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How big can a comet get? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Katie, how do you like your gelato? Definitely with
0:12
Speaker 1: two scoops of basically any flavor. So it's all about
0:16
Speaker 1: quantity for you, that right, It's all about gelato. What's
0:19
Speaker 1: to complain about? All right? So is that also true
0:23
Speaker 1: for things out in space? Bigger is always better? I mean,
0:27
Speaker 1: the sun is gigantic, and I only have good things
0:31
Speaker 1: to say about that. So you know, all right, you
0:33
Speaker 1: should leave a five star review for our star? What
0:36
Speaker 1: about things like comets? Is bigger always better there? I mean,
0:40
Speaker 1: especially if they're made out of ice cream? So a
0:43
Speaker 1: big old comet streaking above our sky leaving a trail
0:47
Speaker 1: of sprinkles? Who doesn't want that? Well? What if it's
0:50
Speaker 1: sprinkling its way towards the earth like impact style? Well
0:54
Speaker 1: then I can order a triple gelato with no consequences. Hi.
1:13
Speaker 1: I'm Daniel. I'm a particle physicist and a professor at
1:16
Speaker 1: U C Irvine, and I am Katie, and I'm the
1:19
Speaker 1: host of the podcast Creature Feature. And I enjoy ice
1:24
Speaker 1: cream as much as I enjoy physics, which is a
1:27
Speaker 1: lot but not too much moderation in all things? Is
1:31
Speaker 1: that the vibe I'm getting? That's probably right? In both cases,
1:34
Speaker 1: if I have too much physics at once, I also
1:37
Speaker 1: get a brain freeze. Or did you mean like after
1:40
Speaker 1: a nice large meal you need a little bit of
1:42
Speaker 1: physics to sort of like balance out the palette. I mean,
1:44
Speaker 1: I think that's what digestion is, right, Absolutely well, Welcome
1:50
Speaker 1: to the podcast Daniel and Jorge explain the universe in
1:54
Speaker 1: which we try to digest the entire universe. We serve
1:58
Speaker 1: it up on a platter d you and give it
2:00
Speaker 1: to you in tiny little spoonfuls, hoping that helps you
2:03
Speaker 1: understand the mysteries of black holes, the incredible froth and
2:07
Speaker 1: quantum nature of reality, the mysteries, the puzzles, the insides,
2:11
Speaker 1: all of it. We sprinkle delicious treats on top and
2:13
Speaker 1: serve it up to you. It's the Moves Bouge of
2:16
Speaker 1: particle physics. My typical co host and friend, Jorge Champ
2:21
Speaker 1: can't be here today, so as usual we are joined
2:23
Speaker 1: by the wonderful Katie. Katie, thank you very much for
2:26
Speaker 1: joining us again today. Yeah, happy to be here again.
2:28
Speaker 1: Want to point out Jorge and I have never been
2:30
Speaker 1: seen together in the same room. Raises some questions, doesn't it?
2:34
Speaker 1: Does that mean that Jorge transforms into you or you
2:37
Speaker 1: transform into Jorge. At this point, who can say who
2:40
Speaker 1: is who Isn't that the lesson of jack Bile and
2:43
Speaker 1: Hide exactly the quantum mechanical interpretation of modern literature. It's
2:46
Speaker 1: really the jackal Hide wave function, that's right, got to
2:49
Speaker 1: collapse the wave form. Well, we are happy to talk
2:52
Speaker 1: physics with either Katie or Jorge, so thanks for joining us.
2:55
Speaker 1: And while we nibble on our gelato, we ponder the
2:58
Speaker 1: mysteries of the universe, but we also ponder the mysteries
3:01
Speaker 1: of our own neighborhood. You might think that astronomers have
3:05
Speaker 1: our backyard the Solar system, mostly figured out, and that
3:08
Speaker 1: the open questions in physics revolve around things very very
3:12
Speaker 1: far away and far in the future and far back
3:14
Speaker 1: in time. But you might be surprised to learn that
3:18
Speaker 1: our own neighborhood remains something of a mystery to us. Now,
3:22
Speaker 1: that doesn't seem right, because my understanding as we've already
3:26
Speaker 1: got real estate on Mars and have every crevice, every
3:30
Speaker 1: crater of the Moon mapped out, So how can there
3:33
Speaker 1: be any mysteries left here in our solar system? Well,
3:36
Speaker 1: it's probably true that some entrepreneur has planned the first
3:38
Speaker 1: gelato stand on Mars that's pretty close to Earth. And
3:42
Speaker 1: you know, the Solar System is actually really really vast.
3:46
Speaker 1: The Earth is tucked in really tightly, very close to
3:49
Speaker 1: the Sun, but outpassed Jupiter and outpassed the icy planets.
3:53
Speaker 1: There's a lot of mysterious stuff going on. What's the
3:56
Speaker 1: furthest we've ever sent any of our instruments out into space.
4:01
Speaker 1: We haven't gotten past our own Solar System. We have
4:03
Speaker 1: sent some probs really deep into space, just like launch
4:07
Speaker 1: them out there and see how long they last. And
4:09
Speaker 1: the one that's the furthest out the object the humans
4:12
Speaker 1: have built that has gone the deepest into space is
4:15
Speaker 1: Voyager one. But even Voyager one hasn't officially left the
4:19
Speaker 1: Solar System yet. In around three hundred years, it might
4:22
Speaker 1: reach the outskirts of the Solar System, but unfortunately it's
4:26
Speaker 1: power runs out in five so by the time it
4:29
Speaker 1: gets there, it'll just be a dead lump. Well so
4:32
Speaker 1: we so, you know, you'll be fifty gelato by that point. Anyway,
4:39
Speaker 1: I can only hope. So there could be some space
4:42
Speaker 1: gopers in our space backyard and we wouldn't even know it.
4:45
Speaker 1: That's right. There are mysteries right here in our own backyard.
4:48
Speaker 1: There are things we do not understand. One way to
4:51
Speaker 1: explore the mist to send probes deep into the outskirts
4:54
Speaker 1: of the Solar System. But that's pretty slow. You know,
4:56
Speaker 1: it takes years for things to get out there because
4:59
Speaker 1: it's so day far away. You know, it takes months
5:02
Speaker 1: to get to Venus or Mars, but to get out
5:03
Speaker 1: to Pluto can take a decade. To get further out
5:06
Speaker 1: deep into the farthest reaches of the Solar System to
5:09
Speaker 1: explore its fringes takes even longer. But there's another way
5:13
Speaker 1: to study our deep, mysterious backyard, and that's to wait
5:16
Speaker 1: for it to come to us. Because sometimes things out
5:19
Speaker 1: from the outskirts do fall into the Solar System, and
5:23
Speaker 1: these things are called comets. They accelerate to incredible speeds
5:26
Speaker 1: as they whip around the Sun and then go back
5:28
Speaker 1: to where they came from. So how do comets find us?
5:32
Speaker 1: Did they see some kind of flyer way out in
5:35
Speaker 1: space It at the Earth sale about two point five
5:39
Speaker 1: light years away? Is it just random chance? Are they
5:42
Speaker 1: drawn into our Solar system? They hang out there in
5:45
Speaker 1: the deep reaches of the Solar System, and we're not
5:47
Speaker 1: exactly sure what sometimes triggers them to fall in. It
5:51
Speaker 1: might be the passing of a nearby star, or the
5:53
Speaker 1: gravitational tug of the Milky Way, or something else. Entirely,
5:57
Speaker 1: we don't even really understand what's going on out there
6:00
Speaker 1: and what is out there waiting to maybe fall into
6:04
Speaker 1: the Solar System. For those of you who have seen
6:06
Speaker 1: don't look up and worry about things hitting the Earth.
