The Supermassive Podcast - BONUS - Can we gravitationally "hitch hike" out of the Solar System?

Episode Date: April 11, 2025

What the bloomin’ hell is a Gravastar? Are fast radio bursts like solar flares on steroids? Plus an interesting question on multiverses that can't be summed up in a short sentence. Izzie Clarke, Dr Becky Smethurst and Dr Robert Massey dive into The Supermassive Mailbox and take on your questions. Keep sending in your wonderful ponderings. Email them to [e-mail] or via Instagram @SupermassivepodThe Supermassive Podcast is a Boffin Media production. The producers are Izzie Clarke and Richard Hollingham. Hosted on Acast. See acast.com/privacy for more information.

Hello and welcome to another bonus episode of the Supermassive Podcast from the Royal Astronomical Society with me, science journalist Izzy Clark, astrophysicist Dr. Becky Smethurst and the Society's Deputy Director Dr. Robert Massey. We are ready and waiting to answer your questions that you've sent in. Keep them coming. You can send us a question by emailing us at podcast at rs.ac.uk or messaging us on Instagram at supermassivepod. I'm not going to lie, we have had a flurry of quite difficult questions. They're very good. They're very good. But I'm just going to let people know that if you're sending in other questions, we do take silly ones as well.

Yes, easy ones. Easy ones too. Ones that don't make my head hurt. I have the easier job. I'm just the messenger. It's great. Okay, so buckle up, Becky and Robert. Becky, let's start with this one from Peter in the Netherlands, who is pondering about leaving the sailor system. His email says, Hi, Dr. Becky talked about interstellar passing objects in her December edition of Night Sky News on YouTube, and now I find myself wondering, with the idea in the back of my mind that we are pretty much flying to and from asteroids, landing there and bringing back samples, and that the best plan to avoid an asteroid collision on Earth

is to gravitationally alter their orbit slightly with a spacecraft, how much of a stretch would it be to gravitationally tack on to one of these interstellar passing objects and this way hitchhike our way out of the solar system? Thank you for your work, it's great, so keep it up. Yeah, that is a really good idea, Peter. And I think most of us would love to grab a sample, like a rock from an interstellar object, right? That has formed around another star in our galaxy,

and then it's been kicked out, and it's made its way just to happen to pass through the solar system. Like if you're wondering, does this happen? Yes, we've spotted two so far in the past couple years that have actually done this. The problem is with a mission like this, is that first of all,

interstellar objects are incredibly unpredictable. We've no idea when we're gonna detect one, we've no idea which direction it's gonna be coming from. And also they're usually traveling very fast, right? Cause they're moving through interstellar space, they've been accelerated probably by a few sort of like flybys of other star systems. And so they're usually traveling in a range of like 20 to 40 kilometers a second. So capturing one is the hard part, right? So you've got all these problems

to deal with, but we have seen some research papers exploring this idea of an interstellar object, sort of interceptor, if you will. So last year we had one from Alan Stern and collaborators. Alan Stern was the head of the New Horizons mission that went to Pluto. So a lot of experience in sort of this area and they think it'll be possible to do this in the 2030s. So actually not that far away. And I think what's going to help is actually, so ESA, the European Space Agency has a mission that's launching at the end of the decade in 2029, that's called the Comet Interceptor

Mission. That's going to do exactly what it says in the tin. It's actually going to launch and then essentially wait at one of those stable points in the sun earth systems. You know, we talked about Lagrange point two, it's where like JWST is, it's where ESA's Gaia mission is, you know, we talked about Lagrange Point 2, it's where like JWS-T is, it's where ESA's Gaia mission is, you know, they're very stable, so it sort of always is the same distance from the Sun and Earth. And essentially, if you pop something there, it'll just wait there, and then wait for a comet to sort of appear from the outer edge of the solar system. Again,

this is also quite unpredictable as well, because there's so many of them out there, are massive long orbits that we also don't know all of them and when they're going to come back in towards the inner solar system. So we'll just wait there for one to appear and then hopefully be able to intercept it to study the comet. And that'll be really exciting because it's come from the far reaches of the solar system and that's why we think sort of like water and a lot of like sort of the life proteins and everything that you might need might come from.

