Latest / Daniel and Kelly’s Extraordinary Universe / What is the future of exoplanet research?

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What is the future of exoplanet research? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, or hey, did you follow the launch of the
• 0:10
  Speaker 1: James Webb telescope. Yeah, I thought, I want to be honest,
• 0:13
  Speaker 1: I was in Hawaii, so I wasn't plugged into the news,
• 0:16
  Speaker 1: but I saw that it was all over the place
• 0:18
  Speaker 1: and people were very excited and where you like terrifying
• 0:20
  Speaker 1: in the edge of your seat that it wasn't gonna work. Well,
• 0:23
  Speaker 1: I'm just glad it didn't explode on launch. I guess
• 0:25
  Speaker 1: that's always a good thing. So would you say that
• 0:26
  Speaker 1: the NASA team did like a good job of getting
• 0:29
  Speaker 1: everybody emotionally invested in this ten billion dollar project. It
• 0:32
  Speaker 1: was pretty dramatic, you know, and whenever you have a launch,
• 0:34
  Speaker 1: you know, anything can happen. And I know they had
• 0:36
  Speaker 1: some blaize and in some you know, expectations and people
• 0:40
  Speaker 1: were hanging by the seat of their pants right to
• 0:42
  Speaker 1: see the telescope opened up. But you know, it worked
• 0:44
  Speaker 1: so well and unfolded so smoothly. I was wondering if
• 0:47
  Speaker 1: it might have made like a better story if it
• 0:49
  Speaker 1: hadn't gone so well, if there's been some like ups
• 0:51
  Speaker 1: and downs. Were you hoping something would go wrong? Daniel, Yeah,
• 0:56
  Speaker 1: you know, you need a little bit of a dip
• 0:57
  Speaker 1: at the end so that our heroes can like triumph
• 0:59
  Speaker 1: and last moment I see, so the engineers can swoop
• 1:03
  Speaker 1: in and fix all the mistakes that the physicist me
• 1:05
  Speaker 1: exactly in the end, the engineers are always the heroes.
• 1:08
  Speaker 1: I'll watch that movie. I am Jorhan, made cartoonists and
• 1:26
  Speaker 1: the creator of PhD comics. Hi. I'm Daniel. I'm a
• 1:29
  Speaker 1: particle physicist and a professor at U SEE Irvine, and
• 1:31
  Speaker 1: I'm definitely buying a ticket for the movie called Engineers
• 1:35
  Speaker 1: Save the Day. But they do it every day, Daniel,
• 1:37
  Speaker 1: you don't need to buy a movie ticket. It's happening
• 1:40
  Speaker 1: around you all the time. But we need Hollywood to
• 1:42
  Speaker 1: like dramatize it, to you know, glorify these people. I see,
• 1:45
  Speaker 1: I see. Yeah, we need a big name movie star
• 1:47
  Speaker 1: or maybe cartoonists to play these characters on film. So
• 1:50
  Speaker 1: who's going to play you in the Hollywood version of
• 1:53
  Speaker 1: your life? I have thought about that question, Daniel. It's
• 1:57
  Speaker 1: gonna be Harry Chump. But welcome to our podcast. Daniel
• 2:01
  Speaker 1: and Jorge explain the Universe, a production of My Heart
• 2:04
  Speaker 1: Radio in which the scientists and the engineers really do
• 2:07
  Speaker 1: save the day by helping you crack the mysteries of
• 2:10
  Speaker 1: the universe. On this podcast, we think that the entire
• 2:13
  Speaker 1: mystery is like a fantastic puzzle. It's like a Christmas
• 2:16
  Speaker 1: present waiting to be unwrapped, and we cannot wait to
• 2:19
  Speaker 1: discover what the universe has to tell us. So we
• 2:23
  Speaker 1: love to talk about everything that's out there in the universe,
• 2:25
  Speaker 1: everything that's close by, everything that's far away, and explain
• 2:27
  Speaker 1: all of it to you. That's right, because scientists not
• 2:30
  Speaker 1: just save the day, but they also help us understand
• 2:32
  Speaker 1: the day, What makes the day? How how can we
• 2:35
  Speaker 1: have days and nights? Those were big questions in the
• 2:37
  Speaker 1: history of human civilization, and we figured it out. We
• 2:40
  Speaker 1: figured out that we are sitting on a big round
• 2:43
  Speaker 1: rock going around a big bright orbit that's a continual
• 2:46
  Speaker 1: explosion of fusion energy. And we didn't know that before,
• 2:50
  Speaker 1: but now we do. And probably there are lots of
• 2:52
  Speaker 1: unsung heroes in the history of those discoveries. Like we
• 2:55
  Speaker 1: talked about Galileo who looked through the telescope, but who
• 2:58
  Speaker 1: built that telescope, who really polished those lenses and make
• 3:01
  Speaker 1: sure the thing actually worked. Yeah, a lot of amazing
• 3:03
  Speaker 1: technicians who are behind the tools that scientists make. They
• 3:07
  Speaker 1: rarely get credit, right. I mean, they do get their
• 3:09
  Speaker 1: name in the three thousand author papers, right, or they don't.
• 3:13
  Speaker 1: Sometimes they don't. They just end up in the acknowledgements.
• 3:15
  Speaker 1: At least they got paid, right. You do pay the engineers, right.
• 3:19
  Speaker 1: I pay my engineers absolutely. But we have learned incredible
• 3:24
  Speaker 1: things about the nature of the universe. And every time
• 3:26
  Speaker 1: we open up new eyeballs, we illuminate new parts of
• 3:29
  Speaker 1: the universe, and it always comes with surprises. It always
• 3:31
  Speaker 1: tells us that the universe isn't quite as we expected.
• 3:35
  Speaker 1: And while we've been looking at the night sky for
• 3:37
  Speaker 1: thousands of years, it's only been the last few hundred
• 3:40
  Speaker 1: years that we've understood that there might be planets around
• 3:43
  Speaker 1: other stars, and only the last few decades that we've
• 3:46
  Speaker 1: been able to actually see some of those planets. Yeah,
• 3:49
  Speaker 1: it's pretty mind modeling. I get to think about the
• 3:51
  Speaker 1: arc of human history, right, and human knowledge, Like we
• 3:54
  Speaker 1: started out in caves or in Savannah's just you know,
• 3:57
  Speaker 1: trying to stay alive, thinking that what we can see
• 4:00
  Speaker 1: with our eyes is everything that there is about the world.
• 4:02
  Speaker 1: But then that's sort of expanded to the whole planet
• 4:05
  Speaker 1: and to the whole Solar System, and to the whole
• 4:07
  Speaker 1: galaxy and the whole multiple galaxies and galaxy clusters, and
• 4:10
  Speaker 1: maybe even other universes. That's why I'm always telling people
• 4:13
  Speaker 1: that physics matters, because it changes the whole context of
• 4:17
  Speaker 1: what it means to be alive, you know, the whole
• 4:19
  Speaker 1: scope of the universe. The stage on which your entire
• 4:22
  Speaker 1: life takes place on is determined by what we know
• 4:26
  Speaker 1: about the universe. And what's incredible is how much more
• 4:29
  Speaker 1: we know than people knew a thousand years ago, and
• 4:31
  Speaker 1: even a hundred years ago, and even twenty or thirty
• 4:34
  Speaker 1: years ago. There are things that are now routinely known
• 4:37
  Speaker 1: by just random people walking around on the street that
• 4:39
  Speaker 1: professional astronomers were dying to know just years ago. Yeah,
• 4:44
  Speaker 1: physics matters, and it also antimatters technically, right, there's a
• 4:48
  Speaker 1: certain symmetry about your role in human society. Fortunately, we
• 4:52
  Speaker 1: matter more than we antimatter, so there's a matter antimatter
• 4:55
  Speaker 1: asymmetry to physics. You have more matter than antimatter, or
• 4:58
  Speaker 1: more matter in general. I have noticed I've seen how
• 5:00
  Speaker 1: much coffee and cookies you guys consume in your seminars,
• 5:03
  Speaker 1: and donuts it's really more about the donuts. But yeah,
• 5:05
  Speaker 1: in the last few years, we've realized we've learned a
• 5:07
  Speaker 1: lot about our contacts are sort of place in the galaxy,
• 5:11
  Speaker 1: in the universe, and even in the last few decades
• 5:13
  Speaker 1: are sort of consciousness about where we are in the
• 5:16
  Speaker 1: universe and how rare we are has really sort of
• 5:18
  Speaker 1: almost exploded in a way. Absolutely, And as we learn
• 5:21
  Speaker 1: more about the universe, we get more answers, and those
• 5:23
  Speaker 1: answers just inspire more questions. Are the things that we
• 5:27
  Speaker 1: are seeing typical or are they weird and unusual? Are
• 5:31
  Speaker 1: there things out there still waiting to be discovered, what
• 5:33
  Speaker 1: surprises we just beyond our ability to see out into
• 5:37
  Speaker 1: the universe? And so to be On the podcast, we'll
• 5:39
  Speaker 1: be asking the question what is the future of exo
• 5:47
  Speaker 1: planet research? Exo planets? That's always a cool word. It
• 5:50
  Speaker 1: is a really cool word. I love putting exo in
• 5:52
  Speaker 1: front of everything. We have exo planets, we have exo moons.
• 5:55
  Speaker 1: One day will drink exo coffee. Well, I can't wait
• 5:58
  Speaker 1: for the exo physicists, you know, get them out of here.
• 6:02
  Speaker 1: I hope one day we have exo podcast listeners meeting
• 6:05
  Speaker 1: people in other Solar system subscribing to the podcast. Well,
• 6:09
  Speaker 1: technically every listener is an extra podcast listener because they're
• 6:12
  Speaker 1: not in the podcast, right, Extra means like outside of Yeah,
• 6:15
  Speaker 1: that's true. Yeah, they're in orbit around the podcast. Yeah. So,
• 6:18
  Speaker 1: in the last few decades, there's been sort of an
• 6:20
  Speaker 1: explosion in our knowledge about planets and other solar systems,
• 6:23
  Speaker 1: that is, planets that are not in our Solar system,
• 6:26
  Speaker 1: that are not you know, going around our Sun. It
• 6:28
  Speaker 1: really is incredible how much we have learned just in
• 6:30
  Speaker 1: the last few decades. In the nineties, we had never
• 6:33
  Speaker 1: seen another planet around another star. For all we knew,
• 6:36
  Speaker 1: this was the only star in the universe that had
• 6:39
  Speaker 1: planets around it, in the same way that we still
• 6:41
  Speaker 1: don't know if there is life around any other star.
