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Astronomers this week announced that they had discovered an asteroid or comet on a trajectory that brought it from outside the Solar System? Is this the first case of an object from deep space? And what can we learn from this discovery?
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Show Notes
Exorocks, exoroids, extrasolar asteroids
GD 61
Pan-STARRS Observatory
Pan-STARRS
Vega system
Three-body interaction
Pole, Pericenter, and Nodes of the Interstellar Minor Body A/2017 U1
C/1996 B2, which is also known as, Comet Hyakutake
Comet 96P/Machholz 1
Comet C/1980 E1 (Bowell)
Transcript
Transcription services provided by: GMR Transcription
Fraser Cain: Astronomy Cast, Episode 464: The First Object from Outside the Solar System. Welcome to Astronomy Cast, a weekly facts-based journey through the cosmos where we help you understand, not only what we know, but how we know what we know. My name is Fraser Cain, I’m the publisher at Universe Today, and with me is Dr. Pamela Gay, the Director of Technology and Citizen Science at the Astronomical Society of the Pacific, and the Director of CosmoQuest. Hey, Pamela, how are you doing?
Dr. Pamela Gay: I’m doing well. How are you doing, Fraser?
Fraser Cain: Very well. Is there some kind of news, maybe? You have any news? You have anything to shamelessly self-promote? Should we encourage people to go to our Patreon campaign?
Dr. Pamela Gay: Yes, yes, we should do that. Go to our Patreon campaign. So, you can support Fraser and I by going to Patreon.com/AstronomyCast, and once our Patreon is consistently bringing in enough money to fund Susie and Chad, the next step is, we want to grow this project. We want to do new and interesting things, and we’ve been doing this as volunteers for ten years, and we’ll keep doing it as volunteers, but we’d love it if you gave us the freedom to get paid, and put more effort into it, and do a better project. And we’ve seen with Fraser’s, Guide to Space, just what amazing work can come out of just spending that little bit of extra money. So, if you want to help us get our quality up and bring you more and more things on a regular basis, Patreon.com/AstronomyCast.
Fraser Cain: Awesome. All right, let’s get on with today’s episode. So, astronomers, this week, announced that they had discovered an asteroid or comet on a trajectory that brought it from outside the solar system. Is this the first case of an object from deep space, and what can we learn from this discovery? All right, this is breaking news. Like I said, I feel a little weird about us talking about breaking news. I feel like Astronomy Cast will be this historical record of astronomical knowledge, but this is such an exciting announcement that we just had to talk about it here. What happened?
Dr. Pamela Gay: So, my goal isn’t to talk just about this new object, but to talk about why, in general, we’re looking for exorocks, exoroids, extrasolar asteroids – whatever the heck you want to call them – why we care about chunks of ice and rock that come from other solar systems. And so, the inspiration for this came from the fact that on October 19th, there was this new thing discovered shooting through our solar system. And as it was observed, we realized this thing shooting through the solar system doesn’t have a comet, doesn’t have gas and dust coming out from volatile sublimating and doing their thing.
And so, what had originally assumed to be a comet because of its orbit, was quickly realized – oh, it actually walks, and talks, and acts like an asteroid. We need to rename this thing an asteroid. But asteroids don’t come from the outer solar system, and the more we looked at it – we, being other people – the more other people looked at it with their telescopes, the more it was realized this thing is at a high velocity on a weirdo orbit, and everything about its trajectory indicates that some alien star threw a rock at us, and that rock is now passing through our solar system and gives us a chance to get all sorts of really cool insights about our place in space.
Fraser Cain: Yeah, let’s talk, a bit, about the chain of events of the discovery. So, it was discovered by the Pan-STARRS Observatory, which is one of these automated asteroid observatories that we’ve mentioned in the past, but it had already moved through its closest point past the sun when it discovered.
Dr. Pamela Gay: Right, and this is one of our greatest frustrations. So, it was found on October 19th, but it turns out that on October 14th that’s when it was closest to the Earth, and it actually made an approach that put it only 60 times the Earth-moon distance away from the Earth, but it’s not the brightest rock in the sky, and it’s kinda super tiny, so we didn’t notice it. So, we found it when it was already on its way out on a fairly high velocity, and we’ve done everything we could to point every telescope we can at this object trying to learn as much as we can.
