The Supermassive Podcast - 16: Mysteries of the Kuiper Belt

Episode Date: April 23, 2021

“It’s like the evidence left over after a crime.”   This month Izzie and Dr Becky venture into the outer Solar System to explore a sea of weird rocks, a squashed snowman and ice volcanoes on a demoted planet.    They are joined by Dr Meg Schwamb from Queen’s University Belfast and Alice Bowman, Mission Operations Manager for the New Horizons mission at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland.   Becky also explains the science behind a possible ‘fifth force of nature’ and Dr Robert Massey takes on your questions and tells us what to look out for in the spring night sky.    You can send your questions or space book club recommendations to [e-mail] or tweet @RoyalAstroSoc using #RASSupermassive.    The Supermassive Podcast is a Boffin Media Production by Izzie Clarke and Richard Hollingham. 

Do we know how many objects are in the Kuiper Belt? Is it dark energy? Please tell us! There might have actually been another Neptune-sized planet in our solar system that got ejected. Hello, welcome to the Supermassive Podcast from the Royal Astronomical Society, with me, science journalist Izzy Clark, and with astrophysicist Dr Becky Smethurst. This month we're journeying beyond the outer planets the Kuiper Belt and exploring how it holds the secrets to our own solar system's formation. So pack some snacks it's going to be a long and rocky road

trip plus we'll be joined by an engineer from New Horizons to tell us about the mission that's seeing it all up close. So Robert Massey, he's here with us, the Deputy Director of the Royal Astronomical Society. How did the Kuiper Belt get its name? And I've noticed that I've said Kuiper Belt and Becky says Kuiper. So let's put that one. Oh, don't ever listen to how I pronounce anything. I get everything wrong.

Well, the story is actually it was proposed as a concept before the discovery of Pluto by the American astronomer Frederick Leonard. And then the British astronomer Kenneth Edgeworth, I think about 1943, was someone, again, suggesting material in the early outer solar system that wouldn't have been close enough together to form planets so would be left in a belt beyond Neptune.

But the belt was named for the Dutch astronomer Gerard Kuiper, which is what I'm going with, who oddly didn't actually believe that any of that material would be left because at the time he went with the general assumption that Pluto had about the mass of the Earth. It's actually a lot smaller and it cleared away the material. So he didn't actually believe there would have been a Kuiper belt and yet that's what it's named for. So there have been efforts over the years to call it the Edgeworth Kuiper belt and some people will do that from time to time and I think the International Astronomical Union even debated whether to make that name change but didn't agree it so most of the time we just stick with Kuiper belt because it's simple but Edgeworth definitely deserves some credit as well. I'm amazed that astronomers

haven't tried to make it like the EKB yet. Like not trying to make it into an acronym like we do with everything else. There is still time. There is, isn't there? It's still time. Cheers, Robert. We'll catch up with you later in the podcast when you help me take on some listener questions. The Kuiper Belt itself is a sea of ice and rock

at the edges of our solar system, just past Neptune. And it's essentially the leftovers from planet formation. These are the objects that had to come together first before everything else that followed, ranging from dwarf planets to icy blocks. I spoke with Dr. Meg Schwarm from Queen's University Belfast, who explained how the Kuiper Belt was formed. The real way I think of the Kuiper Belt is kind of like the evidence left over at a crime scene, right? It's the fingerprints where you can see what happened, right? And you put it all together. So the idea being is that some of these objects we think

formed in place. So these objects are telling us about planet formation and how do you take the primordial stuff that existed in the disk that formed our solar system, right? And how it formed little things that eventually grow into a planet but didn't. Other things that are in the Kuiper Belt were actually in placed during Neptune's migration. And so they're actually from further in, including Pluto, and they got put out or dumped into this region as Neptune migrated. So I think this is sort of one of those moments when we talk about our solar system's formation that you say, hang on, sorry, what? So talk us through this migration of Neptune.

Are you saying that Neptune wasn't always where it is now? Not only Neptune, all of the giant planets. And there might have actually been another Neptune-sized planet in our solar system that got ejected along the way. So we might not even have our full complement of giant and ice giant planets sitting in our solar system that we did three billion years ago. And so it's really by studying the orbits and the properties of the Kuiper Belt, as well as the asteroid belt, that astronomers have been able to put this story together.

