The Supermassive Podcast - Why isn't Pluto a planet?

Episode Date: June 30, 2025

Izzie and Dr Becky decided that little ol’ Pluto doesn’t get much attention anymore. So we’re giving the dwarf planet some time in the spotlight. Why isn't Pluto a planet? How small is it? And what makes it so unique?Thank you to Prof Alan Fitzsimmons from Queens University of Belfast joining us episode.Join The Supermassive Club for ad-free listening and share you questions, images and more. Or email them to [e-mail] or on Instagram @SupermassivePod.The Supermassive Podcast is a Boffin Media production. The producers are Izzie Clarke and Richard Hollingham. Hosted on Acast. See acast.com/privacy for more information.

Hello and welcome to the Supermassive Podcast from the Royal Astronomical Society with me, science journalist Izzy Clark and astrophysicist Dr. Becky Smethurst. We decided that little old Pluto doesn't get much attention anymore, so we're giving the dwarf planet some time in the spotlight. Yeah, it's about time. It is, it is, yeah. So in a moment, we'll hear from Alan Fitzsimmons, Professor of Astronomy at Queen's University

of Belfast to tell us more about Pluto and why it was reclassified. And Dr. Robert Massey, the deputy director from the Royal Astronomical Society, will take on listener questions later on in the show. So Becky, you get the opening question this time. How did you feel when Pluto went from being a planet to a dwarf planet? Becky Massey I mean, I was a little bit sad like everybody, right? I think we can't help but anthropomorphise these things. We're like, sorry, Pluto. I don't like change. And yeah, I was, you know, still one of the generations that grew up, you know, being

like, there's nine planets and you know, what do you do now? It's all your mnemonics now that Pluto is not at the end and all this kind of thing. But I think, you know, these feelings are slightly irrational because they are just inanimate objects, you know. And in the IAU, the International Astronomical Union, they were trying to tidy up all these designations of objects that we have in the solar system. The number of bodies that we knew about was growing as we detected more and more things beyond the orbit of Neptune and also big things in the asteroid belt as well, like Ceres. And it was sort of just getting a little bit messy to be like, well, those are planets because we knew about those for ages, but

those aren't planets because we just discovered them and they're a bit fun. Yeah. Sorry, there's no more room. There's no more room. Yeah. You know, it was either we had nine planets or we had, you know, like a growing list, which the mnemonics also wouldn't have been able to cope with, I guess. But some of those things even were bigger than Pluto as well. We have to remember that when Eris was discovered and it was bigger than Pluto, people were like, there's not 10 planets in the solar system now. Yeah. So I think I was sad, but at the same time, I understood the reasoning behind why you would want to define a planet more clearly. Yeah. Whether we all agree with the definition that was come up with, I don't know.

But yeah, I think it's funny how the internet is still mad about this though. So hopefully we can put to bed with our interview with Alan about why this was necessary in the case. Exactly, we will. And he was actually in the room where it happened when there was the vote. So we'll get to that later on in the show. But you will still find Pluto out in the depths of our solar system, where there is, you know, as a dwarf planet. And Professor Alan Simmons from Queen's University of Belfast studies comets and asteroids in our local slice of space.

And he explained why Pluto is unique to other objects in our solar system. Well, first of all, when it was discovered in 1930, it was the furthest object known from the sun and much further out than the planet Neptune, which was the record holder up until that point. It was then realized that it had this really strange orbit. Most of the major planets in our solar system, their orbits are fairly circular with the possible exception of Mars,

which is slightly elliptical. But this was incredibly elliptical in the sense that it actually crosses the orbit of Neptune. But it's great because it's in what we call a gravitational resonance. That means it goes around the sun twice for exactly every three times. Neptune orbits the sun. And that means although their orbits cross, they can never hit each other.

So it's been like that for literally billions of years. Even though you say that, I still feel that element of jeopardy of like, but what if, but no, we'll trust the numbers. Yeah. Now the next thing that made it special and somewhat unique and is still kind of unique is that about almost 50 years after its discovery in 1930, in 1977, a moon was discovered orbiting Pluto called Charon. And Charon is huge compared to Pluto. It's about half the size of Pluto. So it makes it the biggest moon relative to its kind of planetary-sized parent that we have in the solar system. Our moon, or it's our Earth, is only about a quarter the size

of our planet. Amazing. And so can you put it into perspective? Like how, I was going to say how big, but probably how small is Pluto? Well when Pluto was discovered, it was expected it would be about the size of the Earth. And over time, estimates of the size got smaller and smaller and smaller. It's smaller than our moon. It's got a diameter of about 2,400 kilometres. So it really is a small body, but that doesn't

make it any less interesting. It just means it's really tricky to study with telescopes here in the inner solar system around Earth. Yeah, absolutely. So let's talk about some of those interesting features. What are some of those surprising or unexpected features discovered on Pluto? What's it like? Well, if you're standing on the surface of Pluto, first thing to realise is that it's not only very cold, it's very dark because you're so far away from the sun. You get hundreds of times less light during the day on Pluto than you do here on Earth because it's so far from the sun. Now, you'll also probably be standing on ice rather than rock,

