WEBVTT - Could we see moons around exoplanets? 0:00:08.480 --> 0:00:10.800 Hey, Daniel, do you ever worry about the ethics of 0:00:10.960 --> 0:00:12.200 using a telescope? 0:00:12.520 --> 0:00:15.120 What do you mean? What are the ethical questions about 0:00:15.200 --> 0:00:16.239 looking through a telescope? 0:00:16.400 --> 0:00:17.720 I mean, like what they're looking at? 0:00:17.840 --> 0:00:19.560 Well, I'm not pointing them at my neighbor, if that's what. 0:00:19.640 --> 0:00:22.760 You mean, not your next door neighbor. What about your 0:00:22.800 --> 0:00:23.800 next galaxy neighbor. 0:00:23.840 --> 0:00:26.000 Are you asking if we have the right to look 0:00:26.079 --> 0:00:27.920 at distant objects in the sky? 0:00:28.320 --> 0:00:30.160 Yeah, you know, like what if there are aliens there 0:00:30.400 --> 0:00:32.640 on a planet or a moon and we're like spying 0:00:32.640 --> 0:00:33.640 on them? 0:00:34.159 --> 0:00:36.239 Well, I hope they're not offended if we catch them 0:00:36.280 --> 0:00:38.560 sunbathing or I guess starbathing. 0:00:38.920 --> 0:00:41.720 Aren't all stars suns? But yeah, don't you think aliens 0:00:41.720 --> 0:00:42.760 have a right to privacy? 0:00:42.880 --> 0:00:45.559 I don't know. Maybe they're alien celebrities, so they're like 0:00:45.760 --> 0:00:46.960 starbathing stars. 0:00:47.240 --> 0:00:50.639 Wait, are you saying celebrities can have privacy either? Are 0:00:50.680 --> 0:00:51.760 you secretly a starker? 0:00:52.560 --> 0:00:55.960 No, I'm saying astronomers are just interstellar paparazzi. 0:00:56.280 --> 0:00:58.319 Well, oh, it sounds like they need to draw their 0:00:58.360 --> 0:01:00.639 curtains more. Why just have you don't get the rest 0:01:00.640 --> 0:01:17.640 of us punch in the face, Hi am horhem a 0:01:17.680 --> 0:01:20.440 cartoonist and the author of Oliver's Great Big Universe. 0:01:20.720 --> 0:01:23.520 Hi, I'm Daniel. I'm a particle physicist and a professor 0:01:23.560 --> 0:01:26.000 at u C Irvine. And if it gets the aliens 0:01:26.000 --> 0:01:28.240 to come, I want them to punch us in the face. 0:01:29.040 --> 0:01:31.840 Us in the face. How about just you in the face? 0:01:34.200 --> 0:01:36.559 I mean, please, don't volunteer my face for your science. 0:01:36.800 --> 0:01:39.279 Us volunteering humanity's collective face. 0:01:41.640 --> 0:01:43.160 Some of us are sensitive in the face. 0:01:43.319 --> 0:01:44.760 It might be worth a puncher too, to learn that 0:01:44.760 --> 0:01:46.120 we're not alone in the universe. 0:01:46.760 --> 0:01:48.560 Can we pick where they're going to punch us, you know, 0:01:48.760 --> 0:01:50.240 like when you're playing as kids. 0:01:50.720 --> 0:01:52.600 You mean in the Daniel part of the face, rather 0:01:52.640 --> 0:01:53.800 than the joey part of the face. 0:01:54.520 --> 0:01:58.360 Definitely the Daniel part. But anyways, Welcome to our podcast, 0:01:58.440 --> 0:02:02.560 Daniel and Jorge Explain the Universe, a production of iHeartRadio. 0:02:02.080 --> 0:02:04.280 In which we try to teach you all about the 0:02:04.280 --> 0:02:07.080 mysteries of the universe, rather than punching you in the 0:02:07.080 --> 0:02:10.200 face with them. We think that it's possible to gently 0:02:10.240 --> 0:02:14.280 absorb all of the crazy intricacies of how the universe works, 0:02:14.320 --> 0:02:18.320 from its tiny little particles to its mysterious swirling black holes. 0:02:18.680 --> 0:02:22.400 Without getting bruised, basically anywhere on your body. We seek 0:02:22.440 --> 0:02:24.480 to serve up the mysteries of the universe in a 0:02:24.720 --> 0:02:26.200 gentle and comfortable manner. 0:02:26.280 --> 0:02:28.440 That's right. We bring you the one two punch of 0:02:28.520 --> 0:02:32.200 science and bad dad jokes to talk about all the 0:02:32.240 --> 0:02:34.280 amazing things that are happening in the universe, all the 0:02:34.320 --> 0:02:37.240 peaceful things and also all of the combatitive things, and. 0:02:37.280 --> 0:02:39.040 The mysteries that we love to dig into. Are the 0:02:39.040 --> 0:02:41.680 ones that tell us about our context in the universe. 