6:09
Speaker 1: You don't have to worry too much about things like asteroids,
6:12
Speaker 1: those rocks that are orbiting the inner Solar system. But
6:15
Speaker 1: comets are much more dangerous because they can be hard
6:18
Speaker 1: to predict, and they're moving much more quickly when they
6:20
Speaker 1: do enter the Solar System. I watched Don't Look Up,
6:23
Speaker 1: and I find it interesting because I think there is
6:26
Speaker 1: a big divide in terms of how realistic people find
6:31
Speaker 1: it in Those who are either climate scientists or even
6:34
Speaker 1: in any related science find it very realistic, whereas other
6:39
Speaker 1: people think, oh, this this is just two on the nose,
6:41
Speaker 1: it's too outrageous. You mean, like the social response to
6:45
Speaker 1: the scientific warning, or you mean the science itself, the
6:47
Speaker 1: social response to the scientific warning that's in the movie. Yeah,
6:51
Speaker 1: that was pretty sobering. Actually, I think that was mostly
6:53
Speaker 1: the point of the movie. The actual science a bit
6:55
Speaker 1: where they're like at the white board figuring out the
6:58
Speaker 1: trajectory of the comment. That was like the first two
7:00
Speaker 1: minutes of the movie. After that, there was a great
7:02
Speaker 1: much science, But that part was pretty accurate. You know though,
7:05
Speaker 1: I heard that they had to find somebody to play
7:08
Speaker 1: a math double for Leonardo DiCaprio. When they zoom in
7:11
Speaker 1: on the whiteboard, that's not actually his hand doing those calculations,
7:15
Speaker 1: which means there's a whole other career. I didn't even
7:17
Speaker 1: realize I was missing out on, you know, Hollywood math double.
7:21
Speaker 1: Who do you think you would be in terms of
7:23
Speaker 1: Hollywood's math double. I'd like to be Jeff Goldblum's math double.
7:28
Speaker 1: I want to do his math. Jeff, if you're listening,
7:30
Speaker 1: please hooking me up. I don't want you to hurt
7:33
Speaker 1: yourself doing maths, so please let me take the fall
7:35
Speaker 1: for you. But speaking of taking the falls, some of
7:39
Speaker 1: these comets that enter the Solar System are pretty small.
7:42
Speaker 1: There's just a few kilometers wide. But there's some been
7:44
Speaker 1: some recent discoveries that are stretching people's brains about how
7:48
Speaker 1: big a comet can be. So you're saying that asteroids
7:54
Speaker 1: are not typically that dangerous whereas comets are. Why is
7:59
Speaker 1: that is that base stun the stuff that they're made
8:01
Speaker 1: out of, or their behaviors. It's mostly based on our
8:05
Speaker 1: ability to see them. Commets orbit in the Inner Solar System,
8:08
Speaker 1: and so we can point our telescopes and we can
8:10
Speaker 1: watch them, and we can see where they're going, and
8:12
Speaker 1: we are not worried about them because we know where
8:15
Speaker 1: basically all the big ones are. They reflect enough sunlight
8:18
Speaker 1: for us to track them and predict their path for
8:20
Speaker 1: a few hundred years. Once it astronomer gets like four
8:23
Speaker 1: or five six measurements of the motion of an object,
8:26
Speaker 1: they can pretty well predict its path. But comets have
8:30
Speaker 1: very long periods. Some of these things have like hundreds
8:33
Speaker 1: or thousands of years long period, which means the first
8:36
Speaker 1: time we see it might be when it's headed towards
8:39
Speaker 1: the Earth, which is why you might not get a
8:41
Speaker 1: whole lot of warning. And they're going much much faster
8:44
Speaker 1: because they're falling in from much further away. And those
8:48
Speaker 1: of you who watch these guys might remember that this
8:50
Speaker 1: happened in This is not just fiction. In comment entered
8:54
Speaker 1: the Solar System and then smacked right into Jupiter. It
8:58
Speaker 1: was spectacular. You could see it with your own telescope
9:00
Speaker 1: in your own backyard, earth size fireballs rising from the
9:03
Speaker 1: surface of Jupiter. It was like astronomical schadenfreud. You know,
9:06
Speaker 1: it's pretty awesome, but we were glad it wasn't hitting us.
9:09
Speaker 1: Those poor Jupidtonians Jupidonians having to have that name. Man,
9:19
Speaker 1: we'll have to ask or hey, what he would prefer
9:21
Speaker 1: as a name of that. It's definitely not jupiter Lyns.
9:23
Speaker 1: That would be pretty awkward Jupeians. Maybe a much bit Cans,
9:30
Speaker 1: my fellow Jupidicns. We can't necessarily know when a comment
9:35
Speaker 1: is coming, but should we really be that worried? Our
9:39
Speaker 1: atmosphere is pretty hot, so it seems like it could
9:43
Speaker 1: melt a comment, right. Our atmosphere is pretty hot, and
9:46
Speaker 1: you can melt a comment if it wasn't too big.
9:48
Speaker 1: But remember the impactory that took out the dinosaurs million
9:52
Speaker 1: years ago was only a few kilometers wide, So anything
9:56
Speaker 1: bigger than that is going to make it to the
9:58
Speaker 1: surface of the Earth and deposit a lot of kinetic energy.
10:01
Speaker 1: And so that's why it's really important to think about
10:03
Speaker 1: questions like, well, how big can a comment get? And
10:07
Speaker 1: so today in the podcast will be asking that exact question,
10:15
Speaker 1: how big can a comment get? Um Empire State building size?
10:21
Speaker 1: That's that's my guest. You just like the mental visual
10:24
Speaker 1: of the Empire state building crashing into the earth. Somebody's
10:28
Speaker 1: got to do that in Hollywood. Maybe blue whale size,
10:31
Speaker 1: because I also like the image of a blue whale
10:33
Speaker 1: crashing in Earth. Man talk about a belly flop, right,
10:36
Speaker 1: a blue whale coming from space and hitting the ocean. Ouch,
10:40
Speaker 1: that sounds like it hurts well as usual. I was
10:42
Speaker 1: curious what people out there in the Internet thought about
10:45
Speaker 1: this question. Have people thought about how big a commt is?
10:48
Speaker 1: Do they have any idea how large these snowballs from
10:51
Speaker 1: the far reaches of space can be? So I asked
10:53
Speaker 1: folks to volunteer to answer random physics questions to contribute
10:57
Speaker 1: to the podcast. And if you would like to participate, lease,
11:00
Speaker 1: don't be shy. You are very very welcome. No expertise
11:03
Speaker 1: is required. Just email me two questions at Daniel and
11:07
Speaker 1: Jorge dot com. So before you listen to these answers,
11:10
Speaker 1: think to yourself, how big do you think a comet
11:13
Speaker 1: can get here's what people had to say, pretty big.
11:17
Speaker 1: But then it starts getting into like whether you classify
11:19
Speaker 1: as common or a planet. I think comments can get
11:23
Speaker 1: as big as some of the largest planets out there.
11:26
Speaker 1: I think if something happens where planet gets out of
11:30
Speaker 1: orbit or start pades away, um, then those planets could
11:36
Speaker 1: then become free. Practically, I never thought that comments could
11:42
Speaker 1: or like pigeonholed into a certain size. I think, you know,
11:45
Speaker 1: it could just be a stray ice ball. But size
11:47
Speaker 1: doesn't really matter for comments. Well, based purely on imagination,
11:54
Speaker 1: I think comments can get as big as our moon.
11:58
Speaker 1: I ventured to guess comments can become as large as
12:00
Speaker 1: they can until they are too large to be called commets.
12:04
Speaker 1: From what I know, commets are this frozen stuff of
12:09
Speaker 1: dust and solids and gases. So it depends on what
12:15
Speaker 1: the commet has in it, because most of the stuff
12:19
Speaker 1: gets melted away as it enters and becomes warmer and hotter.
12:25
Speaker 1: What would prevent a comment from getting too big? I
12:28
Speaker 1: guess the two things that I can think of our
12:31
Speaker 1: If it's too big, it could break up easily, and
12:34
Speaker 1: hence you won't have one comment, you'll have multiple comments,
12:37
Speaker 1: and that's related to the structure of it. The other
12:40
Speaker 1: thing is that if you have something that's very big,
12:44
Speaker 1: it's likely not made out of a large percentage of
12:48
Speaker 1: ice crystals, is probably going to be highly metallic and
12:51
Speaker 1: won't develop the tails of the comments. So that still
12:54
Speaker 1: doesn't answer the question of how big can the comment get.