Can you talk me through that? What was going on with our giant planets in the formation of the solar system that we know today? How has that changed? So we think that the giant planets, so Jupiter, Saturn, Uranus, Neptune, and maybe this extra Neptune, were sitting in a very tight configuration. And so the remnants of things that didn't form into another giant planet, we're sitting on the outside of all of these planets. And so occasionally stuff diffused in and they would sort of scatter around, kind of like one of those arcade games, right? Going around, bumping off and scattering

from off the planets gravitationally. And so the orbits will shift a little bit, but not very much. But over time, if you get enough of those, you might be able to nudge the planet's orbit just a little bit. And so Uranus, Neptune, and this extra ice giant were scattered outward. Eventually, that extra ice giant looks like it was scattered out of the solar system, and Jupiter moved inward. And so Pluto actually got caught up in this mess. And so it was minding its business in this plantasimal disk and got swept up along with many other Kuiper Belt objects into the Kuiper Belt. And so actually we can see some of these signatures.

So we have these two really cool populations on the Kuiper Belt. Then we have those things that formed in place, plus all these things that were from further inward that tell us about the conditions there. So it's kind of cool that we get to, plus all these things that were from further inward that tell us about the conditions there. So it's kind of cool that we get to study both of these populations and how they've been sort of mashed together by this reorganization of our solar system. And so how do we know that this is what went down? You know, how are scientists like yourself trying to put that puzzle together?

are scientists like yourself trying to put that puzzle together? Yeah, I think you never know for 100% certainty, which is what I love about science. It's by looking at both the orbits, or the properties of these small bodies, their composition. So we see that it's sort of pointing to, hey, these look like two different things that were shoved together. And then we can also look at evidence in the asteroid belt that also helps to support that. On that, can we talk about the properties of the objects that are in the Kuiper Belt? We've said that they're rocky or they're icy. What else do we know about them? You know, how big or how small can they get? Yeah, so we study them by looking at their light, by how much they reflect back in optical or near-infrared or even infrared light. So it tells us a lot about its properties, its surface properties.

We can look at and see if there are absorptions from different types of ices or even the signs of silicates, rocky material on these objects with spectroscopy. The one challenge is because these objects are so far away, it's only the very largest and brightest we've been able to get spectroscopy on. The largest of these, so the things that are round dwarf planets which are about a thousand kilometers in size, these things have methane on them, nitrogen, ice, things we thought were primordial that comets tend to have on their surfaces.

We also see that they're all a little different. So the different dwarf planets called Pluto or Makemake or Eris, all these round worlds, right, they all have sort of different amounts of these volatile ices. And so they're each sort of their own laboratory, which is kind of cool. So even just thinking about in terms of planet formation, they're all telling us something slightly different. And these really large guys, these are sort of the stepping stone planet formation right

before you get to forming sort of a core of a Neptune or Jupiter. Then there's smaller things that are, you know, 100 meters, 500 meters. And those are things that build up to make sort of the dwarf planets. And so for you, what are the future challenges or aims to understanding the Kuiper Belt that bit more? Yeah, I think there's lots of really cool things I think that'll happen in the next decade. So I mean, one thing that has happened recently is that, you know, we had a spacecraft that flew by Pluto. So we got the big object that was dumped into the Kuiper Belt, and Arrokoth, which is a cool object that formed in place, right? And so this is that object that people might have

seen that was discovered what in 2019 and it looks a bit like a i guess a flattened snowman that yeah that's essentially what it looks like i like to say it's two raviolis stuck together okay all that but flattened snowman works too that really cool. And that data is still being analyzed. So I think there's a wealth of data that's going to come from studying these things. These populations of objects in the Kuiper Belt and beyond are going to potentially tell us about whether there's a ninth planet, like a real giant planet kind of thing, or being, you know, way beyond. There are theories that suggest that based on sort of the very distant objects that are just sort of at the edge of the Kuiper

belt that might be due to the influence of a ninth planet. So I think is by studying more and looking for objects that are further out in the Kuiper belt and beyond, we're going to be able to answer that question. And just in general, how did these things form? What did they look like initially in that initial disk before Neptune came through? And what does this tell you about how you form planets? For me, all of that stuff is going to be answered in different ways in the next decade or two or three, when the Rubin Observatory turns itself online in 2023. So to me, that's going to be the really exciting survey on the horizon. She's not wrong. That is going to be so exciting. That's Dr. Meg Schwarm from Queen's University, Belfast.