0:02:42.200 --> 0:02:45.400 Is where we are in the universe weird and unusual? 0:02:45.560 --> 0:02:49.520 Or are there many such backyards with many such podcasts 0:02:49.840 --> 0:02:51.720 giving all the same dad jokes? 0:02:51.960 --> 0:02:54.040 Yeah, that has been one of the biggest questions in 0:02:54.080 --> 0:02:57.160 the universe is are we alone in the universe? Or 0:02:57.200 --> 0:03:00.800 are we one of many many alien civilization out there 0:03:00.840 --> 0:03:03.640 in space? And are we the only ones making dad jokes? 0:03:04.320 --> 0:03:06.840 And how many of them are spying on us while 0:03:06.880 --> 0:03:08.760 we're sunbathing in our backyards. 0:03:08.880 --> 0:03:11.079 Well, I guess you know, technically, in an infinite universe 0:03:11.360 --> 0:03:14.120 that there's probably a planet out there where dad jokes 0:03:14.120 --> 0:03:17.440 are like the epitome of intelligence and literature. 0:03:17.480 --> 0:03:19.359 Are you saying that's not our universe? Are you saying 0:03:19.400 --> 0:03:20.280 that's not our planet. 0:03:20.400 --> 0:03:24.399 That is definitely not. I think there's a reason they're 0:03:24.400 --> 0:03:27.480 called dad jokes, not just jokes. But maybe there's an 0:03:27.520 --> 0:03:29.600 alien species out there where you know, it's like the 0:03:29.639 --> 0:03:30.720 height of width, you know. 0:03:30.800 --> 0:03:32.320 Right, Well, we should try to sell our books on 0:03:32.360 --> 0:03:35.400 that planet then, because we have a lot of readers. 0:03:36.000 --> 0:03:40.240 Yeah, would be intergalactic bestsellers, not just international bestsellers. 0:03:40.440 --> 0:03:43.120 But we're not just interested in whether our books will 0:03:43.160 --> 0:03:46.320 sell to alien species. We're interested in whether there are 0:03:46.440 --> 0:03:49.960 aliens out there, whether life exists in other parts of 0:03:49.960 --> 0:03:52.960 the galaxy. And part of that question is asking whether 0:03:53.080 --> 0:03:56.720 our whole setup is unusual. Are there stars with planets 0:03:56.760 --> 0:03:59.520 around them? Do those planets have similar conditions to the 0:03:59.560 --> 0:04:03.000 planets here? Is there something weird and strange about the 0:04:03.040 --> 0:04:05.000 Solar System? Or is it very common? 0:04:05.240 --> 0:04:08.240 Yeah? Is the planet Earth a rare gem that exists 0:04:08.240 --> 0:04:10.520 out there in the cosmos or is it sort of 0:04:10.560 --> 0:04:12.720 like a you know, cheap chot sky that you can 0:04:12.720 --> 0:04:13.400 find anywhere. 0:04:13.440 --> 0:04:15.440 In just a few decades ago, we didn't know the 0:04:15.480 --> 0:04:20.320 answers to basic questions like are there planets around other stars? Fortunately, 0:04:20.320 --> 0:04:23.000 as we develop new and more powerful eyeballs, We've been 0:04:23.040 --> 0:04:26.200 able to discover those planets, and now we are pushing further. 0:04:26.520 --> 0:04:29.400 We are asking deeper and more subtle questions about the 0:04:29.480 --> 0:04:33.719 nature of those planets, their atmospheres, their surfaces, even what's 0:04:33.760 --> 0:04:35.040 in orbit around them. 0:04:35.160 --> 0:04:37.400 So today on the podcast, we'll be tackling the question 0:04:42.440 --> 0:04:48.039 could we see moons around exo planets? Now, Daniel, I 0:04:48.040 --> 0:04:51.400 imagine these are like moons, like the orbiting celestial bodies, 0:04:51.440 --> 0:04:53.400 and not like aliens mooning. 