Thankfully, because it has such a high velocity, it’s chugging across a pretty good area of the sky allowing us to quickly get its orbit fairly nailed down.
Fraser Cain: And what is that orbit?
Dr. Pamela Gay: It’s leaving us. It’s leaving us behind.
Fraser Cain: Where did it come from?
Dr. Pamela Gay: Well, –
Fraser Cain: And then, where is it going?
Dr. Pamela Gay: So, this is the crazy thing. If you look on the sky to see what on the sky is lined up with where it came from, it’s kinda lined up with the Vega system. Its exit is kinda lined up with the Pegasus constellation, but to say it was flung at us from Vega – which is what I’ve seen in a few Twitter streams – kind of ignores the fact that we’re all orbiting the galaxy. So, where things are right now, and where they were when this rock, well, was sent on its attack trajectory, aren’t exactly the same thing.
Fraser Cain: Right. And the speed of Vega moving, and the direction that Vega’s moving, and it’s – Vega’s a bright star – it’s a little further away. And then, the speed that the solar system is moving, those don’t line up.
Dr. Pamela Gay: Doesn’t work.
Fraser Cain: Right, so it came from out there somewhere –
Dr. Pamela Gay: Yes.
Fraser Cain: – that-away.
Dr. Pamela Gay: Yeah, so it’s currently exiting our solar system at 97,200 miles per hour. For those of you working in metric – yay, kudos, you’re doing the right thing – it’s 156,400 kilometers per hour. So, it’s going a little fast; a little fast, you might say.
Fraser Cain: Can you compare that to, say, the speed of what an asteroid might be going? One that’s just orbiting the sun every – I know the Earth is orbiting the sun at 30 kilometers per second, but I don’t know what that is in kilometers per hour – as I fill time as you do a Google search.
Dr. Pamela Gay: So, Vesta, which is one of the more inner asteroids, it’s chugging along at a whole 19 kilometers per second. Now, we have mixed units.
Fraser Cain: Yeah, and that was my point is that kilometers per second and miles per hour, what I wanted to really get to is that this sucker is moving fast.
Dr. Pamela Gay: So, Vesta is going along at 42,000 miles per hour. So, we’re looking at something that is a lot more.
Fraser Cain: Yeah, at more than double the speed of an asteroid. Is it on an escape trajectory?
Dr. Pamela Gay: It’s totally on an escape trajectory, and I love when I look at its orbital bits and pieces because we use the term, ellipticity, to refer to how non-circular something’s orbit is, and a perfectly circular orbit has an ellipticity of zero. As something gets to having a flatter and flatter, more oval-shaped orbit, that ellipticity gets closer and closer to one. This sucker has an ellipticity greater than one which means it’s on a hyperbolic orbit. It came in; it’s going out. We’re never gonna see it again unless it gets flung back externally, and we hit it on another orbit, and that is improbable and, I’d say, unlikely to happen.
Fraser Cain: Right. So, then the question is, what could have sent it into this kind of an orbit? It’s not one of these Oort cloud objects. So, it’s not like it just fell out of the Oort cloud, and it’s gonna be on this big, long orbit. It came from somewhere else. Where did it likely come from, or what is the conditions that caused it to be on this orbit?
Dr. Pamela Gay: So, we can say absolutely nothing about this particular exorock at this time. But in general, the kinds of things that can fling rocks are anything that generates a shock wave, if you have some sort of a crazy three-body interaction, these are all things that are able to transfer energy from one object – an exploding star, a bunch of different things that have shared orbital energies where some of that energy gets dumped – from one object to another. These kinds of multi-body interactions can give something a good, solid kick. And then, there’s always the – it got hit with something probability.
So, we don’t know exactly what caused it. It could’ve been a shock wave. It could’ve been a three-body interaction. It could’ve just been something that got hit, and it got kicked away just like we get Mars rocks periodically dumped on us because another rock hit Mars. Something hit it and sends it our way. It was thrown at us.