Can I just say, Izzy, speaking of mispronouncing things, I don't think I've ever heard anyone say make make, like out loud before. Like I've been saying make make this entire time. And I've just realized that's wrong. Do you know what? When I was researching this, I was looking at it like make make. Oh, I've never heard of that before. And then I was like, oh my gosh, it's Make Make. I'm so glad that you had that as well.

I was like, I'm not going to admit to that. But you're a bigger person than I am. Yeah, I'm an actual astronomer. I've been to Hawaii. I should know that it's Make Make, not Make Make. Anyway. Anyway, there are so many questions to unpack here. And can I just say now we are going

to be devoting next month's episode to planet nine so before we get any messages saying we want more information it is coming I promise so yeah it's my favorite topic we couldn't have not talked about yeah Becky and I have been like when are we doing planet nine we are doing planet nine next month I promise so Becky do we know how many objects are in the Kuiper Belt? Yes, kind of. So we've actually observed just over 2000 objects in the Kuiper Belt, sort of in the very old fashioned way of, you know, taking a picture, you've got the background stars, you've got anything that might be in the solar system, then you take a picture, say a week or a month later, and you look to see if anything's moved and you can sort of figure out

the distance and figure out if it's in the Kuiper Belt or not but as you can imagine those things are very faint these little you know hundred kilometer clumps you know very far away so we're pretty sure in fact we know that we've not found them all right it's not just 2,000 objects in the Kuiper Belt no way so the other thing that we actually detect is Kuiper Belt objects passing in front of stars and they actually block out the light from stars very briefly. And so if you can sort of pick that out, then you can say, okay, well, something like Kuiper Belt objects passed in front of it. And then from sort of an estimate of like how dense that is and how many stars there are, what are the chances that that might happen? And then you can get an estimate of how many of those much smaller objects that you don't see with a telescope you don't see with light

exist as well then you've got an idea of okay here's the distribution of sizes of things in the kuiper belt and then we know the mass of the kuiper belt because we know how much it affects the other planets in the solar system right and so we can estimate that actually quite small i looked up this mass and to be honest i would have have got it way, way wrong. It's only about 2% of the mass of the earth. So there's really not a lot of stuff out there, but because they're obviously only like a hundred kilometer sized chunks, even with 2% of the mass of the earth. And so we estimate that number to be around about a hundred thousand objects, at least over a hundred kilometers wide in that region of space so i think it's just worth pointing out like even though we think of it as this sort of you know big

asteroid field there really isn't actually that much mass out beyond the orbit of neptune yeah that's so interesting i wouldn't have thought that and this is far out and I know that we haven't had many examples of these but how do these objects compare to interstellar objects you know can they reveal anything about what's beyond our solar system I think eventually yes when we start to detect more of these interstellar objects and we've had a mua mua definitely we've had a second one as well possibly yeah um because we do think that some of these koi belt objects will have been ejected from the koi belt in the lifetime of the solar system you're gonna even though it is very sparse there's still going to be interactions over four and a half billion years right you wait long enough and eventually something will come along you know

there'll be interactions or collisions and that will send stuff flying out into interstellar space so we think the same thing can happen around other stars in the milky way as well it's going to start flinging stuff out like amoeba so if we can compare sort of the composition of things in the quiver belt and the composition of things that come flying through our solar system then we can get some idea of the differences between different solar systems and it'll all depend on what the gas cloud that that solar system or that star system formed from in the first place but that'll give us a really good idea of well are we unique or are we different in terms of what we formed from in the milky way or

not or is it fairly uniform so i think in the future as we observe more and more of those things then yes but at the minute probably not right. And then looking at planet formation, you know, what actually makes a planet rocky versus a gas giant? You know, how can we get the two different types of planets? Yeah. I mean, it's literally a case of whether the gas is there or not for you to form it into your planet. And if you think about closer into the sun, it's a lot hotter.

