Dark Comets with Darryl Seligman

Why did Oumuamua, the first discovered interstellar object, accelerate faster than it should? Neil deGrasse Tyson and Chuck Nice explore the mysteries of the newest objects in the solar system: “dark comets” and interstellar objects with astrophysicist Darryl Seligman.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Neil deGrasse Tyson?

  So Chuck, I love having spanking brand-new PhDs come here as a guest. Because we get spanking brand-new information. Yes, and to learn that there's a whole new kind of object in the solar system: dark comets. Yes. I think he coined the phrase, too. Yeah, without a doubt. And of course, when you encounter a dark comet, you get superpowers.

• 0:20Neil deGrasse Tyson?

  Wishful thinking. Coming up, new information about what's flying around our solar system on StarTalk.

• 0:27Neil deGrasse Tyson?

  Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.

• 0:40Neil deGrasse Tyson?

  This is StarTalk. Neil deGrasse Tyson here, your personal astrophysicist. Got Chuck Nice with me, Chuck. What's up, Neil? All right, man. I hear you're working on a stand-up special? Yes, we are trying to sell it right now, so if you're... It's all done? It's done. If you're at Amazon or Netflix, hi.

• 1:02Neil deGrasse Tyson?

  Well, good luck with that. Yeah, thanks. Good luck with that. So you know what we're gonna talk about today? What's that? Dark comets. Ooh, sounds like a Marvel movie. I'm dark comet. A dark comet. Dark comets. I've seen the term, and I don't know how they all define it. Okay. Because my specialty is galaxies and cosmology and like what's going on in the solar system. That's too small for you. No. Okay, we can't be bothered with comets, Kevin. Dark comet. We have one of the world's experts on this subject, Darryl Seligman. Daryl, welcome to StarTalk.

• 1:36Speaker 01

  Thank you for having me.

• 1:37Neil deGrasse Tyson?

  Yeah, so you are assistant professor at Michigan State University?

• 1:42Speaker 01

  Yeah, well, starting next year, I'll be an assistant professor. Right now, I'm an NSF fellow.

• 1:46Neil deGrasse Tyson?

  Oh, that's between your PhD and your first tenure-track job?

• 1:51Speaker 01

  Yes, exactly.

• 1:51Chuck Nice?

  Brand new!

• 1:53Neil deGrasse Tyson?

  Wow, look at that. Just birthed by the National Science Foundation. Look at that. So, the National Science Foundation has what's called a postdoctoral fellowship, where, once you get your PhD, it's money, you just do whatever the hell you want. Ooh. It's like freedom that wouldn't otherwise be there if you immediately went right into academia. So Darrell, what was the title of your thesis, if you can remember it? Cause I barely remember the title of my thesis, because there's a lot of words and a subtitle and, but it's about comets.

• 2:24Speaker 01

  Well, it was actually about interstellar objects.

• 2:26Neil deGrasse Tyson?

  Interstellar objects, okay, well, let's start there. For the longest while, we presumed there was stuff flying between the stars.

• 2:35Speaker 01

  That's right.

• 2:36Neil deGrasse Tyson?

  But nobody ever saw one, because occasionally you'd expect them to pay us a visit.

• 2:41Chuck Nice?

  Or at least pass through.

• 2:43Neil deGrasse Tyson?

  Pass through, that's what I mean. They'd just come in and go out, and we've been looking for centuries.

• 2:47Speaker 01

  Yeah.

• 2:48Neil deGrasse Tyson?

  And your main topic of study is something that doesn't exist yet?

• 2:54Speaker 01

  Oh, well, no, I was pretty lucky, because so when I was a third year graduate student, I was doing just pure fluid dynamics for astrophysics. And then as a third year graduate student, Amuamua was discovered.

• 3:07Neil deGrasse Tyson?

  So just to be clear, so a fluid to an astrophysicist is what?

• 3:11Speaker 01

  A gas.

• 3:12Neil deGrasse Tyson?

  A gas, exactly, okay. So liquids and gases are both fluids to a physicist?

• 3:18Speaker 01

  Right.

• 3:19Neil deGrasse Tyson?

  Right, okay. So then, why does Amuamua have anything to do with fluid dynamics?

• 3:25Speaker 01

  Well, it doesn't have too much to do with fluid dynamics, to be honest, but it was such an exciting opportunity that we just kind of dropped everything else we were, yes, we dropped everything else we were doing and started working on that. So I don't know how closely you were following back in 2017, but it was one of the most exciting times for astronomy, because basically this thing got discovered and it was also moving super fast.

• 3:47Neil deGrasse Tyson?

  Right.

• 3:47Speaker 01

  So it was only observable for a couple of weeks from ground-based telescopes, and then upwards of three or four weeks.

• 3:54Neil deGrasse Tyson?

  Would you expect it to be moving fast if it's coming in from interstellar space?

• 3:59Speaker 01

  Yes, you would expect it to be moving fast.

• 4:01Chuck Nice?

  And why would it be faster than anything else?

• 4:03Speaker 01

  So because the planets are all moving in the same direction around the sun. Amuamua comes in and it's coming from a totally different direction, and then It looks like it's moving really fast compared to our motion.

• 4:17Neil deGrasse Tyson?

  Because we're going in opposite directions to each other?

• 4:19Speaker 01

  Yeah.

• 4:20Neil deGrasse Tyson?

  Okay, got it, got it. So, uh, Mua Mua, we found this thing.

• 4:25Speaker 01

  Yes.

• 4:25Neil deGrasse Tyson?

  Called it a Mua Mua, which sounds Hawaiian.

• 4:27Chuck Nice?

  It does.

• 4:28Neil deGrasse Tyson?

  I think it's, was it discovered by a telescope in Hawaii?

• 4:31Speaker 01

  So it was picked up by Panstars, which is a telescope in Hawaii that is funded by the Department of Defense, and they're looking for near-Earth objects.

• 4:40Neil deGrasse Tyson?

  Okay.

• 4:40Speaker 01

  So small-kilometer-scale objects that, some of which, yes.

• 4:47Neil deGrasse Tyson?

  It'll knock you on your ass.

• 4:50Chuck Nice?

  Exactly.

• 4:51Speaker 01

  So some of those objects are potentially hazardous. So we, it's very important that we find them with ample time to do something if, uh...

• 4:59Chuck Nice?

  If they're gonna hit us?

• 5:00Speaker 01

  Exactly.

• 5:00Neil deGrasse Tyson?

  With ample time to kiss your ass goodbye. You need enough time to get that out of the way. So, it seems to me, from what you say, Panstars had no expectation of finding interstellar objects, but it has the ability to do so regardless. Is that a fair statement?

