The Supermassive Podcast - When Space Goes Rogue....

Episode Date: April 1, 2026

The Supermassive Team are going rogue (more so that usual!) This time, it’s all about the non-conforming objects in space. Black holes, planets and the other rogue objects Izzie and Dr Becky can think of... Plus, Dr Robert Massey takes on your questions and shares his stargazing tips for April. A big thank you to Gavin Coleman from Queen Mary's University, and Astronomy Now magazine editor and owner, Stuart Clark. For more accessible astronomy, the recommend you read their brilliant articles on astronomynow.com. Join The Supermassive Club for ad-free listening, forum access, and extra content from the team. And email your questions to [e-mail] or follow us 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.

So it's a black hole that's kind of wandering around through space. We have not found anything. I just want to make that really clear. We can get rogue black holes. It's not quite as surprising that we can get rogue stars. So welcome to the supermassive podcast from the Royal Astronomical Society with me, science journalist Izzy Clark and astrophysicist Dr. Becky Smethurst. In this episode, we are going rogue. It's all about the non-conforming objects in space, black holes, planets and other rogue objects that we can think of.

It sounds like a science fiction episode, you know, when planets go rogue. I think we added to this ever-growing list of science fiction films that we will never make or envision. Someone out there can. You know where those creative writing classes where they get prompts? Here's your creative writing prompt for this week, right? When planets go rogue. Put us in your acknowledgments.

Thank you very much. You very welcome. And shout out to listener Mike in Oregon who actually recommended that we cover this as topic. Yes, thank you, Mike. So Dr. Robert Massey, the deputy director of the Royal Astronomical Society, is also here, obviously. It's not an episode without him. So, Robert, can you just give us a quick rundown of what exactly is a rogue object? I'm just thinking of those B-movie titles now, is it? But yeah, I mean, rogue objects in astronomy, they're not inherently evil, they're not bad, but they are a bit unconventional. So there's everything from rogue asteroids and comments to

interstellar space, so ones that aren't bound to any star. And you can think of those as, there are examples of those that come into the solar system from time to time. So think Umuamoa and Atlas as transient visitors that came by the sun and then disappeared back into interstellar space. The rogue stars founded intergalactic space, probably thrown out when galaxies collide. And there are, finally, there are lots of rogue planets too. And these are planets that are found between stars. And, you know, maybe they were rejected from a solar system or they formed away from solar systems in a nebula. The first of which, detected more than a quarter of a century ago in the Orion Nebula, and we found hundreds now.

I think there's more than 500 candidates in James Webb data alone. So a lot of them out there. Yeah, and actually this is what I want to talk about more, because our first interview is going to be about rogue planets. So let's explore that more. What exactly are they, and how are they different from what we know about our own planetary system? I spoke with Dr. Gavin Coleman from Queen Mary's University in London. So Rogue Planet is there. Effectively, planets, they're orbiting freely in space without any stars around. It's just how we typically think of planets in general. So these planets, free-floating objects, they're kind of in a very weird space.

How they form is a very open question currently, and there's kind of two routes that they can form. And this depends on the mass and the size of the objects. We kind of think that more massive planets like Jupiter or even more massive than Jupiter probably form similar to stars. And so that's where gas cloud or just collapses in on itself. and forms a star that way. We kind of think that actually, these more massive planets,

they form the kind of the smallest members of that kind of formation routes. So they're kind of the smallest ones that can do that. That kind of cuts off at about a Jupiter map. That, however, won't work for planets that we kind of think of like Mars or Earth or Neptune because these are more rocky worlds. So for these free-floating objects,

we kind of think that they have to form similar to planetary systems that we kind of know about. And so actually from modeling of like single star systems, you can do this by having the planets form in their system and then they have interactions with each other. And so that then forces one of the planets to be ejected. This can also happen in binary systems where if you have two stars, a circuit binary system, like Tatarine, for example, planets that form around those, they interact with the binary stars and the binaries act to kick them out of the system. That's right. Okay. And so like with that kicking

out, that's when they're like, you know, kind of flung out of the system really and out there on their own. Yeah, exactly. Yeah, they're just sort of left out there, going out a few kilometres of seconds. They're quite slow generally, but they're just out there on their own, so we kind of see also some of these objects of like, if you think of a mua or Borisov, which are these sort of interstellar objects or asteroids, effectively, they're just coming to our system. They effectively would have gone through the exact same formation pathway as well. Okay, so are we saying that they're always spherical when we talk about rogue planets and we look at them and sort of how we kind of think about the planets in our own solar system?

Or does that open up that kind of discussion on how do we classify these things, which I know astronomers love to do and it's hard to get everyone to agree on it as well? So that is actually a very interesting question. And we actually addressed this at a conference a couple years ago. We were like trying to define what a free-floated planet is. And we kind of do agree in that sense of how the International Economic Union define a planet where they have to be spherical, they have to be a certain mass in a certain size.