Yeah. So any hydrogen gas or helium gas that really makes up the gas giant planets right it's the very light gases that kind of gas is going to be you know hit by radiation from the sun given a load of energy the molecules are going to are in it are going to go crazy right and there's no way that you're going to be able to bring the molecules in that gas together and condense it down to form an atmosphere it's just going to have too much energy but further out from the sun is a lot colder that gas is a lot more slow moving so it's going to be pulled in by the gravity of objects forming out there especially when those objects literally snowball like the gas giants did

and collect all of that gas so it's literally about whether that is there but also about the size of the things that you form as well. And the Kuiper Belt, they're only 100 kilometers across, right? Their gravity is not strong enough to pull in that kind of hydrogen gas and then hold onto it as well. In January, 2006, NASA launched New Horizons. It was a mission to study the dwarf planet Pluto, its moons and other objects in the Kuiper Belt. Now here we are in 2021 and it's way beyond Pluto, but it's still sending back data. Now we're joined by Alice Bowman, Mission Operations Manager for New Horizons. So Alice, can you talk us through this? Like where is New Horizons now? how fast is it going? Oh, goodness. Well, New Horizons is at 50 AU astronomical units. So that equates to about 7.5 billion kilometres.

So really far away. It's travelling at about 58,000 kilometres per hour. Gosh, that is speedy. So how can New Horizons travel this distance? You said 50 AU, that's 50 times the distance from us to the sun. That is quite far away. It is. And I think for the operations team, this really becomes real when we send instructions or commands to the spacecraft. And it takes almost seven hours right now to get to the spacecraft. And then, of course, seven hours more until we receive an acknowledgement from the spacecraft. So

distances are huge. And again, we're sending these commands at basically the speed of light. Gosh, wow. So what's powering New Horizons? As we said, it launched in 2006. So how is it still going, if you don't mind me asking? Yeah, that's a very good question. Yes, I need to know. Yeah, good question yes i need to know yeah um good question um because we're so very very far from our sun we can't use solar panels to gather power for the spacecraft so

this spacecraft is nuclear powered as with all power sources, there's a decay that happens. So when we launched the spacecraft in 2006, our power was about 240 watts. And now we've traveled 15 years or so, and we are at about 182 watts of power. So we have to be very careful with managing that power. Does that mean there's a projected lifetime then for New Horizons? Like eventually it will just have too little power to communicate back to us? Exactly. The most power hungry component on the spacecraft is the transmitter. And so we believe that the mid 2030s is at the point where we would not be able to turn and send data back to Earth. Although the spacecraft can go on and collect particle kind of data because the amount of power it takes to operate those instruments is much lower than the transmitter. So it could hold loads of secrets and we might just never know about it. That's brilliant.

So, you know, what has New Horizons found so far? Oh, my goodness. Have you seen the pictures of Pluto? With the heart. That's my favorite thing. Yeah, exactly. This heart-shaped glacier. Exactly. And, you know, when that heart showed up on our screens, it was like, here's Pluto in your face. You took so long for earthlings to get there and see what I look like. And here you go. This is a big old heart. And it was astounding. So on Pluto, all those things that we found, the glacier fields, the water, ice, mountains, the methane, frost, the atmosphere. There's about 12 layers of haze in the atmosphere. When we passed Pluto, we turned the spacecraft and looked back and had the sun lighting up the atmosphere of Pluto,

and it was actually blue. Can you imagine that? Just like on Earth, although not quite as vibrant a blue as on Earth. Ice volcanoes, crevices. I think for me, it's mostly the diversity that Pluto has that was so surprising. And we only imaged one side of the planet. So I think we should go back and image the other side. Yeah, who knows what could be on the other side.

So I remember it was announced in March 2019 that the mission had actually been extended. And this was after it had been to Pluto and it had also been past the Kuiper Belt object as well, the little snowman that we saw, right? So once it's been to both of these two sort of worlds and visited and sent data back, like what's its job now almost?