• 6:43
  Speaker 1: We didn't even know if there were planets around any
• 6:46
  Speaker 1: other star until the ninety nineties, and slowly we saw
• 6:49
  Speaker 1: one and then two, and now, as you say, there's
• 6:51
  Speaker 1: been a veritable explosion of these discoveries. Right well before
• 6:55
  Speaker 1: the nineties, I guess we imagined it or we assumed it,
• 6:58
  Speaker 1: right like we saw these stars out there and the
• 7:00
  Speaker 1: verse in the galaxy, and we imagine, like, you know,
• 7:02
  Speaker 1: we can't be the only star with the planet, so
• 7:04
  Speaker 1: there must be planets around other stars. We just didn't
• 7:07
  Speaker 1: have like direct evidence or proof of it. That's right,
• 7:09
  Speaker 1: we didn't have direct evidence. But you know, if you
• 7:10
  Speaker 1: read back into the history, it's sort of surprising how
• 7:13
  Speaker 1: long it took people to put those two things together
• 7:15
  Speaker 1: to realize, Hold, on a second, there are planets around
• 7:18
  Speaker 1: our star. There might be planets around other stars. That
• 7:21
  Speaker 1: seems sort of obvious, but it wasn't until a few
• 7:24
  Speaker 1: hundred years ago that people put those two ideas together
• 7:26
  Speaker 1: and wondered how many planets might be out there in
• 7:29
  Speaker 1: other solar systems. And these days it's sort of a
• 7:31
  Speaker 1: bonanza of exoplanet discoveries, and that make even more explosive
• 7:35
  Speaker 1: as we get the new James Webb Space Telescope up
• 7:38
  Speaker 1: and running, which just launched recently in December, right, that's right,
• 7:41
  Speaker 1: very exciting moment for the entire astronomy community. Everybody on
• 7:45
  Speaker 1: pins and needles as their ten billion dollar toy launched
• 7:48
  Speaker 1: and then unfolded in space without a hitch. And it's
• 7:52
  Speaker 1: always very exciting in these moments when you open up
• 7:54
  Speaker 1: a new eyeball onto the universe, because it shows you
• 7:57
  Speaker 1: things that nobody has ever seen. No human has ever
• 8:00
  Speaker 1: known these facts, and we will soon get data from it,
• 8:03
  Speaker 1: and he will tell us things about the universe that
• 8:05
  Speaker 1: no human has ever known before. So to give us
• 8:08
  Speaker 1: some contexts in sort of the current status of exoplanet
• 8:11
  Speaker 1: research or search for other planets outside of our solarcism,
• 8:15
  Speaker 1: we thought we'd bring in a guest, a very special
• 8:17
  Speaker 1: scientist who specializes in sort of tewing up all of
• 8:21
  Speaker 1: these exo planets. All right, so it's my pleasure to
• 8:24
  Speaker 1: introduce our guest on today's podcast, Dr Jesse Christensen. She's
• 8:28
  Speaker 1: a Project scientist of the NASA Exo Planet Archive and
• 8:32
  Speaker 1: also a research scientist at the NASA Exo Planet Science
• 8:36
  Speaker 1: Institute at cal Tech. She has a pH d in
• 8:39
  Speaker 1: two thousand seven from the University of New South Wales
• 8:42
  Speaker 1: in Australia. She's won a bunch of awards, including in
• 8:45
  Speaker 1: two thousand eighteen the NASA Exceptional Engineering Achievement METAL and
• 8:49
  Speaker 1: also the University of Southern Queensland Research Giant. I was
• 8:53
  Speaker 1: wondering if that was actually a typo on your CV.
• 8:55
  Speaker 1: Is that giant or grant? It is actually giant? So
• 9:01
  Speaker 1: you are a giant of research in someone's eyes, I
• 9:04
  Speaker 1: am a giant research? Was it a giant grant as well?
• 9:07
  Speaker 1: I wish it had come with like a giant novelty thing.
• 9:09
  Speaker 1: It didn't. I've got a little framed thing though. It's nice.
• 9:11
  Speaker 1: She's also very active on Twitter as Aussie astronomer, where
• 9:15
  Speaker 1: she recently coined a new phrase in astronomy, which is
• 9:19
  Speaker 1: the name of people who live in the milky Way.
• 9:22
  Speaker 1: You called us the milky Wegians. I did, I did,
• 9:26
  Speaker 1: after some thought, after some consideration, that's what I landed on. Wait,
• 9:30
  Speaker 1: what's the term milky Wigian milky region? I was looking
• 9:33
  Speaker 1: for other places that ended in way, and I landed
• 9:36
  Speaker 1: on Goalway, and people from Goalway are called goal Regions.
• 9:40
  Speaker 1: And I was like, there, it is so milky regions.
• 9:42
  Speaker 1: It sounds sort of like witchcrafty maybe, like or am
• 9:45
  Speaker 1: I thinking wicked Wickan? Oh yes, so so not milky Wickens.
• 9:49
  Speaker 1: That would be something different. That's the other planet exactly.
• 9:52
  Speaker 1: That's right. That's what happens when which is spilled their
• 9:55
  Speaker 1: breakfast cereal all over themselves. They're milky Wickens. Anyway, we
• 9:59
  Speaker 1: are a milky regions, all of us, and we are
• 10:01
  Speaker 1: curious about the nature of the galaxy and the planets
• 10:04
  Speaker 1: in it and all the planets that are around stars
• 10:07
  Speaker 1: other places in the galaxy, and so we've asked Jesse
• 10:10
  Speaker 1: to come on the podcast and answer all of our
• 10:12
  Speaker 1: questions about exo planets past and future. Thanks very much
• 10:15
  Speaker 1: for joining us today. Thank you for having me. I'm
• 10:17
  Speaker 1: excited to be here. Wonderful. So first I think we
• 10:19
  Speaker 1: should get started just with the basics of exo planets.
• 10:23
  Speaker 1: How is it that we can see exo planets planets
• 10:26
  Speaker 1: around other stars? From Earth? I mean, if I look
• 10:29
  Speaker 1: up in the night sky, we can just barely see
• 10:31
  Speaker 1: the stars. How is it possible to see planets going
• 10:34
  Speaker 1: around those stars? You've really hit on the verb there.
• 10:37
  Speaker 1: So see, we don't actually see almost any of the
• 10:41
  Speaker 1: planets that we find. What we do is we look
• 10:44
  Speaker 1: at the stars that they orbit and observe changes of
• 10:47
  Speaker 1: those stars that are induced by the presence of the planet.
• 10:50
  Speaker 1: And we can do this a few different ways. The
• 10:52
  Speaker 1: planets pull gravitationally on the stars, so the stars actually
• 10:56
  Speaker 1: wobble in the sky, and we can see that when
• 10:58
  Speaker 1: we measure their velocity, and we measured their precision very
• 11:01
  Speaker 1: precisely the stars are all kind of just wobbling around
• 11:03
  Speaker 1: in the sky a little bit. If they have planets.
• 11:06
  Speaker 1: Another way we see them is if the planet orbiting
• 11:08
  Speaker 1: the star blocks some of the light from the star.
• 11:10
  Speaker 1: If it's lined up just right and eclipses the start,
• 11:13
  Speaker 1: then we see that the brightness of the star changes.
• 11:15
  Speaker 1: So you're right, it's very difficult to see planets. So
• 11:18
  Speaker 1: what we really do is look at the stars and
• 11:20
  Speaker 1: see the changes induced by the planets. It's pretty wild
• 11:23
  Speaker 1: to think about that all the stars are out there,
• 11:25
  Speaker 1: at least the ones with planets are wiggling, you know,
• 11:27
  Speaker 1: like if you look at the night sky, that means
• 11:29
  Speaker 1: most of those stars are wiggling. Even our Sun is wiggling. Yeah,
• 11:32
  Speaker 1: so actually Jupiter, which has about one percent the mass
• 11:36
  Speaker 1: of our Solar system, is actually dragging our Sun around
• 11:39
  Speaker 1: the middle of our solar system. So if you were
• 11:41
  Speaker 1: an alien civilization looking at our Sun, you would basically
• 11:44
  Speaker 1: see that it's moving with this roughly twelve year periodicity
• 11:48
  Speaker 1: in the middle of our Solar system, and from that
• 11:50
  Speaker 1: you could infer that there was a giant planet on
• 11:52
  Speaker 1: a twelve year orbit pulling it around, and then you
• 11:54
  Speaker 1: could guess that we had a Jupiter like planet, could
• 11:57
  Speaker 1: they guess that we're here? If they had really really
• 12:00
  Speaker 1: really really really precise instrumentation, more precise than the instrumentation
• 12:03
  Speaker 1: that we have been able to develop so far, they could,
• 12:06
  Speaker 1: in fact in further presence of Earth and in fact
• 12:08
  Speaker 1: the whole Solar system. But this is a leap in
• 12:10
  Speaker 1: technology that we have not made yet, and that makes
• 12:12
  Speaker 1: me wonder, like, what can they know about Jupiter? So
• 12:16
  Speaker 1: you say that they could see the jupiters here, what
• 12:18
  Speaker 1: exactly can they know because they can't see it directly,
• 12:20
  Speaker 1: So can they know things like it's orbital period, and
• 12:23
  Speaker 1: it's mass and its volume and what it's made out of?
• 12:26
  Speaker 1: What can we actually know about these planets? Right? So,
• 12:29
  Speaker 1: if they could only see the wobble of the star,
• 12:32
  Speaker 1: basically the only thing they'd be able to measure would
• 12:34
  Speaker 1: be its orbital period, so how long it takes to
• 12:36
  Speaker 1: ground the star and the component of its mass that's
• 12:40
  Speaker 1: along the line of sight between the star and them,
• 12:43
  Speaker 1: Which is to say that if Jupiter is lined up
• 12:45
  Speaker 1: just right so that it's orbiting between the star and
• 12:48
  Speaker 1: the observer, then that is the maximal pull that we
• 12:51
  Speaker 1: can see. That's the maximum wobble will be if it's
• 12:54
  Speaker 1: lined up just right. But most of the planets aren't
• 12:56
  Speaker 1: lined up just right. They're tilted a little bit compared
• 12:58
  Speaker 1: to that that plane, so some of the pull of
• 13:00
  Speaker 1: the star is in a direction we can't see. It's
• 13:02
  Speaker 1: in a direction, you know, orthogonal to our line of sight,
• 13:05
  Speaker 1: at right angles to our line of sight, so we
• 13:07
  Speaker 1: don't see that component. We only see the component of
• 13:09
  Speaker 1: the wobble that's in our direction. So we get a
• 13:12
  Speaker 1: minimum mass, we call it. So you get an orbital
• 13:14
  Speaker 1: period and a minimum mass. So if a Jupiter, for instance,
• 13:16
  Speaker 1: they'd get some minimum mass of one jupiter mass and
• 13:18
  Speaker 1: then be like, okay, it's a gas giant. And we know,
• 13:21
  Speaker 1: given the way things are constructed in the galaxy, if
• 13:24
  Speaker 1: you have something that weighs the jupidter mass, you know
• 13:26
  Speaker 1: that it's mostly hydrogen and helium. It's not mostly rock
• 13:29
  Speaker 1: or mostly ice. It's mostly hydrogen helium. So you could
• 13:32
  Speaker 1: infer that it was a gas giant. So you'd have
• 13:34
  Speaker 1: its period, you'd have its mass, a minimum mass, and
• 13:36
  Speaker 1: you'd have some guess at its bulk composition. The other
• 13:39
  Speaker 1: thing you could know if you know what kind of
• 13:41
  Speaker 1: star it's orbiting. Is it's temperature, because the orbit all
• 13:44
  Speaker 1: period tells you how far away from the star it is.
• 13:47
  Speaker 1: So Earth with our period of three hundred and sixty
• 13:49
  Speaker 1: five years, is just the right distance to get the
• 13:51
  Speaker 1: right amount of radiation from the Sun for water to
• 13:54
  Speaker 1: be liquid on the surface. And that's kind of the
• 13:56
  Speaker 1: holy grail of what we're doing right now, trying to
• 13:58
  Speaker 1: find planets that at this right temperature so be able
• 14:00
  Speaker 1: to guess it's temperature, it's it's rough equilibrium temperature, knowing
• 14:03
  Speaker 1: how far it was from the Sun. So you can
• 14:05
  Speaker 1: actually get a lot just from this wobble on the sky.
• 14:07
  Speaker 1: I think that's really fascinating you say that you can
• 14:09
  Speaker 1: guess what's in the planet just from knowing how big
• 14:12
  Speaker 1: it is. Is that just from knowing like how much
• 14:14
  Speaker 1: hydrogen and helium and lithium and uranium there is out
• 14:18
  Speaker 1: there in the universe that you're guessing how much of
• 14:20
  Speaker 1: a serving of each of those components a big planet
• 14:23
  Speaker 1: might get. Yeah, so we can start with what we
• 14:26
  Speaker 1: think a protoplanetary disk is made of. So when a
• 14:29
  Speaker 1: star is born, it's born from a cloud of dust
• 14:32
  Speaker 1: and gas, and the amount of dust in that cloud
• 14:35
  Speaker 1: dust is basically like the solid materials that aren't in
• 14:38
  Speaker 1: gash is formed. The amount of dust in that cloud
• 14:40
  Speaker 1: basically puts a limit on how many rocky planets or
• 14:43
  Speaker 1: rocky cores of bigger planets you can make out of
• 14:45
  Speaker 1: this protoplanetary disk. It's like making a cake. If you
• 14:48
  Speaker 1: only have two eggs, you're only going to be able
• 14:49
  Speaker 1: to make one cake. If you have six eggs, maybe
• 14:52
  Speaker 1: you can make three cakes or one three tier cake.