But our classification just says they don't have to be around the start. But generally, yes, we would expect these free-phoded planets to be spherical because that's effectively just gravity from the object itself, pulling it into a spherical shape, similar for the geocast giants as well. Okay. And so, you know, if we think of our own solar system, a lot of our own planets have different characteristics. Does that apply to rogue planets? Do we get different types?

Or is there like a consistency of what they're like because they're not really attached to a system in any way? We would probably expect them to be very similar into what we're actually in the solar system, but also what we see in exoplanetary systems as well around other stars. Because if they form the same way as these planets, they're just kicked out after two million years, say, just whilst they're still effectively babies

or they're kind of growing in that point, they should be similar to the planets that we kind of know about already. There's probably going to be more of an atmosphere on them because there's no radiation from the stars to actually wipe the atmospheres away. So they may hold a bit more atmospheres, but generally we'd expect them to probably be very similar

to the ones we see. The only big difference would be that there's no main energy source for these objects. So the surfaces could be very, very different or very cold in that sense, but that's going to be another kind of worms that is to try and figure out what those things are going to be. And this might be a silly question, but I'm going to ask it anyway. Are they constantly on the move or are some of them stationary?

Because I think we always think about planets in some sort of orbit. So how do these rogue, free-floating planets kind of exist in that state as well? So if they've been ejected from their systems, they've kind of just been, they've been flung out with some velocity. So they're going to have some velocity going. But if we also think that, yes, planets are formed around stars and they're kind of static in that system, sun is also, or stars are also orbiting the Milky Way in our galaxy, at least. So they're on some kind of orbit around some gravitational center,

black holes normally in this case. So we'd expect like free-floated planets to be effectively similar to that. I think if we think of the Milky Way as an image, we'd think of it as the stars. We could probably apply the exact same image to what planets are going to be, look like if we mapped where all the free-floating objects are as well. It'd be something very chaotic and messy, but also very vast as well. How much do we know about, you know, how common are they?

And are there areas where we see them more so than in other places within space? It's a very, very young field. I mean, free-fondent objects is more of a byproduct of research in the last 20 years. It's only in the last few years where we've actually now got up to about 15 objects that we kind of think of free-floating objects. We've only one with a mass measurement. There was at the start of this year, a publication of a planet that was seen both from ground-based observatories

and from Gaia-based satellite, and that allowed them to actually determine the mass of the object to be about 60 Earth masses. So that's about similar size to Saturn, a little bit smaller than Saturn. So that's kind of the most interesting one in it, because it's the only one we kind of know what its mass is and exactly where it is in space. A lot of the observers do a lot of statistics.

They're expecting to see maybe 20 planets per star in the galaxy. That's going to be quite high, and their error bars are about 20 as well. So it's 20 plus or minus 20. We should be expecting, though, to see quite a few of them up and arm. Yeah, so how do you actually find them? Because I imagine they must be really hard to spot, right? They are. So how we find these objects typically is also we look towards a glassic bulge.

We look at a background star, and as the light from that state, comes towards us, it interacts with the planet and we get lensing of the background light, so we kind of see sort of a bump in the light curve. And so we've found quite a few looking that way, but we should expect them to be in most places as well. It's just trying to find them is the problem. Because of this lensing, you kind of need to work on statistics. Later this year, the Roman Space Telescope will hopefully launch from NASA, and one of its main missions is to find free-floating objects. So it's going to do its exact thing of looking towards the galactic bulge, trying to see how many of these rises in the light curves

it can see at the background star, and then we can infer that their planets actually causing that increase. What can these free-floating planets tell us about planetary systems or how planets form? Like what are some of those big questions that you're hoping to answer? So for me personally, one of the big things that we can get out of this is we can get a mass distribution out of the observation. So that's kind of knowing if we could say, right, there's this many Jupiter mass place, there's this many Earth mass players, this many Neptune mass plates. We can kind of cut and see what the distribution is around the galaxy.

And then that will help the theorists like myself out, where we can then put that into our models and see, right, what do our models have to do to actually form those? And bear in mind that these models are also forming the planetary systems. We can then start comparing all of these data sets together, which then tells us effectively how planets, even our solar system form in the overall running of all the parameters that needs to go into these large models effectively. Thank you to Gavin Coleman. So Becky, can we talk about this some more?

