The Supermassive Podcast - 39: Jupiter The Monster

Episode Date: March 24, 2023

Izzie and Dr Becky explore the largest planet in our solar system, Jupiter. What do we know about this big ol’ planet? And what are the missions that will find out even more? The team is joined by Scott Boulton, Principal Investigator of NASA's Juno mission, and Professor Emma Bunce from the University of Leicester, also involved with ESA's Jupiter Icy Moons Explorer (aka JUICE). Plus Robert Massey shares his top stargazing tips for spring.  Everyday STEM Science - Space! by Izzie Clarke https://www.panmacmillan.com/authors/izzie-clarke/everyday-stem-science-space/9780753447963 The Year in Space by The Supermassive Podcast https://geni.us/jNcrw The Supermassive Podcast is a Boffin Media production by Izzie Clarke and Richard Hollingham. 

Hello and welcome to the Supermassive podcast from the Royal Astronomical Society, with me, science journalist Izzy Clark and astrophysicist Dr Becky Smethurst. Yeah, this month we're exploring the largest planet in our solar system, Jupiter. What do we know about this big old planet and what are the missions that we'll find out even more? I mean, it absolutely is the monster of our solar system. It holds a special place in my heart that I know Becky will disagree with. Justice for Saturn. Sorry, sorry. But today it's all about Jupiter. Okay, so deal with it. And obviously, Dr. Robert Massey, the Deputy Director of the Royal Astronomical Society is here too. So Robert, tell us about Jupiter. What's it like as a planet? You're definitely right that the keyword is big, at least by the

standards of our solar system. And for us, that means it's bright as well. It's reflecting a lot of sunlight. It's brighter than any star apart from the sun and every planet except Venus and just occasionally Mars when it's at its closest to the Earth. Now, this planet is 140,000 kilometers across. So you could fit 1,300 Earths inside it, which always blows my mind a little bit. And it spins so fast in just under 10 hours that it actually bulges out of the equator. And you can see that even with a pair of binoculars. You look at it and you think, oh, it's not round. It's actually slightly bulging out a bit.

And with a telescope, it's really obvious. It's mostly hydrogen and helium, like our sun. And that's because it's really obvious it's mostly hydrogen helium like our sun but that's because it's got a strong gravitational field so it can hold on to those lighter gases a lot more easily than planets like the earth can and if you were able to stand on its surface it doesn't have a solid surface lots of caveats here but if you were sort of at the bit you know the bit you can see the top of the atmosphere the gravitational field there would mean you'd weigh two and a half times what you do on earth now that's not something i in particular would relish it takes about 12 years to go around the sun and we've just had a really

good view of it over the winter and it'll be at its best again in november this year when it'll be really really high up and bright again from the uk so something to look forward to towards the end of this year and i mean i think that puts it into perspective that it spins in just 10 hours but if just like the size of it i mean that would be fast for earth yeah but then you think about just how big it is and you're like no hang on that's that's too much yeah like if you think about it like on a winter night like on earth like a longer night you could set up a time lapse where you could see the entirety of jupiter rotate oh my god that's incredible. It's insane, right?

I now really want to do that. Why have we just gone through the window and we're like properly seeing it at its best point? Like, ah, missed the boat on that one. It's your challenge for your telescope, Izzy. You've got the telescope. You can do this now. Yes, I will. I just need all the thermal layers.

Put a date in your diary for November. Sorry, busy. Just got to watch Jupiter all night. Cheers, Robert. Then we'll catch up with you later in the show to help me take on some listener questions. So our interest in Jupiter goes way back. In 1609, Galileo used his newly improved telescope design

to observe moons orbiting Jupiter. And fast forward to 1989, and NASA's Galileo mission became the first spacecraft to orbit an outer planet. So what do we know about Jupiter? And how is NASA's current mission to the giant planet changing that? I spoke with Scott Bolton from Southwest Research Institute in San Antonio, Texas, who's the principal investigator of the Juno mission. So Jupiter is the monster in our solar system. It is extreme.

It's the planet on steroids. Okay, so not only is it the largest, but it has the most hazardous radiation belts, the largest magnetic field. It's spinning the fastest. It's moving around in 10 hours, this giant planet, right? So all the material in its magnetosphere is sweeping around in just 10 hours, even stuff that's far away. And its magnetic field goes all the way back out to