0:04:53.320 --> 0:04:55.800 Or maybe alien death stars. Right, we don't care. We 0:04:55.880 --> 0:04:56.880 just wanted to discover them. 0:04:58.360 --> 0:05:00.640 Wait wait, wait, wait, I think we maybe should. If 0:05:00.680 --> 0:05:03.320 there are alien death stars, maybe we don't want to 0:05:03.320 --> 0:05:05.640 meet them. Maybe these are not the aliens we're looking for. 0:05:06.680 --> 0:05:09.479 I think we'd rather know they're there than live in ignorance, 0:05:09.480 --> 0:05:09.960 wouldn't we. 0:05:10.120 --> 0:05:11.920 If we know they're there, then they know we're here. 0:05:12.040 --> 0:05:14.040 We could just use that Jedi mind trick, that's. 0:05:13.960 --> 0:05:16.159 Right, make them forget and dazzle them with our dad 0:05:16.240 --> 0:05:18.960 jokes and then it'll be like what what And then 0:05:18.960 --> 0:05:21.440 they won't want to associate with us, and then problem solve. 0:05:22.040 --> 0:05:23.920 These aren't the jokes you're looking for. 0:05:24.080 --> 0:05:28.040 That's right, or they'll want to annihilate us right away, But. 0:05:28.040 --> 0:05:31.599 We are curious about the environments of these planets. Having 0:05:31.640 --> 0:05:34.000 moons affects life on Earth and tells us a lot 0:05:34.040 --> 0:05:37.120 about the history of that solar system, and just in general, 0:05:37.160 --> 0:05:40.000 we want to know, like our solar system is pretty mooney, 0:05:40.360 --> 0:05:42.880 are other solar systems mooney as well? 0:05:43.160 --> 0:05:45.839 Mooney and wonderful? Because I think, as you said earlier, 0:05:46.040 --> 0:05:47.800 up until a little bit a few years ago, a 0:05:47.800 --> 0:05:50.160 few decades ago, we didn't even have confirmation there were 0:05:50.200 --> 0:05:53.279 other planets out there, right, We just imagined or assume 0:05:53.320 --> 0:05:55.440 there were, but we had not actually seen any. 0:05:55.640 --> 0:05:58.039 Yeah, it could have been that we were one of 0:05:58.480 --> 0:06:02.320 very very few, perhaps singular solar systems that had planets 0:06:02.320 --> 0:06:04.520 around it. It could have been that the reason that there's 0:06:04.640 --> 0:06:06.840 life here around our Sun is that it was the 0:06:06.839 --> 0:06:10.239 only one with a rocky habitable perch. Now, of course, 0:06:10.279 --> 0:06:12.520 we know the opposite is true. We know there are 0:06:12.520 --> 0:06:15.960 planets all over the galaxy. We've seen a few thousand 0:06:16.040 --> 0:06:19.240 of them, and we estimate that there are zillions of them, 0:06:19.279 --> 0:06:22.800 that they're almost literally everywhere in the galaxy. That's a 0:06:22.839 --> 0:06:25.000 real change in the way we see our whole context 0:06:25.240 --> 0:06:26.000 in the universe. 0:06:26.320 --> 0:06:28.840 Yeah, because imagine even like jumping from our sun to 0:06:28.880 --> 0:06:30.520 the stars in the sky was kind of a big 0:06:30.600 --> 0:06:32.680 leap for humanity too, right, Like, we can look at 0:06:32.680 --> 0:06:35.240 our sun and it looks circular, at least if you 0:06:35.279 --> 0:06:37.000 see a projector of it or through a filter, you 0:06:37.000 --> 0:06:39.640 can see that it's a giant ball. But the stars 0:06:39.640 --> 0:06:41.560 in the sky just look like little pinpoints, And so 0:06:41.560 --> 0:06:43.200 it must have been a pretty big leap to think, 0:06:43.320 --> 0:06:45.479 you know, those pinpoints are actually stars. 0:06:45.600 --> 0:06:47.640 It is a pretty big leap. And to understand how 0:06:47.720 --> 0:06:50.400 big a leap it is to understand how far away 0:06:50.440 --> 0:06:53.039 they are is pretty tricky. I mean, even the Greeks 0:06:53.120 --> 0:06:56.160 knew that the other stars were likely suns, but they 0:06:56.160 --> 0:06:58.760 thought they were much much closer than they actually are. 0:06:58.839 --> 0:07:03.200 The Greeks couldn't understand how far away these stars actually were. 0:07:03.279 --> 0:07:06.240 So yeah, it really expands your whole mental picture of 0:07:06.320 --> 0:07:09.359 the universe to understand that our sun is one of 0:07:09.520 --> 0:07:12.120 many of those stars, and that therefore there are lots 0:07:12.160 --> 0:07:15.120 and lots of places where life might exist in the universe. 