How fast can a rogue planet travel? Are they like really high velocity objects? I guess it depends on how the planet was ejected from around its star in the first place. Plus, the problem with this, first of all, is actually it's very difficult. to measure the speed of a rogue planet as well. Usually when we find them, it's because they pass in front of these other objects. And so what we're measuring really is how long the other object changed in brightness for. And from that, you can sort of work out a speed because you know the rough size of the object. It passed in front of this rogue planet. The problem is that doesn't

capture like the actual speed of the rogue planet. It only captures the speed in one direction. It could also be moving in another direction. And so you've only got sort of one vector of its speed of three possible vectors, right, that it could be going in. Vectors meaning directions, right? You've got the horizontal, but you've not got the vertical or the towards are away from you, right? Yeah. So also it doesn't tell us like which star they were ejected from. And this is the big problem because when you're measuring velocity in space, you have to measure it relative to something else. Yeah, yeah. So you're measuring your velocity as you're measuring it relative to us, but it might have got a kick from the first. You have to measure it.

fact that whatever star it was orbiting around was already moving around the center of the galaxy at some speed anyway. So you kind of want to measure it relative to something else. The maximum that we sort of can get out with all of these caveats seems to be around about 100 kilometers a second or so. She said confidently. Yeah. I think that's the thing though. There's just so many caveats on that number that we don't really know. I think we can get a better idea if we look at the interstellar objects that have passed through our solar system. So it's asteroids, comets, just lumps of potatoey rock, basically, that have passed through. So Amuamua, which was one of the first ones detected, that was at about 88 kilometres a

second at speed through the solar system. So that's 196,000 miles an hour for those who work in Imperial. And again, that's relative to the sun, you know, when you're measuring that speed. Borasov, the second one found was half of that at about 44 kilometers a second, and the most recently found one, 3i-A-A-A-A-A-A-A-A-A-A-A-A-W, was somewhere in the middle at about 68 kilometers a second. For context, Earth orbits the sun at about 30 kilometers a second. And the fastest planet in the solar system is Mercury at 48 kilometers a second. So Borisov a little bit lower than Mercury, but Amu Amu and Atlas way above that, right? So they're very fast moving and it's how it was first Amuamu was identified as an interstellar object in the first place. So this is the kind of

speeds that we're looking at anyway, just to give you an idea. Yeah. And so we're saying they're not Super, super, super fast, but even then there's quite a lot of variety as well. And I guess it's so contextual. Yeah. And listener Sarah Bird on Instagram asked, could there ever be life on a rogue planet? I think everyone kind of wants to know the answer to this, right? Yeah, I think we knew that question was coming. Yeah.

It's such a good one. Everybody wants to know. I mean, technically, as far as we know, we don't have any proof of this, right? but technically, yes, you could get life on a planet like this if the life didn't need light to survive. So it wasn't like, you know, plant life needs light to survive. And also has another energy source somewhere and it's protected from radiation in some way. Okay. That's a big one, right?

Because radiation in interstellar space is a big deal. Like we're protected thanks to like the sun's magnetic field essentially does deflect a lot of like high energy particles and high energy radiation away from us. So for example, if you had a rogue planet with a very, very thick, like icy crust with a liquid ocean underneath it, not necessarily water, just some form of liquid and some form of ice on the crust. And there was then some form of internal heating going on. So whether that's like volcanism, maybe it's radioactivity towards the core of the planet, then perhaps with those conditions life could survive. Because we have seen life surviving in those kind of conditions here on Earth, right? So deep ocean hydrothermal vents, right? So like volcanic vents under the water

that are just like pumping out like warm air, water. Yeah, gas is of some form that warm the water around, right? Then we've seen life thriving and surviving next to those kind of systems. So yes, technically, I doubt you would have any surface life on the rogue planet just because of the intense radiation and, you know, the stripping of the atmosphere that would probably echo when it's moving that. through space. So yeah, it's technically yes, but it's not like we have any evidence for it. Many, many more caveats in coming. I'm just imagining the headlines now, right? Like,

astrophysicists, says life because I'm on rogue planet. Like, we have not found anything. I just want to make that really clear. Okay, so we've covered rogue planets, but what are the other rogue objects in space? Science journalist and editor of Astronomy Now, Stuart Clark ran me through the options. Definitions kind of vary. When we're talking about rogue this and rogue that, the definitions are a bit loose. But when it comes to black holes,

what people seem to be thinking about is any black hole that's quite large, perhaps a seed for a supermassive black hole that we usually find in the center of a galaxy, but somehow it's become detached from that position. So it's a black hole that's kind of wandering around through space unattached to the center of a galaxy.

And how does that happen? That sounds mad, frankly. Yes. So in the present-day universe, it's super rare for something like that to happen. However, if you go back into the depths of time to when smaller galaxies were colliding to become bigger galaxies, well, each of those galaxies should have

had a massive black hole in their center, which you would usually think would eventually merge together to create the supermassive black holes at the centers of the galaxies we see today. But just like any collision in the universe, sometimes they miss. So they don't actually collide and merge, but they slingshot around each other. And so one gets thrown out of the center of the galaxy, usually the smaller one. maybe it then floats around still gravitationally attached to the galaxy but just outside in the halo or maybe the kick is so big that it's just thrown into intergalactic space we simply don't know how many of those kinds of things there are around and i guess if it is that latter one then they're escaping

that gravitational boundary i suppose and we get that float well we say float but i mean do we how fast these things can travel? Is it fast? I mean, it's, I'd just have so many questions. Yeah, they'd have to be, they'd have to be relatively fast to escape the gravitational pools of their galaxies. If they leave the galaxy, sort of enter intergalactic space, then they could still be confined by the gravity of the cluster that they're in.