Saturn. So it's extreme in every way. I mean, it probably not only was the first planet, but it probably dictated how the whole solar system was formed, even the collection and distribution of volatiles and organics that led to life and led to Earth. And it's storms, you know, the Great Red Spot goes all the way back as far as we've had telescopes to detect it. So it's thought to be maybe 300 years or more. So it's got the biggest storms as well. The storms are being driven by its fast

rotation. It also receives sunlight that drives our storms, but it's probably driven mostly internally. Even its magnetosphere and aurora are probably driven by this giant engine of the magnetosphere that's whipping around so fast. Yeah. I mean, it's incredible. I love it as a planet. And I think the red spot that we look at, it's so iconic. For anyone that hasn't seen that, what is going on there? Do we know why it's red? Do we know's chemicals. It's the chemical composition. And when you look at Jupiter, you see these stripes, right? These zones and belts, they're very beautiful. And they're different colors, right? Orangey and yellow. And then you have this whitish one, summer zone, summer belts. They're actually moving in different directions, kind of like our weather, but the weather pattern is much more complex in that it has different zones and they go in one direction and the other ones go in another. They're going at different speeds. The colors are probably representative of composition of

the clouds and the material, but also the depth. It could be a hang glider's dream if they could survive. I mean, you've got all these vortices. They look like hurricanes or tornadoes, and they're all over the place. The Great Red Spot is just a giant one. It's like a giant, you know, vortex that's just sitting there. We do see it changing. In recent times, we've seen that its size has changed since the days of Pioneer and Voyager. So it is alive. I mean, the whole planet is alive and it's evolving and changing with time. Yeah, absolutely.

And so you mentioned a few missions there. So how do we know all of this about Jupiter? We're going to get to Juno later, but pre-Juno, how have we been able to understand Jupiter and study it as a planet? So the initial idea was just telescopes. Galileo could detect the movement of the moons, but really couldn't see the cyclones spinning around like a vortex. However, as we got more advanced and we started sending spacecraft out. We started inventing instruments that could detect charged particles, magnetic fields, invisible force fields. And so we went

to visit this planet. And when you got close, the first thing we realized was it had a giant magnetosphere. So we started to realize that also from ground-based telescopes, radio telescopes, looked at radio emission coming out of Jupiter and realized it must have a magnetic field. But then, of course, Galileo learned a lot when we dropped the probe into the atmosphere. Yeah, and now we're moving on to Juno. I mean, you're the PI of this mission.

Tell us about Juno. What is its aims and what is it doing around Jupiter? So Juno is a very different kind of spacecraft and mission than anything we had ever tried before. So Voyager and Pioneer and Galileo orbited around its equator, basically. But we didn't have enough measurement to know what its interior was like. So Juno was designed to look at it in a new way. We had more modern instruments, of course, but we also went really close. So we're an armored tank that we knew we were going into this monster and we were armed

so that we could go into that planet really close. We also went into a polar orbit so that we could see from the top to the bottom for the first time. Very, very close. Our orbit was designed to get in close and then get out before we got killed by the radiation. So we are moving really fast. We come very close to Jupiter. We go over its poles and we go to within 5,000 kilometers of its cloud tops, which is very, very close. And we're moving really fast. And so we go from pole to pole in about two hours. And each time we dove in, we tried to understand what was it like inside this planet. The atmosphere was like below the cloud tops and much deeper than the Galileo probe went, we also got very precise measurements to the radio science or the gravity field.

So, we could tell what was the core like, what was it like the structure inside of Jupiter. And the pictures from the Juno mission are absolutely stunning. So, what have been some of the big discoveries that Juno has showed us? And were there any that were quite surprising for you? Almost everywhere, we were surprised in almost every field. And it's a very humbling experience for all the scientists. It's exciting. You like to be surprised. But I don't think anybody expected that we would be wrong by almost everything.

Like what? Like what? So the first thing was, is we took a picture of the pole in the infrared and in the visible and saw giant cyclones all over the pole. So instead of the zones and belts, the stripes like we were used to, they were replaced by giant polar cyclones on both poles. So you had five on one pole, like a pentagon. And on the other pole, you had eight distributed like an octagon.

Nobody expected that. We've been watching them ever since, and they seem pretty stable. Sometimes it looks like one's opening up and there's going to be a new one formed or they'll change. But by the time we go around again, that new one was kicked out and there's still the same number. So it's a very exclusive club. They don't just let any polygon polar cyclone in there. So that was the first surprise. And we're still trying to figure out how all the atmosphere works. We were searching for, was there a core of heavy elements at the center, a compact core, or was there none at all? And we found out that it was neither. We weren't even asking the right question. What's inside of

