The Supermassive Podcast - 47: Neptune... At Last!

Episode Date: November 28, 2023

They've done it. It has taken them all year but Izzie Clarke and Dr Becky Smethurst have reached the final planet in our solar system; Neptune. Dr Leigh Fletcher from the University of Leicester is back to cover the basics of the planet and Carolyn Kennett, Chair of the Society for the History of Astronomy, tells Izzie about its controversial discovery. Plus, Dr Robert Massey is on hand for some winter stargazing. The Supermassive Podcast is a Boffin Media production by Izzie Clarke and Richard Hollingham for the Royal Astronomical Society. 

Hello and welcome to the supermassive podcast from the Royal Astronomical Society with me, science journalist Izzy Clark and astrophysicist Dr Becky Smethurst. We've done it, it's taken us all year, but we finally reached the final planet in our solar system, Neptune. My second favorite planet, obviously, after Saturn. But I just, I don't know what it is about Neptune. Like, I think it's the color.

I'm just, I'm just a sucker for a blue and it's just the most gorgeous, deep sea colored blue as well it's which is why i think just the color goes with its name right i even painted my nails oh have you actually blue for years yeah just in honor of this episode saturn's out there getting jealous like becky is talking about another planet and i don't know how i feel about this um so coming up lee fletcher from the university of leicester is back to cover the basics of Neptune. And Carolyn Kennett, Chair of Society for the History of Astronomy, tells me about its controversial discovery.

Oh, intrigue. I like it. But as always, Dr. Robert Massey, the Deputy Director of the Royal Astronomical Society, is here. So, Robert, how big is Neptune? It's always good to start with a question i can answer there is he i think so yeah so quite big is the answer it's the fourth largest planet in the solar system still a gas giant or it's an ice giant 49 000 kilometers across which means it's a bit smaller than uranus actually a bit more massive and you could fit 58 earths inside and it's really far away as well which is a crucial point, 4.5 billion kilometres.

So although it's quite big, it always looks really small in a telescope. And you actually need quite good conditions to see it as not looking like a star. So the most you get to see with most telescopes on Earth is a little tiny blue disk. And if you're very lucky, it's Big Moon Triton. And we did see it. I don't know if you remember when we visited Hurstman. So we saw it there because it was just trailing along behind. I think it was further trailing along behind,

I think it was further along than Saturn was. So we have, well, three of us have seen it. You must have seen it. Yeah, I've seen it as like a blue dot. And I'm like, oh yeah. Exactly. If I squint, am I seeing it? Is that? I love it if you use like Stellarium and it's like,

Neptune is there. You're like, is it? Okay. I always end up trying to take a photo with my phone, a night mode shot to be like is it there but then so many stars pop up that i'm like i still don't know where to look well cheers robert we'll catch up with you later in the show for some more questions and those all important stargazing tips okay so that is the size of neptune covered but what is it like as a planet? And how much do we know about it, given that only one spacecraft, Voyager 2, has ever passed this

ice giant? A travesty. A real travesty. Well, Lee Fletcher, Professor of Planetary Science at the University of Leicester, was featured in our Uranus episode. And this time I caught up with him to find out all about Neptune. So Neptune has a stormy atmosphere. It has bright clouds of methane ice, which come and go so rapidly that as Neptune spins once every 16 or 17 hours, those clouds are sheared apart and destroyed and the weather can evolve dramatically from night to night. Now, it does have a banded organization in the same way that Jupiter has those glorious stripes, the belts and zones of Jupiter. We see subtle banding within the atmosphere of Neptune, but that banding, unlike Jupiter, where big storm systems tend to stick around

in the same latitude band where they form, on Neptune, the storm systems can actually drift with latitude. They can move north and south. And the most famous example of this, when the Voyager 2 spacecraft flew by in 1989, it discovered an enormous swirling maelstrom called the Great Dark Spot, the GDS, obviously to rival the Great Red Spot that we know about on Jupiter. But unlike the Great Red Spot on Jupiter, the Great Dark Spot of Neptune actually disappeared within five years. By the time the Hubble Space Telescope took a look at Neptune in the 90s, that Great Dark spot had completely vanished. And we now understand that it's because the great dark storm system of Neptune could move in latitude and actually move to locations where it was unstable, it was broken up, and ultimately just vanished completely from Neptune's atmosphere.