• 5:18Speaker 01

  Well, that, that is true, but I think they originally designed Panstars hoping to find interstellar objects. Because for the last couple of decades, I mean, we know the solar system has ejected a good amount of material in interstellar objects, so it's not much of a stretch to imagine that other planetary systems would also be ejecting material, and we would see them, and the only difference is you just see a small body, but it comes across the night sky and looks hyperbolic. But the fact that we hadn't seen any, we were trying to put limits on the number of them in the galaxy based on not seeing any. But the hope was that Panstars would find one.

• 5:54Neil deGrasse Tyson?

  Right, so if you don't see any for a certain amount of time, you can say, "There can't be more than this number," otherwise we would have seen it statistically.

• 6:03Speaker 01

  Yes.

• 6:03Neil deGrasse Tyson?

  Okay. Now, you said it was hyperbolic. Tell me what you mean there. Because some people are hyperbolic.

• 6:09Speaker 01

  A different sense of the word, hyperbolic.

• 6:11Chuck Nice?

  Yes. So it's the flavor-flave of comics, of comments.

• 6:16Chuck Nice?

  We knew, we knew it was hyperbolic because it was like, "Yeah, boy!"

• 6:21Speaker 01

  So it came into the solar system and left and it's never coming back because hyperbolic means that its orbit is not bound to the sun.

• 6:30Neil deGrasse Tyson?

  Got it. So everybody else has an orbit that is bound to the sun.

• 6:33Speaker 01

  That's right.

• 6:34Neil deGrasse Tyson?

  It could either be like a circle or an ellipse.

• 6:35Speaker 01

  Wow.

• 6:36Neil deGrasse Tyson?

  Right, okay.

• 6:37Chuck Nice?

  So these comets that we see every once in a while, like a Halley's, right? So that's bound to the sun. That's why we see them every once in a while because they're going around and coming back?

• 6:49Speaker 01

  That's exactly right.

• 6:50Neil deGrasse Tyson?

  Halley's comet is like 170, 76 years. So you've only seen that once.

• 6:53Chuck Nice?

  Why you gotta do that to my life?

• 6:56Neil deGrasse Tyson?

  Cause they ain't living to 152.

• 6:57Chuck Nice?

  Come on. Give a brother a break.

• 6:59Neil deGrasse Tyson?

  You will not be 152 years old.

• 7:03Chuck Nice?

  I know I have hypertension, but damn.

• 7:05Neil deGrasse Tyson?

  Just saying.

• 7:08Chuck Nice?

  Yeah.

• 7:09Neil deGrasse Tyson?

  So hyperbolic, so that would be the best evidence that it was not a member of the solar system because comets are coming in from out far away all the time.

• 7:16Speaker 01

  That's right.

• 7:17Neil deGrasse Tyson?

  So why isn't it just an asteroid? Why do you know it's a comet?

• 7:20Speaker 01

  So there is kind of a continuum between comets and asteroids?

• 7:24Neil deGrasse Tyson?

  Uh oh. So now we, okay. So now we get into word issues.

• 7:27Speaker 01

  That's right.

• 7:28Neil deGrasse Tyson?

  Word definitions. Uh oh. Yeah.

• 7:30Speaker 01

  So the things that formed at large distances from the sun, they have ice in them.

• 7:36Neil deGrasse Tyson?

  Which hasn't evaporated away.

• 7:37Speaker 01

  Exactly.

• 7:38Neil deGrasse Tyson?

  Over the years, eons. Yeah.

• 7:39Speaker 01

  Exactly. So when that, a comet gets close to the sun, the ice will heat up and sublimate, producing a dust tail. And that produces a bright, beautiful cometary tail.

• 7:49Neil deGrasse Tyson?

  You can't say evaporate.

• 7:50Chuck Nice?

  Yeah, can't say.

• 7:50Speaker 01

  Right. It's sublimates.

• 7:51Neil deGrasse Tyson?

  You gotta use the real word.

• 7:53Chuck Nice?

  Of course, yes.

• 7:54Neil deGrasse Tyson?

  To regular folk, it's just, it's evaporating.

• 7:56Chuck Nice?

  Yeah, exactly. But no.

• 7:57Neil deGrasse Tyson?

  Sublimates. Remind us what sublimate means.

• 8:00Speaker 01

  So that is when the ice in a, well, not just in a comet, but when ice transitions straight to the gas form.

• 8:07Neil deGrasse Tyson?

  Straight, straight away without nothing in between.

• 8:09Speaker 01

  That's right.

• 8:10Neil deGrasse Tyson?

  Yeah. So what they call dry ice.

• 8:11Chuck Nice?

  Oh, okay.

• 8:12Neil deGrasse Tyson?

  That just smokes away.

• 8:14Chuck Nice?

  That, right.

• 8:15Neil deGrasse Tyson?

  You've never seen liquid dry ice, have you?

• 8:16Chuck Nice?

  No, no you haven't.

• 8:17Neil deGrasse Tyson?

  Right.

• 8:17Chuck Nice?

  It goes right to the, "And now ladies and gentlemen, coming to the stage," it goes right, straight from the ice.

• 8:23Neil deGrasse Tyson?

  To the smoke.

• 8:24Chuck Nice?

  To the smoke.

• 8:26Neil deGrasse Tyson?

  Yeah, in fact, if you have an ice tray in your freezer.

• 8:29Chuck Nice?

  Okay.

• 8:30Neil deGrasse Tyson?

  You go away on a long vacation and come back, the ice cubes are littler.

• 8:33Chuck Nice?

  Yeah.

• 8:33Neil deGrasse Tyson?

  Have you ever checked this?

• 8:34Chuck Nice?

  I have seen that.

• 8:34Neil deGrasse Tyson?

  Yeah.

• 8:35Chuck Nice?

  Yeah, you see them, they shrink up inside the actual tray.

• 8:37Neil deGrasse Tyson?

  Yeah, they're actually sublimating.

• 8:39Chuck Nice?

  Cool.

• 8:39Neil deGrasse Tyson?

  Yeah, okay, so, so, so, keep going, I interrupted you. We're distinguishing between

• 8:44Speaker 01

  Comets and asteroids.

• 8:45Neil deGrasse Tyson?

  On the continuum of asteroids and comets, go.

• 8:46Speaker 01

  Right. We expected that the interstellar objects that get ejected from other planetary systems, that they most likely would have formed at large distances and then had a lot of ice in them. So we'd expect them to be comets.

• 9:00Neil deGrasse Tyson?

  Is that because if they form at a large distance, they're not strongly held by the gravity of their host star?

• 9:06Speaker 01

  Yeah.

• 9:06Neil deGrasse Tyson?

  So they can be knocked off?