Fraser Cain: And what do we know about it? What do we think it’s made of? How big is it?
Dr. Pamela Gay: From what I’ve been seeing so far, it’s small. The initial size, I saw, was that it was 160 meters across. I haven’t been able to confirm that with multiple sources. So, it’s not huge and as for what it’s made of, these are the things we’re still trying to figure out. A paper came out just as I was prepping for this show. It’s the Pole, Pericenter, and Nodes of the Interstellar Minor Body, A/2017 U1. People are still just publishing papers on its orbit.
It’s gonna take time for us to take all the data that has been taken by all the different telescopes that have been pointed at it and start to figure out what it’s made of. But, this starts to bring up the question of, why do we care? Why are we turning on a dime and saying, you, very largest telescope, biggest telescope in the world – telescope people fight to get time on – stop what you’re doing. Look at this tiny rock as it flies by.
Fraser Cain: Really? You don’t think that people won’t understand why turning the greatest observatories of the world on the first object discovered from outside the solar system?
Dr. Pamela Gay: Well, they know that it’s cool; it’s awesome. But, scientifically, do you know why it’s super interesting?
Fraser Cain: Because it’s never been seen before?
Dr. Pamela Gay: But, it’s more than it’s never been seen before. It’s also what we have the potential to learn from it. Now, this isn’t the first exo-object that we’ve seen. So, those of you out there who are like, this is the first time we’ve seen an exo-object! No, we’ve seen exodust – which is boring – and we’ve seen, what we believe, are extrasolar comets more than once. The ones that we look at as candidates are comet, C/1996 B2, which is also known as, Hyakutake – which is just really fun to say – 96P/Machholz 1, then we also have comet, 1980 E1.
So, the question is, what can we learn? Well, what we’ve seen from these comets is that they appear to have completely different composition ratios from what we see with our own comets. So, if someone tells you they’re made of completely different stuff, they’re not made of completely different stuff. They’re made of the same stuff because the entire universe is made of the same stuff; it’s just combined in different ways. Fraser and I are made of the same stuff. It’s just combined in totally different ways, and more of mine ends getting turned into hair.
So, with these comets, we were able to realize that they had the stuff comets are made of – volatiles, gas – that was in different ratios, showed a different spectrum than what we’re used to. What we’re hoping is that in looking at this asteroid, we’ll see an absorption spectrum that, maybe, looks different than the absorption spectrums that we’re used to seeing in our own asteroids. And if that’s true, it will help us understand just how different our solar system is or isn’t from other solar systems. Either way, it will be amazing. Either it looks exactly like Vesta or Ceres, or any of those asteroids we have out there forming a continuum of compositions, or something super weird where we see different ratios, and we have to rethink how the stuff of supernovae combine to form solar systems.
Fraser Cain: And of course, the great tragedy is that there is no way for us to take a sample of this object.
Dr. Pamela Gay: No, in a perfect world – which is, clearly, not the one we live in – in a perfect world we would’ve found it on its way in and not on its way out. And we would’ve had time to observe it a lot longer with ground-based telescopes. And in an even more perfect universe – which is, seriously, not the one we live in – there would’ve been a spacecraft out there that we could redirect at it, as we’ve done with spacecrafts in the past when they finish one mission, and we recycle them on another.
But, coincidences don’t always happen the way you’d like, and we found it on its way out, and there is, coincidentally, nothing nearby. I mean, imagine if this thing was gonna blow past OSIRIS-REx at a few thousand kilometers off the port. That would be fabulous. We’d totally open it up, take a look; not something we can do.
Fraser Cain: Yeah, that would be too bad. And of course, to try and actually chase it down now –
Dr. Pamela Gay: Can’t.
Fraser Cain: We don’t have rockets capable of putting payloads at that kind of a velocity. We’ve talked about this a bit, that trying to drop – people would say, why don’t we throw nuclear waste into the sun?
Dr. Pamela Gay: No.
Fraser Cain: The Earth is going 30 kilometers per second around the sun, and we don’t even have rockets that can, really, do that kind of change in velocity. We can barely send things like New Horizons and Voyager’s over, say, 16 kilometers per second, which is an escape velocity of the solar system. That’s it. So, it’s so sad.