12:56
Speaker 1: I would guess I don't know, three or four or
13:00
Speaker 1: bus sizes. I don't know. I would imagine it will
13:05
Speaker 1: get as big as it can without the dust squishing it,
13:09
Speaker 1: because aren't commits quite low density. I suppose the gravity
13:14
Speaker 1: might turn it into an asteroid. I'm not sure about
13:18
Speaker 1: what the definitions are there, but I hope that's helped
13:22
Speaker 1: in some way. That's a good question. I imagine they
13:26
Speaker 1: could get bigger than an asteroid, depending on how much
13:34
Speaker 1: gravity maybe they had when they were out far far
13:38
Speaker 1: far in the far reaches of the solar systems or
13:41
Speaker 1: the orc clouds, or wherever they get all their ice from. Like,
13:45
Speaker 1: maybe they're just a particularly big chunk that gathered a
13:49
Speaker 1: whole lot and solidified before it came rushing in towards
13:54
Speaker 1: the center of our solar system. All right, so nobody
13:57
Speaker 1: else that empire states building or whale sized. Well, I
14:02
Speaker 1: am interested in the question of when does it become
14:05
Speaker 1: a planet. Is the only thing separating something like a
14:09
Speaker 1: comet and a planet just its signs? Or is there
14:12
Speaker 1: some other property to a comet that makes it not
14:16
Speaker 1: a planet? Oh man, this is such a tangle of names.
14:19
Speaker 1: The astronomers have made such a mess of what they
14:23
Speaker 1: call things. Is it a centaur, is it a trans
14:25
Speaker 1: Newtonian object? It is a minor planet. There are such
14:28
Speaker 1: ridiculous and sometimes conflicting rules about these things. In this case,
14:32
Speaker 1: you can actually make a nice little line between what's
14:35
Speaker 1: a comet and what's not. What you call a comet
14:38
Speaker 1: is something that has an atmosphere because the Sun is
14:42
Speaker 1: heating it up and it's out gassing. So imagine some
14:45
Speaker 1: icy ball thousands of au away from the Sun. It's
14:48
Speaker 1: just going to be sitting there frozen. But if it
14:50
Speaker 1: falls in towards the Solar System and the Sun starts
14:53
Speaker 1: to heat it up, then some of those ices are
14:55
Speaker 1: going to turn into gas, and they're going to give
14:57
Speaker 1: that comet a little atmosphere, which they call a co
15:00
Speaker 1: and it might even give it a little tail if
15:01
Speaker 1: some of it is blown off behind it. So that's
15:04
Speaker 1: what distinguishes an asteroid from a comet or a planet,
15:07
Speaker 1: or even a minor planet, or a or trans neptunity sorry,
15:11
Speaker 1: trans Neptunian objects, not trans Newtonian. Nobody launched isamutany into
15:16
Speaker 1: outer space yet they should have, though, that would teach
15:20
Speaker 1: him a thing or two about gravity. So if these
15:24
Speaker 1: comets have atmospheres, could this mean that some form of
15:29
Speaker 1: life could conceivably breathe it in or is it just
15:32
Speaker 1: inherently unfriendly towards life? Oh, I was hoping you were
15:36
Speaker 1: going to go there, the biologist, and you can't resist
15:38
Speaker 1: asking that question. Now, of course, we can never say never,
15:42
Speaker 1: because life is weird and could take all sorts of
15:44
Speaker 1: strange forms. But these would be very short lived atmospheres.
15:49
Speaker 1: This is something that doesn't exist when it's out there,
15:51
Speaker 1: deep into space. It only appears when the comet is
15:54
Speaker 1: falling towards the Sun and it's not gravitationally bound like
15:59
Speaker 1: these things are not big enough to have an atmosphere.
16:02
Speaker 1: The reason an asteroid doesn't have an atmosphere is that
16:05
Speaker 1: doesn't have enough gravity to hold onto it. Even the
16:07
Speaker 1: Moon doesn't have enough gravity to hold onto it. If
16:10
Speaker 1: you like pumped an atmosphere onto the moon. We all
16:13
Speaker 1: just drift away in a few dozen years or maybe
16:15
Speaker 1: a hundred. So a commet, it's atmosphere sort of transient.
16:18
Speaker 1: It keeps losing it and then it keeps replenishing it
16:20
Speaker 1: by outgassing it. So it'd be pretty hard situation, I
16:23
Speaker 1: think for life to form. So you'd basically just get
16:26
Speaker 1: a few puffs of atmosphere as life, but you wouldn't
16:31
Speaker 1: have millions of years to evolve. On this comment more
16:36
Speaker 1: of a vape situation. If you're a life form, Yeah,
16:40
Speaker 1: unless you're something really weird form of life, which can
16:43
Speaker 1: like go into stasis for a long long time and
16:45
Speaker 1: then wake up again, like those insects that wake up
16:48
Speaker 1: every seventeen years and like take a few breaths, live
16:51
Speaker 1: a very short life as the common is diving towards
16:53
Speaker 1: the sun, and then go back to sleep. Well, you know,
16:55
Speaker 1: there is a life form already out in space that
16:58
Speaker 1: can go into stays us and can survive the rigors
17:03
Speaker 1: of the vacuum of space at least for short periods
17:07
Speaker 1: of time, and those are tartar grades. So who knows,
17:10
Speaker 1: maybe some of those tartar grades we accidentally dropped on
17:13
Speaker 1: the moon, will someday find their way to sort of
17:17
Speaker 1: ride a comet for a little while. You think maybe
17:20
Speaker 1: they're gonna just like jump off the moon because there's
17:23
Speaker 1: such a little gravity there, land on a comet and
17:26
Speaker 1: ride it around the Solar system. That sounds pretty awesome,
17:28
Speaker 1: like doctor Strange love Tartar Grade, little tiny silver surfers. Well,
17:37
Speaker 1: that sounds like a great science fiction novel. So what
17:40
Speaker 1: we're talking about today are these comets, and these comments
17:43
Speaker 1: are again distinguished from asteroids because they have a coma
17:46
Speaker 1: and they can have a tail. A tail is not
17:48
Speaker 1: actually necessary for it to be a comet. A lot
17:50
Speaker 1: of people think about comments. They think about tails because
17:53
Speaker 1: when you look up in the sky, that's how a
17:55
Speaker 1: comet looks different from just like a star or something
17:57
Speaker 1: else shiny. Technically, though, astronom will call it a comet
18:01
Speaker 1: even if it doesn't yet have a tail, like before
18:04
Speaker 1: it's really fallen into the inner Solar system, it can
18:07
Speaker 1: still just have a coma. The other weird thing about
18:09
Speaker 1: comets is that they don't always just have one tail.
18:13
Speaker 1: They can have two different tails simultaneously, so just kind
18:18
Speaker 1: of a split stream going on or these tails made
18:21
Speaker 1: out of different stuff, so comments on that, like these
18:24
Speaker 1: dirty snowballs, and some of the stuff when he gets
18:26
Speaker 1: heated up, turns into gas and then the sun blows
18:29
Speaker 1: that away. So one of the tails of a comet
18:32
Speaker 1: is a gas tail, and that's pointing away from the sun.
18:35
Speaker 1: A lot of people think like the comets tail is
18:37
Speaker 1: pointing behind it, sort of like a rocket's exhaust or
18:41
Speaker 1: like you know those wiggle motions in a cartoon. That
18:43
Speaker 1: means that something is moving fast, but it's actually pointing
18:45
Speaker 1: away from the sun, like the sun is blowing gas
18:48
Speaker 1: away from it. So that's the gas tail. The other
18:51
Speaker 1: tail is typically made out of dust to like little
18:53
Speaker 1: bits of rock or whatever from the core of a comet,
18:56
Speaker 1: the non ice parts, and those are a little heavier
18:58
Speaker 1: so they don't get blown by the solar wind and
19:00
Speaker 1: they do actually follow more like the trajectory of the comet.
19:03
Speaker 1: So you have one tail that's sort of flying out
19:06
Speaker 1: behind the comet along its path and the other one
19:08
Speaker 1: that's getting blown away by the sun. And these are
19:11
Speaker 1: not always pointed in the same direction. So if you're
19:13
Speaker 1: really lucky, you can see a comet with both of
19:15
Speaker 1: these tails. Simultaneously, it looks pretty spectacular. So for thinking
19:19
Speaker 1: of a comet like a runway model, the gas tail
19:24
Speaker 1: is its hair getting blown out of its face by
19:27
Speaker 1: some conveniently placed fans, and the dust tail is like
19:33
Speaker 1: it's cloak, kind of wafting behind it as it struts
19:36
Speaker 1: down the runway, hopefully not towards Earth exactly. And if
19:39
Speaker 1: you are running with a tail wind right when the
19:42
Speaker 1: comet comes around the Sun and it's now going back
19:45
Speaker 1: into the outer Solar System, then its tail is pointing
19:48
Speaker 1: in the direction it's moving. It's like an anti tail
19:51
Speaker 1: because the Sun is now behind it, and so it's
19:53
Speaker 1: blowing gas in the direction the comet is moving. So
19:56
Speaker 1: the tail isn't always even behind the comet. Sometimes it's
19:59
Speaker 1: ahead of comment. So if we see a giant comet
20:03
Speaker 1: that has a tail pointed in our direction, that does
20:06
Speaker 1: not mean we're not in danger, because it could be
20:08
Speaker 1: coming right this way. That's right. You need me at
20:11
Speaker 1: the white board or somebody else doing those calculations before
20:14
Speaker 1: you know whether or not we should abandon the planet.