In the same way, we believe that there are trillions, perhaps, of rogue stars that in inhabit the intergalactic space or the intra-cluster medium, if you want to call it that. There's probably black holes in there as well. So there was a study from about 2021, I think it was, in which some researchers started new simulations. And they suggested that there could be 10 or a dozen or so, some smaller black holes, sort of in orbit around the Milky Way, which were stripped out of, little dwarf galaxies that the Milky Way 8 in order to become the size it is today. Wow.

And then how do we know that these exist? Because imaging black holes or trying to better understand them, that in itself is quite a process to then try and find one that is roaming, as it were, is another question. So how does scientists try and study these things? Yeah, it's really difficult because unless the black hole runs into something, it's not going to give off any light. So you could, with the advent of Rubin and other survey telescopes like that,

these sort of fast transient surveys, we could keep our eyes open for x-ray events that seem to have no other explanation. Or we can always have, say, a gravitational lens interaction as a black hole floats in front of something else. But they're super difficult to spot. We don't really have many theoretical predictions for, them as well because generally cosmological models of galaxy formation have just tied black holes to the centres of their halos. It's only in these recent years that these other researchers have started to look more in detail at that process. Hopefully we might start seeing some signals

through the Rubin data. It's a little bit anyone's guess at the moment. Yeah, okay. And then another object that I'd like to talk about are rogue stars. I suppose if we can get rogue black holes, it's not quite as surprising that we can get rogue stars. So what happens to make a star go rogue? Yes, what happens is that it has a gravitational interaction now that could potentially be with another star or more likely it's probably a close encounter with the supermassive black hole at the centre of our galaxy or another galaxy and that just slingshots the star out of the galaxy and as we sort of spot them whizzing out of the galaxy

we call them rogue stars. And are they common? Do we see this a lot? There's some studies that suggest that say in the Virgo cluster, for example, there are probably trillions of stars that have been thrown out of their galaxies And just from random interactions, you know, you would expect this gradual leakage of the stars over time. Every galaxy, for example, is going to be going through this, a sort of an evaporation process, if you like, as stars interact with one another.

So one will gain energy, one will lose energy. That will mean that one moves outwards a little bit while the other falls closer to the central black hole. And over eons, this will either call. stars to fall into the black hole and disappear that way, or have close encounters with the black hole and be ejected. And what of the impact that a travelling star could have? If we have a rogue star that's travelling through space and it comes across other systems, you know, how chaotic can that be? Can that be disruptive or have we just not seen that yet? It can be disruptive, but actually they need to get extremely close to the solar system

to cause the planets to move in their orbits. For example, I think there's one study that suggests that they have to come closer than about 100 astronomical units in order to stand any chance at all of perturbing the existing planets' orbits. That's a fairly rare occurrence. However, what is more likely is the disturbance to the Oort Cloud So the aught cloud and the comets, if you have a star,

and it doesn't need to be a rogue star in the sense that we've just been talking about them, this can just be a general field star that happens to, you know, its orbit brings it relatively close to us. That could potentially disturb the aught cloud and send a shower of comets, you know, falling in towards the sun. Right. And would we ever see a system where a rogue star, would also have a planetary system around it.

Like I'm trying to think of like the mechanics of that as well. I think that's possible. I kind of don't put anything past celestial mechanic. It's true. Yeah, fair enough. So potentially I don't see why not. It'd be fascinating if there were. That's something we'll look into. And so are there any other objects that we need to talk about

when it comes to rogue objects in space. I mean, space in itself is, as you say, unpredictable. Yes, indeed. So, I mean, we're all really familiar now with at least one type of rogue object, if you want to call it that. And these are the interstellar comets

that we've been seeing, like Three-Ey Atlas, and then there was Borisov and Amur-Moor before then. But if you look back at some of the other bright comets that we've seen over the decades and indeed centuries, probably some of those were interstellar comets as well. So if you want to think of a rogue object as something that's not bound to the object it's supposed to be bound to. So you'd think of a comet as being bound to a parent solar system, for example.

Then there's all of those kinds of things as well. One thing that does absolutely fascinate me, and it kind of comes back a bit full circle to what we were starting with, or talking with at the beginning is black holes, but this time not supermassive black holes, but much, much smaller primordial black holes. Those by definition are kind of rogue in that they're not part of the galaxy evolution process.

They're just a byproduct of the original formation of the universe and the intense gravitational fields that play there. So they could potentially be, floating around in space. And I know of at least one researcher who was looking to see if he could search for them by looking for deviations in the GPS system. So the idea there is that you would have a primordial black hole or small asteroids, but both about similar masses.