though we believe there is rock on the surface of Pluto. And you'll be in an atmosphere. This is one of the big surprises that came out in the 1980s when scientists are using the technique of stellar occultations from Earth, watching Pluto pass in front of a star. So they didn't just cut on and off really quickly, but the starlight gradually faded away and came back again, which is the signature of an atmosphere. Now, it's not a very thick atmosphere, but there's an atmosphere nonetheless. It wasn't known, however, if this was a permanent atmosphere or initially or whether or not it was being generated by volcanoes or something like that on the surface, what we did know is that it's so cold out there on Pluto that because we were studying it near

the point in its orbit where it's closest to the Sun and therefore warmest, when it receded in its orbit out to its furthest point from the Sun, it was possible that it would get so cold, the atmosphere would literally freeze out and dissipate and freeze out onto the surface in kind of a wonderful frosty crystalline layer, only to be then heated and regenerated as gas the next time it comes around the Sun. That's crazy, right? We used to have things having an atmosphere, not having an atmosphere, not just having an atmosphere every now and again once go orbit. From Earth, we can study the ices on the surface of Pluto through spectroscopy. It's been known for decades that there's carbon monoxide and methane ice on the surface. That's because it's very cold. It's out there on the edge of our planetary system. We're looking at a temperature of

perhaps minus 220 degrees centigrade and low, it really is quite chilly. It just reminds me that every time I listen to people talk about Pluto, you read up about Pluto, you're like, it's a bit mad. It's just ridiculous. There was this probe that went to visit Pluto and it has helped us understand it more. So can you tell us about the New Horizons probe? What was it? When did it go and visit? And how has that changed our understanding of Pluto? Yeah, New Horizons was an amazing mission from NASA. One of the smallest but fastest interplanetary spacecraft that's ever been built. It was launched in 2005,

and by using Jupiter's gravity en route, it basically only took 10 years to get there. It took a decade, but that's pretty fast compared to most other spacecraft. In 2015, it flew through the Pluto system. Now, I say the Pluto system because in the run-up to New Horizons getting there, Pluto and its moon Charon had been studied by the Hubble Space Telescope. Over the years, they'd found another four small moons with the Hubble Space Telescope. So, they nearly had a system of Pluto plus five moons to study as they barreled through the Pluto system. And when they got there, because this was on the edge of the solar system,

we really didn't know what to expect. And what New Horizons found was an amazing small world in its own light with all kinds of features that you could not see clearly or detect it all from Earth. So for example, one side of Pluto is dominated by a huge glacier made of nitrogen ice. And you can actually see how it's flowed across the surface over time. There's also surprisingly a great difference in ages between different parts of Pluto. Now we date ages on objects

like Pluto by counting craters because there's small asteroids and comets out there that on occasion will hit these objects and the more craters you have on a surface that must mean it must have been around for longer so it's older. Now there are some regions of Pluto which look like they're about four billion years old either dated back towards the beginning of the solar system but there are some which have hardly any craters at all particularly around these glaciers which tell us that those features are perhaps only a few million years old and so we've got a picture now of a world where some parts of it are very old but others are very dynamic. The other thing we found for example are mountains

but interestingly enough they're not like the mountains here on Earth. Whereas some of these mountains and indeed smaller hills we saw are mostly made of ice and they're made of water ice and methane ice which is of a smaller density so they're lighter than the nitrogen ice they're sitting on. So you can actually think of these as small, as kind of floating icy mountains that are floating on the ice below them, which is just crazy, right? It is. It's so bonkers. So is there any evidence to suggest that Pluto could harbour or support any form of life?

It's really cold and although the ingredients for life are there, there's a lot of light elements, there's water ice, there's carbon-based molecules. It's just too cold and too frigid to support any kind of life. And it's even difficult to think of a kind of life that we don't know right now that could survive there. But you're underneath the recent modeling of Pluto implies that it may be warm enough beneath the surface for that water to exist in a liquid state, but we still don't understand whether or not it might be in a kind of a subsurface ocean or whether it's just water permeating through rocks underneath because we know there's rock involved in the composition of Pluto as well. So it's pretty uncertain at the moment, I'd say.

At this point, maybe I could throw up the usual astronomers crying, saying, we need another spacecraft to go out there. throughout the usual astronomers' crime, saying, we need another spacecraft to go out there. Thank you to Alan Fitzsimmons, and we'll hear all about why Pluto was demoted in just a moment. So Becky, how many dwarf planets are in the Kuiper belt? We always have this discussion. And are they all quite similar? So technically, there are five dwarf planets in the Kuiper belt. So you've got Pluto, there are five dwarf planets in the Kuiper belt. So you've got Pluto, Orcus, Haumea, Qua'wa, Sean wanted to say, and Makemake, which I have pronounced makemake on this podcast before and Robert's gone, mmm, makemake, makemake, makemake, makemake, makemake, makemake, makemake.

But in terms of just how many objects are there in the Kuiper belt in total, like it's how long is a piece of string, right? Because it's like the Asteroid Belt, it's just rubble of all sizes, right? And just going down to the smallest specks of dust even. So the line between what is a dwarf planet and what is just lump of asteroidy rock is also kind of gray, like the line between planet and dwarf planet as we'll hear in a minute. So the thing that sort of takes objects from being dwarf planets and from the five that we recognise to being just asteroid is something called hydrostatic equilibrium. Equilibrium, everything balanced, right? It's this idea that you've got strong enough gravity because your object is heavy enough so that you would round it.