20:17
Speaker 1: And these comments come into different groups. Some of them
20:19
Speaker 1: are short period comets which come from the Piper Belt.
20:23
Speaker 1: This is a region of just like icy stuff. Planetism
20:26
Speaker 1: as just past Neptune, you know, past Neptune. This like
20:29
Speaker 1: a whole, big, messy pile of stuff. That's why people
20:32
Speaker 1: argue about whether Pluto should be a planet, because Pluto
20:36
Speaker 1: is the first thing we saw out there that was
20:37
Speaker 1: about that size, and then we discovered, oh my gosh,
20:40
Speaker 1: there's a lot of these like frozen balls out there.
20:42
Speaker 1: There are about Pluto size. We call Pluto a planet,
20:46
Speaker 1: we've got to call them all planets. So like after Neptune,
20:49
Speaker 1: the solar systems basically just a big mess. Sounds like
20:52
Speaker 1: a lot of planetary gate keeping. Just because Pluto's a
20:55
Speaker 1: mess doesn't mean it shouldn't be a planet. It's not
20:58
Speaker 1: just that Pluto is a mess. It's Pluto, and it's
21:00
Speaker 1: like seventeen thousand friends are all a mess, And do
21:02
Speaker 1: you want a solar system with seventeen thousand planets in it?
21:05
Speaker 1: You know, I guess it just depends on way to
21:07
Speaker 1: think of a solar system. But you know, to me,
21:08
Speaker 1: these arguments are just about names gues. It depends on
21:11
Speaker 1: if they're bringing pizza money or if they're just coming
21:14
Speaker 1: there for the free food. That's right. Anybody who brings
21:17
Speaker 1: gelato is welcome. But some of these little icy balls
21:21
Speaker 1: out there and the Kuiper Belt can get nudged and
21:24
Speaker 1: fall into the Solar System. And these are called short
21:26
Speaker 1: period comets, meaning that they take months or years to
21:30
Speaker 1: go around the Solar System. But there's another group, these
21:33
Speaker 1: long period comets that come from another source that much
21:36
Speaker 1: further out passed even the Kuiper Belt way past Pluto,
21:41
Speaker 1: many many, many thousands and millions of kilometers, and that
21:44
Speaker 1: comes from this blob called the Oort Cloud, which is
21:48
Speaker 1: this theoretical cloud of icy many planets. And I say
21:51
Speaker 1: theoretical because we're pretty sure it's there, but we've never
21:55
Speaker 1: actually seen it, so we only know about it's possible
21:59
Speaker 1: existence based on the garbage that it throws our way exactly.
22:04
Speaker 1: We can't otherwise explain where these comments come from. And
22:08
Speaker 1: so based on these comments about fifty years ago, Yon
22:11
Speaker 1: Ord suggested maybe there's this huge group of icy balls
22:15
Speaker 1: out there and just a tiny fraction them are occasionally
22:18
Speaker 1: falling towards the Earth. So I want to talk a
22:21
Speaker 1: lot more about the Ord Cloud and what it contains
22:23
Speaker 1: and the size of the comets that might be lurking
22:26
Speaker 1: in there. But first, let's take a quick break. All right,
22:42
Speaker 1: we're back and we're talking about what's going on in
22:44
Speaker 1: the messy outer reaches of the Solar system. Well passed Pluto,
22:49
Speaker 1: well passed, all of the trans Neptunian objects, well passed
22:52
Speaker 1: everything that might be called a planet, deep deep, deep
22:56
Speaker 1: out there, more like a thousand or two thousand astronaut
23:00
Speaker 1: coomical units past the Sun. There is this graveyard of
23:04
Speaker 1: icy objects which might form future comments. So we only
23:08
Speaker 1: know about this based on this sort of space junk
23:14
Speaker 1: that comes our way. We've never actually seen the cloud
23:19
Speaker 1: itself exactly, and that's because it's so far away. You know.
23:23
Speaker 1: The an astronomical unit is the distance between the Sun
23:26
Speaker 1: and the Earth, and the orc cloud starts like thousands
23:30
Speaker 1: of astronomical units, maybe up to fifty thousand astronomical units
23:34
Speaker 1: from the Sun. We're talking like one to two light
23:38
Speaker 1: years away. And it's really hard to see these objects
23:41
Speaker 1: when they're so far away because they don't reflect a
23:44
Speaker 1: whole lot of sun because not much sun gets there,
23:46
Speaker 1: and they're so small that not much of their light
23:49
Speaker 1: comes back to us. You know, they're not glowing on
23:51
Speaker 1: their own like stars. We can only see them if
23:54
Speaker 1: the light reflects it just the right angle and there's
23:57
Speaker 1: enough of it. So we've never seen it directly. We've
24:00
Speaker 1: only seen the ones that are falling towards the earth,
24:03
Speaker 1: and from that we're trying to guess what's out there.
24:06
Speaker 1: It's like if you couldn't see clouds, but you could
24:08
Speaker 1: measure rain, and you're wondering, like, what's up there in
24:11
Speaker 1: the sky. Maybe there are these huge reservoirs of water
24:14
Speaker 1: floating above us. Or it's like when you can't see
24:17
Speaker 1: a squirrel in a tree, but you know it must
24:19
Speaker 1: be there because you keep getting little pieces of acorn
24:22
Speaker 1: shell showering down on your head. Yeah, exactly. And the
24:26
Speaker 1: range of speculation for like how much stuff is out
24:29
Speaker 1: there is enormous. It could be that there are billions
24:32
Speaker 1: of icy objects out there. It could be that there
24:34
Speaker 1: are trillions of icy objects out there. It all depends
24:38
Speaker 1: on also, like how big they are, Like there could
24:41
Speaker 1: be billions of things like twenty kilometers wide or larger,
24:44
Speaker 1: but if you get too smaller and smaller objects like
24:46
Speaker 1: just kilometer or so, there could be even trillions out there.
24:50
Speaker 1: And it's a lot of stuff that we're talking about.
24:53
Speaker 1: They speculate that if you add up all of this stuff,
24:55
Speaker 1: it's like five to ten times the mass of the Earth.
24:59
Speaker 1: So it's not a small amount of basic material that's
25:02
Speaker 1: orbiting out there in the distance waiting for its trip
25:06
Speaker 1: around the Sun. So how much can we determine just
25:10
Speaker 1: based on the sort of fall off that happens from
25:15
Speaker 1: this proposed or cloud, like do we know the shape
25:18
Speaker 1: of it or can we just kind of basically guess, well,
25:21
Speaker 1: it's there and maybe it's big. A lot of it
25:23
Speaker 1: is guesswork based on modeling. We try to think about
25:25
Speaker 1: how the Solar system formed, how stuff would end up,
25:28
Speaker 1: what's likely to be out there, and that really informs
25:31
Speaker 1: a lot of our understanding of the Solar system for
25:34
Speaker 1: things that we cannot see. And that doesn't mean that
25:37
Speaker 1: it's bolognay, it's not just something we're making up. You know,
25:39
Speaker 1: this is a really valuable part of how we do sciences.
25:42
Speaker 1: We try to tell a complete holistic story of the
25:45
Speaker 1: Solar system and say, if this is true and that
25:48
Speaker 1: is true, what does that mean about the early times
25:50
Speaker 1: or the late times or what's going on. It's really
25:53
Speaker 1: valuable and you know, you can take the measurements that
25:55
Speaker 1: we have and you try to make them consistent with
25:57
Speaker 1: that story. And so they think about this huge cloud
26:00
Speaker 1: out of gas and dust and ice crystals that helped
26:02
Speaker 1: form the Solar System. The reason we talk about ice
26:05
Speaker 1: in the far reaches of the Solar System is because
26:07
Speaker 1: it's cold out there and ice melts, and any water
26:10
Speaker 1: that was closer before the snow line they call it
26:13
Speaker 1: would have been liquid or vapor, and so it wouldn't
26:16
Speaker 1: form these icy objects. So we think, based on these models,
26:19
Speaker 1: that the Orc Cloud has sort of two different shapes.