0:07:15.400 --> 0:07:17.480 Yeah, and those stars out there are really far away, 0:07:17.480 --> 0:07:21.200 that's why they look like pinpoints. And so basically, until recently, 0:07:21.280 --> 0:07:24.560 it was almost impossible to really see a planet on them, right. 0:07:24.640 --> 0:07:26.600 It was very tricky, and for a long time people 0:07:26.600 --> 0:07:30.239 thought it might be impossible. But astronomers are very clever 0:07:30.360 --> 0:07:32.920 and very hard working, and now we have lots of 0:07:32.960 --> 0:07:36.680 tricks to discover planets around other stars, and so now 0:07:36.720 --> 0:07:39.960 people are pushing into what many people believe is impossible, 0:07:40.440 --> 0:07:44.240 understanding the atmospheres, the surfaces, and maybe even the orbiting 0:07:44.280 --> 0:07:46.040 bodies of those planets. 0:07:46.160 --> 0:07:48.040 I wonder what did I'm sure we'll get into it, 0:07:48.120 --> 0:07:50.560 But what's the driving question here to know whether an 0:07:50.560 --> 0:07:53.360 exoplanet has a moon? Like do you think maybe the 0:07:53.400 --> 0:07:56.200 moon is the one that's habitable, or you're just trying 0:07:56.240 --> 0:07:57.480 to study other moons? 0:07:57.560 --> 0:08:00.560 I think all of those things. Moons might be the 0:08:00.600 --> 0:08:03.760 most commonplace for life in the universe. It might be 0:08:03.920 --> 0:08:06.880 that moons around big planets are the best place for 0:08:07.040 --> 0:08:10.600 life to evolve, and the humanity is very, very weird 0:08:10.960 --> 0:08:14.040 for developing directly on the surface of a planet. On 0:08:14.080 --> 0:08:16.640 the other hand, moons also tell you a lot about 0:08:16.640 --> 0:08:19.080 the history of the Solar System, how it formed, how 0:08:19.080 --> 0:08:20.880 it came to be, which tells you a lot about 0:08:20.880 --> 0:08:23.720 where you expect to find planets that might have life 0:08:23.720 --> 0:08:27.040 on them. So it's as much about understanding the detailed 0:08:27.120 --> 0:08:30.440 history of other solar systems and thinking about where we 0:08:30.520 --> 0:08:31.960 might find life well as usually. 0:08:31.960 --> 0:08:33.840 We were wondering how many of you out there had 0:08:33.840 --> 0:08:36.120 thought about this question and wondered if we could see 0:08:36.240 --> 0:08:37.680 moons in other planets. 0:08:37.720 --> 0:08:41.280 Thanks very much to everybody who offers their unprepared insights. 0:08:41.360 --> 0:08:43.640 We really enjoy this segment of the podcast and we 0:08:43.720 --> 0:08:46.280 want to hear from you. Please don't be shy write 0:08:46.280 --> 0:08:49.240 to us to questions at Danielandjorge dot com. 0:08:49.280 --> 0:08:51.120 So think about it for a second. Do you think 0:08:51.280 --> 0:08:55.880 we could ever see moons around exoplanets? Here's what people 0:08:55.880 --> 0:08:56.320 have to say. 0:08:56.559 --> 0:08:59.520 Just finished listening to the podcast with the exoplanet researcher 0:09:00.080 --> 0:09:03.640 and do I think we could see them? No, but 0:09:03.760 --> 0:09:07.760 we do have confirmed existence of moons around exoplanets. I 0:09:07.800 --> 0:09:09.720 believe that number is currently at two. 0:09:10.040 --> 0:09:12.000 I think we will definitely be able to see moods 0:09:12.000 --> 0:09:15.600 throughout exoplanets. James Web will be able to analyze the 0:09:15.640 --> 0:09:19.080 atmospheres of exoplanets and it might even be strong enough 0:09:19.080 --> 0:09:22.760 to see moons. And if not, James Web, there's probably 0:09:22.920 --> 0:09:24.680 going to be another set of eyeballs in the future 0:09:24.720 --> 0:09:25.719 that we'll be able to do it. 0:09:26.600 --> 0:09:29.240 I think that in order to be able to detect 0:09:29.320 --> 0:09:33.840 moons of exoplanets, we would need very sensitive telescope and 0:09:34.000 --> 0:09:39.120 other instruments capable of measuring the lightest, faintest of changes 0:09:39.559 --> 0:09:42.760 in the light emitted from other stars. 