So the weather conditions on Neptune are really powerful, unexpectedly powerful, given how far away it is from the sun. In fact, it has some of the fastest recorded wind speeds of anywhere in the solar system, despite its extremely cold and frigid temperatures. So just how fast are we talking? So the winds do change from place to place on Neptune, but I believe the fastest recorded winds are getting up to about 1,200 miles per hour. Imagine a wind on Earth getting to anywhere near that strength. Oh my goodness. Okay. And so in terms of distance from the sun, you know, Neptune is 30 times the distance to the sun than we are. So quite far away. how does that influence temperature you know how cold is it on

Neptune so you're absolutely right by being so far away from the sun it's only receiving a tiny tiny fraction of the energy that we do here on earth and that means that the temperature at the cloud tops of Neptune can get down to something like 50 or 60 degrees above absolute zero. So you're talking minus 210 degrees there, which is quite astonishing. And of course, when you get so cold, that means that vapors that are normally in a gaseous form here on Earth can condense to form clouds. And that's what we're seeing with the methane. Now, those cold temperatures actually make Neptune quite difficult to observe at some wavelengths of light. And particularly, I do my research out in the infrared where we're detecting the heat energy coming from the planet. And that's really hard to do when your planet is

only at 50 or 60 Kelvin. An ice block, essentially. An ice block. So what you need actually actually, in that case, is the exquisite sensitivity of something like the James Webb Space Telescope. The composition of Neptune includes some hydrogen and helium, a bit like Jupiter and Saturn, but is primarily made of much heavier stuff. So I'm talking about things like methane, like ammonia, like hydrogen sulfide. So I'm talking about things like methane, like ammonia, like hydrogen sulfide. These are all common elements in our universe, but they're found to be concentrated within these ice giants. And is that what gives it that famous blue look, all of that methane? Is that what it is?

Yeah, you're absolutely right. Methane gas is a really good absorber of red light coming from the sun. So it eats away at all of that red light. And the only light that's then left to reflect back is the blue light. Now, we also think that it's not just the abundance of methane that gives it that gorgeous royal blue colour out there in the distant solar system, but it's also the absence of aerosol and haze particles within the atmosphere. The atmosphere is so turbulent with its weather systems that it really effectively removes those haze particles so that they don't scatter the light. If they were to scatter the light, you'd get a much more greeny, whitish sort of appearance appearance which is what you see when you look

at uranus which has more of these aerosols present so there we have a difference in the composition of aerosols which we think explains the differences in the colors of uranus and neptune and so when we talk about some of the characteristics you know last time we talked about uranus and its rings does neptune rings? I don't feel like it's very well known for having that. Yeah. In fact, all four of the giant planets, Jupiter, Saturn, Uranus and Neptune all have rings. OK, it's just that Saturn is obviously the most dramatic and spectacular and everybody knows and loves them. Neptune does have rings. It has five rings. OK, they're quite narrow, they're quite dusty and dark. So they were only really discovered in the 80s, I believe, and then first imaged by the Voyager 2 spacecraft. And we don't know a lot

about them. They're still confined by the gravitational interactions of Neptune itself with the small moons and satellites that are orbiting around. But there is a really peculiar ring called the Adams ring.. The Adam's ring is one of the larger ones, but it's got clumps in it. And these clumps, they're known as ring arcs. They seem to be agglomerations or packets of material that have come together gravitationally. And whilst they have existed now for at least 35 years or so, they do seem to change with time. They overlap each other, they change in their brightness, they change in their extent. And it's the only place really in

the solar system where we see something as weird as that going on in the ring arcs of Neptune. How are we able to study Neptune? So of course, when Voyager 2 flew past Neptune in 1989, it really revealed the whole Neptunian system to us for the very first time. We'd never been able to see some of the moons and rings and things on Neptune itself in any way before. So Voyager 2 was an incredible mission of discovery from that perspective. So how do we study Neptune beyond Voyager 2? Thankfully, we do have today modern telescopes are capable of looking at Neptune from ground-based facilities and from things like Hubble Space Telescope. And of course, the new kid on the block is the James Webb Space Telescope.

So all of these facilities are great at looking at the sunlit side of Neptune. And I'm being very particular there about saying sunlit side, right? That's because Neptune's orbit is so long, 165 years it takes to go around the sun. And it's got an axial tilt, just like Earth, which means it experiences seasons in the same way, spring, summer, autumn, and winter. But because the seasons are so long, we've only ever seen southern summertime and springtime conditions, okay? We've never seen what's going on at the North Pole of Neptune. And because even when Voyager flew past, the southern hemispheres of those moons were in sunlight, that means that there were regions of those moons that no eyes, human or robotic, have ever been able to see before. And we can't do that from Earth. We have to go there with some future mission to explore. And are those future missions

coming? Do you have good news for Earth, Lee? I wish I had better news. What I can tell you is that the astronomy community and the planetary science community recognises that Neptune is a target that one day we have to go to explore. The trouble is it's so far away that it's quite difficult to get there. You almost have to use a Jupiter gravity assist to give you that extra energy. And Jupiter is only in the right place in the solar system to do that once every 12 or 13 years or so. And even then, you still need quite sophisticated technology to get us all the way out to Neptune and crucially, to then slow down and go into orbit around Neptune itself. So there are concepts out there that can do this. They're a tad expensive. So if you and your listeners have a few billion down the back of the sofa to be able to help us out, that might allow us to get this mission realized. load of similarities between Uranus and Neptune, both as ice giants. So we think that that's got the priority for now. That doesn't mean that we won't get there eventually. And one reason that we really want to do Neptune is this strange moon called Triton. Triton is potentially a captured

object from the Kuiper Belt. It's a world of ice. It's got nitrogen ices, carbon monoxide ices, methane ices all across the surface and a little bit of water ice thrown in as well. But weirdly, for an icy body 30 astronomical units away from the sun, it appears to be geophysically active. That means that there are active plumes of material erupting from the surface of Triton and populating a thin nitrogen atmosphere around that strange satellite. This is really strange. And if we can explore Triton, maybe that will give us a great handle on what the other worlds of the Kuiper Belt are really like. And so that mission to Neptune and Triton, when it does come along one day, hopefully in my lifetime, will be absolutely spectacular.