• 14:54
  Speaker 1: So you're really constrained by these ingredients in your initial
• 14:57
  Speaker 1: disk of material that's creating your planets. But that's sort
• 15:00
  Speaker 1: of statistical, right. It's like if somebody took everything in
• 15:03
  Speaker 1: the grocery store and then blended it up into a tornado.
• 15:05
  Speaker 1: You're talking about like how much flour and how many
• 15:08
  Speaker 1: eggs might fall into a planet. You don't actually know
• 15:10
  Speaker 1: for an individual planet whether it's like unusually large lump
• 15:14
  Speaker 1: of uranium and its core something. Is that right? Right? So,
• 15:17
  Speaker 1: for instance, if you were in an American supermarket and
• 15:19
  Speaker 1: you blended everything up, your planets would have a lot
• 15:22
  Speaker 1: of cereal in them. There'd be a lot of breakfast
• 15:24
  Speaker 1: cereal compared to other countries that I've lived in right,
• 15:27
  Speaker 1: there wouldn't be any veggie mate for example, exactly, you
• 15:29
  Speaker 1: wouldn't have your vegemite flavored planets. One thing we do
• 15:32
  Speaker 1: know is if you have something the size of Earth
• 15:36
  Speaker 1: that's not really big enough if it's just a hydrogen
• 15:38
  Speaker 1: and helium bowl to hold itself together compared to all
• 15:42
  Speaker 1: of the other forces that are going on in the
• 15:44
  Speaker 1: formation and evolution of a planetary system. So if you
• 15:46
  Speaker 1: have something that's the size of Earth, you're pretty sure
• 15:49
  Speaker 1: it's mostly rock, just given you know the amount of
• 15:52
  Speaker 1: gravitational pole you need to hold something together. So you
• 15:56
  Speaker 1: couldn't really have like a tiny gas dwarf because it
• 15:58
  Speaker 1: would just disperse. And that's the wabbling rate. But from
• 16:01
  Speaker 1: the eclipse, and I think we can can we tell
• 16:03
  Speaker 1: other things about the planets. If the planet's eclipsing, we
• 16:05
  Speaker 1: can get so much more information. Is really quite great,
• 16:09
  Speaker 1: and that's the method that I use. So now I'm
• 16:11
  Speaker 1: going to like percetialize about the transit method. So if
• 16:14
  Speaker 1: the planet goes in front of the star, and you
• 16:17
  Speaker 1: know how big the star is, and you can measure
• 16:19
  Speaker 1: how much dimmer the star gets, then you know how
• 16:22
  Speaker 1: big in size the planet must be to block that
• 16:25
  Speaker 1: much light. So, for instance, Jupiter in front of the
• 16:27
  Speaker 1: Sun blocks about one percent of the light. So if
• 16:30
  Speaker 1: you're looking at a sun like star and you see
• 16:32
  Speaker 1: that something's blocking one percent of the light, you know
• 16:34
  Speaker 1: it's a Jupiter sized planet. Once you have size and mass,
• 16:37
  Speaker 1: now you can really start to say things about the
• 16:40
  Speaker 1: density of the planet and what it might be made
• 16:42
  Speaker 1: of and really start to constrain, oh, it must be
• 16:45
  Speaker 1: rock and a gaseous atmosphere. The other cool thing about
• 16:49
  Speaker 1: planets that go in front of stars is that their
• 16:51
  Speaker 1: atmospheres go in front of the stars as well. Now
• 16:54
  Speaker 1: picture the Earth to the Earth is a rock and
• 16:57
  Speaker 1: it has this thin gaseous atmosphere around it. Now you're again,
• 17:00
  Speaker 1: let's be this alien civilization looking at the Sun. If
• 17:03
  Speaker 1: you were lined up just right so that the Earth
• 17:05
  Speaker 1: passed in front of the Sun and block some of
• 17:07
  Speaker 1: the light, then the sunlight would go through the Earth's atmosphere,
• 17:11
  Speaker 1: but just the pain a little bit through the thin
• 17:13
  Speaker 1: layer of atmosphere. Yes, it would be a tiny amount
• 17:16
  Speaker 1: of the atmosphere, but the molecules in that atmosphere, so
• 17:19
  Speaker 1: our atmosphere has got oxygen, it's got nitrogen, it's got water.
• 17:23
  Speaker 1: The molecules in the atmosphere block some certain wavelengths of light. So,
• 17:27
  Speaker 1: for instance, if you look at the Earth's atmosphere at
• 17:30
  Speaker 1: one point four micron wavelength light, which is where water absorbs,
• 17:34
  Speaker 1: the Earth actually looks bigger because the atmosphere is opaque
• 17:37
  Speaker 1: at one point four microns because of the water. So
• 17:40
  Speaker 1: this is what we do for planets around other stars.
• 17:42
  Speaker 1: We look at their size as a function of wavelength
• 17:45
  Speaker 1: to work out when is their atmosphere opaque and when
• 17:48
  Speaker 1: is it transparent, And that tells us what molecules must
• 17:51
  Speaker 1: be in that atmosphere, blocking light at certain wavelengths and
• 17:54
  Speaker 1: letting it through another wavelengths. So we have this like
• 17:56
  Speaker 1: spectral fingerprint of the atmosphere of the planet on the
• 18:00
  Speaker 1: really just the brightness of the star changing at different wavelengths.
• 18:02
  Speaker 1: And then you start to be able to say, okay, cool,
• 18:05
  Speaker 1: this planet's got me sane, it's got carbon dioxide, it's
• 18:08
  Speaker 1: got iron rain coming down out of the atmosphere. You
• 18:11
  Speaker 1: can tell so much cool stuff. If you can see
• 18:13
  Speaker 1: into the atmosphere. It's like watching the star rise over
• 18:16
  Speaker 1: the planet, right, It's like sunrise and sunset. It's incredible exactly,
• 18:20
  Speaker 1: and our atmosphere, you know, it does interesting things to
• 18:22
  Speaker 1: the Sun as sunrise and sunset, And it's the same
• 18:24
  Speaker 1: kind of thing. The more atmosphere the light is going through,
• 18:27
  Speaker 1: the more imprint of the planet's atmosphere, it goes on
• 18:30
  Speaker 1: the sunlight. And you said a couple of times, like
• 18:32
  Speaker 1: if things are lined up just right, you know, if
• 18:35
  Speaker 1: Jupiter passes across the line of the Sun between you know,
• 18:39
  Speaker 1: the Sun and these observing aliens, then these methods can work.
• 18:42
  Speaker 1: It seems like things have to be lined up kind
• 18:45
  Speaker 1: of in a lucky way. Doesn't that really limit our
• 18:47
  Speaker 1: ability to discover exoplanets? Yeah, so using the transit method,
• 18:51
  Speaker 1: it really does limit us. So an earthlike planet around
• 18:54
  Speaker 1: a star like the Sun has about a one in
• 18:56
  Speaker 1: two hundred chance of transitting from our point of view
• 18:59
  Speaker 1: as we look at all the stars around us. What
• 19:01
  Speaker 1: that means is that you really have to look at
• 19:02
  Speaker 1: a lot of stars in order to catch the ones
• 19:05
  Speaker 1: that are lined up just right. So the NASA Kepler
• 19:07
  Speaker 1: mission that I worked on for ten years looked at
• 19:10
  Speaker 1: two hundred thousand stars to try and find the systems
• 19:13
  Speaker 1: that were lined up just right. So that's with the
• 19:15
  Speaker 1: transit method. There are other methods like the wobble method.
• 19:18
  Speaker 1: You don't need to be lined up just right. There
• 19:19
  Speaker 1: is also, going back to your very very original question,
• 19:22
  Speaker 1: there's a method called the direct imaging method, which is
• 19:25
  Speaker 1: basically exactly what it sounds. If the star is close
• 19:28
  Speaker 1: enough to us that the separation between the star and
• 19:31
  Speaker 1: the planet on the sky is big enough we have
• 19:33
  Speaker 1: we actually have like pretty exquisite instrumentation that you can
• 19:36
  Speaker 1: use to block out the starlight very carefully and look
• 19:40
  Speaker 1: around the star to find any little glowing points of
• 19:43
  Speaker 1: light which could be planets. So we do have a handful,
• 19:46
  Speaker 1: maybe a few dozen now directly image planets. Now, this
• 19:49
  Speaker 1: mostly only works for very big planets, like even bigger
• 19:52
  Speaker 1: than Jupiter, that are quite young, because as planets are
• 19:55
  Speaker 1: forming and the and the balls of gas and contracting,
• 19:57
  Speaker 1: they're radiating out this heat which makes them bright at
• 20:00
  Speaker 1: certain wavelengths. So we can directly image some kinds of
• 20:04
  Speaker 1: young giant planets and then it doesn't matter how they're
• 20:07
  Speaker 1: lined up, But we do have to be looking at
• 20:08
  Speaker 1: the system at the right time to kind of maximize
• 20:10
  Speaker 1: that separation between the star and planet. So there's still
• 20:12
  Speaker 1: a timing issue. It's sort of like you're trying to
• 20:15
  Speaker 1: measure the number of cats in your neighborhood, but you
• 20:17
  Speaker 1: know you're not very good at spotting them, and so
• 20:19
  Speaker 1: like every time you see a cat, you imagine, well,
• 20:21
  Speaker 1: I saw this one cat. That must be actually two
• 20:23
  Speaker 1: hundred cats out there that I'm not seeing. You have
• 20:26
  Speaker 1: to have this like estimate of your inability to see
• 20:29
  Speaker 1: planets so you can like extrapolate from what you do
• 20:31
  Speaker 1: see to what's actually out there, right, And that's actually
• 20:35
  Speaker 1: exactly what I did on the Massa Caple mission. I
• 20:38
  Speaker 1: injected fake planets into the data to see how good
• 20:41
  Speaker 1: we were finding them, like you know, pretending to I
• 20:44
  Speaker 1: just put cats everywhere, and I was like, okay, how
• 20:45
  Speaker 1: many cats do we see? I know that I secretly
• 20:47
  Speaker 1: hid two hundred cats in this neighborhood. How many cats
• 20:50
  Speaker 1: did we see? So that's exactly what I did, and
• 20:52
  Speaker 1: that was how we were able to say that, you know,
• 20:54
  Speaker 1: Kepler found two and a half thousand planets. From that,
• 20:58
  Speaker 1: we were able to infer that the aleaxy has billions
• 21:01
  Speaker 1: of planets. Given the numbers of stars we looked at
• 21:03
  Speaker 1: and the number of planets we found, the most exciting
• 21:05
  Speaker 1: discovery from the Kepler mission is that exer planets are
• 21:08
  Speaker 1: everywhere in our galaxy. So, just to force all the
• 21:10
  Speaker 1: conspiracy theorists, you injected fake data into a NASA mission,
• 21:14
  Speaker 1: but you told people you were injecting fake Yes. And
• 21:18
  Speaker 1: I had to jump through a lot of hoops to
• 21:20
  Speaker 1: do this, and it was quite funny. I had to
• 21:22
  Speaker 1: keep the simulated data on a separate server that was
• 21:25
  Speaker 1: never given access to the outside world. There was no
• 21:27
  Speaker 1: way to log into the server from the outside. And
• 21:30
  Speaker 1: even now years later, whenever somebody announces a new Kepler planet,
• 21:35
  Speaker 1: I have to go and double check that the period
• 21:37
  Speaker 1: and characteristics of this new planet aren't a match for
• 21:40
  Speaker 1: the you know, fake planet that I injected into that
• 21:42
  Speaker 1: light curve. So there's a lot of safeguarding to make
• 21:44
  Speaker 1: sure that the simulated data is never mistaken for real plants. Wow,
• 21:48
  Speaker 1: and how many cats have you found out there? So
• 21:50
  Speaker 1: we think that almost every star has planets around it.