26:22
Speaker 1: That's like an inner or cloud that's sort of like
26:25
Speaker 1: a doughnut sort of flat, like the rest of the
26:27
Speaker 1: Solar System. And this might be from like a few
26:29
Speaker 1: thousand a U out to like twenty thousand a U.
26:33
Speaker 1: And then there might be like a larger spherical or
26:36
Speaker 1: cloud surrounding the entire Solar System, like a huge ball
26:39
Speaker 1: that goes out to like fifty thousand a U or
26:42
Speaker 1: even further. And that's sort of like at the edge
26:46
Speaker 1: of the interstellar distance. You know, other stars are like
26:49
Speaker 1: a few light years away. So now we're talking about
26:52
Speaker 1: like the very edges of our little corner of space
26:55
Speaker 1: bumping up against other stars, edges of their space, and
26:59
Speaker 1: so may be this sort cloud and these big icy
27:03
Speaker 1: for us to donuts can only exist between solar systems
27:07
Speaker 1: because otherwise they get too warm or they get pulled
27:10
Speaker 1: in and then become a comet that eventually melts or
27:13
Speaker 1: collides with something. Exactly in order to be an ice blob,
27:17
Speaker 1: you have to be far away from the star, and
27:19
Speaker 1: that's why Earth, for example, is not an ice ball.
27:21
Speaker 1: It's just too warm and mercury and venus, and that's
27:24
Speaker 1: why the icy planets are far away from the Sun.
27:27
Speaker 1: And as you say, these things are too far away
27:29
Speaker 1: to get melted. So that's where you go to find
27:30
Speaker 1: gelato on your trip between stars. I'm glad I don't
27:34
Speaker 1: have to walk as far here for gelato, but it
27:37
Speaker 1: would still be worth it. Right, Gelato is just that good.
27:40
Speaker 1: But it's really fascinating to me because it shows you
27:42
Speaker 1: something of the tug of war between solar systems. We
27:45
Speaker 1: tend to think of stars as like totally separate. We
27:47
Speaker 1: have our solar system, they got their solar system, and
27:50
Speaker 1: maybe very rarely two stars will come near each other
27:53
Speaker 1: and there'll be chaos. But in reality, there's like a
27:56
Speaker 1: constant tug of war at the boundaries between the Solar system.
28:00
Speaker 1: Like imagine you're halfway between two stars and you're feeling
28:04
Speaker 1: gentle gravity from both stars, and so you're being tugged
28:07
Speaker 1: one way, tugged another way, And that's these stars are
28:10
Speaker 1: moving relative to each other, that gravity is changing. So
28:13
Speaker 1: maybe you get like bumped from one solar system to another,
28:17
Speaker 1: which means that, like some parts of our Worth Cloud
28:21
Speaker 1: might not be from our Solar system. They might have
28:23
Speaker 1: like started out in another solar system and then got
28:26
Speaker 1: past two hours, maybe several times. Maybe they're like hopscotching
28:30
Speaker 1: from solar system to solar system. Could that be one
28:32
Speaker 1: reason that our solar system is able to host our
28:36
Speaker 1: comfy little planet Earth without having gotten pummeled by too
28:39
Speaker 1: many comments? Could there be a benevolent Solar system out
28:43
Speaker 1: there absorbing or sucking in more comments. I like your
28:48
Speaker 1: optimistic theory of the universe that there's somebody out there
28:50
Speaker 1: looking out for us by eating all the gelato before
28:53
Speaker 1: it falls to Earth to kill us. It could be yeah,
28:56
Speaker 1: you know, maybe not intentionally, but just by here a
29:00
Speaker 1: chance a son out, they're kind of preventing more of
29:04
Speaker 1: these frozen ice balls from colliding with our Solar System,
29:08
Speaker 1: it could be, or it could be even closer to home.
29:11
Speaker 1: A lot of folks think that our gas giants Saturn
29:14
Speaker 1: and Jupiter provides something of a gravitational shield against impactors
29:18
Speaker 1: in the inner Solar System, and that like a lot
29:20
Speaker 1: of the icy balls in the or cloud are there
29:23
Speaker 1: because they got thrown out of the Solar System early
29:25
Speaker 1: on by these gas giants as things were like still
29:28
Speaker 1: coming together, and so now they're like lurking outside waiting
29:32
Speaker 1: for their chance to come back into the light. Well,
29:34
Speaker 1: it seems like for some planets that maybe protecting all
29:38
Speaker 1: life on Earth, we should come up with a more
29:40
Speaker 1: flattering name than gas giants. But you know, I guess
29:45
Speaker 1: that's it's accurate at least. Well, you know, we did
29:48
Speaker 1: name them after the most important gods, you know, like
29:50
Speaker 1: Jupiter and Zeus, so that you know, that's pretty flattering. Right,
29:54
Speaker 1: there's no planet named Zeus. Zeus is the Greek version
29:57
Speaker 1: of Jupiter, isn't it right? Yes, that's right, that's right.
29:59
Speaker 1: I think z would be a much better name for
30:01
Speaker 1: a planet than Jupiter. Right, I'm petitioning that we renamed
30:04
Speaker 1: Jupiter Zeus because then the people who live on it
30:06
Speaker 1: would be called Zeusians. That rolls off the tongue much nicer,
30:09
Speaker 1: and then you can't have that schoolyard chant of girls
30:12
Speaker 1: go to Jupiter to get more stupider. So I'm all
30:15
Speaker 1: for it. Heard that one that's terrible. Well, it goes
30:19
Speaker 1: either way. You can say boys go to Jupiter to
30:22
Speaker 1: get more stupider, girls go to Mars to drive cool cars,
30:25
Speaker 1: or vice versa. But you know, I think we should
30:28
Speaker 1: be breaking those rigid gender roles in terms of planets.
30:32
Speaker 1: Totally agree. And so one question about what's out there
30:35
Speaker 1: in the or cloud is just like how did it
30:37
Speaker 1: get formed and what's its composition? But a big and
30:41
Speaker 1: important question, and one that might really affect our future
30:44
Speaker 1: is how big are the things out there? You know,
30:47
Speaker 1: a lot of the comets that we have seen coming
30:49
Speaker 1: in our Solar System are just a few kilometers wide,
30:51
Speaker 1: and they're big enough to be spectacular. But people wonder, like,
30:55
Speaker 1: are their planet sized objects out there in the or cloud?
30:58
Speaker 1: Could one of them fall into the inner Solar System
31:01
Speaker 1: and like really do some damage. So if there's an
31:04
Speaker 1: ice ball hang out there that is planet sized, would
31:08
Speaker 1: it be considered a planet before it becomes a comet?
31:12
Speaker 1: Or is it just considered some kind of ice ball.
31:15
Speaker 1: I think that the new definition of planet makes it
31:18
Speaker 1: basically impossible because an object has to like clear its
31:21
Speaker 1: own path, that has to basically have its own unique
31:24
Speaker 1: path through the Solar System to be called a planet.
31:26
Speaker 1: But I also think that there are now conflicting definitions
31:29
Speaker 1: of what a planet is. But as soon as it
31:31
Speaker 1: falls in towards the Solar System and develops a coma,
31:35
Speaker 1: then it's a comet, even if it used to be
31:37
Speaker 1: like the Moon sized or Pluto sized, or even I
31:40
Speaker 1: guess Neptune sized, right, Like one of the listeners was
31:43
Speaker 1: guessing planets that lose their orbits could be comets, Like
31:46
Speaker 1: that's really crazy to think about. They would be at
31:49
Speaker 1: least ice planets. So could there be a big ice
31:54
Speaker 1: ball the size of Earth that at some point comes
31:57
Speaker 1: in and smashes into our Solar System? Like? How much
32:01
Speaker 1: sleep should I lose after otarting this podcast? Well, we
32:04
Speaker 1: just don't know, is the thing. It's a mystery to us.