Like what's it looking for? Well, I have to say that we are still bringing back data that was collected at Arrokoth. Quite an interesting little snowman, if you will, kind of a flattened snowman. So we still are bringing down data and we are imaging other Kuiper Belt objects, of course not as close as we got to Arrokoth, but we've imaged over 30 Kuiper Belt objects and we are actually searching for another Kuiper Belt object to fly by. It must be incredibly dark. So how do you actually take photos with New Horizons? Well, the cameras were built to operate in this very dark environment. I know it doesn't seem like a lot of light, but we can plan those observations so that we are looking at the sunlit side of those objects. sunlit side of those those objects and one of the other techniques that's used for these very very dark faint objects is to take many many images and then we call it stacking we stack them up and so

with a lot of images those faint points of light are brought up so that you can see them with your eye as mission operations manager like you've been involved in this so closely. Do you have a personal highlight that stands out to you from New Horizons? Wow. Besides all the amazing pictures, images, and data that we've returned with New Horizons, I would have to say it was the July 4th anomaly. We were three days from starting our intense imaging of the Pluto system. So that was a nine-day imaging period. And July 4th was our opportunity to send the set of commands to the spacecraft. And during that process, we lost comm with the spacecraft. And it looked like the flyby imaging was in jeopardy, because there was no way in the

state that spacecraft was in that we could collect all this wonderful data. So I think that's what really stands out to me yeah the stress the stress of that situation so how do you how did you get it back online like what happened yeah well I have we have an amazing team and we worked over the next couple of days and on July 7th the morning that this nine-day sequence was going to start we saw the spacecraft had acknowledged all the commands that we sent and it was in a state where it could accomplish the flyby I can't even deal with thinking about that kind of level of like I'm so impatient and the idea that you would have to wait

that long to find out if everything was okay and there's almost like nothing you could do like i can understand why that stands out as a highlight to you just overcoming that and then the feeling of knowing that everything was okay at the end yeah so just massively outweighed the stress before it so what what is next for new horizons what do you what do you hope to see coming back can you tell us anything or are you sort of sworn to secrecy uh no not sworn to secrecy um well our scientists have been using the subaru telescope that is a japanese telescope it's out in hawaii to search for kyberbot objects that might be in the path or near path of our spacecraft to do a close flyby. Also searching for objects that we could image.

Once they find those objects, they use the Hubble Space Telescope to refine those orbits so that we can uplink them and build a command set for imaging. Coming up in May, just in a few weeks, we will be putting the spacecraft into what we call three axis mode, or I call it picture taking mode. And we're going to be imaging three of these Kuiper Belt objects that our scientists discovered last fall. Thank you so much, Alice. That was an absolutely just fascinating insight to how, you know, space missions like this actually work. That was Alice Bowman, Mission Operations Manager for New Horizons at the John Hopkins Applied Physics Laboratory in Laurel, Maryland.

This is the Supermassive Podcast from the Royal Astronomical Society with me, astrophysicist Dr. Becky Spellis, and with science journalist Izzy Clark. We'll keep going with the Kuiper Belt in a moment, but can we take a look at some recent science news? I mean, someone set off the new science alarm. Whee! It's happening! It's happening!

Scientists at the Large Hadron Collider near Geneva have spotted an unusual signal that may be the first hint of a new kind of physics. Becky, are we really looking at a potential fifth force of nature? We could be, yeah. And it's not just this experiment at CERN either. There's been another experiment at Fermilab that they've just announced results as well

that completely separate experiment, completely different, also suggesting could be this fifth force of nature. So people are getting very excited, but we should rein in the excitement just a little bit uh because it's not quite that sort of level of statistical significance yet we need to sort of start shining it from the rooftops but people are sort of starting to think this could be the case so at cern what they were doing was they were smashing protons together in their big large hadron collider this big 27 kilometer long tunnel they've got built under France and Switzerland. And essentially what they do in those collisions is they just see what pops out

and see what happens, right? So one of the things you can create in those collisions is a bottom quark or a beauty quark. So if you know any of particle physics, right, they have this thing called the standard model, which is all of the particles and all of the forces which govern those particles, except for gravity, which is general relativity, right? And with all of that model, you can essentially use those forces to predict how any particle will behave in any situation you can put it in, right? And then we do experiments, but then we test whether the experiments give us the same thing as the model. And if they give us the same thing,'re like great our model's right pat on the