• 21:54
  Speaker 1: The smaller the star, the more planets they have. So
• 21:57
  Speaker 1: m Dwarfs, which are the most ubiquitous star in our galaxy,
• 21:59
  Speaker 1: is seventy of the hundreds of billions of stars in
• 22:02
  Speaker 1: our galaxy. Endors we think that endors have multiple rocky
• 22:05
  Speaker 1: planets like Earth around them, which is wild because that
• 22:08
  Speaker 1: means there are hundreds of billions of rocky planets now galaxy,
• 22:11
  Speaker 1: which is so cool. That is really very cool. Yeah,
• 22:14
  Speaker 1: it's amazing. And you're sort of part of the James
• 22:17
  Speaker 1: Webb Space Telescope as well, right, So I am interested
• 22:21
  Speaker 1: in sideline to the James web Space Telescope. So I
• 22:23
  Speaker 1: haven't done a lot of atmosphere work myself. I do
• 22:25
  Speaker 1: more of the demographic stuff that Daniel was talking about,
• 22:28
  Speaker 1: working out how many cats we couldn't see because of
• 22:30
  Speaker 1: the cats we could see. So James Webb is more
• 22:32
  Speaker 1: going to be looking at the cats very carefully and
• 22:34
  Speaker 1: being like, Okay, this is a Siamese, and this is
• 22:36
  Speaker 1: a Burmese, and this is a Calico. And it uses
• 22:38
  Speaker 1: the transit method as well, right, it takes sort of
• 22:40
  Speaker 1: like giant pictures of the space. Yes, So, so the
• 22:44
  Speaker 1: transit method with what I was describing the transmission spectrum,
• 22:48
  Speaker 1: so as the starlight goes through the planet's atmosphere. We've
• 22:51
  Speaker 1: been able to do this with Hubble, and Hubble has
• 22:53
  Speaker 1: been able to give us really exquisite results. But we're
• 22:56
  Speaker 1: really pushing Hubble to the very, very very limits of
• 22:59
  Speaker 1: what it can do. And we're still looking at pretty
• 23:00
  Speaker 1: big planets like Neptune size planets and above. So with
• 23:04
  Speaker 1: James Web which is you know, three times bigger in radius,
• 23:08
  Speaker 1: so nearly ten times bigger in collecting area, we're going
• 23:10
  Speaker 1: to be able to look at smaller planets like Earth's
• 23:13
  Speaker 1: size planets and start to look at the atmospheres of those.
• 23:16
  Speaker 1: And that's you know, obviously I don't have to explain
• 23:18
  Speaker 1: why it's super interesting to look into the atmospheres of
• 23:20
  Speaker 1: Earth sized planets that we find. We want to know
• 23:22
  Speaker 1: how common are things like you know, carbon and oxygen
• 23:26
  Speaker 1: and nitrogen and phosphorus and methane and all of these
• 23:30
  Speaker 1: like super interesting based chemicals that we build life out of.
• 23:33
  Speaker 1: That's the next question. Now we know rocky planets are everywhere,
• 23:36
  Speaker 1: are rocky planets with the ingredients for life everywhere. That
• 23:39
  Speaker 1: would be super cool to know. That would be super cool.
• 23:42
  Speaker 1: And I also heard that you can sometimes look at
• 23:44
  Speaker 1: the weather in some of these exo planets by looking
• 23:47
  Speaker 1: at sort of the delays in the signals in the
• 23:50
  Speaker 1: way of moves around the Sun. Yes, exactly, so on
• 23:53
  Speaker 1: Earth One of the things we can see is the
• 23:55
  Speaker 1: phases of Venus. So Venus, you know, because it's interior
• 23:59
  Speaker 1: to us. Sometimes we see the full face of Venus
• 24:01
  Speaker 1: get illuminated, and sometimes we only see a phase of it.
• 24:04
  Speaker 1: We can do a similar thing with exoplanets around other
• 24:07
  Speaker 1: stars if we measure the brightness of the system very
• 24:10
  Speaker 1: very precisely. As the planet is orbiting around the star,
• 24:13
  Speaker 1: it actually starts reflecting light back towards us as it
• 24:16
  Speaker 1: goes behind the star. So we build what we call
• 24:18
  Speaker 1: a phase curve, and you can see things like you know,
• 24:21
  Speaker 1: jets and weather and spots and stuff coming and going,
• 24:24
  Speaker 1: and you know, it's very crude, but we can basically
• 24:27
  Speaker 1: reverse engineer these phase curves into maps of the surface,
• 24:31
  Speaker 1: and we can see variability. We can see that, you know,
• 24:33
  Speaker 1: the surfaces of these planets, the upper atmospheres, which is
• 24:36
  Speaker 1: really what we're looking at. The upper atmospheres of these
• 24:38
  Speaker 1: planets are changing, which is basically whether and then my
• 24:41
  Speaker 1: husband makes fun of me because he says, we're all
• 24:43
  Speaker 1: just becoming exo meteorologists, not astrophysicists, because we're es measuring
• 24:47
  Speaker 1: where there are other planets. But I still think that's
• 24:48
  Speaker 1: pretty amazing. Yeah, I can't wait for that telecast where
• 24:51
  Speaker 1: you're like throwing you know, sticky magnets with symbols of
• 24:54
  Speaker 1: ferns and clouds up on the planet excerpt. Yeah, and
• 24:58
  Speaker 1: tomorrow and fifty kancree e, get ready for some storms.
• 25:01
  Speaker 1: It's going to be a bad day. It's going to
• 25:03
  Speaker 1: be raining iron. So bring as the storms will be
• 25:06
  Speaker 1: bad tomorrow. You know, keep your umbrellas with you, your
• 25:09
  Speaker 1: diamond umbrellas exactly, your platinum umbrellas. And so the James
• 25:13
  Speaker 1: Webb can do this because it gathers more light because
• 25:16
  Speaker 1: as a larger collecting surface are also because you can
• 25:19
  Speaker 1: see different kinds of light. So that and those two things,
• 25:21
  Speaker 1: and also a third thing. So it's bigger. It's six
• 25:24
  Speaker 1: and a half meters as compared to Hubble, which is
• 25:26
  Speaker 1: to two and a half meters. It's got different wavelength
• 25:29
  Speaker 1: so it's more in the infrared and mid infrared. So
• 25:32
  Speaker 1: remember how I was talking about water, which absorbs at
• 25:35
  Speaker 1: one point four microns. That's in the near infrared. That's
• 25:37
  Speaker 1: not a wavelength of light we can see with our eyes.
• 25:39
  Speaker 1: That's a wavelength of light that you see with like
• 25:41
  Speaker 1: night vision goggles. It's one of the it's a signature
• 25:44
  Speaker 1: of heat and warmth in the infrared, so it's a
• 25:45
  Speaker 1: different wavelength. So that covers a whole bunch of the
• 25:48
  Speaker 1: really interesting molecules that we care about, like carbon dioxide
• 25:51
  Speaker 1: and carbon monoxide and water. And the third thing is
• 25:54
  Speaker 1: we've built these four just amazing instruments which are really
• 25:59
  Speaker 1: engineered to take advant iantage of James Webb's location in space.
• 26:02
  Speaker 1: It's wavelengths all of the interesting things that we're going
• 26:04
  Speaker 1: to look at, So we're going to be able to
• 26:05
  Speaker 1: get much higher resolution spectra, so be able to break
• 26:09
  Speaker 1: those wavelengths of light into into finer and fine negradations,
• 26:13
  Speaker 1: and then you can start to do all sorts of
• 26:15
  Speaker 1: interesting things like look at isotopes. You know, is it
• 26:18
  Speaker 1: heavy water or is it normal water? And what does
• 26:20
  Speaker 1: that mean about where that planet must have formed in
• 26:21
  Speaker 1: that protoplanetary disk, and was the water delivered later from
• 26:24
  Speaker 1: the outer Solar System? All this cool stuff. Once you
• 26:27
  Speaker 1: can start to get more detailed observations. Did you say
• 26:30
  Speaker 1: we can test the water in other planets? Yea. So
• 26:33
  Speaker 1: one of the things we could be able to do
• 26:34
  Speaker 1: if you have high enough resolution is measure isotopes. So
• 26:38
  Speaker 1: isotopes are basically, you know, molecules that have atoms that
• 26:41
  Speaker 1: have different amounts of neutrons in the center of the
• 26:43
  Speaker 1: same amount of protons. So we have something called heavy water,
• 26:46
  Speaker 1: which is basically water where instead of hydrogen and oxygen,
• 26:50
  Speaker 1: it's deuterium and oxygen. And we on Earth we use
• 26:54
  Speaker 1: heavy water to basically measure where we think the water
• 26:57
  Speaker 1: came from on Earth. So where Earth is right out
• 27:00
  Speaker 1: was too hot in the early Solar System for liquid water,
• 27:03
  Speaker 1: So we think that most of the water on Earth
• 27:05
  Speaker 1: was delivered from the outer Solar System by comets. So
• 27:08
  Speaker 1: during the formation of the Solar System was a really chaotic,
• 27:11
  Speaker 1: violent place. You know, planetisms are forming and smashing into
• 27:14
  Speaker 1: each other, orbits are changing and exchanging energy with each other,
• 27:18
  Speaker 1: and you have this huge cloud of material the Kuiper Belt,
• 27:21
  Speaker 1: and then outside of that the aort cloud, which are
• 27:23
  Speaker 1: just you're throwing stuff at the inner Solar System constantly.
• 27:26
  Speaker 1: So we think that the oceans on Earth largely came
• 27:29
  Speaker 1: from comets from the outer Solar System smashing into Earth
• 27:31
  Speaker 1: and delivering like these giant bowls of ice, Like commets
• 27:34
  Speaker 1: are just big bowls of ice and dirt basically. And
• 27:36
  Speaker 1: one of the ways we think this is true is
• 27:38
  Speaker 1: because we've been able to measure the isotopes of like
• 27:40
  Speaker 1: what rate of heavy water is there to normal water
• 27:43
  Speaker 1: on Earth versus the comets that we see. So if
• 27:45
  Speaker 1: you have precise enough spectra of exoplanet atmospheres, you can
• 27:48
  Speaker 1: start to do the same sort of thing, look at
• 27:50
  Speaker 1: isotopes and start to use that to map out where
• 27:52
  Speaker 1: you think things formed. There's a lot of open questions
• 27:55
  Speaker 1: about how planets form and how they migrate to where
• 27:57
  Speaker 1: we see them today. Well, testing the water on the planets,
• 28:00
  Speaker 1: you also said we can measure like how much CEO
• 28:02
  Speaker 1: two there is. Does that mean that we can tell
• 28:04
  Speaker 1: whether the water on those planets is like still water
• 28:07
  Speaker 1: or sparkling water? Yes, this is the peri a planet
• 28:10
  Speaker 1: over here. Is it flavored water like the big trend
• 28:14
  Speaker 1: right now? Almost certainly? Exactly. Well, and Nestlie probably owns
• 28:18
  Speaker 1: the water rights to all these planets already. Oh yeah,
• 28:20
  Speaker 1: almost certainly true. Was somewhere in the legal paperworkners like
• 28:24
  Speaker 1: this water and on all planets all their water to
• 28:27
  Speaker 1: So James Web has these amazing abilities because it's bigger,
• 28:30
  Speaker 1: because they can see deeper into the I R and
• 28:33
  Speaker 1: also because it has these new instruments. Can you say
• 28:35
  Speaker 1: something about the technology that was developed for the James
• 28:37
  Speaker 1: Web telescope specifically, I was reading about these incredible sensors
• 28:41
  Speaker 1: that they use to detect like individual photons. Yeah, so
• 28:44
  Speaker 1: that's actually one of been one of the big breakthroughs
• 28:46
  Speaker 1: in the last few decades. So you know, everybody nowadays
• 28:49
  Speaker 1: has really really fantastic c c D in their phone, right,
• 28:52
  Speaker 1: everybody just pulls out their phone and takes great images,
• 28:55
  Speaker 1: high resolution images. The goal for a long time has
• 28:57
  Speaker 1: been able to do this at other wavelengths. So c
• 29:00
  Speaker 1: CDs us a specific technology to turn visible light photons
• 29:04
  Speaker 1: into electrons and then you know, turn that into images.
• 29:07
  Speaker 1: But at other wavelengths that exchange doesn't happen the same way.