Dr. Pamela Gay: Yeah, New Horizons, the fastest going spacecraft is chugging along at 59,000 kilometers per hour. So, New Horizons – if you let go of the two of them at the same time – would not keep up. So, the idea of chasing this rock down – yeah, it’s not gonna happen. We need Superman, and we don’t have him.
Fraser Cain: Right, exactly. So, then the fact that one of these came through on our watch – it’s like that same question about that we saw a comet smash into Jupiter, on our watch, at a time when the Hubble Space Telescope was going. So, this must happen on a fairly, regular basis then.
Dr. Pamela Gay: And the question is, why haven’t we been detecting these before? And this is the first asteroid that we’ve spotted. Now, the, “we’ve spotted”, is the important part of that statement. When we’re out there looking for moving targets, the places that we’re normally looking are along that ecliptic; that area of the sky that is where the planets are. It’s where asteroids are and, while comets do tend to come from randomized directions, they’re just one small piece of the puzzle, and what we’re actually usually looking for is asteroids on a collision course.
Fraser Cain: Yeah, those are the ones we’re worried about.
Dr. Pamela Gay: We’re not looking, those other places that much. So, there’s a good chance there’s been others of these coming in at weirdo trajectories, zipping through the ecliptic, and just not getting spotted as they cross the plane of the solar system. And who knows how many we’ve missed? But, as we get more and more surveys going, as more and more people have robotic systems, maybe we’ll catch more of these. And the other question is, are they just dark? There’s dark stuff out there, things that are covered in barely reflective materials – carbon molecules, soot, that black stuff like we see on Neemus – that could make them much harder. Asteroids, in general, aren’t that reflective.
So, it could be that after spending a long time in the emptiness between solar systems, these things are just not that shiny and just not that easy to find.
Fraser Cain: One of the things that we’ve talked about, in the past, is this idea of panspermia and that it’s possible that – thanks to asteroid collisions here in the solar system – objects have been moving from world to world, and spreading life from world to world. And every time I’ve brought up this idea of this galactic panspermia with some astronomers, they’re like, no, the amount of material that gets from solar system to solar system – space is too big, and this stuff isn’t getting from place to place. Well, here we are, having spotted a chunk of rock that went place to place during a period that we had telescopes. Chances are there are more of them out there. Is it possible that this is happening more than we thought? Could one of these hit the Earth, for example, and break up?
Dr. Pamela Gay: Is it possible? Yes. Is it probable that the Earth got hit by something that had successfully carried sufficient amounts of life, that some of it was able to survive the passage through our atmosphere, and take root on the early Earth, in that small window of time when life was getting started? It’s where you start looking at the adding up of all of these probabilities and – it’s actually the multiplying up of all of these probabilities – when you start to look at that, it starts to be like, uh-huh. Well, in our solar system where we know life pretty much started, the instant life could start, it seems unlikely that that life was created by infestation from an alien rock.
Now, this is not to say that we haven’t, at some time since then, had invading genetics that successfully made it onto our planet and infiltrated our biosphere.
Fraser Cain: That’s funny because, to me, it says the exact opposite thing that – obviously, I’m not an exo-biologist – but when mold shows up on my sandwich, when mold shows up as soon as mold possibly could, I don’t assume that the mold evolved independently on my sandwich. I assume that the mold came from somewhere else; it infected my sandwich.
Dr. Pamela Gay: And this really does come down to Pascal’s experiment of, does rotting meat create maggots, and you test it by letting meat sit where it’s isolated from bugs, and see what happens. And he did discover, indeed, meat doesn’t rot and get maggots when not given access to flies to lay eggs. But, we don’t know how to take a world and run that experiment, and our mental thought experiment tells us, well, flies are constantly lying on the meat, they’re walking around, they’re leaving their germy footprints, and maybe laying eggs. Whereas, our same thought experiment is like, well, we haven’t been hit by an exorock that we know of, and so, therefore, it seems like the probabilities are exceedingly low.