• 9:09Speaker 01

  That's exactly right.

• 9:10Neil deGrasse Tyson?

  Okay.

• 9:10Speaker 01

  And if they form at far distances, then they haven't been close enough to their host stars for the ice.

• 9:16Neil deGrasse Tyson?

  Yeah, so you get a double

• 9:18Speaker 01

  That's right.

• 9:18Neil deGrasse Tyson?

  force going there.

• 9:19Chuck Nice?

  So may I ask, if, if they are forming at such large distances from their host star, what happens to get them to be kicked out so that they're now slingshotted out into, hey, I'm on, see you, I'm on my way?

• 9:34Speaker 01

  Yeah, no, that's a great question, so, and it's a good question because we also don't know the answer. So

• 9:40Neil deGrasse Tyson?

  Stop asking our guest questions he can't answer, Jack.

• 9:43Speaker 01

  But the most likely thing is you basically have something like a deep space maneuver for a spacecraft, where you slingshot off of a planet, but you have that with something as big as Jupiter.

• 9:54Neil deGrasse Tyson?

  I mean, their version of a Jupiter.

• 9:55Speaker 01

  Yeah, their version of a Jupiter, so something with Jupiter's mass at around five astronomical units, then if you get, if a small body gets close to that planet, it could get slung shot out.

• 10:07Chuck Nice?

  So Jupiter is like a proxy sun, or a Jupiter type? It acts like, like it would be the sun?

• 10:13Neil deGrasse Tyson?

  Well, it messes with the, oh, it, it messes with the orbits and things.

• 10:16Speaker 01

  Right, yeah, it's more, yeah, it's more like when you get close to Jupiter, you start feeling its gravitational influence much more than the sun, and then that will change your orbit.

• 10:24Chuck Nice?

  Gotcha, gotcha.

• 10:25Neil deGrasse Tyson?

  Yeah.

• 10:25Chuck Nice?

  Okay, now I get it, I get it, I get it.

• 10:27Neil deGrasse Tyson?

  Jupiter intervenes.

• 10:28Chuck Nice?

  Intervenes.

• 10:28Speaker 01

  That's right.

• 10:29Neil deGrasse Tyson?

  So, but also, presumably, given enough time, this sys, this other star system may get tugged on by other stars that happen to wander too close.

• 10:38Speaker 01

  Yes, that's exactly right.

• 10:39Neil deGrasse Tyson?

  Yeah.

• 10:39Speaker 01

  That also can happen.

• 10:40Neil deGrasse Tyson?

  Okay, so, again, why are you thinking this was a comet instead of an asteroid?

• 10:45Speaker 01

  So Amumuwa, in every way we expected, acted the exact opposite. So the biggest thing was it had no cometary tail whatsoever.

• 10:54Neil deGrasse Tyson?

  So then why call it a comet at all?

• 10:55Speaker 01

  Well, then it was initially called a comet because they've made a mistake actually at the Minor Planet Center. Then they changed it to say that it was an asteroid because it looked inactive, which means that it doesn't look like a comet because it doesn't look like it has a tail.

• 11:08Neil deGrasse Tyson?

  Doesn't reveal fluff.

• 11:10Speaker 01

  That's exactly right. But then we realized as we were trying to get follow-up observations with the Hubble Space Telescope and the Spitzer Space Telescope that the object had a non-gravitational acceleration.

• 11:22Neil deGrasse Tyson?

  So Spitzer is, specializes in infrared?

• 11:25Speaker 01

  Yes, that's exactly right.

• 11:27Neil deGrasse Tyson?

  So you want to, you want to combine different tools out of the toolkit of the observational astronomer to see it in as many ways as you can?

• 11:36Speaker 01

  Yeah. And Spitzer is really great, like looking in the infrared is really great for comet science for some of the same reasons you use it for things like exoplanets, but because you can see typical cometary gases like CO2 and CO that you wouldn't be able to see from the ground.

• 11:50Neil deGrasse Tyson?

  So Spitzer named for Lyman Spitzer?

• 11:51Speaker 01

  Oh, okay.

• 11:52Neil deGrasse Tyson?

  Former chair of the Astrophysics Group at Princeton University.

• 11:55Speaker 01

  Ah.

• 11:56Neil deGrasse Tyson?

  And I have one of his books on the show.

• 11:58Chuck Nice?

  I was gonna say, you sound like you know him.

• 12:02Neil deGrasse Tyson?

  So I keep interrupting you.

• 12:03Speaker 01

  No, it's okay.

• 12:03Neil deGrasse Tyson?

  Keep going, go.

• 12:04Speaker 01

  Essentially, it had this non-gravitational acceleration but no apparent dust coma. And then, an important point is that these non-gravitational accelerations, we see them on, so first of all, what that means is that the object, you look over time at its position in the sky, and then you figure out its orbit, and then you realize that its orbit could not be explained just from the sun's gravitational influence. So there must be an additional force acting on it. And we measure that.

• 12:32Neil deGrasse Tyson?

  That's what you mean by non-gravitational?

• 12:33Speaker 01

  That's what I mean by non-gravitational. So we measure that in comets all of the time. So there are many comets with non-grav, and I might even slip up and just call them non-gravs, but these non-gravs have been measured, and that's happening because as that ice sublimates, it produces like a rocket-type recoil effect.

• 12:48Chuck Nice?

  Oh, okay.

• 12:49Neil deGrasse Tyson?

  So every jet, little bitty jetty thing that comes off, it's a force operating on its trajectory.

• 12:54Speaker 01

  Yes, that's exactly right.

• 12:56Neil deGrasse Tyson?

  So that alone is not unusual or uncommon?

• 12:58Speaker 01

  That alone is not uncommon.

• 12:59Neil deGrasse Tyson?

  But it didn't have any fuzz?

• 13:01Speaker 01

  That's right, exactly.

• 13:02Neil deGrasse Tyson?

  And you want there to be fuzz if you're gonna be non-gravitational.

• 13:05Speaker 01

  That's right.

• 13:06Neil deGrasse Tyson?

  So then you're in a conundrum.

• 13:07Speaker 01

  Yes, and there is another kind of important point, which is that you will also see asteroids accelerating non-gravitationally. It's just that their non-gravitational accelerations, for example, they can be caused by solar pressure, radiation pressure, they're much, much weaker. So a Mu Mu is non-gravitational acceleration. The weird thing is not that it had one, it's that it had one with no dust coma, but it was much stronger than those that could be operating on an asteroid.

• 13:35Neil deGrasse Tyson?

  So, because I think asteroids, many of them are very dark, so that they would absorb sunlight.

• 13:40Speaker 01

  Yes.

• 13:40Neil deGrasse Tyson?