Yeah. So it's not gonna be just some lumpy potato like you get with a lot of asteroids. It's gonna look like a round thing. Yeah. Like we are used to picturing planets and moons and things like this. The problem is there's no definitive mass, like mass cutoff, like some threshold you can define of like this many, you know, trillions of kilograms where all of a sudden there's this clear line that something becomes round and becomes a dwarf planet. So for example, there is an object called Salacea that if it had a typical asteroid composition of the things that

we would expect asteroids to be made of, the same elements, molecules, things like that, same rock, then it wouldn't be in hydrostatic equilibrium. Well, if it had a less than typical asteroid composition, maybe some heavier elements, things like that, then it would be in hydrostatic equilibrium and therefore it would be round and classed as a dwarf planet. So we're not entirely sure where Salacia falls. So this is why I said, technically there is five, but like, no question marks. Yeah, exactly. Yeah. I mean, like, and when we look at Salacia, we know it has a moon as well.

Right. So in that sense, you think of it being like, you know, like Pluto and Charon and like, almost like a binary planet, dwarf planet system, you know? So it's a really intriguing object, Salacia. And I think, you know, if people can, I think they'll try and, you know, drill down on what it actually looks like. Is it round? Because obviously all we get is just sort of a fuzzy blob of light from it, given that it's so far away. And I think those are my favourite kind of objects, you know, sometimes that and they could belt those ones on that boundary. And I wouldn't be surprised if we had more of those popping up very soon, thanks to the Vera Rubin Observatory. I know.

Oh gosh. So at the point of recording, we've had some of the first images and it just, I was reading a BBC article and it said literally in one of the first paragraphs, if there is a ninth planet we will find out within the year. Yeah. And I was just like, oh my goodness me. Yeah. And to put into context why, right, that Rubin in its like seven days of commissioning data, it talked to me like, does it work? It detected 2000 new asteroids.

Oh God. In just seven days. None of those are anything to worry about, first of all, but that is more. Sorry, my god was like but that is more asteroids. My god was like, that's so exciting, not fear. No, no fear. But yeah, 2,000 new asteroids is more asteroids than have been discovered in the past 200 years. Oh my goodness me. Yeah. I mean, mostly those are in the asteroid belt because they're the easy targets they found very clearly. But you know, these little things, this is what I'm saying, like you can get down to the little things. But if there are big things further away,

they're gonna be as detectable as well with Rubin because it has such a massive, what we call, field of view. You know, when you like, you point your phone camera and you can switch to like the wide lens versus, you know, the point five, the one, the three, right? This one is just like, you can just keep going out with Rubin and it can look at this massive patch of sky at once and it can move really fast as well. So it covers this huge area very quickly. And so seeing things move is like what Ruben is just going to be like excelling at. And it's not over exaggerating the fact that me and my colleagues have been waiting for this observatory to come online for, I mean, I've been waiting for 10 years from people have been waiting for a lot longer as well.

Right. We have been anticipating this for so long. And I, it's almost like when JD Boast T launched as well, I kind of can't believe we're finally here. Yeah. And seeing that data the other day, and hearing that number of 2000 asteroids, I just, yeah, hit the roof. I'm not gonna lie. My, my, the ship has sailed, but I'm like, should a PhD, this would be an exciting time to do a PhD. But anyway, we move, we'll move on. Let's talk about New Horizons. Like, do you have any favorite discoveries from New Horizons? Ooh, that one's a bit difficult because there was so many.

To be honest, I actually saw Pluto, I know the whole episode is about you, but I don't think my favorite discovery was the Pluto discovery. There was a lot, but I think it was actually, did you remember the little snowman, Arakoth? Yeah, it was called all the more tool and that the name was changed. But if you remember, so after the flyby of Pluto that New Horizons did, I think it was 2015 that was the trajectory of New Horizons was just shifted slightly so that as it just continued to sail past Pluto, because it didn't break or anything, it just went whoop, and kept going into the Kuiper Belt, they changed it ever so slightly. So they would actually

do a flyby of one of these trans-Neptunian objects, as we call them in the Kuiper Belt. In this case, Arakoth. And the closest approach, it was about 3,500 kilometers from its surface, and it was on the 1st of January, 2019. So if you remember on New Year's Day, we got the images and pictures. And it was a snowman. It was in winter because it revealed that it was essentially what we call this contact binary asteroid, where you've had two smaller asteroids come together. But instead of sort of colliding and breaking apart and just being very almost like messy

in a collision. It was a very slow collision so much that they just kind of like stuck together and became one thing. And they're probably slowly maybe going to become, you know, one sort of more rounded asteroid. Who knows? Over time. Yeah, but all they might say is this weird snowman. That's the best way to describe it. If you're picturing literally putting a head of a snowman onto the body of a snowman,

that is what this thing looks like. And it was such an amazing surprise at the time. I remember people being like, what? What? You know, it wasn't like it was picked because we knew that it was a contact binary. It was just a complete surprise. And it was just one of the things that was, oh, that's going to be close to where New Horizons is currently heading.

And we shift ever so slightly so that it comes close enough. So it's led to so much more science in terms of understanding how our solar system came together, how planets form, how asteroids form, how dwarf planets form as well to become these larger objects. These collisions between these bits of rubble don't have to necessarily be destructive or violent. They can be gentle, leading to these snowmen. necessarily be destructive or violent, they can be gentle leading to these snowmen. In 2006, the International Astronomical Union, aka the IAU, reclassified Pluto as a dwarf planet. And as we've already talked about, I don't think some of us have forgiven them yet.