0:09:43.559 --> 0:09:46.440 Yes, in terms of finding excello planet moons to be 0:09:46.760 --> 0:09:50.480 to measure the gravity between that planet, that exoplanet a 0:09:50.640 --> 0:09:53.040 star and see if we can account for any extra 0:09:53.040 --> 0:09:54.960 gravity that would be from the moon or maybe some 0:09:55.040 --> 0:09:57.800 sort of nudger or tug on that moon. 0:09:58.360 --> 0:10:00.360 I think this depends on your definition of what it 0:10:00.400 --> 0:10:03.320 means to see a moon. It seems like it would 0:10:03.360 --> 0:10:06.840 be nearly impossible to imagine directly imaging any especially given 0:10:06.840 --> 0:10:09.600 that we haven't directly imaged and exo planet yet. But 0:10:09.640 --> 0:10:11.800 if we had a specially large planet around a star 0:10:11.880 --> 0:10:14.600 with a big enough percentage of its star's mass, and 0:10:14.640 --> 0:10:16.160 if it in turn had a moon that was a 0:10:16.200 --> 0:10:19.640 significant percentage of its mass, then I would imagine that 0:10:19.640 --> 0:10:23.760 they could probably detect the combined wobble of the interaction 0:10:23.800 --> 0:10:24.720 between those three. 0:10:25.040 --> 0:10:28.840 All Right, a lot of optimism here. I feel everyone's like, sure, yeah, eventually, 0:10:29.080 --> 0:10:31.920 sort of in one way or another, Yeah. 0:10:31.720 --> 0:10:34.079 There's this bubbling sense that eventually we could figure out 0:10:34.080 --> 0:10:37.640 basically any problem that in our future lies more and 0:10:37.679 --> 0:10:41.679 more powerful techniques and telescopes and smarter people that could 0:10:41.840 --> 0:10:44.400 extract this kind of information from the universe. I love 0:10:44.440 --> 0:10:47.200 that it's so inspiring to hear people's optimism. Yeah. 0:10:47.280 --> 0:10:49.880 Yeah, And I think by smarter people you mean the engineers, right. 0:10:51.720 --> 0:10:54.000 I mean my students and my students'. 0:10:53.559 --> 0:10:56.079 Students and the engineers that actually do it for them, right. 0:10:56.320 --> 0:10:57.439 I think that's what you're saying. 0:10:57.280 --> 0:10:59.200 Right, I know, we just submit the work order and 0:10:59.200 --> 0:11:02.079 it comes back. You know who knows who does YadA, 0:11:02.120 --> 0:11:03.599 YadA YadA. You gotta telescope. 0:11:03.640 --> 0:11:06.480 That's right, We toy anonymously. That's what happens to all 0:11:06.520 --> 0:11:07.199 smarter people. 0:11:07.280 --> 0:11:09.400 No, of course, the field of astronomer is filled with 0:11:09.440 --> 0:11:12.120 people who analyze the data, and people who build the devices, 0:11:12.200 --> 0:11:14.760 and people who plan for the next generation of devices. 0:11:14.800 --> 0:11:18.320 It's a whole ecosystem of smart people, from physicists to 0:11:18.440 --> 0:11:22.920 planetary scientists, to engineers to computer scientists, all sorts of 0:11:22.960 --> 0:11:24.120 people all working together. 0:11:24.600 --> 0:11:27.000 Well, this is a pretty big question, or I guess 0:11:27.040 --> 0:11:29.280 a small question is how do you see the moon 0:11:29.640 --> 0:11:33.200 around a planet orbiting a star that is light years 0:11:33.720 --> 0:11:35.679 or at least millions of miles away. It's a pretty 0:11:35.679 --> 0:11:36.199 tough question. 0:11:36.320 --> 0:11:38.760 It is a pretty tough question, and it's going to 0:11:38.800 --> 0:11:42.679 require us to get even better at seeing those planets. 0:11:42.960 --> 0:11:45.600 All the techniques we have for seeing moons are basically 0:11:45.679 --> 0:11:48.960 like super powerful versions of the ways that we see planets. 0:11:49.040 --> 0:11:51.240 All right, well, let's break it down for people, Daniel. 