  And that if you were, you're absorbing momentum of photons. So it's like a solar sail at that point? Oh, yeah, if, well, the solar sail would reflect light.

• 13:48Speaker 01

  Just moving extremely slowly.

• 13:49Neil deGrasse Tyson?

  But in either case, the light pressure is acting on the system. Yeah, that's crazy. Okay, so it's a nice conundrum, and by the way, so I'm a big reader of the history of science. Why wouldn't you have a conundrum for an object that has never been detected before?

• 14:05Speaker 01

  Yes.

• 14:05Neil deGrasse Tyson?

  A class of object that we've never seen?

• 14:08Speaker 01

  Yes.

• 14:09Neil deGrasse Tyson?

  Why wouldn't it be filled with things that? That don't make sense. That don't make sense.

• 14:12Speaker 01

  Well, it basically made me think, like, I am really grateful for a Mu Mu, because I feel like a Mu Mu, if you look back for the last couple of decades, it was the most intensely studied small body over a very short period of time. So there were something like 700 and something observations over the span of a couple of weeks, just of this one object.

• 14:31Neil deGrasse Tyson?

  It's evidence of how unusual it was.

• 14:34Speaker 01

  Right, but because of that, and because we then had to point Spitzer and Hubble at it, we then had to get the trajectory really, really accurate, and then we noticed this non-gravitational acceleration. So it made me think, maybe there are just these other objects in the solar system that are doing the same thing, it's just we had never noticed them before, because how do you detect comets? You see their commentary tails.

• 14:53Neil deGrasse Tyson?

  Right.

• 14:54Speaker 01

  You don't see the non-gravitational accelerations, which are actually...

• 14:56Neil deGrasse Tyson?

  Dark comet.

• 14:57Speaker 01

  Yes.

• 14:58Neil deGrasse Tyson?

  Ah, I get it.

• 15:00Speaker 01

  There we go.

• 15:01Neil deGrasse Tyson?

  Okay.

• 15:12Speaker 03

  I'm Nicholas Costella and I'm a proud supporter of StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.

• 15:28Neil deGrasse Tyson?

  Is there a consensus? Cause we're now eight years into it, right? So you should, you should know something by now.

• 15:33Speaker 01

  So I would say that, well, I would like to say that me and Jenny Berger's recent theory about a Muamua is the consensus, but unfortunately there are a lot of theories.

• 15:43Neil deGrasse Tyson?

  Einstein had a theory. You had a hypothesis.

• 15:45Speaker 01

  We had a hypothesis.

• 15:46Neil deGrasse Tyson?

  So say that again.

• 15:49Speaker 03

  Neil gets very touchy about his theories and hypotheses. Okay.

• 15:52Speaker 01

  Fair enough. I respect.

• 15:54Neil deGrasse Tyson?

  You're in my office here at the Hayden Planetary Museum of Natural History. You're gonna say it right.

• 15:59Speaker 03

  Yeah, you're in very good company, by the way, of people who's like, no, you have a hypothesis.

• 16:05Neil deGrasse Tyson?

  Okay, go ahead.

• 16:06Speaker 01

  So Jenny Berger and I have this recent hypothesis.

• 16:08Neil deGrasse Tyson?

  This is a collaborator.

• 16:10Speaker 01

  A collaborator of mine who's a professor at Berkeley. Essentially, a Muamua was similar to a dark comet that it was, the acceleration was driven by the outgassing of volatile like ice-like material, but it just had very little dust coma. And that's why we didn't see the dust coma for whatever reason.

• 16:27Neil deGrasse Tyson?

  Okay, so that would explain it.

• 16:29Speaker 01

  Yes, that would explain it.

• 16:30Neil deGrasse Tyson?

  A little bit after the fact, it'd be better if you had predicted that such a thing would exist.

• 16:34Speaker 01

  Right.

• 16:35Neil deGrasse Tyson?

  But now you're just forced to sort of kludge an answer, which sounds plausible.

• 16:40Speaker 01

  Yeah.

• 16:40Neil deGrasse Tyson?

  But have others followed behind it?

• 16:42Speaker 01

  So there's a lot of argument about what the type of volatile that was driving it.

• 16:47Neil deGrasse Tyson?

  Explain to people what volatile is, because any normal person thinks if something volatile, it means it'll burst into flames.

• 16:52Speaker 03

  Explode.

• 16:53Neil deGrasse Tyson?

  So geologists have a whole separate usage of the term, so catch up on that.

• 16:58Speaker 01

  Yeah, it just is about what type of ice could be driving the acceleration. So.

• 17:03Neil deGrasse Tyson?

  Well, just a volatile thing.

• 17:04Speaker 01

  A volatile thing is something that has ice in it.

• 17:07Neil deGrasse Tyson?

  Oh, only that? I thought it just.

• 17:09Speaker 01

  When I say volatiles, I just mean ices, basically. Because when you put them in space, they will sublimate.

• 17:14Neil deGrasse Tyson?

  Okay, so I thought anything that can turn to gas is volatile. Is that not true?

• 17:19Speaker 01

  That is technically true.

• 17:20Neil deGrasse Tyson?

  Is water in space volatile?

• 17:22Speaker 01

  Yes, but so water in its ice phase is what I mean by volatiles.

• 17:26Neil deGrasse Tyson?

  Okay, and you wouldn't find a swimming pool of liquid water out there anyway. Got it, okay. So in practice.

• 17:31Chuck Nice?

  It all starts as ice.

• 17:32Neil deGrasse Tyson?

  It's ice, it's ice that can sublimate.

• 17:35Speaker 01

  Yes.

• 17:35Neil deGrasse Tyson?

  These are your volatiles. Ice of any kind. Not just water ice, but like ammonia ice, I guess. Maybe some more CO2 ice.

• 17:41Speaker 01

  CO2, CO.

• 17:43Chuck Nice?

  Water ice.

• 17:43Speaker 01

  Nitrogen.

• 17:44Neil deGrasse Tyson?

  Nitrogen ice.

• 17:45Speaker 01

  Yeah, so they have that on Pluto. So there is nitrogen ice on Pluto. So to back it up, essentially in the solar system comets, they, the primary driver of activity, the, the main thing you see is water ice. And then you also see CO2 and CO, which is carbon dioxide and carbon monoxide. So those are the typical ones. But with the Muamua spitzer, the reason they looked at that is you would identify CO2 and CO.

• 18:09Neil deGrasse Tyson?

  Because that, those have spectral signatures in the infrared. With spitzer especially capable of detecting it in ways that Hubble would not be able to.

• 18:16Speaker 01

  That's right. So another issue is that, without getting too much into the details, essentially water could not be providing the acceleration. Because there was not enough energy from the sun.