I think I've read it. But anyway, Alan Fitzsimmons was part of that vote and explain to me why Pluto was reclassified. Well, it is really because of an oversight, an oversight on behalf of astronomers, because we'd never formally defined what a planet is. And you might say, well, it's like a cat, you know it when you see it. But it's not quite true, right? So historically, the planets were the planets out of Saturn that have been identified by the ancient astronomers without telescopes. But since then, we'd had Uranus and Neptune and Pluto. And we've got other

objects out there. And in particular, in 2005, another object was found even further out than Pluto called Eris. Eris is almost exactly the same size as Pluto, literally within about 50 kilometres. It's actually slightly more massive and we know that because it's got a small moon orbiting it that's been seen from the Hubble Space Telescope and other ground-based telescopes. So if Pluto is a planet, is Eris a planet? And what about the objects that are slightly smaller out there like Haumea, which has rings around it and a couple of moons, and it's kind of this weird rugby ball shape, and Maki Maki, and all kinds of objects. How many planets do you want in the solar system? That's the question. But it really was the discovery of Eris in 2005 that convinced the

astronomical community through the International Astronomical Union that, yeah, we're going to have to decide what's a planet and what isn't a planet. If something isn't a planet, what is it? Okay. So let's go through that. What is the criteria for being a planet and how does Pluto fall short? Right. Okay. So after a lot of discussion and debates, there's three criteria you need to call something a planet in our solar system. First of all, it's got to orbit the sun. And that's important because Jupiter's moon, Ganymede, is larger than the planet Mercury, but it doesn't orbit the sun, it orbits Jupiter.

So by definition, Ganymede is a moon of Jupiter and not a planet. Okay. Okay, so that's the first thing. Got that, yep. Yep. The second thing is that, well, technically it's got to have enough mass to obtain hydrostatic equilibrium. And basically what you're saying is that it's got to be big enough that its own self-gravity can overcome all the internal forces to mold it into a sphere. Why planets, when we think of planets, are balls and not just irregular objects like the much smaller asteroids and comets that orbit our sun. So it's got to have enough

gravity that it will mold it into a ball basically, or pretty close to a ball. And Pluto matches those first two criteria. But the third criteria, and this is the one that's kind of remained most, well, there's been a lot of discussion about it over the years, is the third criteria is that it has cleared its orbit of other things, which means that about that distance from that Sun or around that distance from the Sun, that object's gravity is big enough that there's no other stable orbits at about that distance. And that's where Pluto falls down because we have a huge number now, hundreds of other objects that aren't only at the same distance

as Pluto from the Sun. They're in the same three to two resonance with the planet Neptune. We call them Plutinos colloquially because they're smaller versions of Pluto, but there's a lot of them out there. Pluto's mass isn't big enough to actually disturb their orbits enough so that they disappear. You can't have a stable orbit around that distance if you're going to be a planet and that's where Pluto falls down. I see. Okay. Although I do think Neptune and the Plutinos could be an excellent band name. I think the thing here, and I think this is a question that we get quite a lot though,

why is it that a dwarf planet though can still have moons? That doesn't make it what we classify as a planet. So can you just cover that if you can? Okay, sure. Well, what's important is actually the orbit about the sun. Now, to be honest, if you're big enough and you bring in something small close enough. Almost anything could be a moon, or it could be a planet in that definition. No, I mean, okay, I don't think I could be a planet. I don't need quite that much. But for example, let's go to the Earth.

Now the Earth we call a planet, and it is surrounded by objects called near-Earth asteroids, but those orbits aren't stable. They only last in their orbits somewhere between an average 10 to 20 million years. Either they hit the Earth very rarely, or they hit the Sun more frequently, or they'll be ejected to another part of the solar system. But if we look at those tens of thousands of near-Earth asteroids, about 15% of them have little moons next to them. Something as small as a kilometer across or so can have its own even smaller moon. So having a moon certainly can't mean that you're called a planet.

And so you were at that vote when Pluto was reclassified. So what was that like? Well, it's pretty interesting. It came at the end of this two-week-long meeting in Prague in 2006. It's a general assembly of the International Astronautical Union, and there were a few thousand people there, although only a few hundred took part in the vote because it was held on the last day of the meeting in the end, and a lot of people were leaving at that stage I think. But it was kind of interesting because there'd already been one idea of what the definition of a planet should be in the first week and really very few people actually liked it. So we kind

of threw that out. Then we came up with this second one. In fact, there was a couple of Eurogrion astronomers who had proposed this previously. They said, this might be a good definition of a planet. The more we thought about it, we thought yeah okay, that this kind of works. And what worked about it was that it would mean that Pluto wasn't officially a planet anymore, but the meeting as a whole came up with this new category of objects called dwarf planets. Everybody felt like that's a pretty good compromise. The important point is this, as you discover more things in science, you've got to reassess what you call stuff, how we categorize stuff, and how you understand what's going on out there.