Jupiter is, there is a core, but it's sort of dilute and fuzzy and quite large. And so there's a gradients in it as you go in. Nobody really expected that. There may be a small compact core in the center of that, but the question of how Jupiter formed was thrown another curve ball. And one thing that we've talked about in this podcast before is Jupiter and its magnetic field. So have you found out anything about that, thanks to Juno? Yeah, we mapped out the magnetic field. And the magnetic field has not only got a lot of structure, we discovered a big spot in the middle of it that we called the great blue spot that kind of looks like the great red spot, but in magnetic field eyes. And it's not far from the great red spot. It's a little bit in the south. And at some point, it once in a while goes over the great red spot because the great red spot is

moving around at one speed. But of course, the magnetic field is moving around much faster. And once in a while, they go over each other. I don't know how they might affect each other, but we have this giant great blue spot, which we've actually been able to measure changes in. So we've seen what we call secular variation. So far, we've only measured a change in the magnetic field over time at Earth. And here we now see that Jupiter has the same thing. And we're also looking at where is the magnetic field formed? And it seems in a pretty shallow region. And so we're seeing a coupling for the first time between an atmosphere, the magnetosphere, and maybe the gravity field. And that's something that Juno has really uncovered that these three, we kind of always knew that they must have been

interacting, but often they were studied separately. We're now having to join forces, you know, interdisciplinary perspectives are all is what really drives Juno science at this point. So finally, what's next? So we finished what was called our primary mission in the summer of 2021. And that was all dictated by a number of orbits. We were trying to go really close to Jupiter 32 times to spread out and map the planet at every longitude. And then we said, okay, what can we do now that we've mapped the planet out? And our orbit was getting twisted by Jupiter's giant gravity field. And so as it got twisted, we realized we were going to go

cross the planes of the satellites at their orbital distance. We designed it so we could go close. So we went by Ganymede in the summer of 2021. In September of 2022, we went by Europa, really close, made maps and new images and things like that. new images and things like that. And then in December of this year and February of next year, we'll go by Io. And all the whole time we're being twisted around. So we're also getting closer and closer to the Northern Hemisphere. So we're getting close-ups of these incredible polar cyclones, right? We also, as you said, the images are amazing. And that's part of the, is that we're watching the beauty of Jupiter reveal itself in the sense that the clouds are all twisted. It almost looks like a Van Gogh painting. And the lightning, there's these little polar or I should say top ice clouds that are probably

ammonia ice. We call them pop up clouds. That's where we think a lot of storms and lightning are occurring. We're getting closer and closer to that, making maps of this. You're seeing inside. So you're looking for these hot spots that look like where the Galileo probe went in. So we're studying the northern hemisphere in both the gravity field, the magnetic field, as well as the atmosphere.

But we're also studying the satellites. And equally exciting, we're getting closer and closer to the rings of Jupiter. They're not like Saturn's, but they're very close to Jupiter, but they're not well understood. They haven't been a lot of observations or telescopes or a spacecraft that could go in that close. And so we're actually getting really close and we're going to learn a lot about the rings and probably the tiny moons that might

be moving around inside of those, sort of like a mini Saturn ring system. Thank you to Scott Bolton. See, at least there's been some mention of Saturn there for you, Becky. It's fine. That's a coveted tick. Thank you. I appreciate it. So we talk about Jupiter and its main four moons, but how many moons does Jupiter actually have? And do we know where they've come from? Yeah. So the current count for the number of moons that Jupiter has is 95. And that has gone up by three since February 2023, when three more were announced, like the discoveries were announced. So we're discovering all the time because these three that have been recently discovered, you know, they're like a kilometer across. So they're not very big. They're not that easy to spot, you know, compared to the Galilean moons, which are all over like 3000 kilometers across. Ganymede is actually larger

than Mercury, which I think helps to put it into perspective. You know, there are some people that argue that these moons should almost be classed as planets because they are, you know, such major players like in the solar system. So yeah, all the other moons, though, of Jupiter are less than sort of 250 kilometers across. Most of them are in that sort of one to five kilometer range. So we think that those sort of smaller moons orbiting further out from Jupiter are very likely to be captured asteroids, that Jupiter's just gone, yoink, I'll have you, basically. Thank you very much. Yeah. There's probably a lot more of those where that came from that we just haven't been able to spot

yet, maybe smaller than a kilometer as well. But the larger moons, especially those Galilean moons around Jupiter itself, we think they actually formed around Jupiter. So like in situ, if you will, in the very same way that the planets formed around the sun, sort of with this disc of swirling material, where you have this sort of like coalescence of all of these much smaller bits of rock that then, you know, come together and eventually form the planets or around Jupiter, form Jupiter's moons. And I think it's brilliant. You know, I will never forget the first time I looked through a telescope and you see Jupiter and you see his four main moons. You're like, oh my gosh, those are other moons. That's one, that's another planet.

But also those are its moons. And it's just that, almost that entry point into looking at other planets. You're like, oh my goodness, this is just brilliant. Well, I love it because they're all obviously on the same line, the galilean moons as well so it looks like a mini solar system as you look at it you know like every artist impression that you've seen of the solar system it's like finally seeing that in real life you know well absolutely and that leads me on to my next question because we talk about jupiter's system and you know when we're looking at other systems outside our own. So what can studying Jupiter's system tell us about other systems out there in space? There's all the systems, Izzy.