• 18:28Neil deGrasse Tyson?

  To sublimate the water.

• 18:29Speaker 01

  Yeah, that's right. Sublimate enough water to provide enough push to get the acceleration.

• 18:34Chuck Nice?

  Cool.

• 18:34Speaker 01

  But a much better accelerant is hydrogen. So our hypothesis, not theory.

• 18:42Chuck Nice?

  He thought about it too. He was like, I'm gonna say it because I'm here.

• 18:51Neil deGrasse Tyson?

  Okay.

• 18:52Speaker 01

  The hypothesis is that there was water, water ice in Muamua, but then as it travels through the interstellar medium, it's exposed to these very high energy particles called cosmic rays, and that will break down some water and trap hydrogen in there. And then as the ice heats up, as a Muamua comes through the solar system, it will just gently release this trapped hydrogen.

• 19:14Neil deGrasse Tyson?

  Which has a greater impulse.

• 19:16Speaker 01

  Yes.

• 19:16Neil deGrasse Tyson?

  To accelerate. The object than

• 19:18Speaker 01

  That's right.

• 19:19Neil deGrasse Tyson?

  Then just evaporating water would.

• 19:21Speaker 01

  That's right. So it's both the fact that hydrogen is a lot lighter than water, but also it takes much less energy to sublimate hydrogen than water.

• 19:29Neil deGrasse Tyson?

  Wow, okay. So, all right, but you said there's nearly a thousand papers on this object.

• 19:33Speaker 01

  That's right.

• 19:33Neil deGrasse Tyson?

  And you're saying, but you and your colleague have this hypothesis.

• 19:37Speaker 01

  Right.

• 19:38Neil deGrasse Tyson?

  Are you lone wolves out there?

• 19:40Speaker 01

  No, no, no. So essentially, it comes down to can you, can a hypothesis explain all of these mysterious properties? Another thing is you could have the acceleration driven by radiation pressure. It's just for that to work, it would have to be ultra-thin or ultra-low density. So, Amaya Moore Martin at Space Telescope has this idea that it was an ultra-low-density fractal aggregate, which basically means it's a very large snowflake.

• 20:07Neil deGrasse Tyson?

  So it's large, but very low density?

• 20:09Speaker 01

  That's right.

• 20:09Neil deGrasse Tyson?

  Right, so there's a lot of So you can push it?

• 20:12Speaker 01

  That's right.

• 20:12Neil deGrasse Tyson?

  And push it? Yeah.

• 20:13Speaker 01

  Yeah, that's right. So the solar photons which very subtly push asteroids could suddenly push this thing.

• 20:19Neil deGrasse Tyson?

  It's a lot, a lot, right. So because it's not, because it's not, doesn't have a orbital companion, there's no way you can know the mass of this thing. You have to make assumptions about it.

• 20:28Speaker 01

  So, yes, that's totally right. Yes. That is a detail that I intentionally swept under the rug, but yes.

• 20:33Neil deGrasse Tyson?

  No, this rug here is clean.

• 20:37Neil deGrasse Tyson?

  All right, so is that, is that the betting person's explanation? The way to test this was, is there another one of these objects?

• 20:44Speaker 01

  Right.

• 20:44Neil deGrasse Tyson?

  And I seem to remember there was.

• 20:46Speaker 01

  Yeah, there, so there was another one, another interstellar object, but this, this was 2i Borisov. So that was detected in 2019. And that was very clearly a comet. So that had a big dust tail.

• 20:58Neil deGrasse Tyson?

  Okay.

• 20:59Speaker 01

  But the exciting thing is that the Vera Rubin Observatory in LSST, which I'll probably refer to it as, is coming online just next year.

• 21:07Neil deGrasse Tyson?

  Vera Rubin, another astrophysicist,

• 21:09Speaker 01

  Mm-hmm.

• 21:10Neil deGrasse Tyson?

  died a few years back. She discovered dark matter in galaxies.

• 21:14Speaker 01

  Yeah.

• 21:14Neil deGrasse Tyson?

  Back in the 70s. So we named a whole observatory after her. And this is an observatory Unlike any other in what important way?

• 21:22Speaker 01

  Right, so it is coming online right now at the beginning of next year.

• 21:27Neil deGrasse Tyson?

  That would be 2025.

• 21:28Speaker 01

  2025, right.

• 21:29Chuck Nice?

  What's the observatory gonna do?

• 21:31Speaker 01

  So it's going to observe the entire southern hemisphere almost every night. So it'll be like panstars now, which is in the northern hemisphere, but it'll look almost every night to see anything moving in the sky, but it goes almost five orders of magnitude more sensitive than panstars.

• 21:49Neil deGrasse Tyson?

  So five powers of 10.

• 21:50Speaker 01

  Yeah, so we'll be finding many more moving objects in the solar system. And we should be finding many more interstellar objects.

• 21:57Neil deGrasse Tyson?

  I think people don't appreciate that if you just go to a telescope and get images and bring them home, you don't know if anything is moving on that image.

• 22:04Chuck Nice?

  Right.

• 22:05Neil deGrasse Tyson?

  You know?

• 22:05Chuck Nice?

  You gotta get it over a period of time.

• 22:07Neil deGrasse Tyson?

  Basically snapshots.

• 22:08Chuck Nice?

  Right.

• 22:09Neil deGrasse Tyson?

  You need exactly those kind of data.

• 22:11Speaker 01

  Right.

• 22:12Neil deGrasse Tyson?

  To see if something goes bump in the night.

• 22:14Speaker 01

  That's right.

• 22:14Neil deGrasse Tyson?

  So the Rubin telescope should blow open the whole field.

• 22:17Speaker 01

  Yes, absolutely.

• 22:18Neil deGrasse Tyson?

  Gotcha.

• 22:19Chuck Nice?

  Wow, that's pretty cool.

• 22:20Speaker 01

  So it's pretty exciting.

• 22:21Chuck Nice?

  Yeah, it is.

• 22:22Speaker 01

  Coming around.

• 22:23Chuck Nice?

  Okay.

• 22:23Neil deGrasse Tyson?

  Are there any other explanations for this?

• 22:26Chuck Nice?

  Aliens.

• 22:28Chuck Nice?

  Come on, guys.

• 22:30Chuck Nice?

  Why are we trying to act like we're not gonna talk about the elephant in the room?

• 22:32Neil deGrasse Tyson?

  That's the easiest explanation.

• 22:34Chuck Nice?

  Which has gotta be, right?

• 22:35Neil deGrasse Tyson?

  Like, ever. Or ancient astronauts or something.

• 22:38Chuck Nice?

  Right, yeah.

• 22:39Neil deGrasse Tyson?