And there will be these revisions. And when you do that, then sometimes things like Pluto will be put into a different box from what it was there before, but it doesn't change anything about Pluto itself. It's a fascinating world. Absolutely. And I mean, the science, it adds up, it makes sense, but still people feel that connection and like justice for Pluto. So why do you think the public is still so emotionally attached to Pluto as that, you know, ninth planet?

Well, I think it's a function of time because everybody or most people now, including myself, grew up knowing there were nine planets. And if you are a science geek like me and Paul, probably you are as well. You learn the order of the planets at school going out. My very easy method just feeds up naming and then nothing. Yeah, that's it. That's it. So I think people grew up with nine planets and suddenly in the news, they read that, oh no, scientists have decided there's eight planets. And because what gives them the right to do that is the idea. But it's because they don't realise that there

are many other objects out there and there are these other dwarf planets. We now have five dwarf planets in the solar system. And so when people ask me why do we have nine planets in the solar system anymore, well, I said, well, the choice isn't nine. We've got eight. Or do you want 13? Yeah. And it's probably going to be 20 or 30 when as new discoveries roll in and we categorise more dwarf planets out there. How many planets do you want? Thank you to Alan Fitzsimmons, Professor of Astronomy at Queen's University of Belfast. This is the Supermassive Podcast from the Royal Astronomical Society with me,

astrophysicist Dr. Becky Smith-Hirst and science journalist Izzy Clark. That's me. So before we get onto our Pluto questions, as we're one of the world's most popular astronomy podcasts, I don't mind tooting our own horn on that front. I think this is a real tone shift. We can't really not mention the significant proposed cuts in the NASA science budget. Robert, Becky, let's have both of your thoughts on this. Robert, these come from the White House. What would they mean if they were approved by Congress? Well, I mean, they just look really big and really awful. I mean, it's not just NASA, it's cuts to a lot of science programs in the US across the

board. Many of us here, in other countries, in the UK in particular, we're really just honestly shocked by what's being suggested. It's been described as an extinction level event for some aspects of US science. To give you some numbers, NASA as a whole, the proposal is a 20% cut, but for the science program, that's a 47% cut. If you look at the individual proposals, astrophysics cut by two-thirds, heliophysics, so physics of the sun cut by 50%, planetary science down by a third. The Mars sample return mission, we've got the Perseverance rover that's been dutifully basically putting samples in canisters to return them to Earth, so cancelling that whole thing seems crazy.

Da Vinci and Veritas missions to Venus, that's an exciting place to be exploring because of that tiny, tiny possibility there might be life there. And possibly even the closure of the Goddard Space Flight Center. So this is really bad news. I just think this is heartbreaking. I think that's the only way I can think of it. The idea of not having a Mars sample return mission when so much effort has gone into that. All of that collection, all of these potential ways to get those back for that to just be

scrapped is a kick. It is a huge kick. Yeah, it's kicking the teeth. There have been rumours for a long time. Now we've had like a proper huge 400-odd page document detailing every single thing that's going to be cut, not just for NASA, but also for the National Science Foundation in the US as well. And like I think a lot of us will read that say the Nancy Grace Roman Space Telescope would go the same way. So I know we talk about JDBS-T as being the follow-up to Hubble. But actually,

it's the Roman telescope that's the follow-up to Hubble because JWST is infrared. It's not quite the same as Hubble. Hubble is going to die at some point. The Nancy Grace Roman telescope is pretty much built. It's going through a load of testing and everything. And we all thought with this budget that it would just get completely cut. It hasn't been cut, thankfully. But again, it's been told that I think the budget cut is huge on it in terms of like, I think it's sort of like in the 80 90% number, I can't remember the numbers off my head, we can look it up. But like it's huge. And basically, it's just kind of like, figure out how to do this on a shoestring budget

now. And you know, this whole episode is about Pluto is being 10 years in July, it'll be 10 years since New Horizons first took proper images of Pluto and transformed what we thought Pluto was and what it looked like. Now New Horizons is one of the missions that the White House wants to cut as well. It's painfully extensive. Yeah. Well, the thing about New Horizons that gets me and then also do you remember a Cyrus Rex that went to the asteroid and collected... I mean, we literally talked about it in one of our recent episodes.

Yeah, yeah. So that and also in the same way to New Horizons, it was our way, it's still out there, it's still flying through space, we just give it a little nudge and it'll visit somewhere else and that was the plan for New Horizons, it was the plan for Osiris and they've renamed it Apex because it's going to Apophis, which is the asteroid that will come really close to Earth in 2029 I think it is. So those missions were like, they were on their way and now NASA have gone, no, funding completely cut. So like you were saying, like these missions are in space. So what does that mean to cut

the funding? Well, it means there'll be no funding for the deep space network to collect the signals back from those missions that they will send back to Earth. There'll be no funding for people to then grab that data and analyze it and put it out to the world and make it available for the scientists. So basically those missions are just going to fly past those objects. And we'll just not know what they found, which is insane. It's just, it is sad. I'm sat here just like, sort of rubbing my forehead in disbelief because, okay, yes, it's all of this science that could be and is well technically actually happening right now that we would just leave by the wayside.

It's also the legacy of space exploration, you know, if Goddard were to go, I mean, that is such an iconic part of spaceflight history. And then it's also the people, the collaborative effort, the possibilities of discovery and that collective effort, that international collective effort that again is, it's just really sad. I think that's what I can say. It's just, it's so frustrating. It's remarkable.