back gold star for us in this experiment they were looking at something called these bottom quarks or beauty quarks they're sometimes called and what happens to these is they're very unstable and they decay into either something called a meson which is two quarks plus an electron and a positron which is its antiparticle or a meson and a muon and an anti-muon pair yeah okay so essentially there's two ways it can it can decay and be like oh no i'm too heavy i need to be something else and they should happen at exactly the same rate okay given everything we know about forces in physics and everything they should have at the same rate in this experiment they found that the electrons were being produced way more

than the muons so one was happening more than the other. So there must be some other force that's interfering with it. Ooh. At Fermilab, they were trying to measure these muons. And they were trying to measure what happens to muons if you put them in a magnetic field. And all particles spin, right? But if you put it in a magnetic field, they start to wobble like a top. And again, the standard model predicts how much they should wobble lo and behold the experiment measured a different amount of wobble that the

standard model predicted again suggesting there's some extra force that's interfering with this thing very exciting okay so i mean it's a bit it's a bit of a long story to explain i guess but it's really exciting because there's two very different experiments suggesting a different force is interfering that we've never thought about before and there's gonna be some new physics but the cern experiment has a one in a thousand chance of being a statistical fluke and the fermi lab experiment has a one in forty thousand chance of being a statistical fluke that might sound very high but particle physicists they're not like astronomers we're like one in ten thousand good good we go to go they're like what we need a one in 3.5 million chance of a fluke before they start to accept anything right okay so these are like the first hints but they're not there yet so this is why they're probably going to be doing more experiments

trying to get more data they're turning the lhc back on next year after a big upgrade to reach higher energies and more energy in the collisions and so they're hoping that that will mean more of these decays and better statistics and then we can finally shout from the rooftops like that's our fifth force that we didn't think the astronomers are there like can we say it now is it dark energy please tell us is it anything to do with dark matter have you finally finally did the one job that we set you oh that's so brilliant um well i guess we'll just have to keep an eye out as we i think we say this every single episode it's like we'll just wait and see yeah and we will continue to wait and see but you're allowed to be a minor level of excited yeah I'm gonna I'm gonna ring the science alarm I'm I was excited when I saw that headline um but I guess we should probably get back to the

kind of out so we have had a lot of questions um so thank you to everyone that sent them in we didn't have time for all of them there were some good ones as well I was reading through them like yeah there were loads how are you gonna pick and luckily there were a couple of duplicates i was like great everyone's happy um so robert can you take this one from peter who's in south australia and he asks what is the largest object in the kuiper belt well effectively uh peter it's the it's pluto because pluto is the kind of prototype Kuiper Belt object. King of the dwarves. Another name given to them sometimes is exactly a trans-Neptunian object.

And those of us who are old enough recall its demotion from being a proper planet to a dwarf planet about 16 years ago, which was a trauma for those of us who grew up in nine planets, but we'll wait for the new planet nine to come along. So Pluto then is the biggest object in the Kuiper Belt and it has a diameter of 2,377 kilometers, which incidentally makes it quite a lot smaller than our moon. But one of the objects in the Kuiper Belt in this region, the scattered disc out beyond the main belt, Eris, is only a tiny bit smaller, only about 50 kilometers smaller. And that's also given the category of being a dwarf planet they're all very very faint I mean you have to be quite an advanced amateur astronomer for example to see these things but they are out there and some of them like Pluto and Eris are quite big

why is it that Pluto did get named a dwarf planet and and reclassified reclassified fine booted out why did it get renamed well it was yeah this was a big controversy 16 years ago so there was a lot of debate about what and still is in some circles about what constitutes a planet and what doesn't and the definition i think the thing that pluto fell down so it has the right shape it has to be round it has to go around the sun rather than something else so moons don't don't count but the thing it lost out on was that it wasn't really big enough to clear the space around it so the the IAU, the International Astronomical Union, which decides these things, took the view that it would have to be a bit bigger and clearing space around it. So if you imagine something like