Oh, fingers crossed for that mission. Yes, please. Yes, please. That was Lee Fletcher from the University of Leicester. Okay, so Becky, what stops a planet like Neptune from becoming the size of a gas giant, say, like Saturn and Jupiter? I mean, it's really just about the availability of material, right? As the solar system forms, you've got this swirling disk of hydrogen, some helium,

and then just sort of like a smattering of heavier elements that end up forming like the rocky planets. But as the sun forms and it heats up, you know, it goes from protostar to star then the energy that it's pushing out outwards is then going to impact with all that very very light hydrogen and helium in the rest of the sort of solar system's disk and as that energy impacts with that gas it essentially like picks it up and just sort of like sweeps it out of the solar system and takes it away so the gas giants really have this very narrow window of time to form where there's actually hydrogen and helium available in the solar system for them to build up. And so gas giants really do have to form very quickly or the material is gone. And there is

sort of like a threshold where like runaway growth starts to happen, where they just take in loads and loads of the hydrogen gas that's around them. that's around about we think about a hundred times the earth's mass so jupiter really easily goes over that jupiter's like was 317 times more massive than the earth so we think it formed by this runaway uh growth saturn's right on the edge it's about 95 times the mass of earth so maybe it just sort of started to pick that up just as all of that material got swept away. But Uranus and Neptune, Uranus is 14 times more massive than Earth and Neptune 17 times more massive than Earth. So they're nowhere near that threshold. They never had that runaway growth at all. Just what they could attract in that very

short window of time when the hydrogen helium is actually available in the solar system. Okay. And Leigh briefly mentioned Neptune's moons there. So how many are there? And do we know what they're like? Yes, there's 14 known moons of Neptune. They're all named after water deities because the IAU are nothing if not consistent

with their naming conventions. And it's actually a really fun system so triton is the biggest of the moons that robert mentioned before you can see that with a really good telescope from earth and it's actually much bigger than pluto but smaller than our moon to put it into sort of context for how big it actually is and it's the only planetary sized mass moon in the solar system so think like something big enough to like round itself okay that is moving or orbiting its planet in the opposite direction to what its planet is rotating so we call that like retrograde motion if you remember we talked about this in previous episodes as well it's also inclined to like neptune's equator like the plane that it orbits in as well so it's very very

likely that it was a rocky planet that was captured into orbit by neptune at some point okay it's actually really quite cool if you think about it like the next largest moon in the solar system that we think was captured was saturn's moon phoebe which is only 0.03 percent of triton's mass wow so it's like it's like it's absolutely smashed the record yeah yeah right so it's a pretty big deal and also it's probably really catastrophic for like any other moons that were in orbit around neptune at the time it probably caused them you know to go through lots of collisions there's probably a big rubble disc that formed as well and we think that actually the seven moons inside of triton all formed from the rubble disc that triton's

capture actually formed because they're all moving prograde they're very regular moons as well they were sort of all orbiting in the same direction a very regular system and they orbit within neptune's rings okay as well so we think maybe even the rings that like due to maybe even collisions between moons inside of the orbit of Triton as well, but also sort of very young, sort of quite recent collisions. Then you've got six more irregular moons outside of Triton. So again, they're either orbiting in the other direction or they're on a really irregular plane or something like tilted to Neptune. And the furthest out is called Neso, N-E-S-O. And it has a very elliptical orbit and it comes as close to Neptune as 21 million kilometers away and as far away as 77 million kilometers from Neptune. That is half of the Earth-Sun distance.

That's wild. Why? Probably again, a capture, right? But just to put it into more context, right? That's further out than Mercury orbits the Sun, that NISO orbits Neptune, right? It takes 27 years for it to orbit Neptune, right? So it's the moon with the furthest known orbital distance in the entire solar system. That's wild. So what a pretty fun system that Neptune has. I know.