It's the US, you know, seeming happy to give up its decades of leadership in this area. It does have big ramifications for us too, because the European Space Agency has relied on a collaboration with NASA for so many of its projects over the years. We have too, the UK specifically. There are things like the Gravitational Wave Observatory, LISA, another Venus mission, Envision, the new Athena X-ray observatory. These are things where we really depend on US input. Without that, it's going to be a real challenge. I guess if it happens, then what many of us are just hoping, and it will be difficult, is that Europe, including the UK, works on building its own capacity, that we have our

own space sovereignty. But it would still, for all that, be really gut-wrenching if the US is no longer a reliable partner. I just really hope that the Congress sees sense and throws out the package and says, no, you're not doing this. We're in the real world. We know there are cuts fairly often to budgets and they get trimmed. Sometimes, if you're lucky, they grow, but quite a lot of the time they're trimmed. But to do it on this scale, it's just crazy and it'll be really, really damaging. So I just hope it doesn't happen. So do we know what the proposed timeline is? I think it plays out over the year. So as I understand it, this all goes through the Congress, presumably over a period of months. And then there is a slight risk that if they

haven't made a decision by the end of the year, the president, the administration can act to a certain extent on their own under some obscure legislation or a obscure process that was last used in the early 1970s about them being able to determine the budget now. But I hope that we don't get to that. I hope that Congress just says, no, you're not doing this. It's much too important to just decimate these amazing things that we've got to have these things that if nothing else offers some hope in the world, all those amazing wider impacts of science, the inspiration that comes from space and astronomy, let's just not destroy that. Heather Hyslop I think it's time to cheer things up with some questions from our listeners.

Samon Lett Please, please. We should say again, this isn't approved by Congress yet. It still has to go through Congress. There is opposition on both sides of the political spectrum in the US, so this isn't a guarantee yet. And you can also make your voice heard as well with petitions and writing to your members of Congress and picking up the phone and speaking to them if you're in the US as well and you don't want to see this happen. Yeah, absolutely.

Okay, Robert, let's start things with this question from Lewis Donaldson on Instagram. He asks, with Pluto's odd orbit, is there risk of collisions with Neptune or influence from its gravity? Yeah, so if you look down on the solar system from the north, so imagine you're high above the north pole of the Earth and the north pole of the Sun and so on. Then the orbits of Neptune and Pluto do indeed appear to cross. From 1979 to 1999, Pluto was actually closer to the Sun than the outermost ice giant, so it was a bit closer in. But this is a 2D map, right? Because the orbits of the two worlds are actually at very different inclinations. They're tilted compared with each other, and that means they never really come close at all. Pluto is simply never that

close to Neptune. The planet Neptune and the dwarf planet Pluto are actually also in a two to three resonance, where Pluto completes two orbits for every three that Neptune does. That interaction as well stops them from ever getting closer than a couple of billion kilometers. Now that's a very big discussion. To give you an idea, the Earth is 150 million kilometers in the sun. So you know, you think they're close together, they're really, really not. And the outer solar system is on a big scale.

There is basically no prospect because of that resonance and because of the tilts of the orbit that they will ever come close. Okay, thanks, Robert. And Becky, Brian Ross has posted in the Supermassive Club, and he was the first one to do so. So perhaps in the back to him. Yeah, exactly. And he says, if Pluto were a second moon of the Earth, what would be the most interesting difference considering its chemical makeup? Would it still retain its atmosphere, or would it be way too

warm? And what would its furthest stable orbit be? Thanks, y'all." And he says, and you have to do an American accent. And I hope that was up to standard. It doesn't work in a northern accent. You're like, thanks, y'all. It doesn't work the same. It doesn't work the same. Anyway. Yeah, great question, Brian. I think a fun fact always blows people's minds that they haven't really come across this before is that our moon is actually six times heavier than Pluto and twice the diameter of it. So in terms of if you were going to move Pluto to where the moon is, it does on sky view, it would look a lot smaller than the moon does now in the sky if it was at the same distance. than the moon does now in the sky if it was at the same distance. Now in the rest of my answer to this question, I am going to assume that Pluto is a captured moon rather than forming in situ around the earth. I'm a record scientist. I state my assumptions upfront. Yes, we will allow that. Carry on.

That would mean that Pluto would keep its current composition because obviously things that form on the outskirts of the solar system versus on the inskirts of the solar system, or the inside of the solar system. That sounds weird. It's starting to get a little weird. On the inskirts, I'll do it again, towards the inside of the solar system have very different compositions for the fact that you just have the different materials separating out because of the solar wind, throwing the lighter things out to the far reaches and keeping heavier things further in, etc. etc. But assuming it was captured, rather than having formed there around Earth, that would mean Pluto

would keep its current composition. Meaning I can now say that it would look a different colour to the Moon as well, if you were going to put it in the Moon's orbit, right? It would look that sort of yellowish kind of colour that we associate with Pluto from the New Horizons images, you know? Now, given that it would be much closer to the Sun than where it was now, it most likely would lose its atmosphere, Brian. So, yeah, it doesn't have a magnetic field, right? That's the thing that protects Earth, for example, from all the high energy radiation from the Sun. It basically diverts all of that radiation, most of the radiation anyway, so that our