All of them. Every single one of them. Yeah. It can tell us a lot, actually, because especially with this idea of how moons and planets migrate from where they form to where they're actually orbiting, you know, a planet or a star right now. So if we think about Jupiter's system, we actually ended up in a situation where three of those Galilean moons are in what's called resonance. So for every one orbit that Ganymede makes, Europa makes two orbits, and Io, very close into Jupiter, makes four orbits. And the reason they've ended up like that is because they formed, migrated inwards,

and essentially got trapped there in that resonance, sort of like gravity sort of keeping them like that, and sort of the tidal forces. You've then got Callisto, which is the furthest out of Jupiter's moons, which is still migrating inwards. And eventually, we think it will be captured in that resonance so that for every one orbit, Callisto makes, Ganymede makes two, Europa makes four, and Io makes eight. So instead of one, two, four, you've got one, two, four, eight, so carrying on the chain. So watching that happen, I say, I mean know it's going to be a very very very long time in the future that actually does happen next week oh if only that would be

the dream wouldn't it um but sort of this migration is very important if we think about then what happens to planetary systems if this happens as well we when we simulate our solar system forming we know that jupiter must have tried to migrate inwards at some point and actually sat and held it back and stopped it, which means that maybe that's the reason Earth is even here in the first place because if Jupiter made it this far in, we probably would have been shot out of the solar system

along with a lot of other bodies in the solar system. And this is how we think actually that, do you remember from our exoplanets episode, we talked about hot Jupiters? jupiter sized planets orbiting very close into their stars like with orbits like you know days weeks even and they're incredibly hot because of that we think that's how they've got there so studying jupiter's moon system actually ends up sort of helping us learn how hot jupiters around exoplanets form and also why that didn't happen in our own solar system as well. So Jupiter has lots of moons and one

upcoming ESA mission is off to explore the icy ones. It's called JUICE, aka the Jupiter Icy Moons Explorer, and it's the first European mission to go to the Jupiter system. It'll be looking at the Galilean moons Europa, Callisto and has a particular focus on the largest of them all which is Ganymede. But why are we going there and what is JUICE hoping to find? Professor Emma Bunce from the University of Leicester has the answers. She's been involved with building two instruments on JUICE and we spoke at a rather crucial time. So we've got to the really exciting part. The launch window starts on the 13th of April. So hopefully JUICE will go as quickly as possible within that launch window.

So it's going to be launched April 2023 and then we'll spend eight and a quarter years in what we call the cruise phase between leaving Earth and arriving at Jupiter. So the arrival of Jupiter is not until 2031. That will be Jupiter orbit insertion. Okay so first of all the spacecraft will go into orbit around Jupiter and then we'll do a number of things like the Europa flybys. We'll have an inclined phase where we will have Callisto flybys. And then the spacecraft will transfer to Ganymede. So the orbit's getting smaller such that it gets closer to Ganymede. That phase takes about a year and will involve multiple Ganymede flybys.

And then finally, we'll be ready to go into orbit at Ganymede in December 2034. So we're launching in April 2023. And we will get to the Ganymede orbit, which is the real focus of the mission in December 2034. And then the mission will last until 2035. Wow. Okay, so quite the journey. Indeed. We'll get onto the icy moons in a moment, but it's starting off around Jupiter. So what can it tell us about Jupiter as a planet? So JUICE is going to spend that first part of the mission, so between 2031 and 2034,

really exploring the Jupiter system as a whole. And in some ways, that is an extension of the work that the Galileo mission did back in the 1990s. But with a much more capable spacecraft and with new technology, new instruments, we're going to be able to look at Jupiter's atmosphere with some of the more up-to-date instruments for imaging and for spectroscopy to find out what the cloud motions and composition of the atmosphere, let's say. And we'll also be able to look at Jupiter's giant magnetosphere. So this is the space environment containing Jupiter's magnetic field and charged particles extending out far into space around Jupiter. So this very large magnetosphere then rotates around with the planet

and the planet's magnetic field and sweeps past all of these moons that we're interested in. And we'll be able to look at how that rotating magnetosphere is interacting with each of those moons. So that's a really exciting part of the mission as well. There's a lot to learn about how the system acts as a whole. Yeah, and I was going to say, you know, what's the importance of understanding all of these mechanisms of Jupiter's system and its icy moons? Why do we want to explore this in the first place? Well, I think we have to come back to that question of habitability. I think there are lots of reasons why we as scientists are interested in exploring the system.