We often joke about this, but it sort of seems to be like the forgotten planet. You're just like, oh yeah, Neptune, that's got stuff going on. But anyway, we're not going to look at it or talk about it. Anyway, let's look at saturn i'm joking um and so we've had this other question from benji 182 and they ask has neptune's orbit migrated substantially i mean yeah we think all of the planets orbits have migrated somewhat according to our you know main model of planet formation in the solar system what's called the

nice model although is it nice or nice i can never remember if it's nice is in like the the place in And what, according to our main model of planet formation in the solar system, what's called the NICE model, although... Is it NICE or NICE? I can never remember if it's NICE as in the place in France or if it's the NICE model. One or the other. Somebody will tell me in the comments at some point. But yeah, so according to that model, which it's sort of in a bit of contention at the minute,

but it's kind of the best model we still have. So we think that Neptune formed around about 25 times the earth sun distance from the sun and it's migrated outwards to its current position around about 30 times the earth sun distance and the reason we think this happened is because of the orbits of what's known as the trans-neptunian objects right so you know asteroids dwarf planets all those kind of things orbiting beyond neptune in the kuiper belt right i think neptune in the kuiper belt right i think we've talked about the kuiper belt before on the podcast so if we look at the orbital properties a lot of those um objects in the kuiper belt these trans-neptunian objects we find a lot

of them are actually in resonance with neptune so either at the the three two orbital resonance which are called plutinos oh my gosh adorable uh yeah so they make two orbits for every three orbits that neptune makes around the sun and then you've only got a few a little bit further out in the two to one residence they're called tutinos stop so they make two orbits for every one that neptune makes and the fact that you've got lots of one and not so many in another essentially lets us know how far Neptune migrated out and also how fast it migrated as well so I found a paper by Shigeru Iida and collaborators from the year 2000 and they calculated that this process of Neptune's migration happened in the space of about a million to 10 million years so a pretty relatively short

time in terms of like the solar system's history right because we think the sun is around about four and a half five billion years old so you know pretty short time frame that the migration would have happened in we love looking at the history of astronomy here on the supermassive podcast and often there's one prolific figure who makes a huge discovery and we're still talking about it centuries later but when it comes to Neptune there's a little bit of back and forth as to who really discovered the planet and what actually counts as a discovery, as Carolyn Kennett, Chair of Society for the History of Astronomy, explains. Neptune was discovered in the middle of the 1840s, and it was a journey of various people contributing to Uranus' discovery

and its orbital conditions that made people realize that Uranus wasn't moving in the way that people expected it to be. So as it was moving on its orbital path, it wasn't tracking exactly as expected. So from the back of that, people realized that there was most likely something tugging on Uranus outside of it, pulling with a little bit of gravity on the outside. And that set a huge mathematical challenge for someone to try and see what that body was. It was suggested to be another planet. There were ideas from Uranus's position and how it was moving, where that planet could be, how far that planet was out, how big that planet was. And the bigger the planet, the more likely it was to be further

away, the smaller the planet it was going to be closer in. So we have two people who really take up this problem and come up with a solution. Right. And they both did it fairly simultaneously. So who are they? Tell us about these two people then. Well, the first one is Urban Jean Laverieux, who is the head of Paris Observatory in France. And the second person was a very young Cambridge graduate from Cornwall called John Cooch-Adams. John Cooch-Ad Adams, he'd had a huge amount of mathematical ability, gone to Cambridge University from Cornwall, and he'd done exceptionally well in his final exams. And he saw perhaps the challenge of Uranus's strange movement as a

challenge to his mathematical ability. I love that. You're just going to look at this strange pattern from Uranus. So then what happened? So he'd done a number of messing around with the figures and things and came with a result of where he thought the planet would be, how big it was. And he dropped this result round to the house of the current Astronomer Royal, which is airy at that time. So he just randomly goes and knocks on his door. He'll be like, don't mind me, I'm behind. I don't quite know what he expected, whether he would have expected an audience, but he didn't get one and he left the result at Aerie's residence.

Right, okay. Aerie did see the result and he wrote to John Cooch Adams asking for confirmation of one part of the result and no reply was sent. So it's not that John Cooch Adams didn't want to respond, I don't think, because we've actually found half a letter in an archive in Cornwall where he starts to respond. So he's looking from the English side, he's doing that. And then so what was Le Verrier doing? Where does he come into this story? So Le Verrier separately and very independently had also been working on this problem. And he comes up with a solution, which he announces at an academic fair. And then he starts to write to other astronomers

around the world, well, mostly around Europe, asking for help for them to turn their telescopes to look for this body in the sky. But it's interesting because why wouldn't he actually look for it at the Paris Observatory? And that is because at that time, Paris Observatory was smug covered and their instrumentation perhaps wasn't the best. So Airey gets one of these letters. And at this point, he has this kind of moment of realisation that he's also had this very young graduate leave these results, which are incredibly similar, about 12 months prior at his house and he so I think it was a bit of a Mike moment for him. I love that. Okay so that probably just lit a fire under him to sort of get a wiggle on. Yes. Is it a race? What happens? Yes, he mobilises the astronomers within the UK community to start looking for this planet.