atmosphere at least isn't affected. What that would mean is that essentially all that high energy and radiation would hit into Pluto's atmosphere and it would give the molecules of the atmosphere energy and then they would escape the pull of Pluto's gravity. We've seen this with Mars already. Mars doesn't have a magnetic field. It has a very, very thin atmosphere now. We think it may have had a thicker atmosphere in the past, given all of the geological history on Mars. And if you think about it, Mars is 46 times heavier than Pluto, right? So if it happened on Mars, it's going to happen on Pluto that's also closer to the Sun than Mars would be if it was in the moon's orbit. In terms of what could Pluto's

stable orbit be around the Earth and how far away it could be, it's actually not really got anything to do with Pluto, which is always a weird thing when you realize that it only makes sense when you look at the maths and you realize it cancels out on both sides like Pluto's maths, but it's all to do with the Earth's Sun system really, because basically what you're asking by saying what's the furthest out stable orbit it could have is basically when does the Sun's gravity start to have more of an effect than the earth's gravity. And so essentially that's the same whatever kind of massive thing you've

got and it's around about 1.5 million kilometres away from earth. So just over four times the moon distance. Amazing. Thanks, Becky. And Robert, Polish Nerd asks, Kuiper belt objects could be dragged into the inner solar system. Could that happen to Pluto? Yeah, this is talking really about something that happened early in the life of the solar system. The prevailing idea is that Neptune, in particular, and Uranus a bit, really helped shape the Kuiper belt because it moved outwards early in the solar system as a result of the gravitational influence of Jupiter and Saturn. The Kuiper Belt is the bit that's got Pluto, but also all these other bodies, these leftover small icy bodies that are basically de facto comets. If they do get nudged in towards the sun, then some of them become comets because they heat up and all the ices become gas and so on. Anyway, in that time, Neptune was moving through that

region where all these icy chunks were, or planetesimals. A lot of those were then sent in towards the sun. This is all billions of years ago. That process is essentially over now, and Pluto and those other objects are mostly pretty stable. It is possible that something, well, you can speculate about some hidden planet nine out there or something that's disrupting things, but there's still really rather tentative evidence for that. It's possible that some passing star could nudge them, that every so often, every tens, hundreds of thousands of years, stars come a bit closer to the Sun. Not drastically close, but a bit closer. Maybe that would nudge it. I think it's one thing to do that with the Oort cloud,

which is a lot further out. That's the region where long period comets are, where they want to take thousands of years to go around the Sun. Those things are a light year away from the Sun. Much closer in, it's going to be a lot rarer that a star comes that close. So I don't think it's very likely for a very long time. So the Koki Belt is essentially stable and Pluto is quite safe for now. Okay, good. Becky, we've had this question on Instagram which says, how are the glaciers composed mostly of nitrogen ice? Is that the low pressure? It's more to do with the extreme cold than the pressure necessarily. So Pluto is around about a toasty 40 Kelvin, so it's about minus 233 degrees Celsius. Might need a jumper.

Minus 387 Fahrenheit, if you must. At these temperatures, nitrogen behaves essentially like water does on Earth. So I mean, Pluto's atmosphere is mostly nitrogen. First of all, it's like 90% nitrogen. The other 10% or so is methane, you know, some trace of the things. But it's so cold that what happens is that the nitrogen in the atmosphere can condense on the surface of Pluto. It freezes out of the atmosphere essentially. Now it is the low pressure in the atmosphere that allows that process to then be cyclical. So it can go from solid and then back to a gas again,

as things change on the planet. So that's how you end up with sort of, I hesitate to use the word seasonal because obviously here on earth, the buildup of a glacier is seasonal. It melts a little bit in the summer. And then as long as you get more snow in the winter, it will eventually form the glacier, right?

So I hesitate to use the word seasonal, but let's think of it as the cyclone nature. And then once you have your nitrogen ice on the surface, nitrogen ice is a lot softer than water ice. So it flows actually a lot more easily than water ice does. And I know it's weird to think of water ice flowing, but it's literally just like the pressure of the fact that you've got so much ice there just like crushing down, right, is what causes glaciers to flow. But that means that on Pluto, you can very easily get a glacier of solid nitrogen ice that forms. So yeah, that's the answer to that question. And I'm sure we've triggered so many Americans by calling them glaciers all the way through running glaciers.

Let me hold it like, what are they talking about? I can't attempt to do any more American accents. I'm going to insult so many people. I'm so sorry. So thank you to everyone who did send in their questions. It's, we just love reading them all and keep sending them in for a future episode. You can email podcast at ris.ac.uk, send them on Instagram at SupermassivePod, or put them on the forum in the Supermassive Club. I honestly, I love reading those questions. It's so great. It's been fun, hasn't it? Yeah. We do read them. We are there.