And they're just floating sort of past. They're so small that they don't perturb the Earth or anything like that. But the GPS signals or the Galileo signals, for example, are so sensitive that it would slightly perturb the satellite and you'd see that in the signals. I ought to drop him an email actually and find out how far he got with that analysis, whether he could potentially see these signals. Thank you to Stuart Clark, editor of Astronomy Now. I'd also just really recommend their website, Astronomynow.com. Yeah, it is, right? They have some great articles on there. And also, that's the place to go if you want even more space in your life and you can get a subscription.

This is the supermassive podcast from the Royal Astronomical Society with me, astrophysicist, Dr. Becky Smedhurst and science journalist Izzy Clark. Can we talk about some recent news of a different type of planet that has recently been discovered? It's not rogue in the way that we've been discussing today, but it is weird. So Becky, do you want to start us off? What is this planet like? Yeah, it is a really strange planet because, so what's been found is something that is a lot less dense than a rocky planet, right? So less dense than Earth. It is bigger than Earth, but its mass then brings its density down. So when we find something like that, we think, okay, either you've got to have something that is dominated by something less dense than rock.

So either you've got like a water world, water being less dense than rock, great, that's a water. exciting a water world, or you've got something like a mini Neptune, right, where it's sort of like not quite a gas giant, but a gas something. A gas something in the thing. You know, something, like you've just sort of shrunk down Neptune a little bit. So you've got quite a big thick gas atmosphere surrounding the planet's core. That sort of is always what we sort of say when we find something that's a less dense version of Earth, but it's bigger, right? So people explore these different options by looking at like the atmospheres of the planets like with the James Space Telescope you take the light from the star that passes through the planet's

atmosphere and you record the fingerprint that the molecules in the atmosphere leave on that light and you can tell that those molecules are there yeah but with this planet that's now been looked at with JWST it doesn't really fit either of the water world or the like mini Neptune planet what could it be or this new study has suggested it might be a molten planet I love it. Okay. So let's look at this some more. I don't think it's entirely clear. What they've done as a model and they've said, you know, they're sort of describing it as a rocky-ish world, but they're kind of comparing it. It's almost like a comparison with the early Earth. So if you imagine the Earth at the beginning of the

solar system when it was probably had a molten surface, that's sort of an implication there. But I think it's really hard to establish, isn't it? I mean, it's, you know, Becky's points about the density and so on there. But I think we haven't got a very clear picture of it yet. There is all this sulfur there, which is relatively unusual, I think. I think there was another example of that, which came out a few years ago where they were talking about alien volcanoes and so on. This implies a much more sulfur-rich surface across the board, and it reminds me, I guess, of places like Io, which is a moon of Jupiter in our own solar system, which is like that. But this would be much bigger. It's also, if you want to think about where it is, it's going around a red dwarf star,

it goes around about every seven and a half days. The red dwarf star is very, very faint. It's only about 1% of the luminosity of the sun. So really quite a cool and not very bright star. So the planet is, you know, being a lot closer in isn't a problem. If you had a planet orbiting the sun every seven and a half days, that would be bad news. So it's, I don't think looking at that, I was trying to work out. It's sort of almost it could be in what you describe as a habitable zone, which in no way whatsoever suggests that it's habitable, not if it's got a molten surface, just that the temperature of the star on its own right is not what's making it particularly hot. It's not that it's, say, close to the star and molten as a result. So exotic, I think, is a fair description. But then so many exoplanets are exotic, aren't they

really? We find huge Jupiter's and all kinds of other worlds that are quite unlike anything we see here. Yeah. So the models have basically come from the fact that to explain this J-D-Brist tea detection of sulfur. And if you think about like sulfur, it's, you know, all the bad egg smells right now from sulfur, right? So that's why they've gone towards this idea of like a volcanic planet, probably one that, at least in their models anyway, they say, we can explain the observations if we start with something like a mini-Neptune and then it shrinks over time as it's sort of like bombarded by radiation from its star. And in the same process, if it has this like magma ocean. Yeah, there's like just a lava world that can just be like, here's all the bad egg smells.

You know, here's all the sulfur. You're like shrinking the hydrogen and increasing the sulfur all the time. And that's how you can end up with, with sort of the sulfur dioxide and the hydrogen sulfide that J2ST is detected. So it is really interesting that from a model, Nichols and collaborators are now like, ooh, could there be a whole new class of ex upon it that we just don't know about, which I think is a reasonable sort of, oh, if statement to make, you know, because that probably is a load of ex uponates that we have no idea, like, what kind they are, you know? Yeah. And I guess what does this actually tell us about planetary evolution? Because as you say, if there's so much more that we don't know, is this the beginning of a can of

worms? Definitely could be with Ex-a-Ponit signs. You never know where they're going to go next. And, well, let's just keep going with the weird things and get onto some of our rogue questions. So, Becky, Johann on Instagram has asked, what if a small rogue black hole came into our solar system? Yeah.