• 29:10
  Speaker 1: So there's a lot of interest in developing infrared detectors
• 29:13
  Speaker 1: and and ultra violet detectors that do as good a
• 29:16
  Speaker 1: job basically as your iPhone does. And that's been one
• 29:18
  Speaker 1: of the real advancements in the last few years. These
• 29:21
  Speaker 1: breakthroughs is making these infrared detectors that you know, can
• 29:25
  Speaker 1: serve the number of photons, which means you don't lose
• 29:27
  Speaker 1: any you can measure absolute numbers of photons, and that
• 29:30
  Speaker 1: do it at a high enough efficiency that you can
• 29:32
  Speaker 1: get really really good measurements even on very faint things,
• 29:35
  Speaker 1: which is a lot of what we're will go for.
• 29:37
  Speaker 1: I'm not going to be able to give you any
• 29:38
  Speaker 1: more technical details than that, because I didn't build any
• 29:41
  Speaker 1: of them. Well, that's all super fascinating, and we have
• 29:43
  Speaker 1: a lot more questions for your ex oplanet research, but
• 29:46
  Speaker 1: first we have to take a little break. All right,
• 30:01
  Speaker 1: we're back and we're talking to Dr Jesse Christensen, project
• 30:04
  Speaker 1: scientists of the NASA Exo Planet Archive. Like your consistent
• 30:08
  Speaker 1: I think you'ven sort of part of this whole sort
• 30:10
  Speaker 1: of revolution in exo planets. I mean, basically, before the
• 30:14
  Speaker 1: nineteen nine we didn't really have direct evidence or even
• 30:17
  Speaker 1: indirect evidence of planets and other stars. But this has
• 30:20
  Speaker 1: also to come about in the last thirty years. Right,
• 30:23
  Speaker 1: was the first discovery of a planet using this wobble
• 30:26
  Speaker 1: method around a star like our Sun. Actually a few
• 30:29
  Speaker 1: years before in nWo we had found planets around pulsars.
• 30:33
  Speaker 1: So a pulsar is what happens at the very end
• 30:36
  Speaker 1: of the life of a star that has puffed off,
• 30:38
  Speaker 1: its out of layers, and it's collapsed into a neutron
• 30:40
  Speaker 1: star and it's spinning super super super fast thousands of
• 30:44
  Speaker 1: times a second. And if you're lined up just right
• 30:46
  Speaker 1: to this spinning star, you actually see pulses of radiation
• 30:49
  Speaker 1: coming out thousands of times a second. So some people
• 30:52
  Speaker 1: who weren't actually hunting for extra planets, the extra planet
• 30:55
  Speaker 1: hunters rofire looking over looking at normal stars. So some
• 30:58
  Speaker 1: people who were looking at pulsars ound this pulsar that
• 31:01
  Speaker 1: was the pulses were sometimes coming early and sometimes coming late,
• 31:04
  Speaker 1: and sometimes coming early and sometimes coming late, and they
• 31:06
  Speaker 1: were like, what's happening, And they realized that there must
• 31:09
  Speaker 1: be something around this pulsar that was gravitationally pulling on it.
• 31:12
  Speaker 1: So sometimes the pulsar was moving towards us and sometimes
• 31:15
  Speaker 1: it was moving away. So there was kind of like
• 31:16
  Speaker 1: a doppler effect, like if you've ever had an ambulance
• 31:19
  Speaker 1: drive past you in the street and it's like, we
• 31:21
  Speaker 1: we this is what was happening to the pulsar, and
• 31:24
  Speaker 1: they realized it had planets, which was cool, but also
• 31:27
  Speaker 1: kind of a bit of a you know, side thing,
• 31:29
  Speaker 1: because pulsars are so strange and people were looking for
• 31:32
  Speaker 1: planets around stars like the Sun. So it's really only
• 31:34
  Speaker 1: been in the last thirty years that we've found planets,
• 31:38
  Speaker 1: and there's been such an explosion. Now we're about to
• 31:40
  Speaker 1: hit five thousand planets, which is going to be a
• 31:42
  Speaker 1: cool milestone that we're going to celebrate at the Extra
• 31:44
  Speaker 1: Plant Archive. But yeah, it's really the fact that technology
• 31:47
  Speaker 1: got us to the point where we could do this search. Yeah,
• 31:50
  Speaker 1: it's a pretty amazing technological feed And you sort of
• 31:53
  Speaker 1: described it as an explosion. Is that sort of what
• 31:55
  Speaker 1: you were expecting back in the nineties or has this
• 31:57
  Speaker 1: here am a number of exp planets? Has that been
• 31:59
  Speaker 1: a surprise? It's really interesting. So when I joined the
• 32:02
  Speaker 1: Extra Planet Hunt, which was in the mid two thousands
• 32:04
  Speaker 1: as a grad student, there were not very many planets
• 32:08
  Speaker 1: known yet, like it was still in the dozens to
• 32:10
  Speaker 1: a hundred or so, but they were being found, which
• 32:13
  Speaker 1: was why I was excited to do this as a
• 32:15
  Speaker 1: grad student and to search for them. And I will
• 32:16
  Speaker 1: say I spent four years searching for them using two
• 32:19
  Speaker 1: different surveys, and I never found a single one. But
• 32:21
  Speaker 1: they still gave me a PhD. So that's good. You
• 32:24
  Speaker 1: can get a PhD and planet hunting without ever having
• 32:26
  Speaker 1: found a planet. That's all right. I've been a particle
• 32:28
  Speaker 1: physicist for more than two decades and I've never found
• 32:30
  Speaker 1: a new particle. So I'm still looking. Well, Solidarity, Daniel Celibarity.
• 32:36
  Speaker 1: And then basically, as more and more surveys came online
• 32:39
  Speaker 1: and in, the telescopes got bigger and the instruments got better,
• 32:43
  Speaker 1: what we've really seen is an exponential rise. If you
• 32:46
  Speaker 1: plot the number of clients with time, it's it's exponential.
• 32:49
  Speaker 1: And I refer to this as Mama Jacks the law
• 32:51
  Speaker 1: because Eric Marma Jack was the first person to note
• 32:53
  Speaker 1: this exponential rise. And basically the doubling time you know,
• 32:56
  Speaker 1: you know how this More's law for computers where the
• 32:58
  Speaker 1: doubling time is like every two year. So the doubling
• 33:00
  Speaker 1: time for extra planets is about every two years or so,
• 33:03
  Speaker 1: so twenty seven months about. So what we're seeing is
• 33:06
  Speaker 1: the number of extra planets we know is doubling every
• 33:08
  Speaker 1: slightly more than two years. If you keep extrapolating, that
• 33:11
  Speaker 1: means we're going to hit a million planets by like
• 33:14
  Speaker 1: twenty thirty seven, which sounds ridiculous, but if you actually
• 33:17
  Speaker 1: look at the upcoming NASA and European Space Agency and
• 33:20
  Speaker 1: Chinese Space Agency missions. There's a lot of real estate
• 33:24
  Speaker 1: that we haven't searched yet that we will search in
• 33:25
  Speaker 1: the next few decades. So I'm actually not surprised if
• 33:28
  Speaker 1: we hit this million in the next fifteen years. And
• 33:31
  Speaker 1: these are just a million planets we've seen, right, The
• 33:34
  Speaker 1: number of planets out there is much much, much bigger. Exactly,
• 33:37
  Speaker 1: these are a million planets that we've been able to
• 33:39
  Speaker 1: individually detect and confirm in some way. And this is
• 33:42
  Speaker 1: the kind of thing that we can now explore and
• 33:45
  Speaker 1: you know, ask fun science questions about. But take us
• 33:48
  Speaker 1: sort of back again to the early nineties. Is this
• 33:50
  Speaker 1: what people anticipated that people know, given the technology that
• 33:54
  Speaker 1: was coming online, we would soon have all of these
• 33:57
  Speaker 1: planets or did people not really understand how many planets
• 34:00
  Speaker 1: were out there? You know, it was a really open
• 34:02
  Speaker 1: question because we had a sample size of one, right,
• 34:05
  Speaker 1: Like our star had planets around it, and there were
• 34:08
  Speaker 1: billions of stars in the galaxy. You know, a lot
• 34:10
  Speaker 1: of people had postulated that that there were planets, and
• 34:14
  Speaker 1: we just didn't know how many. We didn't know whether
• 34:16
  Speaker 1: things like the Solar System were rare and happened very rarely,
• 34:19
  Speaker 1: or whether they were ubiquitous or somewhere in the middle,
• 34:22
  Speaker 1: And from what we can tell, it seems like they're ubiquitous.
• 34:25
  Speaker 1: Like if you have the physics and the ingredients to
• 34:28
  Speaker 1: make stars, then you have the physics and the ingredients
• 34:31
  Speaker 1: to make planets. So I don't think it's a surprise
• 34:34
  Speaker 1: that we've found that they're ubiquitous, but I think it's
• 34:38
  Speaker 1: still an amazing achievement that we've been able to confirm
• 34:41
  Speaker 1: this intuition. I don't think anybody expected it would be
• 34:43
  Speaker 1: exponential in rise, but it really became a big industry
• 34:48
  Speaker 1: in astronomy to go hunting for exoplanets. Once we realized
• 34:50
  Speaker 1: that the technology had finally gotten past that threshold needed
• 34:53
  Speaker 1: to detect extraplanets, that everybody wanted to do it, and
• 34:55
  Speaker 1: it was the new hot thing. Is that what you
• 34:57
  Speaker 1: put in your business card the planet hunter or extra
• 35:01
  Speaker 1: planet hunter. I do usually call myself a planet hunter.
• 35:04
  Speaker 1: It makes me feel very Lara croft Ian. That's pretty cool. Yeah,
• 35:08
  Speaker 1: out of the thousands of the extra planets found, do
• 35:10
  Speaker 1: you have any favorites or any particularly weird ones that
• 35:14
  Speaker 1: we found. I do have a favorite system. So the
• 35:17
  Speaker 1: technology has gotten to the point where we have more
• 35:20
  Speaker 1: data than we can look at, and what that means
• 35:22
  Speaker 1: is a lot of us have turned to citizen science projects.