But this question of habitability and the idea that at Europa and at Ganymede is potentially more water, liquid water in the subsurface underneath icy crusts than is across the entire earth is a fairly mind-blowing discovery that was initially you know the tantalizing evidence coming from galileo and we need to confirm and explore the details and the characteristics of those oceans and and that And that's a really important science question because whenever we're thinking about whether there could be life somewhere else in the universe,

one of the properties that we're thinking about is where is the water? And, you know, looking for water on Mars, etc. And yet you go to the outer solar system and there apparently is just enormous volumes of water in these moons. And so that's what makes them very exciting. This is the next step, I think, is a good way of looking at it. So we are confident that there's a subsurface ocean at Europa and we want to find out more about whether there is a global ocean at Ganymede and whether there is a potential ocean signature at Callisto. So JUICE is going to be able to do that through 35 flybys of those moons, but also this final phase where the

spacecraft actually will go into orbit. And that's the first time a spacecraft will be going into orbit around an icy moon in the outer solar system. So it's very exciting that that's a European mission doing that. Absolutely. I mean, just the idea of these subsurface oceans as well, like you just want to find out more about those, don't you? So what instruments will be on board and what will it be trying to detect? I mean, are we going to be getting images? You know, we've seen some of the Juno images. They're amazing. Is that something we'll get from Juice? Oh gosh, the imaging is incredible. So I was looking at

this detail. So going back to Galileo again, the visible imager, the resolution was around a few kilometres and the best resolution for the imager on juice is going to be around two and a half metres per pixel. Oh, wow. So you can expect to see the most incredible map of Ganymede, which will be amazing. And then obviously we have some instruments like spectroscopy instruments, UV and infrared,

which allow us to consider things like composition so we want to know whether some of that essential chemistry that we're looking for that contributes to this question of habitability is present on the surface you know what what's on the surface of Ganymede and indeed in the tenuous atmosphere that exists around the moon but JUICE also has a laser altimeter which will actually allow measurements of that tidal deformation. So we actually think that tidal forces move the surfaces of the moons, Europa, Io, Europa and Ganymede. And we need to quantify what that motion can be. And so the laser altimeter, for example, will be able to help with that. JUICE also has an ice penetrating radar that is able to

look down to around a 10 kilometre depth in the ice to see what the signals are coming back underneath, what the structure of that ice actually looks like. And the very exciting instrument, which is the UK instrument on board, the magnetometer, is on a very long boom an 11 meter boom which keeps the instrument very far from the spacecraft and allows very precise magnetic field measurements yeah i was going to say just a boom is essentially for simple terms a big long stick a big long stick exactly um whatever you want to call it but yeah and it's it's really important because it allows a precision of measurement that will really allow us to tell the difference between an induced magnetic field signature relating to an ocean and Ganymede also has its own internal magnetic field which is the only

moon in the solar system that we know that has that. And we need to understand the interplay between those two things. And then there's sort of gravitational field measurements that can be done as well that contributes to that question. So they're all working together. And that's really important. And that's why that payload has been selected for JUICE. And so if it has its own magnetic field, does that tell us anything about its core? Or are we literally just, that's the whole point of JUICE, is to try and get to the bottom of that question? Yeah, I mean, fundamentally, the answer, the simple answer is yes. We're going to be able to use the gravitational field measurements to understand the distribution of mass within the interior of Ganymede, the magnetic field measurements will

enable us to work out the properties of the internally driven field. And by looking at the complex terms in the field, you can essentially work out from where they are generated. And that's a really important question. And then obviously the other instruments all working together will just give us unprecedented detail at Ganymede. Thank you to Professor Emma Bunt. And fingers crossed that Juice will begin that journey in just a few weeks. Oh my goodness. I'm going to be watching the launch with just all of my fingers crossed and then waiting very impatiently for the next like eight years. Yeah, waiting. 2030, Wave at 20, 30, come on, tick tock, hurry up.

This is the Supermassive podcast from the Royal Astronomical Society with me, astrophysicist Dr. Becky Smethurst, and with science journalist Izzy Clark. This month, it's all about the largest planet in our solar system, and that is Jupiter. Before we get on to everybody's questions, though, Izzy has some very exciting news to share. Izzy, drumroll please. Yes.

I'm so excited to say that I have a kid's book coming out on the 30th of March 2023. So that is very, very soon. Oh my gosh, that's so exciting. I'm like, what age range is the kid's book for? Any parents or aunts or uncles listening or grandparents want to get it for their kids yeah so it's called everyday stem science space and it's for 9 to 11 year olds but let me say like if you it's if it's been a while since you've done some space science then perhaps this is a good place to begin re-engaging with astronomy um but

no it's it's all about how space science comes back down to earth so it you know i've done a bit of a tour of the international space station in there and we've got a guide to an astronaut suit and our solar system and what goes beyond and ultimately it was so much fun uh the illustrator is a guy called james let. And the colours of this book are amazing. And, you know, it was great seeing it on screen when we were making it. But to see it as an actual book, I got it in hard copy a few weeks ago. And I was like, oh, my God, it's an actual book. It looks amazing.