I think we do, this question was coming as well, didn't we? Yeah, yeah. Okay, so if that happened, right, and instead of like an interstellar object, like an asteroid, you know, like a muamua, instead of if it was a black hole that came visiting the solar system and it made a close past the sun and then shot out again into interstellar space, it would be catastrophic to say the least, right? I'm assuming here that the black hole is, you know, the black holes that we know form at the end of a star's life from a supernova. so anywhere from like say five to a hundred times heavier than the sun, which is the range that we typically see, with things like, you know, LIGO that detects the merger of black holes. That would be the most massive thing in the solar system

if that came shooting through, right? So the gravitational pull towards that black hole would be bigger than the pull from the sun. And so you can imagine that would completely disrupt the orbits of every single thing in the solar system. Like the biggest yikes possible. Yes. Yeah. And depending on how fast,

it was moving. If it was a very like, you know, in and out, that could disrupt things very, very quickly eject things with large speeds. If it was a very slow pass through, then you'd imagine almost the sun would be caught in orbit around the black hole. And then you've got a two-body system now that the planets are orbiting. And again, all of the planets and asteroids and orbits would be disrupted. So it would be very catastrophic. It wouldn't act like a Hoover, which I think is probably what most people are picturing it, just vacuuming everything up in the solar system. because you've got to remember like a black hole is very, very, very, very, very dense, right? So the point of no return, what we call the event horizon, the radius that sort of marks the black hole,

for a 10 times heavier than the sun black hole, that event horizon is only about 30 kilometers across. And space is very, very, very, very, very, very big, right? So most things won't actually get close enough to end up in the black hole and grow the black hole. But you'd probably end up with a lot of rogue objects being created from this one road black hole coming in. If the black hole was less massive, so if instead it was what's known as a primordial black hole, which is a hypothetical type of black hole that forms in the very early universe, just from sort of like fluctuations of how massive and dense things are as gravity sort of just starts to take a hold in the universe, those can be less massive, right?

So in theory, right, this is completely hypothetical. We don't know these actually exist. But if, say, one of those came through that was the mass of a typical asteroid, then that would be no different to what happens when an interstellar objects, you know, like a moon mover comes through the solar system because it would be around about the same mass. It would have the same pull on everything else. There'd be no change to the orbits.

And again, the event horizon would be so small, it would be like nanometers across, right? So it's not going to act like a hoover or anything. So very, very unlikely unless anything gets too close to it. You know, we might not even notice if that happened. Right. If primordial black holes do exist, this could be happening all the time. We might not notice. And we'll park that one.

But it's nothing to worry about. No, I know, but I have so many questions and I really want to get into that. And I'm like, we're going to run out of time. Maybe a whole episode on Primonial Black Cause. And we'll come back to Roe Primonial Black Cause. Yeah, fine. Okay. Robert Benji 182 asks, Will telescopes ever be at a level to observe objects far, far out more than spots of light?

Yeah, Benji, the answer is yes in very many cases. And you only have to look at how telescope to change astronomy in the first place when we move from seeing planets, which as points of light, unless you have extraordinarily good eyesight, some people can see a crescent Venus at uncertain times, and some people can see Jupiter's moons. But the vast majority of us can't do that very routinely to worlds to worlds to worlds. So they went from being spots of light to places, to other worlds. And we saw them as disson, we saw details on them and so on. And similarly, we can resolve galaxies into millions of individual stars with the largest telescopes and even see details on some nearby stars. So as telescopes get better, you can expect even more of this. And it might

take many decades to say you see planets around other stars or rogue worlds as disks with actual detail on them. But I'm pretty confident it will happen. It will just be one of those far future astronomy projects. You might need a telescope effectively as big as the Earth. So you'll be talking about something called an optical interferometer, which is quite tricky thing to do, but they do exist. and somehow being able to operate one of those that had a baseline of thousands of kilometers, and that would start to show you those kind of details. But just imagine the view, you know, being able to look at not just seeing a planet even as just a point of light, which is pretty hard for planets around other stars right now.

There's only a few examples, but actually seeing details on that as well, and imagining them as places as we did when we saw the planets in our own solar system. So the answer to your question is that it's already happened, and it's just continuing as telescopes get better. Yeah, okay, thanks Robert. And Becky, Natchkatz asks, would we know if an interstellar comet got ejected by the death of a star or its resulting neutron star or black hole? Oh, good question. Yeah, it would have a much higher velocity, a higher speed in that case.