Particularly, he communicates with James Chellis at Cambridge, who has the wonderful Northumberland scope. And he turns this amazing scope to the sky and starts a very methodical look, looking through this area of sky using very detailed sky maps. It is incredibly hard as an object to seize. That's carrying on all summer. Meanwhile, Laverrier is in Paris and he contacts the Berlin Observatory, who receive a letter asking for help to look for the planet. And two astronomers from the Berlin Observatory, Gal and Durest, who's the assistant, turn the Berlin scope to the sky. And within hours, they identify the planet. So it took them the first night within hours, they have the planet within their sights. And an announcement comes off the back of that, that they have found this planet, much to the horror of the British astronomical community.

And what is perhaps even worse for the British community is Chalice has already seen the planet during this very methodical search of the night sky, but he had not recognised what he was looking at. He hadn't identified it as a planet. He identified it as a star. So from this point then, who gets the credit for finding this planet Neptune? So Le Verrier, obviously, is the person who gets the credit. He hadn't seen the planet at this point, but he has identified where it is in the sky. And he's done this very complex mathematical work. And John Cooch-Adam, the young graduate, never claimed credit for the discovery of Neptune. He went on to have quite a successful career afterwards within the astronomy community, doing other important work.

astronomy community doing other important work. And he went on to become friends with Laverrier, but there was a huge international almost fallout over this. And I know it's rumbled on down the centuries. And the French community almost accused the British community of stealing the march and saying that they've made up this young graduate with his results. And John Herschel, who was a quite well-respected British astronomer, he wrote back and he said, no, he was very much on the side of Cooch Adams and no, this young man had done these works. And I think it goes to the credit of Cooch Adams that he never kind of stormed into the middle of this. He took himself away from

the fallout and said, no, it was all Le Ferrier, even though his results are there and all in writing and plain to see. But at the end of the day, there is a question of what makes a discovery. Is it the person who identifies that something is there? And at what point do we call that a discovery? Or is it the person that turned the telescope and first identified it through the telescope, which is Gau in Germany, and knew what he was looking at? So I think nowadays, with reflection back through history, we see it in a more nuanced way that all these people contributed in their own way to the discovery of Neptune. Thank you to Carolyn Kennett. Gosh, that was fascinating, wasn't it? Honestly, like,

it's just a who's who. Le Verrier, you know, John Coop Adams, just find it out between you. Okay, bye. But it's fine because they both now have rings of Neptune named after them. Well, there we go. They're both recognised in some way. Everyone's a winner. Yeah.

This is the Supermassive Podcast from the Royal Astronomical Society with me, astrophysicist Dr Becky Smethurst and science journalist Izzy Clark. This month we're talking about Neptune, but before we get onto our listener questions, given that the festive season is almost here. Insert jingle bells. Yes, I'll find some somewhere in there let's talk about presents for the space loving person in your life robert becky and our editor richard hollingham what would you recommend as an ideal space related present for this year robert john star yeah i think so so this is an example of where social media has had a reasonably positive effect on my choice because a lot of my facebook friends have bought this thing called a c star s50 which has appears to be an entirely automated imaging telescope costs a few hundred pounds it's not super cheap

but they're just displaying relatively straightforwardly it seems to be you know absolutely automated in pointing and everything else beautiful images of planets nebulae galaxies star clusters the moon and even with a solar filter the sunset if you're really into astro imaging it looks like a really good bet and everybody seems to be raving about it you know this is like not personal recommendation in the sense i haven't tried it out but the results seem great and i was also going to say if you want to do that kind of stuff you know cheap cheaper and you've got to say a small telescope one thing i do recommend is a thing like a holder to mount a mobile phone on the back because it makes it so much easier if you're taking even

say pictures of the moon or trying to take pictures of a little cluster of stars and you've got a small telescope it really helps just to anchor it in place and move it around so there are lots of different ones out there but that would be a lower cost recommendation but otherwise yeah automated telescopes they're really going great guns does the c star have like a like a camera like inbuilt on it? Is that how it works? It does. It does.

Okay, that's cool. Yeah, and it's really cool. It seems to be just using GPS and so on to line up. It looks really, really simple. I mean, at least as simple as these things get. I've just Googled it now. I'm like, ooh. Are you putting that on your list?

Ooh, who's got £500 they want to spend on me? Exactly, yeah, yeah. Hint yeah yeah intent yeah becky what about you well my publishers would spificate me if i didn't say my own book a brief history of black holes out now in paperback only on ebook versions worldwide um but for me i always prefer presents that are like experiences to look forward to more than necessarily material things especially if it's like in january and february because there's never anything to look forward to in jan and feb so i always think the like the best present for a space lover you could get is some form of trip like a weekend trip or you book something at say like hearst monceau or up in

kielder at the observatory there where they do like stargazing evenings and during the winter like yeah we have to play sort of like you know gamble with the weather but we do have the longest of nights it's cold it's clear it's crisp it's really good stargazing conditions so you know for me yeah book a trip whether that's just like you booked a campsite for for two nights or three nights over the weekend or something like a long weekend. And you can get out just under the stars and enjoy them with friends or family. Like for me, that just sounds like a perfect present to be surprised by.