If I do say so myself. So, yeah. I'm very excited. I mean, I know I would have devoured this as a kid. Like, not even as a nine-year-old. I think if you'd bought me this as, like, a six-year-old know i would have devoured this as a kid like not even as nine year old i think if you'd bought me this is like a six year old i would have been like exactly exactly and i think there are some things in there that maybe slightly younger readers will sort of you know pick up and understand but it's actually part of a series so i've just written

the space one so the overall book the overall series is everyday stem science and there's eight of them in there so there's lots of other ones if space isn't your jam i don't really know why you're listening to this podcast now uh or space isn't your kids jam maybe yeah okay fair enough i'm very sorry for you if you're a parent and that is the case but yeah so yes out on the 30th of march but i'll put a link to it in the episode description so everyone can find it. But enough about that. Let's get on to the questions.

So Robert, Martin Gregg wants to know, would a human crew be able to survive travelling through the Jovian system? And perhaps this is a good place to say that when we refer to Jupiter and some of its moons, that is the Jovian system. The answer is it's really hard, Martin. And the reason for that is it's got an incredibly high radiation level.

They're high enough that they fry the electronics on a spacecraft if it's not really protected. So Juno had to be, you know, I think it gets damaged on each pass around Jupiter. It has to be really hardened and reset all the time. And so it's really difficult to do. So imagine then taking people there into an environment where near the planet itself, you've got 1,000 times the lethal dose of radiation out there. Trying to protect astronauts from that is going to be incredibly difficult. So you'd have to do things like put lots of lead shielding around the craft or water or very dense,

basically dense materials and a lot of it. And that's really difficult with the spacecraft because then you need more and more fuel to launch it and to move it around and so on. So another thing you can try and do is magnetic shielding. But again, I think when you're in that sort of environment, it's a really difficult thing to do. So it's not a very safe place to go, if you ask me. When you get even some of the moons, the ones that we want to visit and JUICE will be looking at, even they have quite high doses until you get out as far as Callisto, I think. So it's not going to be an easy tourist destination anytime too. And to give you a bit of context, we worry about what happens to astronauts on the space station over time. They get a reasonable amount of

radiation over a year if they're up there, about six months a year if they're up there that long. We worry a lot more about what it might do to people travelling to and from Mars. They might get their lifetime dose of radiation or even more that they're supposed to have over that period. So going to Jupiter is on another level altogether. So my honest advice is probably it's not a good place to go and look at. If you're going to go there, look at it from a safe distance.

Okay. And also, surely the journey would just be really, really, really... look at um and if you're going to go there look at it from a safe distance okay and also surely the journey would just be really really very there is the whole issue of getting there yeah that's not trivial either spending years and years in space you know i always say to people on long space missions think of the maybe it's better to travel with people who aren't your friends because you won't you know you've got less risk of falling out whereas if you go with your friends you know and you you really don't want to put that friendship to that kind of test i suggest interesting question you look around your friendship group

and think who would i like to spend eight years cooped up in a small small space i'm now really wondering how the covid19 lockdowns will have affected the percentage of people who are willing to actually go on a long space journey like do you think before people like yeah i'd be up for an eight-year journey to jupiter and now they're like i did not survive exactly no well there's probably another entire podcast on that one um so becky holly mcfall has a question about jupiter's colors she asks why is jupiter so many different colours is it different gases? Yeah it's exactly that Holly so you have different elements and molecules which absorb and reflect different wavelengths of sunlight so the same way that you know if you're looking at a blue wall it's because that blue paint is you know only reflecting the blue sunlight back back to you

so most of Jupiter is hydrogen helium as Robert as Robert said earlier, but as storms form on Jupiter, you get a lot of mixing through convection. So convection is this heat transfer, you know, where essentially what we say all the time, right, heat rises, cold sinks. And so you get this sort of cycle of dredging up of materials from lower down in the atmosphere of Jupiter, like, for example, sulfur with its sort of distinctive yellowish color, you might have phosphorus coming up as well, ammonia, things like that. But then also like hydrocarbons, so these big long chains of carbon bonded with hydrogen, the things that give us methane for very small chains, but then you know, longer chains go up to sort of like

all that petrol and everything like that. When that happens, you then get those materials condensing in the clouds. And then that's how you get this reflection of all these different colours in the sort of clouds that you see on Jupiter. And also these clouds, they split into these different bands because of the winds on Jupiter. So you've seen some of the winds.