And that's what I was alluding to earlier in the podcast is when you asked me. And I was like, okay, I'll get into the details now, I guess, right? Yeah, let's do it. Yeah, so if you have like a, what's known as like a gravitational interaction. So just like two asteroids that come close to each other and maybe one like swings by the other and gains a load of energy like in a slingshot and that's how it gets ejected from its star system. That's going to have a slightly lower speed in terms of the range of things compared to something that's been ejected by a really high energy event like a supernovae, for example. Then it would have, yes, a much higher speed. We've actually seen this happen to binary star systems.

so you have two stars in orbit and then one of them's gone supernova, the other one has been ejected from that star system. They are much easier to observe than rogue planets because it really helps if your object is glowing so that we can see it. Rogue planets obviously only reflect light or cause these little lenses so that they change the background object they pass in front of. So with that we know like ejected objects in sort of like supernova systems end up at like a thousand kilometers a second rather than that maximum I was talking about

before is about like 100 kilometres a second. Oh, very cool. Okay. Thanks, Becky. And Robert De Kidd Flash asks, should we be worried about rogue asteroids any time soon? I mean, the answer to that is yes and no, although mostly no. So we're really good at detecting asteroids that we see in the solar system, so near-earth objects, objects in the main belt, and so on. And we've got a really, really good record of those that might hit the Earth someday. They're called potentially hazardous asteroids. And there are tens of thousands of near-earth objects that come relatively near the earth at some point. A few thousand of those are big enough to be a

cause of a concern which sounds alarming. But if you look at the numbers and you drill down, you find that only a handful of more than a 1% chance of hitting us in the next few hundred years and the total risk over all the times they go near the earth. So, and of those, actually, most of them aren't very big, actually, there tend to be a few metres across. So it's amazing we detect them in the first place. So it is vital that we keep watch on these, but we shouldn't lose too much sleep over them. And there are things like missions to divert them like dark did with Didimos. Now, rogue asteroids are a bit different because they come into the solar system. We should say that that was like a planned thing. That was like, oh, we have to divert didimus.

That was like a test to see if we could divert an asteroid. Just to be clear. Yeah. That's true. Didimos wasn't going to hit the Earth. We have our in case of emergency break glass plan now. Yes. Yeah, exactly. Yeah, that's fair. It wasn't going to hit the Earth, but it was just a test. But rogue asteroids, I mean, you could worry about them a little bit, but not too much. I mean, the problem is that they would be really hard to detect with sufficient warning because they're very, very faint if they're far out in the solar system and you need a warning time of a few years, really. But the good news is that we've only ever seen a handful of them. And of course, they're incredibly unlikely to come near the Earth. They'll likely be tens of millions of

kilometers away at the closest, so really large distance way. And there is evidence, actually, of some of these that have been captured in the solar system. There's a population of 19 interstellar asteroids that was described in a paper, actually Royal Astronrical Society paper in 2020, characterized as something called centaurs, which are asteroids moving between the giant planets and the outer solar system. None of those come anywhere near the Earth. So on balance, I don't think you should worry about it much, just a little bit. It's probably the kind of thing where it's worth understanding how they behave. It's worth thinking about contingencies if we did find one of these things on an incoming course. But the odds of one of those coming close to the Earth, that even

much, much lower than the odds of the nearby asteroids coming to the Earth. And that's already a low number to begin with. So don't worry too much. Don't have nightmares. Yeah, the people in the know are not worried about this. So we're okay. Thank you guys. And thank you to everyone who has sent in questions.

Please do keep them coming. We love reading them. You can email them to podcast at r.org. Find us on Instagram at supermassive pod. Or if you're a member, thank you. some in the forum on the Supermassive Club. And we will get onto stargazing in a moment, Robert. But there's something that people can see in London, which I think they'll also enjoy rather than just looking up. So do you want to tell us more of what's going on at the Royal Astronomical

Society? I absolutely can. This works in bad weather as well. So we're really... Amazing. I mean, goodness. We're really happy that we've got this exhibition called Our Fragile Space by Max Alexander, who's quite a renowned photographer for doing themes of space. in astronomy. It's a real passion of his. And our fragile space is one that has been in places like the UN and the European Parliament and so on. But it's actually in our courtyard at Burlington House in London. So if you know where the Royal Astronomical Society is, we're just in, you know, it's not particularly pre-possessing, fairly grand building, but not as big as some of those around it. Oh, it's pretty nice. It's gorgeous. It is. It is. It's where I'm recording today

as it happens, which is probably one of the sounds a bit echo-y. But out in our courtyard, until the 10th of May, we've got this exhibition, which is talking about the fragility. of the near space environment. So in other words, the bit of space that's right next to the earth, which is becoming increasingly populated by satellites. We've talked about that before, all the stuff around protecting the night sky. And Max's exhibition is all around that theme and has various pictures of people, objects, the skies and so on, reminding us how much we need to protect it. It's entirely free. You know, come and have a look. You don't need to book. You can just wander in off Piccadilly if you're going to the shops or if you're going to see an exhibition in the Royal Academy

and enjoy it and let us know what you think. And we're probably going to have a look. an event in mid-April if people want to book for that as well. Ooh, I can't wait to go and look at that. That's going to be great. And actually, I know we always reveal this at the end, but it's relevant to say it here. Our next episode is going to be on space debris. So it's all, very like we planned this. Wow. But let's look at some stargazing as well. What should we be looking out for in April? Yeah, I mean, the clocks will have gone forward by then, so you get obviously slightly shorter nights and you have to look a bit later, but you've got the beautiful spring stars are still dominant. So Ursa Major in the plough is

overhead. Leo is high in the south. Boethe's an Archerus to the left and Virgo is coming up. A lot of amateur astronomers like this for looking at galaxies because in the direction of the constellation of the constellation of the C-Bereneasus, there are lots and lots and many thousands of galaxies and people love making images with sea stars and so on. Through a telescope, you tend to see them as small fuzzies with a little bit of structure if you're lucky in a bit of shape. It's a good time for like a Messier marathon, isn't it? It is.