Yes. I absolutely agree with that. And also warm clothing to go with. And a warm sleeping bag if you're camping. That's what you can wrap and open. You'll be like, why do I need an Arctic rated sleeping bag? And a flask. Richard, how about you? Why do I need an arctic rated sleeping bag? And a flask.

Richard, how about you? Oh, well, thank you for including me. I would like to recommend a book, actually. It's Tim Peake's book. So British astronaut Tim Peake's book, Space, the Human Story, which I will show up to the camera here on our audio podcast. That no one will ever see. No one will see. Can I make a book? There we go.

I've got it. I literally have it here. We interviewed Tim for the October edition of the Space Muffins podcast. Get in that little plug in there as well. But it's a fascinating book. So essentially, it's a history of human spaceflight. And I'm a nut for the history of human spaceflight.

Love all this stuff. And I've written a little bit about some of these things, but what it gives is an astronaut's perspective. So you get his stories and his selection process, his training all tied in with the history of spaceflight. And he can give, you know, he was a helicopter test pilot before he became an astronaut. So he can give a real perspective on these amazing pilots

like Neil Armstrong the first man on the moon so it's great and also there's a great little stories like he was selected as an astronaut before the UK put any money into astronauts and he came into work one day at the European Astronaut Center was making his coffee and he saw something on a printer and he looked at this thing on the printer that has been left there and it revealed that he was the least likely to fly as an astronaut. So, you know, so it wasn't a great motivation for continuing his training. Yeah, but of course he did get to fly and there's a good chance he could fly again on an all-UK mission,

which may or may not happen in the next few years, privately funded UK mission. So, no, it's really well written. And there's a lot of books by astronauts. And Tim's written his own book about his experience as an astronaut. But I think this just gives a real different perspective on the history without being overly geeky or you know you can get a lot about this you know the technicalities of it which is quite dull but the human story is fascinating

oh my gosh that sounds great we love books about the history of especially if it's told by an astronaut yes please um i think for me i've just been looking at planetary and star projectors like i just think they look so good if you sort of oh so like a scientific they're a scientifically accurate exactly exactly you don't just want it pretty i want it pretty and accurate no exactly and i was just like are there ways that you could get like the latest images from like james webb and then put them in and then i want to do all of that so if someone obviously planetariums and star projectors exist scientifically accurate ones do too but i want one that can be constantly updated as more and more information comes out please um so like nasa puts brand new raw data on the mast archive and you want it on your

planetarium projector like a second later yes please thank you very much if you can speak to some people Becky make that happen yeah but no I think something that's just a bit more simple than that um I was looking at the Royal Museum's Greenwich shop and they have some amazing astrophotography posters which are just lovely so I think if you can't get a projector then just get a nice print um because it's a bit more simple i always think they look really good printed on have you seen these like aluminium prints yeah yeah so like it's just it's just a sheet of aluminium but the ink that you use is like uv resistant as well so it like keeps its color if you do have like a room that like does get a lot of sun or something like that um so they don't fade like a canvas print and it just looks so much sharper

and more vibrant and i think space images particularly yeah look incredible you know so if you if you know of a company that can do that and you can grab you know one of the copyright free nasa or isa images from jdmst you can get your own printed for someone too and that would be a really nice present um the one thing i did see as well that they sell unfortunately it's just for kids but they are um personalized t-shirts and jumpers with like space cadet and things like that all over it i was like why are these only children sizes i would like one my favorite ever t-shirt that i got was when we went to kennedy space center when i was a kid And it just had the NASA, you know, the blue circle logo on it. And then it just said, I need my space.

I got one of those recently. I literally wore this T-shirt to death when I was a kid. And like it was probably like, you know, at age 13, 14. And I think I was wearing it all through uni as it like slowly became a crop top. I'm still wearing one now, but it's not a crop top. I'm still wearing one now, but it's not a crop top. I'm sad. Actually, it's worth checking out the ESA shop,

the European Space Agency shop. Their merch is really pretty good. They have particularly these stylized planets. And I don't know whether they have a Neptune one. They definitely have a Jupiter. They have the plushies, right, as well. The planet plushies. Oh, cute.

Yeah. They're honestly adorable and my favorite things. I'm pretty sure that's the easter shop yeah so i've got a jupiter uh hoodie which i'm not wearing today i'm wearing a doctor who hoodie because it's the anniversary yeah exactly yeah um oh and actually given that everyone else has plugged something um i wrote a kid's book this year. Oh, yes. If anyone would like to buy everyday STEM science space for their 9 to 11-year-old, then we'll link everything below. Smooth.