So that's exciting in itself for the comet mission, but also people said, well, does it have to be a comet for ESA's Comet Interceptor mission? If there is an interstellar object that appears at the right moment, it could also intercept an interstellar object as well if it works out, right? So I think even if it does choose a comet, it's just going to be a nice mission demonstration that this could be possible if you were then going to launch something that specifically was like, I'm going to ignore the comets and just wait for interstellar object. And in theory, once it was in orbit, maybe around this interstellar object, and it fully caught up with it and

done some sort of like gravitational sort of entry into orbit around it, then yeah, you could hit trike out of the sources with it as well. And so yeah, it'd be really interesting to think like, would it get further than like the Voyager probes or something if this entire object was moving fast enough and got a big gravity boost from the sun as well. Yeah, very cool. Okay, Robert, Liam Collins emailed us and says, what the bloom in hell is a gravistar. An explanation for an idiot would be marvelous from Liam after a confused discussion with his son.

I think Liam, you're possibly, I agree, what the bloom and hell is, I'll grab a start on you. You might be getting an explanation from an idiot in this particular case. I read this and I thought my mind was melted a bit having not looked at these before. So it's an alternative to black holes that explains some of the things you see associated with what we think are black holes. And just to complicate matters, the idea it appears to be you have dark energy inside it, which we don't even know what dark energy is, right? It's driving the expansion of the universe. So we've got stuff, we don't know what it is, enclosed by a thin shell of normal matter that might also be incredibly cold. To get around the fact that gravitational wave experiments suggest this may not be the explanation, there's also

the concept of nest stars where there are lots of these things nest inside each other. To say I'm not saying this with a great deal of confidence is fair. That might then mimic the gravitational wave signature. There's experiments where we see black holes colliding and so on. To be honest, black holes sound pretty wacky, but at least we have got good evidence for them. This sounds, I think it's fair to say, rather less likely than black holes do. It's a great and absolutely bonkers idea, but I admire the physicists that came up with it. After several decades, I think we can say that black holes are part of the astronomical consensus. This is a very exotic alternative. Pavel Nasr and Emil Motola, who proposed it in 2001 in a paper then, all credit to you guys for coming up with this. I still tend to think, odd though they are,

that black holes are the more convincing explanation. But yes, that was definitely an out there question and one that left me scratching my head, but I learned something. So that's good. I've always thought grab a stars were just too far fetched almost like it was like, it was like, yeah, okay, you can do as much as you want with equations on a blackboard. But at some point, you've got to take the chalk away from the theoretical physics. Do you know that you're reaching too far? What does it actually look like?

You're invoking something that we don't even know what it is yet. It's just a name for the thing that's causing the expansion. Just put the chalk down. Figure out dark energy first before you start making stars out of it. Becky, the difficult questions continue. Misha and Steve in Herefordshire, it might be Mika, sorry if I've got that wrong, have a question about our universe's fate. They say, we recently heard a documentary on possibilities of what the universe is, e.g. multiverse, infinite, etc. They mentioned that if we are in a multiverse, then, potentially, far, far away in the future, we could create a new universe to escape as our universe comes

to its end. But we're confused as to how a universe we would create would be outside of our existing universe. Surely it would still be in ours, therefore also it would die with it. Appreciate that this is a bit unusual, but we don't know where to find answers. Thank you. We love your podcast so much. Okay, Becky, over to you on that one. Again, I'm not surprised you're confused because multiverses give me a headache too as well, just thinking about it. Maybe it might help just linguistically to start. We think about the definition of uni-verse, right? It means one, it means singular,

and in the physics sense, it's that everything that exists is encompassed by the universe, right? So that includes not just like matter and objects that we see, but space and time itself as well. Um, then there's the concept of multiverses, which let's also be very clear in regards to the last question, also still completely hypothetical. And so I think what multiverses really sort of do is raise this idea of whether there are other universes outside our own, But in this respect, they would be in like other dimensions, perhaps. This is what we know as like the quantum mechanics, like many worlds interpretation of the multiverse. There are then what's known as bubble universes, which my favorite. Yeah, I know. We did a whole episode on multiverses actually, if

you do want to catch up, Maker and Steve. But like, where you can think of that, I guess, is they do exist outside our universe, but in some, I don't want to say space necessarily, because again, the definition of universe is that everything, even space, is included in it. But as you picture it in your three-dimensional brain, yeah, outside of our own universe in this sort of bubble. So first of all, this documentary you watched, I think they had a bit of a blue sky science license to just be like, what if, you know, it's another, we should have took the chalk away from the producers and so they would have thought about, okay, well, you know, if multiverses exist and if, you know, and if we could create one, like, you know, even having enough energy to be able to do