Yeah, this is a fabulous exercise, which I've never done whereby you can try and see every single messier object. There are about 110 of them. And you try and do that in a single night. So you have to obviously start at sunset and go all the way through pretty much towards sunrise to spot the lower one. Yeah, that's what scupper is me. I'm like, I'm going to bed at 11. It's the night. Oh, astronomy going to bed at 11, you know.

Anyway, so people do this. And it is a fun thing to do. You do need clear skies. And there's a couple of, one other object I'll mention is that there's a binary star called Ojiba in Leo, which is made up of two red giants, which I was looking at actually last night before recording. It's got these beautiful two registered stars going round each other and quite an unusual thing. Quite easy to see with the telescope, but not with binoculars. Planets, then, Venus is getting better and better in the evening sky and looks, it looks like a gibus moon. It's going to become

very, very obvious in the next few weeks. It'll be coming towards the Earth. The phase will shrink down. The size will get bigger. And it will just be this really bright, obfusc. for the rest of the summer that you'll spot as soon as the sun sets. On the 18th of April, it's right next to a really young moon, so a really super beautifully thin crescent with a shine. I think Becky has a name for that that she can say rather than me. A tornado moon. A moon, there you go.

Tonya moon, Venus on the 18th April. And then there's also a meteor shower on the 21st of April, not bad because there's not much moonlight interference. You might see maybe 10 meteors an hour, so you have to be a bit dedicated. And the best time is probably about 4 in the morning. So that's probably another reason for dedication. And then finally, there's an outside chance that we might have two bright comets. So we'll see where the one of these works out.

So the first one is called C-2026A1 Maps. They're named after the missions and telescopes that find them. It's what's called a Croyd's sungrazer, which means it's one of many fragments from a much larger comet that's thought to have broken up about two and a half thousand years ago. These objects come incredibly close to the sun. This one is going to be 160,000 kilometers above its surface. So that is much closer than the Earth is to the moon.

So that's how close it will get to the sun. It will go there on the 4th of April. And if it survives, it could become very bright. And it's so bright that it might be glimpsed in daylight for a few days after the 6th of April. Or more likely you might see, say, a bright tail in the western sky after sunset. But it's incredibly uncertain because it might get destroyed by the sun. And then I know, I know. I've got to look.

We've got to look. It would be amazing, wouldn't it? There are beautiful 19th century paintings of things like this where people saw, you know, tails sticking up from the horizon. And in the morning sky in mid-April, so this is one of those unearthly time of night things. You've got to be up about four in the morning. There's also an outside chance that another comic called C-2020-R-3 pan stars will also be visible to the naked eye. Because it's projected possibly not to be too bright, but if it's dust-rich and it throws out a lot of dust, then it can reflect a lot more sunlight and be more visible. So that is also a long shot, but again, worth looking out for.

So as they're so hard to predict, I think it's worth keeping an eye on places like Instagram to see what amateur astronomers are saying and look for photos and reports because you tend to get quite early warning of that because you will have people taking the first possible images they can as they go around the sun or they appear in the sky, get apps like Stellarium and they'll have them on there or you can install them if it's on a laptop. And if they do bright, then also get a pair of binoculars because that'll make it a lot easier to see them if you're eyes. But I personally, we'd love to see two bright comments or once. I know. We'll see. We'll see. We'll do one, right? We're definitely do one.

There's been some that have been visible with binoculars, but I'm like, where is my, you know, people who know nothing about the night sky are looking up and going, whoa, what's that kind of a comment, you know?

I'm like, I want to experience this in my lifetime. And come on. The Pan Stars comet, though, I've seen everything from, you know, it's going to be as bright as Neptune

to as bright as like Cassiopee, the stars in Cassiopee. Exactly. That's a very large range. Yeah. Hail Bob. 30 years. ago now or something like that?

Yeah. Well, yeah, that was amazing. That's the last one. I mean, I think I'm still dining out on Neo-wise, which was what? 2020. And that was pretty good. That wasn't bad, wasn't bad, wasn't it. That was good.

You could just about see that with your eyes as a fuzzy sponge. Yeah. Yeah. It was, you know, a lovely moment, but we want more. Come on. Okay, well, that's it for today. We'll be back with the Q&A in a few weeks' time. And as I mentioned, our next main episode is going to be about

space debris. Contact us if you try some astronomy at home, it's at Supermassive pod on Instagram or you can email your questions to podcast.org.org and we'll try and cover them in a future episode. But until next time, everybody, happy stargazing.