If you can find online, there's a really great GIF or video, a time-lapse of Jupiter as sort of like flattened out into a map. So you can see things moving sort of like left and right in these different bands, which I never get tired of watching, in these opposite directions. And so because it's in these opposite directions, you get these very clear boundaries between sort of different layers in the clouds with different molecules in them that give it that sort of distinctive stripes and then we get very interesting features on the boundaries as well where you've got obviously two things moving in opposite directions yeah and i just think even

the images from juno that we've seen recently just the the amount of detail that you can see in those and all the swirls and the different colors of jupiter it it seems a more familiar planet because of it because we've been able to see it so up close yeah definitely and dolphins and find patterns as if they're just like you know lying on the back garden looking for patterns in clouds on earth it's a similar thing when you get these images of Jupiter right like oh what can you see in the clouds it's it's very oddly familiar yeah and on a similar vein Robert see me so crochet on instagram asks how long is the red spot expected to last forever a hundred years a thousand years and and the honest answer is we really really don't know um we think it was seen with a spot was certainly seen in the mid 17th

century so not that long after the invention of the telescope a few decades later when they got good enough to see those sort of details. And if it's the same one, then it's lasted more than 350 years so far, although there don't seem to have been many observations for about a century from 1713 to 1831. I know people weren't recording it. There is, I've discovered actually, a painting from 1711 by the Italian artist Donato Creti, which is not bad, which shows bands on Jupiter and what looks very like the modern spot, but we're just not sure if it is. But it has been shrinking a lot recently. So if you go back 100 years, it was about maybe 50,000 kilometres across. And so several times the size of the Earth. Now it's only about 16,000 kilometres across, so only a bit bigger than the Earth. It's still enormous. I mean, there's still a storm that's bigger than the whole Earth, but it's half what it was 100

years ago, a third what it was before that. So it might be disappearing. It might be dissipating. It might be that there's some cycle where it shrinks down and grows again, and we just don't know. We've just got to keep watching to find out. And personally, I would miss it because I've never really seen it properly, and I'd quite like to and I've looked at with Jupiter through some quite big telescopes and never convincingly see it might be my eyes my powers of observation I don't know but I still realize it so I sort of hope it bounces back and it becomes obvious just say it was always wrong yeah absolutely it wasn't me you always just missed it every single time maybe that's what happened from 1713 to 1831 as well every single time there is there is an

example yeah one thing i was going to add was that there is an example like this on neptune where something was discovered by the voyager probes called the great dark spot and people at the back in 1989 people assumed or i think might have imagined that was a permanent feature but when the hubble telescope looked at it a few years later looked at neptune a few years later it had gone so there is sort of a precedent for these things. We don't necessarily know how long these big weather systems last. So finally, Becky, we've had a question from Max Mullins and he asks, what is Jupiter's gravitational pull on the planets? So it's actually bigger than you'd think. Like, you know, the sun is like 99% of the mass of the solar system. So you don't think that

Jupiter, even as big as it would, would would have such a massive impact but it really does so first of all you've got to remember that the planets aren't sort of orbiting the very center of the sun like the sun and whatever planet you pick are orbiting the center of mass between them yeah and jupiter is so big that the center of mass between the sun and Jupiter is actually 46 kilometers above the sun's surface. It's outside of the sun, technically. So the sun is always in that tiny bit. Oh, that's a surprise. Yeah, exactly.

I'm always surprised by it. I think it would be like 46 kilometers from the center of the sun, not from the surface of the sun. Yeah, yeah, yeah yeah yeah yeah and so obviously it's because jupiter is the biggest planet that that happens like the bigger the planet the more that that center of mass is pulled from the center of the sun like earth doesn't you know near as much change that sort of center of mass it's still inside the sun so that was very exciting and it me you know it really puts into perspective how much of a big player is in the solar system now obviously we've got to remember that the pull of gravity drops off with the square of the distance

you are away from something. So the further away you are from Jupiter, the less of an impact it is going to have. But it's still enough to change the path of asteroids, for example, even tear an asteroid apart if the gravity that's actually keeping those just sort of like, you know, rubble pile together isn't strong enough.

Jupiter can do that. It's also cleared those just sort of like, you know, rubble pile together isn't strong enough. Jupiter can do that. It's also cleared areas of the asteroid belt and just been like, no, no asteroid's going to hang out here. Absolutely not. Because of its gravity. Then we also think that the reason that the asteroid belt exists in the first place, i.e. why that just sort of all that rubble didn't coalesce to form another planet is because of