Jupiter as it moves through the solar system in its orbit, it has a very strong influence on things around it. Pluto is just too small to do that. It's a lot smaller than our moon. So you can see why that's not going to happen. And that's what it's come down to you know most of us now we sit there and say yeah it's a dwarf planet it's it's pluto you know it's something we've just sent new horizons to a couple of years ago well actually six years ago now wasn't it but you know fantastic results on that so let's just say it's pluto and not worry too much about its designation tell that to the internet yeah all i was going to say this i'm waiting for the tweets everyone take it up with robert don't miss it maybe i'll go on twitter for a couple of weeks becky how about this song why hasn't the kaiserbelt objects formed their own planet instead of being on what someone said

here a giant mess of dwarf planets and asteroids i love that you're not a hot mess you're a giant mess of planets and asteroids um that's Neptune's fault really so we think it's Neptune's fault so Neptune is big especially compared to the Kuiper belt right so remember before I said the Kuiper belt is only two percent of the mass of the earth Neptune is 17 times heavier than earth right so it is big and it has a huge influence on that Kuiper belt which is just beyond the orbit of neptune right so anytime that any of those objects started clumping together neptune was just like no and would just drag them apart again and disrupt anything like that it has a bigger gravitational pull than any of

like two objects do like between them essentially so it can always disrupt that hence why you just end up with this huge big giant mess of dwarf planets and asteroids right in the exact same way that jupiter does to the asteroid belt as well right you could ask the same question about the asteroid belt jupiter's the one that's going nope in that case as well perfect okay that makes sense and robert sean chesman jack prime steve brown and more ask is the kuiper belt separate and distinct from the Oort Cloud? So can we just start with what's the Oort Cloud? What's the Oort Cloud? Right, yeah, well, both the Kuiper Belt and the Oort Cloud

were hypothesised as sources for comets. So when you get, for example, when you think of NEOWISE last year, which was that beautiful bright comet we had in the summer after several ones that didn't really come to anything, it's a long period comet. And what that means is it's come from a very, very great distance in the sun. And the hypothesis, because we can't see them when they're at this huge distance, is that there is this big reservoir, this big sphere of comets called the Oort cloud. And it's anything between 2,000 times as far away from the sun as the earth

is and 100,000 times, which is getting on for a quarter of the distance and the nearest star a really really enormous distance way way out from the sun and that's the oort cloud so that was proposed by jan orte i think in around the 1950s and whereas the kuiper belt is much closer in so really you're talking between about 30 and 50 times as far away from the sun as the earth is so four and a half to about eight billion kilometers away still a huge distance but but nothing like as far as the oort cloud and the and the coipa belt has a sort of donut shape because it's close i guess because it's close enough and associated with the formation of the solar system that if you imagine the planets in the solar system forming from rotating disc material well the the coipa belt objects were within that so they follow the same kind of paths whereas in the oort cloud they're all over the place.

And some of those might have been scattered out from the early solar system, you know, and just ended up in random orbits, which is actually why when you see bright comets like NEOWISE, they can appear anywhere in the sky. The planets, the sun, the moon generally appear in the zodiacs and a belt around the sky. But comets can be anywhere. And that's because they're coming from the Oort cloud and because it's a big sphere shape. Right. Well, I hope that clears that one up and becky ankitsuna and michael dempster want to know does the kuiper belt create an obstacle while taking pictures of deep space through a telescope and could any of these objects reach earth um so no not really they don't really provide any sort of obstacle to us well they're very faint

right you know even if you're uh taking and you know three hour long exposure of a distant galaxy or something like they're not going to be brighter than any star in that field so foreground stars in our own milky way are more of a nuisance than any object in the kuiper belt will be but you've got to remember how sparse this is like Like we said, like 100,000 objects maybe that are over 100 kilometers wide. So, I mean, imagine that in the space that they actually contain in that orbit beyond Neptune.

It's huge, right? If you think about it in this sort of 3D way, they're incredibly sparse. So you're not going to come across that many as you're taking an image like that. And even if you did, and you happen to have a koiper belt object in the foreground like you would a foreground star it would be so small as well you'd really easily be able to mask it out so it's not a big issue i don't think i've ever come across a koiper belt object like okay getting in the way of my

exposure if i did i'd be calling up like people like meg schwann that we talked to before being like hey guess what as an extra bonus in my image i can give you an image of this do you want it and that's never that's never happened right and we're waiting for the day i'm sure meg's waiting for the day that that happens as well yeah because i think there is that idea of if you see things like star wars or whatever trying to dodge all of these objects and like it's not quite as dense as films. Exactly. Yeah. It wouldn't look very good for a film if you're like,