0:11:51.280 --> 0:11:54.320 First of all, what is an exoplanet and what do 0:11:54.360 --> 0:11:55.520 we know about them? 0:11:55.559 --> 0:11:58.400 So an exoplanet is very simply just a planet around 0:11:58.480 --> 0:12:02.320 another star. Planets are the planets around our sun. An 0:12:02.360 --> 0:12:06.040 exoplanet is a planet around for example, Alpha Centauri or 0:12:06.120 --> 0:12:09.400 any other star that's not our Sun XO. Just meaning 0:12:09.480 --> 0:12:11.920 like outside the Solar system. 0:12:11.320 --> 0:12:14.760 M I see like an outer planet? Where I guess not, 0:12:14.840 --> 0:12:16.760 because an outer planet could be the planets in our 0:12:16.800 --> 0:12:19.680 Solar system. Like anything outside of our Solar system that's 0:12:19.679 --> 0:12:21.200 a planet is an exoplanet. 0:12:21.280 --> 0:12:24.320 Yeah, a planet around another star would be an exoplanet. 0:12:24.720 --> 0:12:27.000 And they have to be far away because the nearest 0:12:27.040 --> 0:12:30.600 star is several light years away, which is really really far. 0:12:31.040 --> 0:12:33.960 It's very far compared to the distance between the planets, 0:12:34.280 --> 0:12:36.160 and so an exoplanet is going to be very, very 0:12:36.200 --> 0:12:38.920 different from any planet in our Solar system, just in 0:12:39.000 --> 0:12:40.160 terms of like where it is. 0:12:40.480 --> 0:12:43.120 And we hadn't actually seen one or confirmed there were 0:12:43.160 --> 0:12:46.960 any planets around any other stars until basically like thirty 0:12:47.040 --> 0:12:47.440 years ago. 0:12:47.520 --> 0:12:49.600 Right, Yeah, it's incredible if you make a plot of 0:12:49.640 --> 0:12:52.640 like the number of planets we've seen over time, dating 0:12:52.679 --> 0:12:56.080 back like thousands of years until fairly recently, we'd only 0:12:56.120 --> 0:12:59.520 ever seen like six, right, and then Urinus and Neptune 0:12:59.559 --> 0:13:01.480 are discovered in the last few hundred years, and then 0:13:01.520 --> 0:13:05.000 Pluto and then un Pluto, so we're back down to eight. 0:13:05.080 --> 0:13:08.280 And then it wasn't until the nineteen nineties, only thirty 0:13:08.360 --> 0:13:11.000 years ago, that we finally saw one outside of our 0:13:11.040 --> 0:13:14.560 Solar system. Until then, we only speculated, we only imagined, 0:13:14.600 --> 0:13:17.840 we'd had calculations, we had speculations, but we had no 0:13:18.040 --> 0:13:21.439 actual data until about thirty years ago when we developed 0:13:21.440 --> 0:13:24.240 these techniques to see the planets or to deduce their 0:13:24.320 --> 0:13:26.320 existence around other stars. 0:13:26.559 --> 0:13:29.080 Yeah, because, as one of the listeners who replied earlier said, 0:13:29.160 --> 0:13:31.080 the word see is a little bit tricky, right, We 0:13:31.120 --> 0:13:35.120 didn't actually see planets in other stars. We sort of 0:13:35.160 --> 0:13:37.520 like figure out they were there, but we didn't actually 0:13:37.520 --> 0:13:37.960 see them. 0:13:37.920 --> 0:13:41.319 Yeah, exactly, and so we have these really cool techniques 0:13:41.360 --> 0:13:43.679 to deduce that they exist, and you know, you can 0:13:43.800 --> 0:13:46.560 argue philosophically about what does it mean to see something, 0:13:46.720 --> 0:13:50.360 But we didn't see exoplanets directly until much more recently. 