Jupiter. Jupiter again just went, nope, not happening. Not happening, not in my sense. Not on my watch. This is my patch. The other thing it does is it pulls on the orbits of all the other planets as well. So one of the reasons that the orbits of the planets are elliptical or as elliptical as they are is because of Jupiter pulling on them. And there is actually a study I found from 2008, and I think you're going to love this, Izzy, from Batygin and Loughlin, who ran a simulation of the solar system evolution going forward with all of the gravitational interactions taken into account. And they found that Jupiter's gravity eventually pulls on Mercury's orbit so much that it completely disrupts Mercury's orbit. And depending on like lots of other factors,

there's then four options for what happens to Mercury. Either it just falls onto the sun, crisps, burns and dies. Or it gets completely ejected from the solar system and it becomes like an interstellar object right or it crashes into venus or earth okay slide problem that's a science fiction film right there then yeah we're gonna add that to our list of like science fiction films that we should write yeah we should totally write this and the thing is obviously this is going to happen for like over like one and a half billion years so

obviously our sci-fi has to have a believable reason why we've sped up that time scale but yep um minor details minor details yeah but i think it just really shows like the power that that jupiter does have in in the solar system is sort of the the next biggest thing from the sun oh max what a brilliant question thanks for sorting that one yeah great i'm such a good guy yeah i'm well into that scientific literature being like oh what have i found here jupiter great planet fascinating well thank you everyone for sending in your questions and if you have a question for us, then do email us at podcast at ras.ac.uk. You can tweet us at Royal Astro Sock

or slide into the DMs on Instagram. It's at supermassivepod. So Robert, what can we see in the night sky this month? Well, sadly, Jupiter is really tough to see. It's very low down in the West, but there's a good few other things as usual. So if you look in the evening sky in the first part of April, it's a chance to see Mercury. A long time before it's thrown out, the solar system, I stress. If you look over in the west,

it's never very, very bright and it's only very briefly visible, usually only for a few days at a time, maybe 10 days or so. So the first bit of April, look about 30 minutes after sunset. Obviously, the sun has to set. No chance if the sun's above the horizon. It's dangerous to stare at it anyway. But if you want to glimpse the innermost world, it's a good time to do it. Let the sky darken and then look over and then grab a pair of binoculars, get an app like Stellarium or whatever on your phone and you should be able to find it. In terms of photogenic opportunities, there's a nice one, which is Venus near the Pleiades on the 9th to the 10th of April. That's always, you know, if you get a camera, stop it down. You can see some really lovely views there. The Pleiades is a cluster of stars and Venus is obviously the brightest planet in the sky. If you're travelling and you're very lucky, if you're going down to the northwest Cape of Australia, I think you're probably doing this purposefully.

There's actually a total solar eclipse on the 20th of April. So I know a few people who are going down there and good luck to them. I wish them clear skies. Not going to see anything from the UK, but, you know, in the rest of Australia, for example, they will see a partial eclipse. There's a meteor shower on the 23rd of April, the Lyrid meteor shower. Not massive rates, 15 to 20 an hour. So probably you're going to see maybe half a third of that number on top of what you normally see but it's it's nice to look at and the moon isn't going to be a problem so if you've got a dark clear sky that's definitely worth looking out for and generally we're moving very much into

the the epoch of the time of year rather of spring stars so you're going to have ursa major high in the sky the great bear including the seven stars the plow and really high overhead once you get into the evening sky in april you can use that as a signpost for other things if you follow the curve of the tail or the handle if you prefer you can find the bright star arcturus in boetes or you can go up to the pole star using the pointers and once you've found the pole star the nice thing is it's always in the same place in the sky so you you know if you look out in your garden no matter what the time of year it'll always be there and leo the lion is sitting underneath the plough and the sermaeja. And

this region of the sky, the Milky Way isn't as bright. But what that means is you're more able to see things like galaxies and so on. And most of them do look like fuzzes. But if you want to look at some, you get a decent-ish pair of binoculars, a small telescope, it's a good time to be doing that. And there are a couple of bright compact globular star clusters to see as well. So, you know, the spring sky, it's getting a bit warmer, which is always a plus. The nights are still reasonably long, even after the clocks go forward. So, you know, take advantage of that. Go and enjoy the view. Oh, lots of things to see. Thanks for that, Robert. And I think that's it for this month. We'll be back next month. And I purposely haven't put this in the running order because Becky, next month is going to be all about Saturn.

Yay! Did you do that just for me? Maybe. Maybe it's about time. It's taking us a while. We started this podcast in 2020. So maybe, just maybe it's about time we did an episode on saturn i'm so excited i'm so excited we're gonna bring the a game for this one not that we don't always bring the a game but you

know what i mean i'm gonna be like extra excited for this one oh my god i don't think we're ready for that you're not ready obviously get in touch with us if you have a question for the team it's at royal astrosoc on twitter or you can email your questions to podcast.ras.ac.uk and we'll try and cover them in a future episode so all those burning questions about saturn get them sent in now also for one last time if you love the podcast and you enjoy it and you want to support us just that little bit more our book the year in space is still available it covers all the big news stories from last year. A lot of stuff on JWST, which I know you all love. So, you know, have a look at it.

We'll put a link in the description if you'd like to get a copy. But until next time, everybody, happy stargazing.