Now, this is all guesstimates, and we’ve only had the ability to successfully find these things for a few decades. And we probably only know when life started within a million years or so, a few hundred thousand years; I don’t know the error bars on that measurement. So, it is a guess. It is entirely a guess just like the Drake equation is nothing more than guesses until we have other experiments to look at.
Fraser Cain: It’s a pretty amazing discovery, though, if true. What would make it not true? So, in other words, it’s a claim that this object came from outside the solar system, and that it came on this amazing trajectory, and now it’s on its hyperbolic orbit, and away it goes, and it came from out there. What would make it wrong, that it didn’t come from out there that it actually came from here, and that follow on – it’s like the Torino Scale, where, oh, turns out this Apophis is a four on the Torino Scale and has a high likelihood of – oh, no, wait, nope, no, it’s fine. It’ll be fine.
Dr. Pamela Gay: So, if we were to discover the collisional debris, with the exact same absorption spectra of asteroids, in an as to for unknown orbital plane of our solar system, indicating that there had been a group of rocks happily orbiting together out there. And there was a collision, and one got sent on a new trajectory. But, I don’t know how they could’ve imparted so much energy as to put it at an escape velocity.
Fraser Cain: But, isn’t it possible that they just got their measurements – they haven’t got enough measurements, at enough accuracy, to totally confirm the trajectory that they think they have?
Dr. Pamela Gay: At this point, with two weeks of observations on this high speed of an object, no. Yes, it is escaping. So, I can’t think of a three-body situation with things that we wouldn’t have already noticed. And I can’t think of a collisional situation with things we haven’t already noticed that would impart sufficient energy to get something going this fast in this kind of an orbit. Now, it could be that I’m lacking imagination; that has been said occasionally. But, the folks that are studying this – when you look at the people who are people who are dedicating their careers to studying rocks and their orbital trajectories in our solar system – when you see the people who are willing to say, yes, this is an exoroid, exorock, extrasolar asteroid, yes, we need new names for this.
I trust that our combined creativity would’ve come up with alternatives to explain its orbit and that since our collective creativity has been – nope, this is cool, let’s look at it. Rather than being dubious and being like, no, we can explain it this way. Because we like to be dubious, it’s kind of like a scientist’s job. I’m willing to be excited this time.
Fraser Cain: I can’t believe I’m the skeptical one. But, no, still it is kind of an amazing discovery. To find more of them, what should astronomers do?
Dr. Pamela Gay: Dedicate telescopes to looking at new parts of the sky. We need to look up, rather than sideways.
Fraser Cain: Yeah, I think it’s important to understand how little of the sky we’re actually looking at a high level of detail. It’s a very small part of the sky that is under our view.
Dr. Pamela Gay: And this comes down to, simply, a lack of resources. It is exceedingly important to make sure we’ve identified all of the Apophis’ out there that just might be potentially going to cause earthquaking events. So, this is where we dedicate a lot of our resources. And since what is beyond those parts of the sky – the other parts of our galaxy and beyond that we’re able to study – are just as cool along the ecliptic as they are not along the ecliptic. It’s easy to argue, let’s just take our very, very limited resources, and look there. And this is where amateur astronomers can come in. Everyone loves to find a rock in space, and you even have a rock in space named after you, I believe. And if the amateurs take up the mantle of searching with their digital detectors – their CCDs – and surveying those parts of the sky not being surveyed by Pan-STARRS and its cohort, they may be ones that will be our answer to finding more things like this.
Fraser Cain: Yeah. On that note, thank you, Pamela. We’ll talk to you next week.
Dr. Pamela Gay: Been my pleasure.
Narrator: Thank you for listening to Astronomy Cast, a non-profit resource provided by Astrosphere New Media Association, Fraser Cain, and Dr. Pamela Gay. You can find show notes and transcripts for every episode at AstronomyCast.com. You can email us at info@astronomycast.com. Tweet us @AstronomyCast. Like us on Facebook or circle us on Google+. We record our show live on YouTube, every Friday at 1:30 p.m. Pacific, 4:30 p.m. Eastern, or 20:30 GMT. If you miss the live event, you can always catch up over at CosmoQuest.org or on our YouTube page.
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Duration: 28 minutes
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