32:06
Speaker 1: One thing we do know is that most of the
32:09
Speaker 1: things that fall in from the or cloud tend to
32:12
Speaker 1: be smaller. But there's now a spectrum and we're seeing
32:14
Speaker 1: larger and larger objects. So the thing that should scare
32:17
Speaker 1: you is that as we keep studying, we keep discovering
32:21
Speaker 1: larger and larger objects of the Orc cloud. We'll talk
32:23
Speaker 1: about one particular monster in a minute. So that should
32:26
Speaker 1: terrify you because it might mean that there are really
32:29
Speaker 1: some huge blobs of ice waiting out there. The thing
32:32
Speaker 1: that should help you fall asleep, though, is that we
32:34
Speaker 1: do know that there's an inverse relationship between how many
32:37
Speaker 1: there are and their size. Like with everything else, there's
32:40
Speaker 1: going to be lots and lots of dust screens, and
32:42
Speaker 1: then it's wund be fewer things the size of snowball,
32:45
Speaker 1: and fewer things the size of a bus, and even
32:48
Speaker 1: fewer things the size of you know, there are ten
32:51
Speaker 1: kilometers across. The interesting thing is we don't know what
32:54
Speaker 1: the maximum is like. There might just be one real
32:56
Speaker 1: monster out there. But how big is the biggest monster?
33:00
Speaker 1: If you can't see it, if we're too far away
33:03
Speaker 1: to be able to see it with any of our
33:05
Speaker 1: monitoring tools from here on Earth or even you know,
33:07
Speaker 1: the ones that we send out on the edges of
33:10
Speaker 1: our solar system, how would you be able to guess
33:14
Speaker 1: the size of the biggest ice ball. Yeah, you would
33:17
Speaker 1: have to use some models. You'd have to understand how
33:19
Speaker 1: all those ice balls formed. Then you'd have to develop
33:21
Speaker 1: a simulation that ran through the formation of the Solar system,
33:25
Speaker 1: and you'd look for models that explain what we do see.
33:28
Speaker 1: You know that look at this relationship between size and
33:30
Speaker 1: frequency and correctly predict that, and then you can extrapolate.
33:34
Speaker 1: You could say, well, as they get bigger, if the
33:36
Speaker 1: rate of their occurrence drops by you know, some factor,
33:39
Speaker 1: then you could follow that line forward and try to
33:42
Speaker 1: predict like how big theoretically an object could be. But
33:46
Speaker 1: this is the kind of thing that we do all
33:47
Speaker 1: the time in astronomy, and then we're surprised, Like we
33:50
Speaker 1: have predictions for how big the largest galactic clusters should be,
33:54
Speaker 1: and then we keep finding bigger ones. Were like, well,
33:56
Speaker 1: I guess something was wrong, but that's just the process
33:59
Speaker 1: of science. And so until we actually see these things,
34:02
Speaker 1: were often not sure about what the upper limits are.
34:06
Speaker 1: So we would have to base it on the sort
34:09
Speaker 1: of our existing models and things we can observe and
34:13
Speaker 1: sort of use that to extrapolate what it is. But
34:17
Speaker 1: do we know theoretically if there is a limit to
34:20
Speaker 1: just physically to an ice ball. How big can an
34:25
Speaker 1: object made with a solid core and then sort of
34:28
Speaker 1: an icy exterior get that we know of. I think
34:31
Speaker 1: there are some theoretical limits you good place, Like we
34:34
Speaker 1: know that you could be as big as Neptune or
34:36
Speaker 1: Uranus because we see those and those are basically the
34:38
Speaker 1: same thing. A huge balls of ice with a rocky core.
34:41
Speaker 1: If it gets much bigger than that Jupiter size, that
34:44
Speaker 1: could still exist. If it gets even bigger than that,
34:47
Speaker 1: if it gets like a hundred times to size of Jubiter,
34:50
Speaker 1: then it would be big enough to ignite fusion in
34:53
Speaker 1: its core and it would start to glow. We would
34:55
Speaker 1: definitely see that. If there was another star out there
34:58
Speaker 1: that was actually emitting light, we would see it. So
35:01
Speaker 1: the orc cloud is dark, and that in itself puts
35:03
Speaker 1: a limit on the biggest thing that could be in there.
35:06
Speaker 1: You can't have a glowing star in the word cloud.
35:09
Speaker 1: So like a hundred jupiters is the biggest anything could
35:12
Speaker 1: be theoretically, But that's really big, like Jupiter itself is
35:17
Speaker 1: three hundred times the mass of the Earth. So that's
35:20
Speaker 1: not a very useful limit. It doesn't really reassure anybody.
35:25
Speaker 1: We wouldn't be less dead if we were hit by
35:29
Speaker 1: a half the size of Jupiter, Comment versus twice the
35:33
Speaker 1: size of Jupiter. Comment would be equally dead in both scenarios,
35:36
Speaker 1: is what you're saying? Yeah, exactly, though the astronomers would
35:39
Speaker 1: be like, oh wow, that's really interesting. We're surprised just
35:42
Speaker 1: before we all get blown up. Hey, well that's worth something.
35:46
Speaker 1: At least the astronomers will get their kicks as we're
35:48
Speaker 1: munch agone gelato. But recently we did spot a pretty
35:52
Speaker 1: big monster object in the Orc Cloud heading towards the
35:55
Speaker 1: Inner Solar System. That kind of surprised astronomers. Nobody had
35:59
Speaker 1: ever seen some this large, and it sort of stretched
36:02
Speaker 1: people's brains about how big one of these I see
36:05
Speaker 1: objects could be. It's not Jupiter size, but it is
36:08
Speaker 1: pretty large. So the object that hit the Earth sixty
36:11
Speaker 1: five billion years ago was about five to six kilometers wide.
36:15
Speaker 1: We think based on reconstructions, how much is that in
36:18
Speaker 1: blue whales? That's not a physical unit I'm familiar with,
36:23
Speaker 1: so I have to type that into Google. Wealth blue
36:26
Speaker 1: whale is maybe about thirty long yea, So we're talking
36:30
Speaker 1: about something that's two hundred blue whales long by volume,
36:34
Speaker 1: that would make it like eight million blue whales. That's
36:37
Speaker 1: a lot of blue whales, exactly eight million blue whales
36:40
Speaker 1: rolled into a six kilometer wide ball impacting the Earth
36:44
Speaker 1: would not be a great situation. But that's basically what
36:46
Speaker 1: happened sixty five million years ago. But two astronomers called
36:50
Speaker 1: Bernadelli and Bernstein recently spotted an object that they think
36:54
Speaker 1: is a hundred to two hundred kilometers across, so like
36:58
Speaker 1: much bigger and the one that hit the Earth and
37:01
Speaker 1: caused an environmental cataclysm that changed the future of the planet.
37:05
Speaker 1: This thing is forty times bigger, so we'll lose forty
37:08
Speaker 1: times the number of dinosaurs this time around. You don't
37:13
Speaker 1: think its scales that way. Don't tell me how to
37:17
Speaker 1: do a math. That's a hefty that's a hefty comment.
37:21
Speaker 1: How far away is it? Just asking for general, generally interested.
37:26
Speaker 1: This thing we think started its journey around forty thousand
37:30
Speaker 1: a US away, so deep deep in the Orc cloud.
37:33
Speaker 1: And last time it was spotted middle of last year,
37:36
Speaker 1: it was about twenty a U away, So that's twenty
37:39
Speaker 1: times the distance from the Sun to the Earth, so
37:41
Speaker 1: still really really far away, and so I want to
37:44
Speaker 1: talk about how we spotted this thing, what its future
37:47
Speaker 1: trajectory is, what we might learn about the deep reaches
37:50
Speaker 1: of the Solar System by studying this massive comment. But first,
37:53
Speaker 1: let's take another quick break and I'm going to take
37:56
Speaker 1: some deep breathing. All right, we're back, and we're talking
38:11
Speaker 1: about a ginormous visitor from the far edges of the
38:14
Speaker 1: Solar system. Comment Bernadeli Bernstein. And I don't know anything
38:18
Speaker 1: about Bernardelli or Bernstein, but I'm imagining this very nice
38:22
Speaker 1: friendship between an Italian guy and the Jewish guy having
38:24
Speaker 1: an ice cream, having a gelato, discovering a giant comment. Yeah,
38:29
Speaker 1: maybe they're having some gelato on their bobka, you know,
38:31
Speaker 1: and they're just like really fusing the cultures together. Yeah,
38:35
Speaker 1: having some halva and some here you go. You know,
38:40
Speaker 1: every culture has its take on ice cream. But now,
38:43
Speaker 1: for the life of me, I can't think what is
38:45
Speaker 1: the Jewish version of ice cream? Do we have our
38:47
Speaker 1: own kind of ice cream? I don't know. That's why
38:48
Speaker 1: I said halva, because that's sort of the creamiest dessert
38:52
Speaker 1: I know of. But yeah, I'm I am not sure.
