to remember the universe is expanding yes but that doesn't mean that galaxies are moving away from us it means that space expanding is moving those galaxies away from us it's not the galaxies are moving it's that space expanding makes them appear as if they're moving so if that's a case of space expanding the cosmological horizon also expands with it so everything is moving away from us at the same rate the galaxies and the horizon so nothing will ever cross that horizon because everything is moving away from us at the same rate. Yeah. And Robert, Hossain Mustafa Godrawala emailed to ask,

can we theoretically change the orbit of a comet as we did with an asteroid just so we can see them in our skies more often? I love that. It's a wonderful and at the time sort of armageddon like idea isn't it really you know the idea you divert all these comments into the inner solar system i don't know i like the way that hussein thinks yeah he's thinking outside the box we know what asteroids less asteroids more comments thank you very much i mean i suppose we could i'm not

sure it's a great idea because you don't want to add to the population of stuff in the inner solar system, some of which comes near the Earth. Such a party people, Robert. Boo! Boo! But, you know, that doesn't seem like a brilliant move to me, but I don't see any reason in theory why you couldn't do it.

However, with big enough devices, but if you do do that, then you divert these comets into the inner solar system. What happens is if they go around the sun more often, they run out of their volatile materials more quickly. And so their tails would disappear on a much faster time scale. And we see that with some comets like this comet Enki that goes around the sun every three years or so. Hardly any dust and gas coming off it because it's done it simply so many times. And so the bright comets that you get tend to be things that you know either haven't come into the inner solar system before or they did it you know every on a time scale of

tens of thousands of years got loads of stuff that can come out to make those beautiful sights in the sky um but they do nothing to do with us but comets do change their orbits and they do that because of the influence primarily of the gravity of jupiter which we'll be talking about in our next main episode and an example of that is a comet, which we'll be talking about in our next main episode. And an example of that is a comet called Lexel, which was found in the 18th century. It was probably moved into the inner solar system in 1767. It came really close to the Earth in 1770, actually the closest approach on record for a comet, just 2.2 million kilometers away. And then it was moved out by Jupiter in 1779 and now

we think it might still be in the in the solar system but it doesn't come in very close at all it's in an orbit that it probably keeps it beyond Jupiter oh thanks okay Becky Michael Dealey has a question for you if a star millions of light years away had a planet surrounding it that had some form of intelligent life form and that life form had the wherewithal or inclination to look towards our planet could they be seeing dinosaurs roaming where london is today well i can't comment on whether there was dinosaurs ever in modern day london because i am not a paleontologist i presume so. So let's say dinosaurs on the globe in general. In theory, yes.

If they had a telescope capable of resolving something so incredibly tiny moving on the Earth's surface, sure, sure, you could look back and see the Earth as it was, what, 250 million years ago. Problem is, if they were on a planet and wanted to see dinosaurs, they'd have to be at least as far away as 250 million light years in order to see the Earth at that stage. Our own galaxy is only 100,000 light years across, so it's definitely not a planet around a star in our own galaxy. A star in our own galaxy on the other side would probably just still be seeing woolly mammoths i guess roaming the earth uh andromeda is two only 2.5 million light years

away so i guess they'd be seeing some sort of ice age on earth but i did find something um for you michael uh ngc 4907 um is a beautiful barred spiral galaxy 270 million light years away. So in theory, if they had a telescope that could resolve something as small as a dinosaur on the surface of the Earth 270 million light years away, then yes, that is what they would see. They would see the dinosaurs. But it is interesting to think about, you know, Earth's also been pushing out radio and TV signals from the surface for a very long time.

Some of the earliest signals won't get there. But one thing I like to think about is that, you know, TRAPPIST-1 is a system that people are very excited about. You know, there's seven planets in it. Some of the planets in the habitable zone. That's only 40 light years away, TRAPPIST-1. So if you think about it, if there is life on TRAPPIST-1 and they had the ability or the

wherewithal as michael put it to detect maybe the tv and radio signals that earth had been pumping out then you know they'd still be watching dallas and discovering the joy of painting with bob ross from like 1983 well i'm just thinking, like, when did EastEnders start? Yeah, before both of you were born. In the mid-80s. Oh, I like the idea of that. I really hope that's happening. And Robert, Ravinda Peral wants to know,

what is the most distant man-made object in space that we know about? Are we still receiving data back from this object? Well, the answer, Ravinda, is it's the Space Probe Voyager 1, launched right back in 1977 by NASA, and its goal was to travel, which it did wonderfully successfully, to Jupiter and Saturn, and then it became an interstellar mission. It was leaving the solar system, so it travelled out away from the sun. It's continued to do that, gone through, you know, detects things now. Its remaining instruments do things like detecting changes in the magnetic field and so on.