We're looking. You'll see me respond to the occasional ones. I'm in there. Anyway, Robert, shall we finish with some stargazing? What can we see in the night sky this month? Well, we're still in the summer in the Northern Hemisphere. If you're as far north as we are in the UK, it still doesn't get properly dark at the start of July, but that starts to change at the end of the month. You start to enjoy longer evenings again, assuming that's what you like rather longer days. I'm personally happy with both. enjoy longer evenings again, assuming that's what you like rather longer days. I'm personally happy with both. But it is also the time when the classical constellations of summer start to be visible, a more convenient point in the evening at least. You've got the summer

triangle which is just not a constellation but made up of three bright stars, Deneb, Vega and Outer. That's very, very standout. It's a really good signpost for that region of the sky. They are respectively in the constellations of Cygnus, Lyra and Aquila. So the swan, the lyre, which is a kind of harp and the Aquila, the eagle. And the nice thing about those is the Milky Way runs down through Cygnus and Aquila. So you see those bright stars and if you haven't got a moon in the sky and you're somewhere dark and you know, always say this, if you're on holiday or somewhere, then it's a good place to look for them. You're looking at the inside plane of the galaxy, the inside view of the galaxy. So you've got a rich Milky Way running across the sky, full of clouds of dust and

bright nebulae and star clusters and really just amazing vistas. So if you have a pair of binoculars, pick them up, look at it. There's also one binary, or one double star, rather, you can see called Albireo. That's in Cygnus. Just look that up. That's a lovely blue and yellow combination. It's even better though if you're further south, if you're down in the Mediterranean, because all of that is a bit higher up and you get Sagittarius and Scorpius lower down, higher in your sky. That's very much the richest part of the Milky Way. Absolutely stunning. Now for planets, we're still much the richest part of the Milky Way. Absolutely stunning. Now for planets, we're still slightly in a bit of a famine season. Mars is just about in the evening

sky in Leo, but now really, really small and getting very hard to spot. If you look at the telescope, you see a tiny, tiny disk. You won't see any detail. Venus is nice in the morning sky, but that doesn't mean getting up at dawn, which at this time of year is rather early, half three in the morning or something like that,'t mean getting up at dawn, which at this time of year is rather early, you know, half three in the morning or something like that over in the east. Got to give us phase getting smaller as it goes away from the earth, but more of it is being lit up as it changes its orientation. Don't expect to see much detail about some very skilled observers, see little hints of cloud markings. And then Jupiter is emerging as well, that'll be lower down, but it's so bright that it's obvious. And There are also two meteor showers that might add a few shooting stars each night. I'm not

going to overstate it, but it just might add a little bit of background. The Alpha Capricornids reach a peak at the end of the month on the 30th and the Southern Delta Aquarids, which are best viewed from the Southern Hemisphere. They peak on the same night. You might see a few more meteors in the background as a result. Around that time, there'll be some moonlight, so don't expect anything too dramatic. It's just that nice thing to add to it. If you're up really late or conversely up really early, you might see them. Finally, look, we're still at solar maximum, so do keep an eye out for possible displays of the Northern Lights, the aurora. I saw one a few weeks ago, even the time we're recording this, back in June. There was one near where I live in Sussex, and that's unusual for them to be that

far south. I didn't see that one. I can't keep all of these things. I get the alerts on my phone, and I have to make a decision at three in the morning whether to get up. But do have a look. Also, if you're up late in the evening sky, do look at these beautiful noctilucent clouds, these displays that are good this time of year, 80 kilometers up and they're completely ethereal and they're quite unlike weather lower down. And I know I plug those things all the time. I love them. They are great.

Always, always because I love them. And we get so many nice pictures sent to us. And I just think there're something they are, they're so ethereal and they're just beautiful to see. And also can we, I would love to shout a couple of people from the Supermassive Club because we've had some amazing photos in the Stargazing forum. So we've had one sent in from Michael Stone of M81 and M82, these galaxies, and it was taken in his back, well, he says backyard, with about 10 hours of data in this photo. And you can see the spirals of these galaxies are amazing. And there's one that's just like really zoomed in as well. And I just thank you so much for those. And also to Phil Banting as well for

sharing his photo and Brian Ross as well. And there's one from Pirate Numbers. And it's a picture of the ISS transiting the sun. And so it's just like these little dots of the ISS just going across. Mason Fierce-Klein Those are amazing. Anna-Maria Bixby Brilliant. So yeah, they're so great. Mason Fierce- so great. There are these wonderful prediction sites that tell you when that's going to happen. And it's only a very narrow strip of the Earth's surface. I guess people are just driving to those to find them. It's quite incredible. So yeah, hopefully with their permission, I'll be able to share them on Instagram.

You need to do this Izzy too. Surely there's a case for a podcast adventure. That's it for this month. And we'll be back next time with a very special episode recorded from the UK space conference with some actual astronauts. There's going to be another astronaut special. I'm so excited! Make more astronaut friends. And I'm so jealous because I can't go. I know. I'll just hold a cardboard cot out of you next.

It's like Becky is here. She won't say much because she is made from cardboard. But anyway, yeah. And big me up to all your new astronaut friends. Yeah, absolutely. And there will be another bonus episode on its way. And also to say on the 10th of July, we will also be at the National Astronomy Meeting. It's going to be a live Q&A. So if you're in the Durham area that evening on the 10th of July and would like to come down,

then please do. We'll see you there. Emma Cieslik And it's not just the podcast that's going to be hitting the Durham area as well, because of the National Astronomy Meeting, there's always a public astronomy talk that goes with it as well. So check out the talk from Professor Isabel Hook on supernovae, advanced telescopes in the search for dark energy as well. That's on Monday, the 7th of July. Contact us if you try some astronomy at home. It's at supermassivepod on Instagram, or you can email your questions to podcast.ras.ac.uk and we'll try and cover them in a future episode. Until next time, everybody though, happy stargazing.