38:56
Speaker 1: Desert cultures, I guess don't have an everything exactly except
39:01
Speaker 1: for those of us who ended up in Siberia. Yeah, yeah, right,
39:04
Speaker 1: So we are importing gelato from the far regions of
39:07
Speaker 1: the Solar System into our desert culture. Here as comment
39:10
Speaker 1: Bernard Deli Bernstein comes closer to the Sun, is developing
39:14
Speaker 1: a coma. So that's why we don't call this thing
39:17
Speaker 1: a minor planet or a dwarf Planet's officially a comet
39:20
Speaker 1: because it's grown a coma. They can see this thing
39:23
Speaker 1: out gassing and it's like surrounded by this little puff
39:26
Speaker 1: of gas. So again, just generally interested, no big deal.
39:30
Speaker 1: But do we know the direction this giant comment is
39:33
Speaker 1: going in? We do. We've spotted it a few times,
39:36
Speaker 1: We've made a bunch of measurements, and so we can
39:38
Speaker 1: predict its trajectory. It looks like the closest it's gonna
39:41
Speaker 1: come is in twenty thirty one. It's gonna come within
39:45
Speaker 1: around eleven A U. So that's the closest to the
39:49
Speaker 1: Sun it's gonna get, which means we are totally safe. Right,
39:52
Speaker 1: We are at one a U. So this thing is
39:54
Speaker 1: going to be really far away compared to us, and
39:57
Speaker 1: so this comment is going to swoop actually up it's
40:00
Speaker 1: like not following the plane of the ecliptic. It's actually
40:03
Speaker 1: coming like sort of from below the plane. It's going
40:06
Speaker 1: to swoop up between the orbits of Saturn and Uranus,
40:10
Speaker 1: and then it's going to pass above the Solar System.
40:13
Speaker 1: So these commets aren't necessarily limited to the plane of
40:16
Speaker 1: the Solar System because they come from this spherical cloud
40:19
Speaker 1: of objects the outer word cloud. So it probably had
40:22
Speaker 1: its own trajectory and velocity before it started being influenced
40:27
Speaker 1: by our Sun, right, yeah, probably, and it's probably been
40:30
Speaker 1: falling in towards the Sun for a long long time.
40:34
Speaker 1: They estimate that the period of this commet is about
40:36
Speaker 1: three million years. It's gonna take three million years to
40:40
Speaker 1: loop around go back out into the really far reach
40:43
Speaker 1: of the Solar System, where it's going to start moving
40:45
Speaker 1: really really slow. Right, People think about things moving fast
40:49
Speaker 1: when they're far away from the Sun, but the opposite
40:51
Speaker 1: is true when you're really close to the Sun. When
40:53
Speaker 1: you're moving really really fast, like Mercury's orbit is very fast,
40:56
Speaker 1: Pluto plunks along very very slowly because it's far away
41:00
Speaker 1: from the Sun, which means that the Sun's gravity is
41:02
Speaker 1: not very strong, so it doesn't have to be moving
41:04
Speaker 1: very fast to be in an orbit, in the same
41:06
Speaker 1: way a commet. When it zooms towards the center of
41:09
Speaker 1: the Solar system, it's going really fast as it whips
41:11
Speaker 1: around the Sun, and then it slows down as it
41:14
Speaker 1: gets far out. It's sort of like a ball in
41:16
Speaker 1: a well. It zooms down, it's going it's fastest at
41:19
Speaker 1: the bottom, and then when it comes back up and
41:21
Speaker 1: before it turns around, it's like stops. It's the same
41:24
Speaker 1: thing with a commet. And so it takes three million
41:26
Speaker 1: years to do this whole orbit, all the way deep
41:29
Speaker 1: into the or cloud and then back in towards the Sun.
41:32
Speaker 1: But well, we actually get to see it. If it's
41:35
Speaker 1: eleven au away, we will get to see it, but
41:37
Speaker 1: we'll have to use telescopes, so you won't be able
41:39
Speaker 1: to see it with your naked eye. Even though this
41:41
Speaker 1: thing is a monster, right, it's like almost two kilometers across,
41:45
Speaker 1: it's gonna be too far away for us to spot it.
41:48
Speaker 1: The comments that you can see with the naked eye,
41:50
Speaker 1: Gailey's comet and other stuff, that's because they come close
41:53
Speaker 1: enough to the Earth that you can really see them.
41:55
Speaker 1: But you will be able to see this thing with
41:57
Speaker 1: an amateur telescope, and they suspect that it might grow
42:00
Speaker 1: a tail. Right now, it just has a coma, but
42:02
Speaker 1: as it gets closer and closer to the Sun, it's
42:04
Speaker 1: gonna get heated up more and more and it might
42:07
Speaker 1: develop this gas tail or a dust tail. So that
42:09
Speaker 1: would be pretty useful also because studying that tail can
42:13
Speaker 1: help us understand what is out there in the Orc cloud.
42:16
Speaker 1: What can the tail tell us about the Orc cloud?
42:18
Speaker 1: So we don't know what the stuff out there is
42:21
Speaker 1: made out if we think it's like ice and rock,
42:23
Speaker 1: and we really want to build better models of how
42:26
Speaker 1: the solar system forms so we can understand what is
42:28
Speaker 1: out there, and so we can take measurements of what's
42:31
Speaker 1: in this tail even without going out there. Like when
42:34
Speaker 1: an object is just frozen, all you can do is
42:37
Speaker 1: bounce light off of it and measure like how much
42:39
Speaker 1: light reflects. But if you have vapor, if you have
42:41
Speaker 1: gas and light passes through it, then you can tell
42:44
Speaker 1: a lot more about what's in it because you can
42:46
Speaker 1: look at the frequency of light that passes through it,
42:49
Speaker 1: and it will also glow in its own frequencies, just
42:52
Speaker 1: like you can tell what's in the atmosphere of Venus
42:55
Speaker 1: by looking at the frequencies of light that passed through
42:57
Speaker 1: it and the frequencies in which that gas loows, because remember,
43:01
Speaker 1: every kind of gas glows in different frequencies, is like
43:04
Speaker 1: a little fingerprint based on which kinds of photons it
43:07
Speaker 1: likes to absorb in which kinds it likes to give off. So,
43:10
Speaker 1: because the comet is visiting closer to the Sun and
43:13
Speaker 1: some of its icy components are being turned into gas,
43:16
Speaker 1: we can then study that tail and try to understand like, oh,
43:19
Speaker 1: how much methane is there, or how much carbon is there,
43:22
Speaker 1: how much oxygen is there in these frozen objects, and
43:25
Speaker 1: that will really inform the models we build about how
43:28
Speaker 1: the Ord Cloud came to be and where everything is
43:31
Speaker 1: distributed in the Solar system, and it could maybe tell
43:34
Speaker 1: us like how big the largest ice balls might be
43:37
Speaker 1: in the Orc Club exactly. The more data we have
43:40
Speaker 1: about these details, the better we can build our models
43:43
Speaker 1: to really specifically predict what's out there in the Orc Cloud.
43:47
Speaker 1: Because this is the biggest one we've seen, is it
43:50
Speaker 1: likely that it's the biggest thing in the Orc Cloud?
43:52
Speaker 1: Almost certainly? Not right, Probably there are many more of
43:56
Speaker 1: these things waiting out there to fuse different culture together
44:00
Speaker 1: as astronomers from around the world come together to find them.
44:03
Speaker 1: But there are probably much bigger ones that we just
44:06
Speaker 1: have not seen yet. So mark down on your calendars
44:09
Speaker 1: nine years from now, get your telescopes out, and start
44:14
Speaker 1: looking at that comment. Hunh exactly. And another fun way
44:17
Speaker 1: to think about commets is not just the size of
44:20
Speaker 1: their central object, like we're talking about the icy, frozen core,
44:24
Speaker 1: like how much stuff there is to the commet, which is,
44:27
Speaker 1: you know, a useful way to think about it if
44:28
Speaker 1: you're worried about the comets hitting the planet. But there's
44:31
Speaker 1: another way you can measure the size of the comment,
44:33
Speaker 1: and that's by the size of the coma. They make
44:36
Speaker 1: this gaseous envelope that surrounds the commet. As it gets
44:39
Speaker 1: heated up, some of these things get like crazy big,
44:43
Speaker 1: it's ridiculous, it's bonkers. These things are not gravitationally bound.