got to pass you this asteroid belt. Well, that was easy. Well, I hope that covers everyone's questions. And if you're listening and you want to send in a question, then do so. You can email podcast at ras.ac.uk or tweet at royal astrosoc and we'll take a look so robert what about some of the things that we can see this month and in fact the royal astronomical society have been looking to the ground for something recently haven't they we have this is our vice president steve miller who um is an emeritus professor so he's retired and doing quirky

things as a lot of retired academics do and one of the things he did was to put a question on Gardner's question time about what had happened to the moon trees now the moon trees were grown from seeds that were taken around the moon by Apollo 14 so that you know they that's what they did it was they took various things and Stuart Ruser, the NASA astronaut flew them in 1971 then gave them back to institutions in the US and we think

so trees grew in the US, they were sycamore and the lobly pine was another species and we think that some of them, maybe around 15 ended up in the UK and some of them were used to grow trees here but nobody really seems to know where they are or what happened to them so what we're trying to do and Steve is trying to find out obviously is what happened to these trees so if you know about any of these trees if you know

if you work in I don't know a museum a science center a garden and you happen to know that you've got a moon tree then do let us know because it's a it's an intriguing search an intriguing piece of space history these ones just flying in apollo didn't really seem to have any impact on the way they grew or anything like that so hopefully they've been labeled if they reach the ground there is a more recent example tim peak took some into space but they i think were exposed to radiation and that that did affect their growth but the the ones that went to the moon seemed perfectly happy so yeah if you've got a moon tree in your garden do let us know we'd love to see oh my god i really hope that someone listening actually does and they can help us in this search

for moon trees that's brilliant and so what if we want to look to the skies what else can we be keeping an eye out for this month to uh quote becky it's definitely toenail moon season because um in the uh in the spring side the sky the crescent moon is really really good to observe so we've just gone through it in April when this is going out. But in May, you know, look towards the middle of the month, you'll see a fantastic crescent moon after sunset. It's just because the angle of the ecliptic, the path of the moon and the sun through the sky

is very good at this time of year for that. I should also mention, if you're a Muslim, it's the end of Ramadan, Eid al-Fitr. So, you know, wish people well in observing that if they want to mark it that way too. and venus are coming back into the evening sky and towards uh but basically as you get into may it should be possible to see both of those planets and mercury is at its best around the middle of the month and the two planets are really close together so you know perhaps a photo op on the 28th of may also combining toenail moon and mercury and venus uh on the 14th of may which is

the day before my birthday but fine um venus mercury the toenail moon and mars will all make one big line at sunset i think it's yeah if you've got a wide field camera you know what you're doing it would we'd really love to see those two yeah mars will be really high compared to venus and mercury but you should still be able to maybe get it if you've got a wide angle so fingers crossed and please send in photos if you do manage to snap that we would absolutely love to see it I love the toenail moon they're my favorite you know I was actually walking down the street the other day saw a toenail moon I was like toenail moon I was like what has Becky done like this is your fault so many people complain to me like that's what I think of you now I see that and the first thing i think of is toenails rather than the majesty of the moon and

i'm sorry it's just what it reminds me of and the final thing i was going to mention is i thought this was an intriguing one is it starts with a sort of cheesy um rhyme there's a way of finding stars from the plow's tail you you follow the arc down to the bright star Arcturus and you speed on to Spica in Virgo which is a brighter zodiac constellation and just beyond Virgo is Libra another zodiac constellation and in that grouping is a star called Zubina Shemali which is supposed to look green to some people now there's not a clear explanation for this but it might well be an optical illusion but I just thought you know this podcast we should ask if anybody does see beta lyrae this star as green or not because i would really like to know that but it would be great if people report that yeah we should put

like a twitter poll up um asking people to vote we'll have to see what our listeners think as well well that's it for this month i am so ready for may because that means our episode all about the hunt for Planet Nine. Finally. I mean, it only took us 17 episodes to get there. That one has been 17. How did we go 17 episodes without? I think we've just been teasing it for too long, haven't we? Anyway, remember, if you try some astronomy at home, you should tweet us.

It's at Royal Astrosoc on Twitter. Or you can email your questions to podcast at ris.ac.uk and we'll try and cover them next month for body night until then though happy stargazing