0:13:50.400 --> 0:13:54.200 The first discoveries came from just observing the impact of 0:13:54.280 --> 0:13:57.280 those planets on the stars, which of course we can. 0:13:57.200 --> 0:13:59.800 See, which is kind of crazy to think, right, because 0:14:00.559 --> 0:14:03.600 what possible impact and the Earth have on the Sun. 0:14:03.679 --> 0:14:05.920 The Sun is like a million times heavier than the Earth, 0:14:06.000 --> 0:14:06.560 right or more. 0:14:06.679 --> 0:14:09.240 It's all about making these things more sensitive and getting 0:14:09.280 --> 0:14:12.440 down to the details. Like mostly you're right, the Earth 0:14:12.480 --> 0:14:14.640 has basically no impact on the Sun. But if you 0:14:14.679 --> 0:14:18.120 analyze the Sun super duper closely, then yeah, the Earth 0:14:18.160 --> 0:14:20.360 does have a little bit of an impact on the Sun, 0:14:20.680 --> 0:14:23.000 the same way that, for example, the other planets have 0:14:23.040 --> 0:14:25.960 an impact on the Earth. Mostly, the Earth's orbit around 0:14:25.960 --> 0:14:27.800 the Sun is just a story of two bodies, the 0:14:27.840 --> 0:14:30.480 Earth and the Sun, orbiting their combined center of mass. 0:14:30.520 --> 0:14:32.680 But if you get super dup or precise about it, 0:14:32.880 --> 0:14:34.640 then you have to take into account, like the effect 0:14:34.680 --> 0:14:37.320 of Jupiter and Saturn on the orbit of the Earth. 0:14:37.880 --> 0:14:41.040 So all of these little complications can actually reveal the 0:14:41.160 --> 0:14:44.000 rich structure of the Solar system if you study them 0:14:44.000 --> 0:14:44.920 with enough precision. 0:14:45.000 --> 0:14:47.400 It's pretty mind body to think. I mean, the Sun 0:14:47.480 --> 0:14:50.000 is so big and it's the Earth is just this 0:14:50.040 --> 0:14:52.320 tiny little marble next to it, like that it would 0:14:52.320 --> 0:14:53.640 have an effect on the whole thing. Like I can 0:14:53.680 --> 0:14:56.600 see maybe pulling a little bit more on the part 0:14:56.680 --> 0:14:59.400 of the Sun that's closest to the Earth, maybe some 0:14:59.480 --> 0:15:01.480 of that cosma, But to think that it could move 0:15:01.520 --> 0:15:03.640 the entire Sun is pretty hard to believe. 0:15:03.720 --> 0:15:06.200 Yeah, Well, imagine instead you had two objects that had 0:15:06.200 --> 0:15:09.360 the same mass, right, like two stars the same mass, 0:15:09.840 --> 0:15:12.200 and they're orbiting each other. Clearly they have an effect 0:15:12.280 --> 0:15:14.680 on each other. What they're orbiting is actually a point 0:15:14.760 --> 0:15:17.400 right in between them. Now, as you shrink one of 0:15:17.400 --> 0:15:19.640 those things down and grow the other one so it 0:15:19.640 --> 0:15:23.200 becomes asymmetric, the points they're orbiting moves towards the center 0:15:23.240 --> 0:15:26.000 of the heavier one. If one of them was infinitely 0:15:26.080 --> 0:15:29.080 massive or the other one was massless, then they would 0:15:29.120 --> 0:15:31.160 both be orbiting a point at the center of the 0:15:31.200 --> 0:15:34.480 biggest object. But if the Earth is not massless, if 0:15:34.480 --> 0:15:36.680 it actually does have some mass, then it's pulling that 0:15:36.720 --> 0:15:38.880 center of mass a little bit away from the center 0:15:38.920 --> 0:15:40.920 of the Sun. And if you measure the motion of 0:15:40.960 --> 0:15:44.520 the Sun very precisely, you can detect that. And that's 0:15:44.560 --> 0:15:46.360 why these things are so hard. That's why it took 0:15:46.400 --> 0:15:48.560 so long to see these things, is that it requires 0:15:48.640 --> 0:15:52.440 really precise measurements now of the motion of stars in 0:15:52.520 --> 0:15:53.680 other solar systems. 0:15:53.840 --> 0:15:56.200 Yeah, it's pretty mind blowing. But I guess maybe one 0:15:56.200 --> 0:15:58.200 thing that helped was that we didn't start looking for 0:15:58.320 --> 0:16:02.080 Earth sized planets, right, we start looking for Jupiter sized planets. 0:16:02.120 --> 0:16:04.160 Well, we started looking for anything we could see, and 0:16:04.200 --> 0:16:06.520 we didn't know what was out there, right. We had 0:16:06.560 --> 0:16:09.360 speculation about what kind of planets might exist in other 0:16:09.400 --> 0:16:12.240 solar systems, but we didn't really know what we could find. 0:16:12.800 --> 0:16:15.400 You're right though, that the first techniques we developed were 0:16:15.400 --> 0:16:18.640 more powerful for Jupiter sized planets. The bigger the planet 0:16:18.720 --> 0:16:21.440 and the closer it was to the star, the easier 0:16:21.480 --> 0:16:23.080 it was for us to find them. 0:16:23.240 --> 0:16:25.320 Like, those were the first planets found right where. They 0:16:25.360 --> 0:16:27.880 were basically giant gas planets. 