44:47
Speaker 1: They're just sort of like surrounding the comet. But they
44:49
Speaker 1: can eject so much gas that their commas can be
44:52
Speaker 1: like enormous. There's a comment they found in two thousand
44:55
Speaker 1: seven called commet homes that has a really tiny, small core,
45:00
Speaker 1: but it's coma. Get ready for this because it's gonna
45:02
Speaker 1: sound insane. It's coma is bigger than the sun. Shut
45:06
Speaker 1: the front door of the cellar for the system, and
45:08
Speaker 1: don't let any of these ens. So how can it
45:11
Speaker 1: produce if it's got a small core, how can it
45:13
Speaker 1: produce such a huge cloud of gas? And don't say cuteoba,
45:18
Speaker 1: because I won't believe you. Exactly that's the problem with
45:22
Speaker 1: being flavored ice cream exactly for Jolie gelato, not a
45:26
Speaker 1: good idea. Nobody knows really, and it's a question about
45:30
Speaker 1: like what is this thing made out of and how
45:31
Speaker 1: did it do this? But they saw this comma. It's
45:34
Speaker 1: one point four million kilometers wide. You can actually see
45:38
Speaker 1: it in our skies. It's like a big circular cloud.
45:41
Speaker 1: So we don't really understand it. The core of this thing,
45:43
Speaker 1: common homes is just four kilometers in diameter, and it
45:47
Speaker 1: made this enormous coma. So it could be something about
45:51
Speaker 1: what that common is made out of, or maybe how
45:54
Speaker 1: it was layered. You know, if you get layers in
45:56
Speaker 1: just the right way, you can get like explosive release
45:59
Speaker 1: of energy than like a gradual release. We're just building
46:02
Speaker 1: models and trying to understand it. It's fascinating. And that's
46:05
Speaker 1: why it's so much fun to look up at the
46:06
Speaker 1: night sky, because, as we were saying earlier, there are
46:09
Speaker 1: always surprises. We're gonna make a model of what's in
46:12
Speaker 1: the work clad and what the biggest thing out there is,
46:14
Speaker 1: and then five years later it's gonna say, I got
46:17
Speaker 1: a bigger one for you. How long could something like
46:19
Speaker 1: that last? Like, if you have a small core and
46:22
Speaker 1: it's exuding so much gas in this giant ball, it
46:26
Speaker 1: can't launch that long, right, It's got to be sort
46:28
Speaker 1: of a flash in a pan. Yeah, it can't laughs
46:31
Speaker 1: out long exactly because the Sun is constantly stripping it
46:34
Speaker 1: of this gas. To maintain it has to continuously evaporate
46:38
Speaker 1: or sublimate more and more gas. And actually some of
46:41
Speaker 1: the things in the asteroid belt they think are dead comets.
46:45
Speaker 1: Comets that used to be rocks surrounded by ice that
46:48
Speaker 1: flew around the sun, blew up all of that ice
46:51
Speaker 1: into a coma and are now just totally stripped and
46:54
Speaker 1: are just dead rocks. And so now they're called asteroids
46:57
Speaker 1: because they no longer have a coma. So a comet
47:01
Speaker 1: is like a transitional period in the life of a
47:03
Speaker 1: Solar System object. You can be a comet for a
47:05
Speaker 1: while and then eventually you get downgraded to an asteroid
47:08
Speaker 1: when you've blown all of your gas. I'm trying to
47:11
Speaker 1: imagine what it would be like to sort of pass
47:15
Speaker 1: through that coma of a comet. Would it be like
47:20
Speaker 1: you're in the swirling world of like chunks of ice
47:25
Speaker 1: and gases. Would you immediately be sort of pulverized by
47:30
Speaker 1: these little particles being shooting out from it? What would
47:33
Speaker 1: that experience be like being in the coma of a comet.
47:37
Speaker 1: It's not nearly as dense as our atmosphere. It's very
47:41
Speaker 1: very dilute in comparison, and so it's nothing like being
47:44
Speaker 1: in air, but it is more dense than the rest
47:46
Speaker 1: of space. And so one thing you have to worry
47:48
Speaker 1: about is the velocity. If there are dust greens in
47:51
Speaker 1: this tail or, in this coma that are moving at
47:54
Speaker 1: high speeds, they can carry a lot of kinetic energy
47:57
Speaker 1: and they could, you know, hold your spaceship. We talked
48:00
Speaker 1: about is actually on the podcast recently, about how to
48:02
Speaker 1: protect ships from high speed micro meteorites or death grains.
48:06
Speaker 1: It's a challenge, but we have sent stuff up there.
48:09
Speaker 1: We have sent probes to comets. We had Rosetta, which
48:13
Speaker 1: landed on a comet, and then NASA sent Deep Impact,
48:17
Speaker 1: which actually blasted a crater off of a comet to
48:20
Speaker 1: try to study what it was made out of. So
48:22
Speaker 1: you can send spaceships up to like intercept commets and
48:25
Speaker 1: study them. It's pretty awesome. What did Rosetta and Deep
48:29
Speaker 1: Impact find? Like were they able to get some kind
48:32
Speaker 1: of samples of what the comets were made out of
48:34
Speaker 1: and bring them back to Earth. So there currently aren't
48:37
Speaker 1: any samples from comets that have returned to Earth. But
48:40
Speaker 1: they did send these missions out there and they studied them,
48:43
Speaker 1: and they tried to understand, like, you know, what is
48:44
Speaker 1: the geology of this thing? And the thing that surprises
48:47
Speaker 1: me the most is that looking at the surface of
48:49
Speaker 1: these things, they just sort of look like big rocks.
48:52
Speaker 1: They're sort of familiar, like they look like a big
48:55
Speaker 1: rocky you would see sitting on the ground in Joshua
48:58
Speaker 1: tree or you know, near some are like volcano or something.
49:01
Speaker 1: They're sort of familiar looking objects. They're not otherworldly at all.
49:05
Speaker 1: They have weird shapes and each one tells its history,
49:08
Speaker 1: but we're still sort of studying the data from deep
49:10
Speaker 1: Impact and from Rosetta to understand like the deep geology
49:13
Speaker 1: of what's in those comments. Do those probes remain on
49:17
Speaker 1: the commets forever and just send us back this data.
49:20
Speaker 1: They don't last very long. One of them was orbiting
49:22
Speaker 1: the commet for a while and then sent down a lander,
49:25
Speaker 1: and the lander didn't last for very long. It like
49:27
Speaker 1: took a little bit of data and then sort of
49:29
Speaker 1: died and the orbitter was able to take a picture
49:31
Speaker 1: of it dead on the surface of the commet. So sad,
49:35
Speaker 1: so sad. But yeah, these things don't last very long,
49:38
Speaker 1: all right. So that's a little tour of what's going
49:41
Speaker 1: on out there in the deep edges of the Solar System,
49:44
Speaker 1: including some surprises. There are comments out there that are
49:47
Speaker 1: bigger than a bus, bigger than many school buses, bigger
49:50
Speaker 1: than maybe even millions of blue whales all packed together.
49:55
Speaker 1: And so as usual, the thing that I love is
49:57
Speaker 1: discovering that there are surprises out there in space, not
50:00
Speaker 1: just super far away, but here in our backyard. And
50:04
Speaker 1: that's really fun because it means we can learn the answers.
50:07
Speaker 1: We don't have to rely on aliens coming to visit
50:10
Speaker 1: to tell us the deep secrets of the universe. We
50:12
Speaker 1: could actually send more probes out there and explore the
50:14
Speaker 1: rac cloud, build more space telescopes and get better pictures.
50:17
Speaker 1: These are things that we will know the answers to
50:20
Speaker 1: In a hundred years, astronomers will know so much more
50:23
Speaker 1: about the far reaches of the Solar System, and they'll
50:25
Speaker 1: look back and think of us as living in the
50:27
Speaker 1: dark ages. And I'm just totally happy that there's a
50:30
Speaker 1: big cloud of mysterious giant ice balls of which we
50:35
Speaker 1: do not know the maximum size. I think that's great
50:37
Speaker 1: and perfectly fine. I'll sleep like a baby tonight, have
50:42
Speaker 1: an feather spoonful of gelato, and just enjoy your life. Katie.
50:47
Speaker 1: All right, well, thanks Katie very much for joining us today.
50:50
Speaker 1: Thank you for having me, and thanks to all of
50:52
Speaker 1: you for listening to and in next time, ye thanks
51:02
Speaker 1: for listening, and remember that Daniel and Jorge Explain the
51:04
Speaker 1: Universe is a production of I Heart Radio. For more
51:08
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