Yeah, thanks. Should we get back to some science? Honestly, we had loads of great questions. So I'm hoping that throughout all of the episodes, we've answered some of those already. But Robert, let's start with this one from the jake roberts who asks i hear it's warmer on neptune than on uranus literally how yep great question there literally how exactly so it turns out that neptune and uranus actually have quite similar temperatures at the top of their atmospheres the temperature depends on how deep

you go into that you know what you measure however that is quite hard to explain because Neptune is about 50% further away from the sun so the top of the atmosphere really should be colder but the difference is that Neptune gives out about two and a half times as much heat as it gets in the sun so powerful internal heat source and Uranus doesn't Uranus gives out about the same but there doesn't seem to be a really easy explanation for that. So there's lots of people arguing about what that might be, the age of Neptune, the distinction of whether Triton's doing something with the tides and so on. And I particularly like one explanation I came across, which is that Neptune is undergoing a series of burps from its inner atmosphere. Now, you know, don't ask me to give the details of that, but I do like the idea that digestive problems in an outer planet are making it a bit hotter i wonder if digestive problems make us all slightly i think they might i think they might well do and becky anna l writes what is the most unique thing about neptune compared to the other planets i know what you mean anna l because like what is its unique identifier right like we talked this before. Who even is she?

Jupiter is the biggest. Jupiter is the biggest. Saturn's got its rings. Uranus is on its side. And Neptune is its blue flag. Yeah, I mean, we've already heard, right? It's a pretty cool system that it's got the most distant moon orbiting it. It's got the largest capture moon.

But those are about the moons not necessarily neptune itself right i guess what was quite quite cool was that it was found by maths rather than directly by observations like it was predicted to exist before we found it which as a science nerd i'm like yes neptune's unique identifier is mass. Yeah, mass. But to other people, I guess maybe not. But I think it is so unique, Neptune, in the fact that it has that influence on all of those trans-Neptunian objects that we talked about before in the Kuiper Belt.

The fact that it can shape that whole part of the solar system in terms of where objects orbit, I think is really, really cool. It's almost like the shepherd of the solar system i'm now picturing neptune with like a tea towel on its head dressed up like a little kid in a nativity oh amazing okay uh robert just keep flying jim says from neptune or one of its moons what colors would the sunsets be? You definitely just keep flying, Jim.

It's, well, I just had a reading around this, and basically the colour depends on the composition of the atmosphere and the thickness of the atmosphere and so on. So obviously you're not standing on a solid surface on Neptune, you just sink deeper and deeper down. But if you were floating in the atmosphere, you'll notice that lovely blue colour. You'd be looking out essentially at a blue sky. The difference is that as the sun sets,

the atmosphere absorbs more red light. So that blue daytime sky would probably turn a nice turquoise colour, which sounds suitably exotic. And I'm sure you know that there's an opportunity for space art there. And the moons, well, Triton's the only one with an atmosphere. The rest of them, you're going to have this sort of stark vacuum, vacuum of space, black sky. But even there, Triton's atmosphere is really very, very thin.

So it probably isn't going to do very much to the colour. The sun's going to essentially appear white and then it'll just sink down and the landscape will go black. Okay. Dramatic. Yeah, I know. I was just like, oh, right, blimey. Very exotic, though.

And Becky, NeptuneLover93 asks... Nice name. like oh right why me very exotic though and becky neptune lover 93 asks nice name yeah exactly you had to ask this question on an episode about neptune will neptune also be destroyed when the sun explodes so i guess i have to start by saying that the sun won't explode so it's not big enough the sun to go supernova what will happen to the sun when it runs out of fuel is that will swell up to what's known as a red giant star to try and sort of resist sort of the end of its life essentially it's sort of like its last gasp to be like no i don't want to die don't you dare makes it sound so sad doesn't it but it will swell up to this red giant and it'll be around about the size of the earth sun distance currently so it's going to swell up to be a huge huge thing

so it's going to swallow mercury venus maybe earth i'm not entirely sure what the the final size will be essentially just incinerating those planets great so those will be properly destroyed right in the sense of the question right but the outer planets so the gas giants, the ice giants, they won't be destroyed in that same way as the inner planets. But you are going to have an increased amount of radiation coming from the sun because the sun is all of a sudden a lot closer and a lot bigger than it was before. Which means that the atmospheres of those planets are going to be bombarded by a lot more high energy radiation with a lot more energy. And so they could be stripped slightly of some of the atmosphere. The atmosphere could sort of almost boil off in a way. But that's going to be more likely for Jupiter and Saturn, which are much closer into the solar system than say Uranus and Neptune, which are further out. And also what's quite fun actually is that for a while the

habitable zone of the solar system so that region where you have the right temperatures for like water to exist probably going to get pushed out to the outer solar system around uranus and neptune so like triton all of a sudden could be the place to be yeah orbiting neptune right because that could be the the sort of place that's the most habitable with the rocky planet. But then when we get to the actual full-on end of the sun, if you will, where it has this sort of last gasp fizzle out, basically, where all of its outer layers of its atmospheres do get stripped off, not in a supernova,