So it knows it's moving into interstellar space, or NASA knows it's moving into interstellar space. And it's been working for more than 45 years. You know, incredible technology to be going that long. Obviously, a very, very weak signal from it. And it's expected to keep going until long obviously a very very weak signal from it and it's expected to keep going until 2025 or so i mean it seems to me that's only a year a couple of years away and the power for its instruments comes in this radioactive heat source called a raise it radioisotope generators of the radioactive source decays and the heat then power is used to generate electricity for it

and that you know powers its, which is ridiculously faint now. But soon it will reach the point where that power is just too weak for the signals to reach the Earth. And they already take 22 hours to reach us, to give you an idea of how far away it is now. I think, what is it, 14 billion kilometres away. So I should also, though,

I've got a note on my script here that I need to bring in our producer, His Excellency Richard Richard on this one too. You have a script? A sort of script. Yeah, well, what I was going to mention, I made a documentary a few years ago now called

Space 1977 for the BBC World Service. Great title. Presented by astronaut Ron Garan. It is a great title, thank you. And it's still there actually on BBC Sounds if you want to go astronaut Ron Garan. It's a great title. Thank you. And it's still there, actually, on BBC Sounds, if you want to go and listen to it. It's a really nice programme because we went to the Jet Propulsion Laboratory where Voyager 1 and its twin probe, Voyager 2, are controlled from. And you see on TV, you know, Voyager 1 and Voyager 2,

you see with all these missions from NASA controlled from JPL, this amazing control room, all shiny and lots of plasma screens everywhere. Actually, plasma screens, that's probably old hat. It's shiny stuff. It just looks amazing. It looks spacey. It looks really spacey. The Voyager 1 and Voyager 2 control room is actually in a little offshoot of JPL in Pasadena. It's in this shabby little sort of one-story office block with these cubicles. It looks really grim, like something from the office. I'm just imagining someone who works there now,

like listening to this podcast going, who are you calling shabby? And in one of these cubicles, there's this beige computer which has a little sticker on it that says Voyager 1 Mission Control. And on it, it says, do not switch off. That's literally it. Because there's so little data coming in. I'm picturing it like still running like MS-DOS or something.

It's a very old computer running this. And there are not many people working on it because it's getting so little data back from Voyager 1 and Voyager 2. And they're sort of nursing them really through their final years, these spacecraft. But yeah, remarkable and remarkable people working on this mission. And, you know, until recently, a lot of them had worked on it from the beginning. They're now pretty much retired, but there's still people working on Voyager. There's a guy, was it Edward Stone? Retired 50 years as the project scientist. Yes, that's right. 50 years. Blimey. Yeah, so he was in,

so we interviewed him. He was still very much in charge of the Voyager missions when we interviewed him and I think he's only recently retired. So yeah, extraordinary,

extraordinary mission. I just feel like they're, imagine being the cleaner in that place and just be like, oh, I'm like that bob in the vacuum. yeah you trip over the lead that's so brilliant and i'm becky neil bennison has been in touch about something that we talked about in our q a episode in january and he says excellent podcast as ever although i was

slightly disturbed that dr becky seemed to indicate that the myth that the sun was yellow was busted. Would really like to see her working out and respectfully disagree with her. The sun is a G2V class star. Spoiler, that's yellow. with you as well. So I will give you my working out, definitely. If you look at what's known as the spectral energy distribution of the sun, so that's how much light at each wavelength you're getting from the sun, and you look at that without any atmospheric absorption, so before it passes through the Earth's atmosphere, the peak of the sun's emission is at 500 nanometers wavelength, which is a green color of light. Now there is enough light at other wavelengths essentially for them all to add together. So, you know, blues, reds and yellows and everything to make the sun actually appear white to our eyes. Astronauts aboard the International Space Station, for example, who see the sun without any absorption through the Earth's

atmosphere have reported that the sun does look white to them. It's the atmosphere that makes it yellow. Historically, G2V stars, as you said, have been called yellow dwarf stars, but that is a complete misnomer. G-type stars are all white in colour, not green necessarily as the peak wavelength would suggest, but also not yellow as the atmospheric absorption would suggest. So thanks so much for sending your comment. And I do want to like, you know, encourage people to do what Neil's done here and send in a correction to us because we do make mistakes. We're only human, right? And if we do make a mistake, we want to correct that. So please do write in if you, you know, if you think we have made a mistake in that sense. And I'm happy to show my working as Neil requested as well.

Nice. Okay, well, thank you, everyone. And keep the questions coming. You can email podcast at ras.ac.uk, tweet at Royal Astro Sock, or find us on Instagram at SupermassivePod. We'll be back soon with an episode all about Jupiter. But until then, everybody, happy stargazing.