• 35:25
  Speaker 1: So citizen science projects are usually when scientists make a
• 35:28
  Speaker 1: whole bunch of data available online and ask people to
• 35:31
  Speaker 1: answer a pretty simple question about it, like help us
• 35:34
  Speaker 1: classify this, or mark a bad pixel, or translate this word,
• 35:39
  Speaker 1: or just do some simple repetitive tasks. It needs to
• 35:41
  Speaker 1: be done millions of times, and you know, we train
• 35:44
  Speaker 1: computers to do it too, but people are really really
• 35:47
  Speaker 1: good at seeing things that computers miss, Like our brain's
• 35:50
  Speaker 1: ability to do pattern matching is still unparalleled, Like it's
• 35:54
  Speaker 1: really important that we know the difference between a tiger
• 35:56
  Speaker 1: and a zebra, So you know, our brains are super
• 35:59
  Speaker 1: good at it. So in seventeen, my colleague Ian Crossfield
• 36:02
  Speaker 1: and I set up a citizen science project called Extra
• 36:04
  Speaker 1: Planet Explorers, where we had data from the Kepta Telescope
• 36:07
  Speaker 1: and we basically were just like, help us find planets
• 36:09
  Speaker 1: in it, like here are here are the data, look
• 36:11
  Speaker 1: and see what you see. And we were really really
• 36:13
  Speaker 1: lucky enough to get picked up by BBC Stargazing Live,
• 36:16
  Speaker 1: which is this like annual televised astronomy extravaganza like imagined
• 36:21
  Speaker 1: would Stock for Astronomy, where they do three nights of
• 36:24
  Speaker 1: primetime television, and they were interviewing astronomers around the world
• 36:27
  Speaker 1: and throwing from this telescope to that telescope, what's happening
• 36:30
  Speaker 1: over here. We're looking at Europa. So we were lucky
• 36:32
  Speaker 1: enough to get our project on that TV show and
• 36:34
  Speaker 1: we had ten thou volunteers look at planets, and within
• 36:38
  Speaker 1: fourty eight hours we had found this new system. It's
• 36:42
  Speaker 1: called K two one eight. And I'm going to pause
• 36:45
  Speaker 1: here and apologize because extra planet names are garbage. I'm sorry,
• 36:50
  Speaker 1: astronomers shouldn't be allowed to name anything. But the system
• 36:53
  Speaker 1: is called KT. It's got six planets in it. They're
• 36:56
  Speaker 1: all between the size of Earth and Neptune. The reason
• 36:58
  Speaker 1: I really love this system is that five of the
• 37:01
  Speaker 1: planets are in a resonant chain. So what that means
• 37:04
  Speaker 1: is that their orbital periods are related to each other
• 37:07
  Speaker 1: with very very simple integer ratios. And we see that
• 37:10
  Speaker 1: in our Solar system. So for instance, the Galilean moons
• 37:13
  Speaker 1: of Jupiter, three of them are in a one to
• 37:16
  Speaker 1: two to four ratio so for every you know, four
• 37:18
  Speaker 1: times io goes around, the next one goes around twice,
• 37:21
  Speaker 1: and for every two times that one goes around, the
• 37:23
  Speaker 1: next one goes around once. So they're all locked in
• 37:26
  Speaker 1: this resonance. And that's partly how you can get so
• 37:28
  Speaker 1: many moons like crammed so close together because they're in
• 37:31
  Speaker 1: this really stable formation and they're kept that way by
• 37:34
  Speaker 1: the resonans. So the system K has these five planets
• 37:38
  Speaker 1: that are all in a three to two resonans. So
• 37:41
  Speaker 1: the inner one goes around three times, the next one
• 37:43
  Speaker 1: goes around two times. For every three times that one
• 37:45
  Speaker 1: goes around, the next time go one goes around two times,
• 37:47
  Speaker 1: and so on. The reason that is cool is because
• 37:51
  Speaker 1: the three to two resonans, if you've ever studied music theory,
• 37:54
  Speaker 1: is the perfect fifth interval. So the first two notes
• 37:57
  Speaker 1: of Twinkle Twinkle Little Star. So this this system is
• 38:00
  Speaker 1: basically singing Twinkle Twinkle Little Star to us because they're
• 38:03
  Speaker 1: all in this this perfect fifth resonance. And it was
• 38:06
  Speaker 1: found by citizen scientists and we've got to like announce
• 38:08
  Speaker 1: it on live on TV. Was super cool and has
• 38:11
  Speaker 1: such a fun story. So that's that's my favorite one
• 38:13
  Speaker 1: that I've been able to publish. That's amazing. But I
• 38:16
  Speaker 1: don't know about letting the Internet choose the names. I
• 38:19
  Speaker 1: don't think they usually goes well, planet make planet face right. Yeah. Unfortunately, So,
• 38:23
  Speaker 1: the IAU, the International Astronomic Reunion, has actually had several
• 38:27
  Speaker 1: competitions worldwide competitions to let people name some small number
• 38:32
  Speaker 1: of exer planets. And they've been you know, they've been
• 38:35
  Speaker 1: good and bad ones. I like some of the suggestions,
• 38:37
  Speaker 1: some of them are strange. The problem is that the
• 38:41
  Speaker 1: IAU hasn't been able to get professional astronomers to adopt them.
• 38:44
  Speaker 1: Like if I've published this is KTI one thirty and
• 38:46
  Speaker 1: I've always called it KTI one thirty eight, if you
• 38:48
  Speaker 1: come along and call it, you know, liberty, and the
• 38:51
  Speaker 1: next one's called fraternity, and the next one is called whatever.
• 38:54
  Speaker 1: The third one is that I forget. But one of
• 38:55
  Speaker 1: them is the three French things. I'm not going to
• 38:57
  Speaker 1: call it those. I'm going to call it Katie yes again, Day,
• 39:00
  Speaker 1: that's right, thank you. So there are these names, but
• 39:02
  Speaker 1: they haven't stuck unfortunately. Well the real problem is going
• 39:05
  Speaker 1: to be when the aliens come from that planet and
• 39:07
  Speaker 1: they discover that we name they're planet K two, They're
• 39:10
  Speaker 1: gonna be pretty upset if you don't adopt their local name,
• 39:13
  Speaker 1: or maybe they like it, and this was exacerbated. So
• 39:15
  Speaker 1: just recently we announced the second exo moon candidate. So
• 39:19
  Speaker 1: this is a candidate moon around an exo planet around
• 39:22
  Speaker 1: another star. So the star is kept La seventeen o eight,
• 39:27
  Speaker 1: the planet is kept La seventeen oh eight B because
• 39:30
  Speaker 1: it's the first planet found around the star, and the
• 39:32
  Speaker 1: moon is kept La seventeen o eight B. I like
• 39:36
  Speaker 1: the Roman numeral little I for the first moon around
• 39:39
  Speaker 1: the first planet around the star, Keptla seventeen o eight.
• 39:42
  Speaker 1: And that's just about as unromantic as you can get
• 39:45
  Speaker 1: for for what could be the second moon we've ever
• 39:48
  Speaker 1: found around another planet, around another star. And why is
• 39:51
  Speaker 1: the first planet called B? Why isn't it called A
• 39:54
  Speaker 1: good question? We borrowed this from binary star nomenclature, where
• 39:58
  Speaker 1: the primary star is always A and then the secondary
• 40:01
  Speaker 1: star is always be capital A and capital B. So
• 40:04
  Speaker 1: when we started naming planets, we kept this convention that
• 40:08
  Speaker 1: the primary star is A and we started using little
• 40:11
  Speaker 1: B and little C for the planets. You get into
• 40:14
  Speaker 1: some really interesting corner cases here where you have like
• 40:16
  Speaker 1: a binary star system where both of the stars have planets,
• 40:19
  Speaker 1: because then you end up with you know, such and
• 40:21
  Speaker 1: such big A little B and such and such big B,
• 40:25
  Speaker 1: little B. And it's yeah, it's a lot, it's a
• 40:27
  Speaker 1: lot happening. It's enough to confuse the milky wee jeans
• 40:30
  Speaker 1: and all of us. Super cool. Let's get more into that,
• 40:33
  Speaker 1: but first let's take a quick break. And we are
• 40:48
  Speaker 1: back talking to Dr Jesse Christensen from the NASA Exo
• 40:52
  Speaker 1: Planet Archive. So we've observed all these solar systems, and
• 40:55
  Speaker 1: you said, we've found all these planets and some of
• 40:57
  Speaker 1: them are weird and fascinating and interesting. Isn't it true
• 41:00
  Speaker 1: also that we can only see certain kinds of planets,
• 41:02
  Speaker 1: Like you've talked about how we can see Jupiter, but
• 41:04
  Speaker 1: it'd be really hard for us to see Earth. Is
• 41:06
  Speaker 1: it possible for us to extrapolate to what those invisible
• 41:09
  Speaker 1: planets are, to what those solar systems actually look like
• 41:12
  Speaker 1: based on the few planets that we've seen. How do
• 41:14
  Speaker 1: we make those extrapolations and how uncertain are they? Yeah,
• 41:18
  Speaker 1: there's a lot going on in that question, and there's
• 41:20
  Speaker 1: a lot of people who are working hard on answering that.
• 41:22
  Speaker 1: So one thing I'll say is that we think that
• 41:26
  Speaker 1: planets like the Earth are common, but not because we've
• 41:30
  Speaker 1: actually found any confirmed robust detections and planets like the Earth. Unfortunately,
• 41:35
  Speaker 1: Kepler in the end didn't quite achieve the sensitivity it
• 41:38
  Speaker 1: needed to find earthlike planets. We do know that planets
• 41:42
  Speaker 1: just a little bit closer to the Sun than the
• 41:45
  Speaker 1: Earth is are common, and we do know that planets
• 41:47
  Speaker 1: just a bit bigger than the Earth are common. So
• 41:50
  Speaker 1: we do extrapolate, which is dangerous, always dangerous, but we
• 41:53
  Speaker 1: extrapolate from that to say that Earth sized planets at
• 41:56
  Speaker 1: the right distance from their stars to have liquid water
• 41:59
  Speaker 1: are common. So even that already is an extrapolation to
• 42:02
  Speaker 1: say that earthlike planets are common. We feel pretty good
• 42:05
  Speaker 1: about it, but not, you know, the best. So we
• 42:09
  Speaker 1: haven't actually found a Solar system analog yet, something that
• 42:12
  Speaker 1: has like in a rocky planets out to the distance
• 42:15
  Speaker 1: of Earth and Mars and then outer giant planets like
• 42:17
  Speaker 1: Jupiter Satin, you're in a synectric. We're just not there
• 42:20
  Speaker 1: with our precision yet. But we don't think that they
• 42:22
  Speaker 1: are uncommon given what we do know. And this comes
• 42:24
  Speaker 1: back to the invisible cats argument. We can do complicated
• 42:27
  Speaker 1: population analyses where we you know, fall back on Bayesian
• 42:31
  Speaker 1: statistics and prior knowledge to say, okay, if this system
• 42:35
  Speaker 1: had seven planets, and they were distributed in roughly the
• 42:38
  Speaker 1: same way as the planets of our solar system, how
• 42:40
  Speaker 1: many of them could we have seen? Um And for instance,
• 42:44
  Speaker 1: because the planets in our solar system aren't exactly lined
• 42:47
  Speaker 1: up in the same plane, there's no alien civilization that
• 42:49
  Speaker 1: could see all eight planets transit. You could only ever
• 42:52
  Speaker 1: see a subset and have to infer the larger sample.
• 42:55
  Speaker 1: And so infer is the is the important word there.
• 42:58
  Speaker 1: So again we have to put some prior. We have
• 43:00
  Speaker 1: to say we think that the mutual inclination, so the
• 43:04
  Speaker 1: spread in the orbital planes of the planets, should be
• 43:07
  Speaker 1: less than you know, let's say ten degrees, because if
• 43:10
  Speaker 1: you start to get to spread out, then they start
• 43:12
  Speaker 1: to interact with each other dynamically and become unstapid. But
• 43:15
  Speaker 1: again we're already making assumptions which might turn out later
• 43:17
  Speaker 1: to be wrong. So you put some prior on how
• 43:20
  Speaker 1: spread apart the planets could be. Then you look at
• 43:22
  Speaker 1: how many planets you've seen and say, okay, we've likely
• 43:25
  Speaker 1: missed seventy of the planets are in these systems, which
• 43:29
  Speaker 1: means that there are you know, three and a half
• 43:31
  Speaker 1: times as many. So that's kind of how we do it.
• 43:34
  Speaker 1: We do have to make some assumptions and they may
• 43:36
  Speaker 1: be wrong, but you know, if you give astronomers two planets,
• 43:39
  Speaker 1: they'll start to try and do statistics. So you're seeing
• 43:41
  Speaker 1: the reason we haven't seen other systems like our is
• 43:44
  Speaker 1: it not because we don't see them as you said,
• 43:46
  Speaker 1: we so far we can't have seen them or can't
• 43:48
  Speaker 1: be able to see them exactly. So some of the
• 43:50
  Speaker 1: NASA emissions are sensitive to planets close to the star,
• 43:54
  Speaker 1: so closer in than Earth, and some NASA emissions are
• 43:57
  Speaker 1: sensitive to planets further away, like the direct damaging planets
• 44:00
  Speaker 1: need to be very far away. And there's another technique
• 44:03
  Speaker 1: that I haven't talked about called micro lensing, which is
• 44:05
  Speaker 1: sensitive to planets that are far away. So the wobble
• 44:08
  Speaker 1: method that we talked about and the transit method are
• 44:10
  Speaker 1: both biased towards detecting planets close to the star, and
• 44:13
  Speaker 1: then the other methods are biased to finding planets far away.
• 44:16
  Speaker 1: What we haven't really been able to do a good job.
• 44:18
  Speaker 1: Yet is marry those results together and say, okay, we
• 44:21
  Speaker 1: have a complete census. We have a good idea what's
• 44:24
  Speaker 1: happening in the inner regions of the solar systems, and
• 44:26
  Speaker 1: we have a good idea what's happening in the outer regions.