  Whatever.

• 22:59Neil deGrasse Tyson?

  So I feel a little jealous because if Amuamua got kicked out of some other solar system, star system, and we're a star system, red-blooded star system, we ought to have some Amuamua's of our own.

• 23:10Chuck Nice?

  I've been kicked out of better star systems than this.

• 23:15Neil deGrasse Tyson?

  Yeah.

• 23:16Speaker 01

  Essentially, in the last couple of years, since Amuamua, we've discovered these seven objects within the solar system, which are near-Earth objects, actually, which is what Amuamua was initially.

• 23:28Chuck Nice?

  They thought it was a NEO?

• 23:28Speaker 01

  They thought it was a NEO, that's right. You're picking up on the abbreviation also. So they thought it was a near-Earth object. So these are near-Earth objects which are bound to the solar system, unlike Amuamua.

• 23:39Neil deGrasse Tyson?

  So they have elliptical orbits, not hyperbolic orbits.

• 23:42Speaker 01

  That's correct. We discovered significant non-gravitational accelerations on all seven of these objects, which are also inactive, which means that they don't have comet-like tails.

• 23:53Neil deGrasse Tyson?

  Oh, okay. So therefore you can't credit the normal comet non-gravitational outgassing.

• 23:58Speaker 01

  That's right. But the accelerations we found on these dark comets, I mean, dark comets is just a name I made up. I hope, I think people like it, but. How could you not? So these objects, essentially their non-gravitational accelerations are too strong to be explained by the, similar to Amuamua, the accelerations you see on other asteroids. So we have the hypothesis. That's awesome. That's awesome. We have the hypothesis that these objects are like comets and that they have icy material in them, even though they are close to the sun and have been there for a long

• 24:41Speaker 01

  time. But they're, for whatever reason, not producing a large dust coma.

• 24:45Neil deGrasse Tyson?

  Could you have a layer of something other than ice that encases ice within it?

• 24:51Speaker 01

  Oh, yeah.

• 24:52Neil deGrasse Tyson?

  So that prevents a full-up exposure to the sun's energy?

• 24:55Speaker 01

  Yeah, absolutely. And so that was actually an idea, that was an idea that I wrote a paper on that could have, for Amuamua, like the interstellar medium, the cosmic rays basically could have produced an insulating shell around it that could have prevented outgassing. But that was before we knew that the non-gravitational acceleration was there.

• 25:12Neil deGrasse Tyson?

  Right. So just to repeat what I think you said, you have an object that's icy, has volatile ices, but cosmic rays basically turn the outermost layer of that ice into a, an insulating crust.

• 25:25Speaker 01

  Yeah, that's right.

• 25:27Neil deGrasse Tyson?

  Because the water molecule gets broken.

• 25:29Speaker 01

  Yes.

• 25:29Neil deGrasse Tyson?

  And now it's no longer frozen water. It's just hydrogen and oxygen. What happens to the oxygen?

• 25:34Speaker 01

  Essentially, well, it depends where it is. Like, like in the idea that Jenny Berger and I had, hydrogen and oxygen would be entrapped within the ice.

• 25:43Neil deGrasse Tyson?

  But separately from each other?

• 25:44Speaker 01

  Yes, separately from each other. But this is more like you can create a kind of tar-like material on the. It's kind of like asphalt almost.

• 25:52Chuck Nice?

  Hmm.

• 25:52Speaker 01

  That, but that's not what happened.

• 25:54Chuck Nice?

  So then what?

• 25:55Speaker 01

  Yes. Oh.

• 25:55Neil deGrasse Tyson?

  So where'd you get any carbon?

• 25:57Speaker 01

  Oh, it would have been there originally.

• 25:58Neil deGrasse Tyson?

  Okay, well, and you get that in the CO2 or the CO.

• 26:01Speaker 01

  Yeah.

• 26:01Neil deGrasse Tyson?

  Carbon is not rare in the universe. This is cool, so.

• 26:04Chuck Nice?

  But then how's it re-release then? Because you insulated it, but then.

• 26:08Speaker 01

  The one thing is, I was gonna say though, is that that certainly is not what happened to Amumu. Because I wrote that, it took like, it was discovered in October and then it was May when the acceleration was published. So I wrote a paper before the acceleration was published that explained it like that. And that's, I was certainly wrong about that. It's just that, what I was saying was that, uh.

• 26:26Neil deGrasse Tyson?

  How many branches of life do you still have to say I was wrong?

• 26:30Chuck Nice?

  Yeah, well, listen, that's what, that's what makes science so great. It's like, we're right today, we're not tomorrow, we're right tomorrow about what we weren't today.

• 26:38Speaker 01

  Right.

• 26:39Neil deGrasse Tyson?

  What'd you just say?

• 26:42Neil deGrasse Tyson?

  Sounded good.

• 26:42Chuck Nice?

  Yeah.

• 26:44Neil deGrasse Tyson?

  No, but just to be clear, we don't always say we're wrong about things that have been objectively shown to be true.

• 26:49Chuck Nice?

  Right.

• 26:49Neil deGrasse Tyson?

  When I say, oh, E equals actually, actually equals mc cubed. We didn't, who, who knew?

• 26:54Chuck Nice?

  Right, no.

• 26:55Neil deGrasse Tyson?

  Equals mc squared, we're good there.

• 26:56Chuck Nice?

  Right.

• 26:56Neil deGrasse Tyson?

  And so if you're in mid hypothesis and it's being tested.

• 27:00Chuck Nice?

  Right.

• 27:01Neil deGrasse Tyson?

  That can come and go. And if you're first out of the box with an idea.

• 27:04Chuck Nice?

  Right.

• 27:04Neil deGrasse Tyson?

  That's highly susceptible to later data that shows up.

• 27:08Chuck Nice?

  But nothing better than you yourself.

• 27:11Neil deGrasse Tyson?

  Correct.

• 27:11Chuck Nice?

  Making that adjustment or correction.

• 27:14Neil deGrasse Tyson?

  That's right.

• 27:15Chuck Nice?

  Than somebody else coming along and going, yeah, guess what, man? You, you're a dumbass. This is the way it works.

• 27:22Neil deGrasse Tyson?

  An official science term.

• 27:23Chuck Nice?

  Yeah, that's super cool, man.

• 27:24Speaker 01

  Well, I guess, one thing is that these non-gravitational accelerations, like you were asking, why hadn't we seen them before in the solar system? So they're very difficult to detect. And so with the dark comets, it's been, most of them have been known about, there's one that I've been known about for more than 20 years. It's just, people have been monitoring it for 20 plus years, trying to get the, trying to measure the position. And we finally noticed. So Davide Farnokia at NASA, JPL, basically has to figure out the trajectories of all the bodies in the solar system and.