just like a fizzle out, basically, and then leave behind this sort of white dwarf core of the sun essentially all of those atmosphere layers of the sun will hit the gas giants all at once as it sweeps through the solar system so again depending on you know various different factors essentially those planets could get stripped of their atmospheres maybe leaving sort of like bare core behind but maybe not we're not entirely sure of how much atmosphere is actually going to get stripped or not and again the biggest impact is going to be further inwards towards like jupiter and saturn whatever's then

left over whether it is sort of like thinner atmospheres or these bare cores they're just going to be left orbiting the white dwarf that the sun leaves behind in the center which is just the core of inert helium that it'll just leave behind which will just be slowly glowing so there you go there we go hopefully hopefully that answers your question that wasn't too depressing yeah oh and i shouldn't say that's not going to happen for like five billion years so no one needs to worry the big caveat that we often forget like yeah but hang on a sec don't worry about it don't lose sleep it's all right amazing thanks guys so if you have any questions for the team do send them in you can email podcast at ras.ac.uk tweet at royal astro sock or find us on instagram

at supermassive pod we read all of them so and it's very difficult to choose which one to put into the episode okay so let's finish with some stargazing. Robert, what can we see in the night sky this month? Well, December, look, cold, long, dark skies. A really nice time to go out and look at the stars as long as you wrap up well, as we were saying earlier on. So a couple of things to look out for this month. One is this outburst of an unusual meteor shower called the Andromedas. Now, I say unusual, it's there all all the time but it's usually very weak but there is this prediction that it

might have an outburst on the evening of the 2nd of december however it's just a prediction the amount you might see a couple hundred an hour if you're exceptionally lucky however that it's just not only is it just a prediction it's also they might be quite faint too so the moon's out as well right then so yeah the moon is out so it's in the early evening is the recommendation to go and look at it so after the sunset you know so seven eight o'clock and so on is the time to be looking i'm going to give it a punt i mean frankly what is there to lose you know but if the weather's clear uh and and see what there is if we didn't mention it and then everybody you know looks out and says wow what was that big meteor display you didn't

tell us about michael fish but yeah yeah meteor showers are kind of, you know, like comets and cats. They do what they want, essentially. So we'll see what happens. However, there's then a much more reliable one, the Geminids meteor shower on the 13th to the 14th of December. And that's quite steady, quite bright. If you have a clear sky, the moon's also out of the way. It's just a very thin crescent and it'll set quite soon after sunset. So have a look after midnight for that. That should be really good. It's one of the best showers of the year well i think the perseids in august my favorite because it's warm but then the geminids are my second favorite like half an hour before i'm cold yeah yeah the perseid you can look at without that polar

sleeping bag yeah that's the plus side so look apart from that you've still got a nice suite of planets. Jupiter's really, really good. High up in the skies, Dylan Air is very, very bright in the evening sky. Venus is there in the morning sky. And if you pick up a telescope and look at it, you'll see it's sort of half illuminated, still be around for a bit longer. Very obvious, you know, this time of year we're getting up and it's dark.

Look out, and it's still very obviously there. If you want to see Neptune that we've been talking about, that is still in the sky as well. But you're going to need binoculars at least you're going to need a chart or an app to find it in Pisces and then you know probably impatience and one trick you can use if you really can't tell which is you can look at the star field where you think it is and this is an old-fashioned technique but it basically works plot out a few stars on a bit of paper and then look at it the next night and the night after and see if it moves that's one way of telling you've seen a planet rather than just a just a background star and then finally though this time of year is when the winter stars are starting to be really really

nice so it is coinciding with those frosty evenings and frosty mornings i absolutely love it exactly and orion is there so later in the evening not very late now you know orion will be very very obvious in the southern sky to you know very bright constellation Betelgeuse rise all the nebula the belt stars all the things around that and it's a joy just to look at it with your eye but also just pick up a pair of binoculars and scan around there's so much you know what Orion is almost oddly nostalgic for me when I look at it because it reminds me of like driving back from visiting family at Christmas time and you're like a kid in the car and it's maybe only like driving back from visiting family at christmas time and you're like a kid in the car and it's maybe only like six or seven o'clock but orion is like rising and it's just

over the horizon and you're on a road somewhere in the middle of nowhere and it's really dark and you can see it and so that just feeling of like seeing orion in the early evening in the winter is almost like it's a very it's a very christmasy Yeah, it's like, you know, like, it's beginning to, like, when I see Orion is when I think, oh, it's Christmas time. It's officially here. Well, I think that is it for this month.

We'll be back with a bonus episode in a few weeks and then we'll be bringing you an end of the year episode about the multiverse. We've had lots of emails about this topic. It's finally going to happen.

Can we cover everything in under one hour? topic it's finally going to happen can we cover everything in under one hour i guess we're gonna find out yeah yeah multiverse might need multi episodes we'll see as we'll see anyway get in touch if you try some astronomy at home it's at supermassivepod on instagram or you can email your questions to podcast at ras.ac.uk and we'll try and cover them in a future episode. We've got so many of them now that we had to introduce bonus episodes as well. So make sure you're listening to those. But until next time, everybody, happy stargazing.