• 44:28
  Speaker 1: And that's one of my big scientific goals for the
• 44:31
  Speaker 1: next decade because NASA is about to launch a new
• 44:33
  Speaker 1: mission called the Nancy Grace Roman Space Telescope, which will
• 44:37
  Speaker 1: happen in the second half of this decade, and it's
• 44:39
  Speaker 1: going to do a big micro lensing survey. So this
• 44:41
  Speaker 1: is this other detection technique of the galactic bulge, and
• 44:44
  Speaker 1: it will find a lot of planets in the our
• 44:46
  Speaker 1: solar systems. And then the question is, how do we
• 44:49
  Speaker 1: take the results from Kepler, which is a fantastic job
• 44:51
  Speaker 1: of mapping out inner solar systems, and the results from Roman,
• 44:54
  Speaker 1: which should do a fantastic job of mapping outer solar systems,
• 44:57
  Speaker 1: and you know, overlap them somewhere in the middle and
• 45:00
  Speaker 1: get a consistent answer for what does the whole Solar
• 45:03
  Speaker 1: system look like around these other stars. So that's one
• 45:05
  Speaker 1: of my big goals is to is to be able
• 45:07
  Speaker 1: to join the results from Kepler and Roman together so
• 45:09
  Speaker 1: that we can finally talk about Solar system analogs and
• 45:12
  Speaker 1: how common they might be. It's almost like planets the
• 45:15
  Speaker 1: size of the Earth are kind of hiding out there,
• 45:18
  Speaker 1: which is I guess a good thing. I guess if
• 45:20
  Speaker 1: we're trying to hide from evil aliens. Yeah, if you
• 45:22
  Speaker 1: look at the sensitivity curves of Kepler and what's predicted
• 45:25
  Speaker 1: for Roman Earth is like just snug like right in
• 45:28
  Speaker 1: the middle, just where they meet, Like, it's possible that
• 45:31
  Speaker 1: we still don't quite get there even with Roman Earth
• 45:33
  Speaker 1: is just really small. Unfortunately, I think we'll get there.
• 45:38
  Speaker 1: Another thing that NASA is planning is a really big
• 45:41
  Speaker 1: UV optical infrared mission for twenty or thirty years from now,
• 45:45
  Speaker 1: which will have one of these direct imaging instruments on it,
• 45:47
  Speaker 1: and the goal of that will be to actually take
• 45:49
  Speaker 1: a picture of a planet like the Earth around a
• 45:52
  Speaker 1: star like the Sun, which will be an incredible achievement
• 45:55
  Speaker 1: for humanity. Is that this sort of only way we'll
• 45:57
  Speaker 1: be able to see other Earth like planets like through
• 45:59
  Speaker 1: the pictures or do we just need a new kind
• 46:02
  Speaker 1: of technology or just improve the technology that we have? Oh? Yeah,
• 46:05
  Speaker 1: there's very very cool ideas for new technology that would
• 46:08
  Speaker 1: happen like on the order of fifty to a hundred years.
• 46:11
  Speaker 1: So for instance, one way you can get good resolution
• 46:15
  Speaker 1: is by making one telescope really really big, or by
• 46:19
  Speaker 1: getting two telescopes and putting them far apart and looking
• 46:22
  Speaker 1: at the same thing. And that's called interferometry. There's ideas
• 46:25
  Speaker 1: for an interferometer that would be the size of our
• 46:27
  Speaker 1: solar system, right like, you'd have some telescopes way out
• 46:30
  Speaker 1: in that direction and some telescopes way out in that direction,
• 46:33
  Speaker 1: and they would look at a planet around another star
• 46:35
  Speaker 1: and use the resolution that they gain from being you know,
• 46:38
  Speaker 1: many many au many many astronomic or units apart, which
• 46:42
  Speaker 1: is a distance from the Earth to the Sun to
• 46:43
  Speaker 1: be able to map the details. There's another really cool
• 46:46
  Speaker 1: idea concept for a future thing, which is to use
• 46:48
  Speaker 1: the Sun as a gravitational lens. So everything with mass
• 46:52
  Speaker 1: bends spacetime, right like you're bending spacetime right now as
• 46:55
  Speaker 1: you sit there. So the Sun is bending spacetime. And
• 46:58
  Speaker 1: that's what magnifying glasses, right, They bend light so that
• 47:01
  Speaker 1: it comes together in a certain way to make it
• 47:03
  Speaker 1: look like things are closer. So you could imagine putting
• 47:06
  Speaker 1: a telescope on the other side of the Sun and
• 47:08
  Speaker 1: using the Sun as a gravitational lens to magnify a
• 47:12
  Speaker 1: background star and planets such that you could see it
• 47:14
  Speaker 1: in more detail. Like how cool is that? That would
• 47:16
  Speaker 1: be super awesome. Basically, you're talking about building a lens
• 47:20
  Speaker 1: the size of the Sun, so you're just gathering a
• 47:22
  Speaker 1: huge amount of light which allows us to see dimmer
• 47:24
  Speaker 1: objects and to magnify them as that. Right, you're using
• 47:27
  Speaker 1: the Sun as a giant lens because it's bending spacetime
• 47:29
  Speaker 1: the way a normal you know, glass lens bends air
• 47:33
  Speaker 1: and light. You guys are really thinking big. Now you've
• 47:35
  Speaker 1: got James web up there. You're like, wow, we can
• 47:37
  Speaker 1: do anything. Yeah. The fact that that deployment sequence is
• 47:41
  Speaker 1: going so well is super super relieving. Like so many
• 47:45
  Speaker 1: people have worked on James Webb for so many years,
• 47:48
  Speaker 1: and there were so many moving carts, but so far,
• 47:51
  Speaker 1: fingers crossed, all of the big things have happened and
• 47:54
  Speaker 1: happened the right way. So go, James Webb. Can you
• 47:57
  Speaker 1: also give us something of a map of like where
• 47:59
  Speaker 1: we have looked for these planets. I know that some
• 48:02
  Speaker 1: of these things are capable of seeing planets close by,
• 48:05
  Speaker 1: and some of them are capable of seeing things far away.
• 48:07
  Speaker 1: How we explored our entire galaxy as much as we can.
• 48:10
  Speaker 1: Oh yeah, so actually we really haven't. So our galaxy,
• 48:14
  Speaker 1: our Milky Way galaxy, is what we call a grand spiral,
• 48:17
  Speaker 1: so if you could look down on it, it's got
• 48:19
  Speaker 1: these lovely huge spiral arms, and we're just like out
• 48:22
  Speaker 1: in the burbs. So the galaxy itself is about a
• 48:24
  Speaker 1: hundred thousand light years all the way across, and where
• 48:27
  Speaker 1: about thirty thousand light years from the middle, So we're
• 48:31
  Speaker 1: kind of, yeah, just out on the edges. Basically, basically
• 48:34
  Speaker 1: almost all of the planets that we found so far
• 48:36
  Speaker 1: are within a few thousand light years, So remember a
• 48:40
  Speaker 1: thirty thousand light is to the center of the galaxy.
• 48:42
  Speaker 1: We've really only searched like this little bubble around us
• 48:45
  Speaker 1: out we call what we call the local solar neighborhood.
• 48:47
  Speaker 1: And you know, the five thousand or so planets that
• 48:49
  Speaker 1: we found so far are almost all very close to us.
• 48:53
  Speaker 1: Now I say very close spaces really really really really
• 48:57
  Speaker 1: really really really big even just a few you light
• 49:00
  Speaker 1: years away. With our current technology, basically inconceivable for ust
• 49:05
  Speaker 1: to visit. We can send messages and they will still
• 49:07
  Speaker 1: take years to get there. To our closest star, Alpha Centaur,
• 49:10
  Speaker 1: which is four light years away, it would still take
• 49:13
  Speaker 1: us four years to get a message to even the
• 49:14
  Speaker 1: closest star. So while we have only searched our local
• 49:17
  Speaker 1: stellar neighborhood, that is still a really big blob of space.
• 49:21
  Speaker 1: So now come back and picture the whole galaxy again
• 49:24
  Speaker 1: and think about this tiny circle off to one side
• 49:26
  Speaker 1: that we've been able to explore, and now think about
• 49:29
  Speaker 1: what else could be in galaxy. That's what keeps me hunting, right, Like,
• 49:33
  Speaker 1: that's so cool. It's such a big space. And as
• 49:36
  Speaker 1: our instruments get better and our technology gets better and
• 49:38
  Speaker 1: our ideas get better, we're just going to be able
• 49:41
  Speaker 1: to explore more and more and more of it. And
• 49:43
  Speaker 1: is there a possibility that our local solar neighborhood is
• 49:45
  Speaker 1: like unrepresentative? You know, we have this history in science
• 49:49
  Speaker 1: and especially in physics of generalizing from our experience and
• 49:52
  Speaker 1: then discovering, oops, that was a mistake. Is it possible
• 49:55
  Speaker 1: that what we've learned about solar systems is only applicable
• 49:58
  Speaker 1: to this little neighborhood and that or more planets first
• 50:01
  Speaker 1: star somewhere else, or fewer planets. So do you think
• 50:03
  Speaker 1: it's likely that what we've learned so far is true
• 50:06
  Speaker 1: across the Milky Way? Oh, it is such a good question.
• 50:08
  Speaker 1: And now I'm gonna share something. So my research group
• 50:11
  Speaker 1: just met this morning and a post stuff that I'm
• 50:14
  Speaker 1: working with showed us a plot. And this is like
• 50:16
  Speaker 1: a brand new plot where we're trying to map out
• 50:19
  Speaker 1: how the occurrence rate of planets, how common planets are,
• 50:22
  Speaker 1: changes with properties of the galaxy. And he showed us
• 50:25
  Speaker 1: this plot this morning that showed that a current rate
• 50:28
  Speaker 1: of planets might decrease with your distance from the galactic plane.
• 50:32
  Speaker 1: So remember I said, we're in a big spiral. Now
• 50:35
  Speaker 1: almost all of the stars are in a big disc,
• 50:38
  Speaker 1: but there are some stars that are out of that disk,
• 50:40
  Speaker 1: so they're out of the plane of the galaxy. And
• 50:41
  Speaker 1: so this is literally just he showed us this plot
• 50:43
  Speaker 1: this morning and we were just sat there like, cool,
• 50:45
  Speaker 1: what does it mean? So it could be the fact
• 50:47
  Speaker 1: that as you get out of the plane of the galaxy,
• 50:49
  Speaker 1: it's harder and harder to make planets. And now the
• 50:52
  Speaker 1: immediate question is why is that. We know that stars
• 50:54
  Speaker 1: out of the plane of the galaxy have fewer heavy elements.
• 50:57
  Speaker 1: So you know how I said dust and gas earlier.
• 51:00
  Speaker 1: They have less dust compared to gas. Maybe that means
• 51:02
  Speaker 1: it's harder for them to make planets. We also know
• 51:04
  Speaker 1: that stars out of the plane of the galaxy are
• 51:06
  Speaker 1: older than the stars in the plane of the galaxy,
• 51:08
  Speaker 1: which is where most of the star birth happens, than
• 51:10
  Speaker 1: the stellar nurseries are almost all on the plane. What
• 51:12
  Speaker 1: does age have to do? Why was it harder to
• 51:14
  Speaker 1: make planets eleven billion years ago than it is now?