• 27:57Speaker 01

  Included in the fits for those non-gravitational accelerations. So there's kind of people all over the world who are monitoring objects that we know of and seeing if any of them could be potentially hazardous.

• 28:08Neil deGrasse Tyson?

  You use the term "the fit" for it. What you mean, I think, is if it's pure gravitational, there's a formula where you can forever predict the future trajectory. But if you're not fitting the future trajectory, you have to fit it some other way mathematically.

• 28:22Speaker 01

  Right.

• 28:22Neil deGrasse Tyson?

  And so you add these other terms.

• 28:23Speaker 01

  That's right.

• 28:24Neil deGrasse Tyson?

  That you think you understand.

• 28:25Speaker 01

  Yeah, and you also, I mean, you does it numerically, like numerically, just with a supercomputer, but you basically try all different types of accelerations.

• 28:32Neil deGrasse Tyson?

  Numerically means you can't do it analytically.

• 28:34Speaker 01

  Right.

• 28:34Neil deGrasse Tyson?

  Every step has to have a computation.

• 28:36Speaker 01

  Yeah.

• 28:36Neil deGrasse Tyson?

  That gives you a position in the trajectory.

• 28:39Speaker 01

  That's hard.

• 28:39Neil deGrasse Tyson?

  Whereas if it's analytic, you can just run the formula and then it'll get you the whole way. It's both effective, but one of them admits that we don't fully know the physics of what's going on, so we have to fit the model.

• 28:52Speaker 01

  Yeah.

• 28:53Neil deGrasse Tyson?

  Fit a model to it.

• 28:53Speaker 01

  Yeah.

• 28:54Neil deGrasse Tyson?

  So with the hydrogen and oxygen and comets and all of this, does this affect anybody's sense of where the water on Earth came from?

• 29:03Speaker 01

  Right. Yeah, so this is also kind of based on this student who's been working with me, who's just starting, just started this last year.

• 29:11Neil deGrasse Tyson?

  You just got out of graduate school. And you've got students already? Good for you, man, I love it. Man!

• 29:15Speaker 01

  So that's Aster Taylor, who had a paper published that discussed the possibility that the water, that dark comets could have brought water to the Earth.

• 29:23Neil deGrasse Tyson?

  More so than other comets?

• 29:25Speaker 01

  Well, there's, so people used to think that comets delivered water to the Earth, and we still don't know where the Earth's oceans came from. And part of the reason that we're now not sure if comets delivered the water is because we have spacecraft measurements of water in comets, like the Rosetta mission, went to 67P, and some of the isotopes, which is some of the things about the water in that comet did not match that that we've measured in the Earth's oceans.

• 29:54Neil deGrasse Tyson?

  This would be deuterium.

• 29:55Speaker 01

  Yes, yes, so that's one of them. So the deuterium to hydrogen ratio.

• 29:59Neil deGrasse Tyson?

  Yeah, so hydrogen is just one proton in the nucleus? And the protons define what we label the element to be. So now you throw in a neutron.

• 30:07Chuck Nice?

  Okay.

• 30:08Neil deGrasse Tyson?

  It's still hydrogen, but now it's like a little heavier.

• 30:11Chuck Nice?

  Yeah, so you can't just, it's gotta be hydrogen, something else.

• 30:13Neil deGrasse Tyson?

  Something, you gotta be, you gotta need.

• 30:15Chuck Nice?

  You need something with the name.

• 30:16Neil deGrasse Tyson?

  Right, and so we call it deuterium.

• 30:18Chuck Nice?

  Right.

• 30:18Neil deGrasse Tyson?

  How stable is deuterium?

• 30:20Speaker 01

  Well, it's not that it's stable, it's just the important thing is that the amount of deuterium compared to hydrogen isn't going to change from processing. And it depends very critically at the temperature of formation.

• 30:31Neil deGrasse Tyson?

  It won't change chemically.

• 30:32Speaker 01

  Right.

• 30:32Neil deGrasse Tyson?

  So if the comet doesn't match that in the oceans, you can't credit the comet for delivering the weight.

• 30:37Speaker 01

  That's correct. So, we don't know for sure, and Aster was very careful to say this in the press releases and news articles about their paper, but we can't say for sure that dark comets could have contributed, contributed water to the earth. But they are a new, entirely new population of small bodies that are in the, a new source, potential source. They're in the vicinity of the earth and they potentially have volatiles. So, we would need follow-up observations to figure out if they match up. But, the Hayabusa 2 mission, the JAXA Space Agency mission.

• 31:10Neil deGrasse Tyson?

  JAXA, Japanese Exploration Agency?

• 31:13Speaker 01

  Yeah, it's basically Japanese NASA.

• 31:15Chuck Nice?

  NASA.

• 31:16Speaker 01

  But their Hayabusa 2 mission.

• 31:19Neil deGrasse Tyson?

  What's JAXA?

• 31:19Speaker 01

  It just.

• 31:20Neil deGrasse Tyson?

  Not NASA, but JAXA?

• 31:21Chuck Nice?

  I'm sorry, that just sounds very racist.

• 31:25Neil deGrasse Tyson?

  NASA came first, Drew.

• 31:26Chuck Nice?

  Yeah, this is true.

• 31:27Neil deGrasse Tyson?

  It's America.

• 31:28Chuck Nice?

  Okay, okay. Listen, I don't have a problem with it.

• 31:30Speaker 01

  So, their Hayabusa 2 mission, in the extended mission, it just so happens is going to a dark comet.

• 31:37Chuck Nice?

  Cool.

• 31:37Speaker 01

  So, in 2031, we're gonna have.

• 31:39Neil deGrasse Tyson?

  That'll blow it open.

• 31:40Speaker 01

  It might, well, it's at least going to rendezvous with it. But we'll have enough sensitivity to measure things like outgassing or dust if it's there. So, at the very least, the worst-case scenario, we're gonna have an answer to all this in 2031.

• 31:53Neil deGrasse Tyson?

  Now, literally, comets are dark, even when you, they don't satisfy your definition.

• 31:59Speaker 01

  Right.

• 31:59Neil deGrasse Tyson?

  Right? We think of them as these white things moving through space, but their material is very dirty. On a level, how reflective is a comet?

• 32:06Speaker 01

  Well, it's difficult to say because you don't always see, most of the time you don't even detect the nucleus or the rocky part of the comet, you just see the tail. But asteroids, for example, like asteroids typically have, albedo is the word we use in science, but that's how reflective they are. So albedo is between something like 0.04 to 0.1, which is like 10-ish percent.

• 32:29Neil deGrasse Tyson?