0:16:27.960 --> 0:16:30.920 Yeah, they call them hot Jupiters because they're the size 0:16:30.920 --> 0:16:33.640 of Jupiter and they're very close to the star. The 0:16:33.680 --> 0:16:35.800 closer they are the star, the faster the orbit, the 0:16:35.800 --> 0:16:38.080 easier it is to find them because they tug on 0:16:38.160 --> 0:16:40.720 the star. And so one of these techniques is called 0:16:40.720 --> 0:16:43.600 the radial velocity method. You look at the light from 0:16:43.600 --> 0:16:46.200 the star and you see if it's shifted in frequency. 0:16:46.520 --> 0:16:48.800 If a star is moving away from you, it's red shifted. 0:16:48.800 --> 0:16:51.240 If a star's moving towards you, it's blue shifted. If 0:16:51.280 --> 0:16:54.000 a star is getting wiggled by a planet that's orbiting it, 0:16:54.160 --> 0:16:56.000 then it's going to get red shifted and blue shifted, 0:16:56.080 --> 0:16:58.040 red shitted and blue shifted. It's going to wiggle a 0:16:58.040 --> 0:17:01.080 little bit in its frequencies. And that's what they look for. 0:17:01.200 --> 0:17:04.560 But that's more powerful for big planets and planets that 0:17:04.600 --> 0:17:05.880 are close to their stars. 0:17:06.200 --> 0:17:08.840 But then we develop other ways to look at planets, 0:17:08.920 --> 0:17:10.600 right really quick, What are some of these other ways 0:17:10.600 --> 0:17:11.880 that we can see exoplanets. 0:17:12.080 --> 0:17:14.640 So another way is the transit method, which is basically 0:17:14.680 --> 0:17:17.680 an eclipse. As the planet passes in front of the star, 0:17:17.840 --> 0:17:19.800 it dims it a little bit, it blocks some of 0:17:19.840 --> 0:17:21.760 the light. And so again if you're just measuring the 0:17:21.840 --> 0:17:24.280 light from the star roughly, you're never going to notice this. 0:17:24.560 --> 0:17:27.280 If you make very precise measurements of the light from 0:17:27.320 --> 0:17:29.320 the star, you can see these dips and you can 0:17:29.359 --> 0:17:32.320 see the patterns. If the planet goes around many many times, 0:17:32.359 --> 0:17:35.560 you'll see the same pattern over and over again. Unfortunately, 0:17:35.600 --> 0:17:38.959 this one is also best at seeing big planets that 0:17:39.040 --> 0:17:42.280 eclipse the light more and close by planets that block 0:17:42.359 --> 0:17:45.000 more light from their sun and go around many times, 0:17:45.000 --> 0:17:46.520 so we can see many transits. 0:17:47.400 --> 0:17:50.119 Yeah, like if the Moon didn't reflect any light and 0:17:50.119 --> 0:17:51.680 you can see it in the night sky, you could 0:17:51.720 --> 0:17:53.680 still maybe every once in a while know it's there 0:17:53.720 --> 0:17:55.320 because it would block the light from the Sun. You 0:17:55.320 --> 0:17:56.720 would see an eclipse exactly. 0:17:56.800 --> 0:17:59.280 And there are techniques that will let you see planets 0:17:59.280 --> 0:18:01.040 that are further from the Sun, and these are actually 0:18:01.080 --> 0:18:03.399 the direct imaging ones. We can look at a solar 0:18:03.440 --> 0:18:05.320 system and we can block the light from the sun 0:18:05.440 --> 0:18:07.840 called the corona graph, a little thing that prevents the 0:18:07.920 --> 0:18:10.320 light from the star from getting into the telescope and 0:18:10.480 --> 0:18:12.720 only look at the stuff around it. And now we 0:18:12.800 --> 0:18:16.080 have powerful enough telescopes that you can actually see dots 0:18:16.200 --> 0:18:19.840 around those stars. So these are direct images of light 0:18:20.000 --> 0:18:22.960