that, everything about how much energy went into creating our universe, right? First of all, that would require physics beyond what we currently know, not just the concept of multiverses, but the concept of how to create a universe, accessing different dimensions or distances so far in space that we currently can't reach, right? But basically, I think if multiverses exist, then they are completely separate entities from our own. They are independent of our own as well, and that's true of all multiverse hypotheses. There are some that perhaps if there are bubble universes and they're touching the edge of ours, we might be able to detect, not the cosmic microwave

background, but they would still be independent of our own. So if we created a new one, then that new one wouldn't die with our universe. If our universe was dying, it would be its own separate entity. And also another thing that this documentary probably was like, we'll just gloss over this. Even if our universe did come to an end, it's going to be in so many billions or even trillions of years time, depending on energy budgets and all this kind of, you know, how much is in the universe. But let's face it, humans aren't going to be around to see that. Yeah, we haven't been around in an app like a blink of an eye in comparison to the universe's

timeline. I think as humans, we forget that we are not eternal now, like as a species, like something main characters, we really do have some main character energy. We're going to be around for trillions of years to see this. Literally we've only just been able to figure out stuff about the universe in the past hundred. So raid it in guys. Create multiverses and all this kind of stuff. Like yes, I think it's like a step past like, oh, if we destroy the earth, then we'll have

to go to like Mars or a new planet. Hey, why don't we just not destroy the earth? You know, like, I'm like, not everyone has Wi Fi, like, you know, we know some other bigger steps. Yeah. It's also like, you know, maybe if the universe is dying, we should just die with it. Like, maybe that's the universe is sad. I don't know. You know what I mean? It's just like, we're not going to be around to see that. First of all, we won't last that long, I don't think. But it's very arrogant standpoint to be like, if we're around at the end of time and if we can create a multiverse. Yeah. So I wouldn't lose sleep over that.

Okay. And Robert, Debbie has a question about something that we covered last year. So this is fast radio burst. We've called them FRBs. We also like to call them Furbies and so does Debbie and she says, hi all. Still loving the pod and never miss an episode. Thanks so much for the knowledge you all drop. You're welcome. Onto my query. I was learning about FRBs or Furbies, as I like to call them, and I suddenly wondered, are Furbies like solar flares on steroids? Since it look like they're from magnetars, do they build up tension of their magnetic fields till they snap and send Furbies? Like

when the magnetic field snaps and sends out solar flares from our sun, or are they a totally different process? Thanks from Fridged, Wisconsin, where the air hurts your face. What a selling point to visit. Thanks from Fridid, Wisconsin, where the air hurts your face. What a selling point to visit. This is definitely a buckle up episode then, Debbie, isn't it? Thanks from Sussex, where that question's hurting my head. As a reminder, an FRB is a fast radio burst, so a radio signal lasting up to a few seconds and not really properly understood.

They give out a huge amount of energy in that short time. But despite that, they're so far away, it's a teeny, teeny weak signal. But yeah, one idea is that FRBs or Furbies come from highly magnetized neutron stars, incredibly dense remnants of massive stars, and they're called magnetars. And sometimes their magnetic fields are disrupted, and you can get things like starquakes, and or or the lines the magnetic field lines can reconnect, which is so they jiggle around in the likely imagine like elastic bands snapping and somehow reconnecting. And in each case, these release vast amounts of energy and the second one of these is a bit like the process that leads to thought to be like the process that leads to a solar flare. So the only difference being it's maybe a trillion times as powerful. So you know, there's something of an energy step change there. Imagine this pretty powerful event on the surface of the sun and making it a trillion times more powerful. So credit to you, Debbie. I mean, this was actually discussed in a release in the Hubble team last year. Remember, remember Hubble? You talked about J.W.S.T. Remember Hubble? So it's really

impressive that you made the comparison if you hadn't seen that. I'm sure spring will be in Wisconsin anytime soon. Oh, fingers crossed. Oh, yes. Here's hoping. Right. That's it for all of the questions this time. Do keep sending them in along with your pictures and your ponderings. You can email... Any silly questions? Any silly questions? More potatoes. Yes, exactly.

Robert and Becky need a rest. You can email your questions to podcast at rs.ac.uk or find us on Instagram at Supermassive Pod. And we'll be back in a couple of weeks with a main episode for you all about gravity. But until then everybody, happy stargazing.