  That's black.

• 32:30Speaker 01

  Yes.

• 32:31Neil deGrasse Tyson?

  That's black, okay. Yeah, albedo is between 0.1. If it's 1, it's like a mirror.

• 32:36Speaker 01

  Right.

• 32:36Neil deGrasse Tyson?

  If I remember, the moon is about 7% albedo.

• 32:40Speaker 01

  Okay.

• 32:40Neil deGrasse Tyson?

  And what is Pluto?

• 32:41Speaker 01

  So there are parts of Pluto, like there's a glacier of nitrogen, or nitrogen ice, actually, and that has an albedo upwards of like 90%.

• 32:50Neil deGrasse Tyson?

  Oh.

• 32:51Speaker 01

  So it's very reflective.

• 32:52Neil deGrasse Tyson?

  So it'd be a bright spot?

• 32:54Chuck Nice?

  Oh, you know, I read an article once that was talking about another reason why Pluto isn't a planet is because it reflects so much that it makes it look much bigger than it actually is.

• 33:06Neil deGrasse Tyson?

  Well, initially, I think that would have thrown off our measurements.

• 33:08Chuck Nice?

  Right.

• 33:09Neil deGrasse Tyson?

  But now we got up and close in person.

• 33:11Chuck Nice?

  Yeah, well, now, yeah, we've been there now.

• 33:12Neil deGrasse Tyson?

  Been there.

• 33:12Chuck Nice?

  We've been there now, so, yeah.

• 33:13Neil deGrasse Tyson?

  Been there, done that.

• 33:14Chuck Nice?

  Yeah.

• 33:14Neil deGrasse Tyson?

  So what's in the future of what you're up to?

• 33:16Speaker 01

  So the Rubin Observatory is the most exciting thing, but it should be finding, you know, upwards of tens per year interstellar objects.

• 33:25Neil deGrasse Tyson?

  Yeah, but this will be serendipitous. You can't say, "Go look at this object," or "Look here and discover an object." You're waiting for the data to come to you.

• 33:33Chuck Nice?

  Or to you.

• 33:34Speaker 01

  But also, Rubin should better characterize the orbits of all of the known small bodies in the solar system and find a bunch of much smaller ones. So, given that we have kind of just hit the tip of the iceberg in terms of finding these dark comets, I would bet that we're gonna find many, many more dark comets in subtle non-gravitational accelerations. So that could kind of revolutionize how we think of even comets and asteroids.

• 33:58Neil deGrasse Tyson?

  Oh, cool.

• 33:59Chuck Nice?

  Wow, look at you.

• 34:00Neil deGrasse Tyson?

  Cool. What's especially delightful to learn is that you are entering a field right when an important telescope that feeds that field will be coming online.

• 34:10Chuck Nice?

  Yes. And, yeah, you're gonna have so much data. Ooh.

• 34:14Neil deGrasse Tyson?

  Oh, yeah, in fact, tell them how much data is coming off of the Rubin telescope.

• 34:18Speaker 01

  Yeah, it's a huge amount, it's like...

• 34:19Neil deGrasse Tyson?

  Can't you be quantitative, please?

• 34:25Neil deGrasse Tyson?

  Tell Chuck how much, huge.

• 34:28Speaker 01

  I just don't want to say it wrong.

• 34:30Neil deGrasse Tyson?

  Oh.

• 34:32Neil deGrasse Tyson?

  Yes, not only knowing what you don't know, it's knowing if you don't think you know something. Right. So, last I checked, it was 20 terabytes of data a day. That's crazy. A day. That's a lot. And. You're right, though. It's huge.

• 34:46Speaker 01

  Yeah.

• 34:49Speaker 01

  Yeah, I mean, a big worry is the interstellar objects. I mean, Mu Mu was actually moving pretty slow. So if they're moving much faster, we might not even link them. So we have to figure out computer algorithms so that in that data, we could find fast-moving interstellar objects and potentially dark comets.

• 35:04Neil deGrasse Tyson?

  Because they've gone too far from one image to the next.

• 35:06Speaker 01

  Yes, exactly.

• 35:07Neil deGrasse Tyson?

  So that you, our biases prevent us from connecting the dots.

• 35:11Speaker 01

  Literally, your computational algorithm to connect them doesn't find it. And another thing is, you asked about.

• 35:17Neil deGrasse Tyson?

  You can't discover something, your algorithm doesn't know. Doesn't even know to look for. To look for.

• 35:20Speaker 01

  And then these dark comets, I mean, Mu Mu revealed that it had a non-gravitational acceleration, but we weren't looking for strong accelerations on things that had no cometary tails. So if something has a way stronger non-gravitational acceleration than even a Mu Mu, we would never link it up. So we have to basically make, and an exciting thing, right, with these interstellar objects, they come and leave and they're never coming back. So to follow them up, you have to find them in real time. So it's actually, there's a huge amount of effort right now that we're working on trying to make sure that we do find anything exciting so that we can get the follow-up.

• 35:49Neil deGrasse Tyson?

  That makes sense, because if you miss it, you missed it.

• 35:51Speaker 01

  Yes, exactly.

• 35:52Neil deGrasse Tyson?

  Period. It's gone. Well, I like the idea of an entire new class of object in the solar system that had eluded our algorithms and our telescopes. That's because they're aliens.

• 36:07Neil deGrasse Tyson?

  So, Darrell, this has been delightful and enlightening, and thanks for catching me up.

• 36:13Speaker 01

  Yeah, thanks for having me.

• 36:14Neil deGrasse Tyson?

  Super cool stuff.

• 36:15Speaker 01

  Thank you.

• 36:16Neil deGrasse Tyson?

  Let me see if I can wrap this up. All right. In a bow. What intrigues me most about science in general, especially in my field, is we recognize, we admit, we confess that all we know of the universe is that which our methods, tools, tactics, and telescopes reveal to us. But at no time should we ever think, this is all there is. We once thought that, when all we had was our five senses, no one could imagine that anything would, could, or should exist outside of your five senses. Until the microscope, the telescope, both invented around the same time, broadened our sense and understanding of what actually exists in the universe.

• 37:01Neil deGrasse Tyson?

  That continues to this day. And every new bit of technology, every creative thought associated with those new technologies brings new objects, new phenomena into the portfolio of what makes this universe. And all of that contributes to the majesty of not only what the universe is, but what the universe will become to us as we continue to explore. And that is a cosmic perspective. Daryl, be good, man. Thank you. And we look forward to many fruitful discoveries. When you get some good data from Ruben, you come back. Yes, we'll do. All right.

• 37:46Neil deGrasse Tyson?

  Neil deGrasse Tyson, your personal astrophysicist. Keep looking up.