• 51:17
  Speaker 1: So these are all like super interesting questions that literally
• 51:19
  Speaker 1: we're trying to answer right now. There are good reasons
• 51:22
  Speaker 1: to believe that, you know, planet formation might be different
• 51:24
  Speaker 1: in different parts of the galaxy. For instance, as you
• 51:27
  Speaker 1: get closer and closer to the center of the galaxy,
• 51:29
  Speaker 1: the stellar density gets more and more crowded and the
• 51:32
  Speaker 1: stellar radiation gets more and more concentrated, so it might
• 51:35
  Speaker 1: be harder to make certain types of planets. It might
• 51:38
  Speaker 1: be harder to keep planets once you've made them, as
• 51:41
  Speaker 1: you know, especially as you get closer and closer to
• 51:43
  Speaker 1: the center and things start to get really crowded. So yeah,
• 51:45
  Speaker 1: there's a there's a lot of questions about how planet
• 51:49
  Speaker 1: occurrence might change as you move around the galaxy. So
• 51:52
  Speaker 1: you know, imagine like the first season of a TV
• 51:54
  Speaker 1: show where you're just looking around your local neighborhood and
• 51:57
  Speaker 1: you're like cool, and then the second season is like, oh,
• 52:00
  Speaker 1: this is just like one neighborhood in a huge city,
• 52:02
  Speaker 1: So we're just starting to peek outside our neighborhood and
• 52:05
  Speaker 1: see what could be happening. Not all milky regions are
• 52:08
  Speaker 1: maybe me the same way, exactly exactly. So for instance,
• 52:11
  Speaker 1: life on Earth, if you look at the equations for
• 52:14
  Speaker 1: the chemical energy gradients that describe life on Earth, there's
• 52:17
  Speaker 1: like heaps of carbon atoms and heaps of hydrogen atoms,
• 52:20
  Speaker 1: and heaps of oxygen atom and one phosphorus. So like
• 52:23
  Speaker 1: the literally the rate of life on Earth is governed
• 52:25
  Speaker 1: by how much phosphorus we have, And like, is that
• 52:28
  Speaker 1: true elsewhere in the galaxy? And do other places in
• 52:30
  Speaker 1: the galaxy have enough phosphorus to make life if they
• 52:33
  Speaker 1: use the same chemical energy gradients. That's super interesting and important.
• 52:36
  Speaker 1: You know what, I just pieced it together. So we
• 52:38
  Speaker 1: call people from Norway Norwegians. That's where Milky Way, and
• 52:41
  Speaker 1: then we would be Milky Wegians. Exactly. You got it.
• 52:45
  Speaker 1: You're there. It only took me an hour. It took
• 52:50
  Speaker 1: me eighteen hours. Someone asked what we should call them,
• 52:54
  Speaker 1: and I kind of went away and was like, huh,
• 52:56
  Speaker 1: And then I pondered for a while, and eventually I
• 52:58
  Speaker 1: landed on Milky Regions. And it took you one hour,
• 53:00
  Speaker 1: It took me much longer. See, sometimes astronomers are good
• 53:03
  Speaker 1: at choosing names. There you go, I'll take one one victory.
• 53:07
  Speaker 1: So let me ask you to speculate a little bit.
• 53:09
  Speaker 1: There's this big dark part of the galaxy we haven't
• 53:12
  Speaker 1: seen in so many planets which are currently invisible to us.
• 53:14
  Speaker 1: That suggests that there might be surprises out there. Right.
• 53:17
  Speaker 1: It could just be that it looks the way we expect,
• 53:19
  Speaker 1: but you know, the universe seems to always have surprises
• 53:21
  Speaker 1: for us in store. Can you give us a sense
• 53:23
  Speaker 1: for the sort of range of possibilities? Like what kinds
• 53:26
  Speaker 1: of things might we discover when we turn on these
• 53:29
  Speaker 1: new eyeballs and explore the rest of the galaxy. Yeah, like,
• 53:32
  Speaker 1: what do you think we're going to know in twenty
• 53:33
  Speaker 1: or fifty years. Well, one thing I hope we know
• 53:36
  Speaker 1: in twenty or fifty years is how many Earth like
• 53:39
  Speaker 1: planets are there that we can actually see with our instruments.
• 53:42
  Speaker 1: That would be amazing in terms of what's the unknown unknowns.
• 53:46
  Speaker 1: One thing that's surprised us a lot is the fact
• 53:50
  Speaker 1: that the most common kind of planet we have found
• 53:53
  Speaker 1: is between the size of Earth and Neptune. So in
• 53:56
  Speaker 1: our Solar system there's a big jump. We have all
• 53:58
  Speaker 1: the little planets up to this size of Earth, and
• 54:00
  Speaker 1: then we have all the giant planets that start at
• 54:02
  Speaker 1: Neptune and go up. But there's a gap. So Neptune
• 54:05
  Speaker 1: is about four times the size of Earth, and in
• 54:07
  Speaker 1: our Solar system there's nothing in that gap. As we
• 54:10
  Speaker 1: have explored the galaxy around us, the most common kind
• 54:13
  Speaker 1: of planet we have found is in that gap. It's
• 54:16
  Speaker 1: bigger than Earth but smaller than Neptune. And so do
• 54:18
  Speaker 1: you call it a super Earth or a mini Neptune,
• 54:20
  Speaker 1: or do you have some other crazy name for it.
• 54:22
  Speaker 1: We actually call them both of those things, and kind
• 54:24
  Speaker 1: of depends on what science case you're trying to make.
• 54:27
  Speaker 1: So super Earth's we think are up to maybe one
• 54:29
  Speaker 1: and a half to one point six times the size
• 54:31
  Speaker 1: of the Earth and then above that. We think that
• 54:34
  Speaker 1: they're compositionally more like mini neptunes, but we actually don't know.
• 54:38
  Speaker 1: And one of the big open questions is could they
• 54:41
  Speaker 1: actually be just a different kind of planet, not just
• 54:44
  Speaker 1: a big rock or a small ice school, but like
• 54:47
  Speaker 1: an ocean world, like something that's you know, predominantly water.
• 54:51
  Speaker 1: Is there some other you know, configuration of compositions of
• 54:54
  Speaker 1: rock and iron and ice shells and different kinds of
• 54:58
  Speaker 1: ice and water that can be to these planets. So
• 55:01
  Speaker 1: one of the things I hope we know in twenty
• 55:03
  Speaker 1: to fifty years is what our super earths and what
• 55:05
  Speaker 1: our many neptunes like you know, are they a new
• 55:08
  Speaker 1: type of planet that we don't have an our Solar
• 55:09
  Speaker 1: system because at the moment, only having a bulk composition,
• 55:13
  Speaker 1: so we know the size and we know the mass,
• 55:15
  Speaker 1: it doesn't give us a good idea of how the
• 55:16
  Speaker 1: mass breaks down inside that sphere basically, so we don't
• 55:20
  Speaker 1: know yet, and I'm hoping we will know. The things
• 55:22
  Speaker 1: that have surprised us a lot so far besides this
• 55:24
  Speaker 1: discovery of this new type of planet, it has a
• 55:27
  Speaker 1: lot to do with configurations. So for instance, finding giant
• 55:32
  Speaker 1: planets like Jupiter right next to the star that orbit
• 55:34
  Speaker 1: in just a few days. So the very first kinds
• 55:37
  Speaker 1: of planets we found were these hot Jupiters we call
• 55:39
  Speaker 1: them because they're Jupiters heated up to thousands of degrees.
• 55:42
  Speaker 1: So finding hot Jupiters was a big surprise. Finding these
• 55:44
  Speaker 1: really compact systems of planets like KTE eight but I described,
• 55:48
  Speaker 1: which is a series of resonant planets in this chain.
• 55:51
  Speaker 1: That's also been really new because you know, in our
• 55:53
  Speaker 1: solar system there's nothing between the Sun and mercury. In
• 55:56
  Speaker 1: K two, there's six planets that are closer to the
• 55:59
  Speaker 1: star than Mercury is. They're all really packed in type.
• 56:02
  Speaker 1: So finding these dynamically packed systems. So as we start
• 56:05
  Speaker 1: to explore more space, which includes younger stars, it includes
• 56:10
  Speaker 1: more metal pour stars with with less heavy elements, finding
• 56:14
  Speaker 1: out what kinds of planets they make and how soon
• 56:16
  Speaker 1: they make them. So, for instance, the reason we look
• 56:19
  Speaker 1: at young stars and look for planets is to try
• 56:21
  Speaker 1: and work out how long does it take to make
• 56:23
  Speaker 1: a planet, because different planet formation theories predict different time scales,
• 56:26
  Speaker 1: So we're hoping to like look at young stars and
• 56:29
  Speaker 1: work out how quickly they make planets, and it might
• 56:31
  Speaker 1: and you know, we'll probably be surprised. We'll probably find
• 56:33
  Speaker 1: out they make them super fast, and we'll be like, Okay.
• 56:36
  Speaker 1: So there's lots of lots of things I expect to
• 56:38
  Speaker 1: be surprised by in the next twenty to fifty years,
• 56:40
  Speaker 1: but mostly new types of planets in new types of
• 56:43
  Speaker 1: configurations is what I expect. That's awesome me. One last question, Daniel, Yeah,
• 56:47
  Speaker 1: if you find a combination Neptune Earth, why didn't you
• 56:50
  Speaker 1: call it a nept Earth. I like Neptinia as the
• 56:52
  Speaker 1: mini Neptune substitute. It sounds like a cocktail. And in fact,
• 56:56
  Speaker 1: many of US astronomers have gotten together at more than
• 56:59
  Speaker 1: one conference to drink eptiniece and the next morning you
• 57:02
  Speaker 1: have to wake up and drink a lot of hot
• 57:03
  Speaker 1: jupiters to recover. Right, exactly right? Mean? One last question,
• 57:08
  Speaker 1: Dr Pritsinson, what's it like to be a planet hunter?
• 57:11
  Speaker 1: Like when you discover a new planet? Can you describe
• 57:13
  Speaker 1: that feeling? Sure? So there's this this this phrase you
• 57:16
  Speaker 1: might have heard this saying, you know where the generation
• 57:19
  Speaker 1: that was born too late to explore Earth but too
• 57:22
  Speaker 1: soon to explore space, and I feel in just this
• 57:25
  Speaker 1: incredibly privileged position. I feel like I get to explore space.
• 57:28
  Speaker 1: I get to discover new worlds around other stars. And so,
• 57:32
  Speaker 1: you know the long nights of the telescope, you know
• 57:34
  Speaker 1: it's three am, the instrument has been misbehaving. You have
• 57:37
  Speaker 1: this one candidate you really really want to get a
• 57:40
  Speaker 1: good luck at the sky is finally clear. You get
• 57:43
  Speaker 1: the data and you look at it and you see
• 57:45
  Speaker 1: it's a planet. And you know, I always just like
• 57:47
  Speaker 1: sit back and put my hands on my face and
• 57:48
  Speaker 1: I'm like, yes, okay, yes, great, awesome, And then you
• 57:52
  Speaker 1: move on to the next candidate because you only have
• 57:54
  Speaker 1: like two hours before the sun is going to come up,
• 57:56
  Speaker 1: and some of them won't turn out to be real planets,
• 57:57
  Speaker 1: but you know, there's always this moment where you get
• 58:00
  Speaker 1: to sit there and be like I know something that
• 58:03
  Speaker 1: no one else knows right now, Like I know that
• 58:05
  Speaker 1: this is a planet, and you just get to savor
• 58:07
  Speaker 1: it for a second and just be like that's really cool.
• 58:10
  Speaker 1: And then I usually send like an all caps email
• 58:12
  Speaker 1: to my collaborators We've got one, because you might be
• 58:15
  Speaker 1: the only person in the galaxy that knows about that
• 58:17
  Speaker 1: planet or the universe. I'm never sure whether I'm more
• 58:20
  Speaker 1: scared of us being alone or not being alone? Right, Like,
• 58:24
  Speaker 1: is it a scary thought to be the only one
• 58:26
  Speaker 1: who knows about it? Or is it a scary thought
• 58:28
  Speaker 1: to not be the only one who knows about it?
• 58:30
  Speaker 1: Sounds like you need another and a tiny yes, right,
• 58:32
  Speaker 1: that'll help. I'll settle it all right. Well, thanks very
• 58:35
  Speaker 1: much for coming on and answering all of our very
• 58:37
  Speaker 1: serious and very silly questions about exo planet futures. It's
• 58:40
  Speaker 1: been a pleasure. Yeah, the pleasure is behind. Thank you
• 58:42
  Speaker 1: so much. Thanks for listening, and remember that Daniel and
• 58:53
  Speaker 1: Jorge explain the universe is a production of I Heart Radio.
• 58:56
  Speaker 1: For more podcast from my Heart Radio, or visit the
• 58:59
  Speaker 1: I Heart a new Apple, Apple Podcasts, or wherever you
• 59:02
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