1 00:00:00,240 --> 00:00:05,600 Speaker 1: Now here's a highlight from Coast to Coast AM on iHeartRadio. 2 00:00:05,040 --> 00:00:07,680 Speaker 2: And welcome back to Coast to Coast George Nori with you. 3 00:00:07,880 --> 00:00:11,680 Speaker 2: Josh Wynn is a professor of astrophysics at Princeton University. 4 00:00:12,240 --> 00:00:15,640 Speaker 2: His research group explores the properties of planets around other 5 00:00:15,720 --> 00:00:18,800 Speaker 2: stars and tries to understand how planets form and evolve 6 00:00:18,840 --> 00:00:21,880 Speaker 2: and make progress on the age old question of whether 7 00:00:21,880 --> 00:00:25,720 Speaker 2: there are planets capable of supporting life out there. His 8 00:00:25,840 --> 00:00:29,080 Speaker 2: latest book is called The Little Book of Exoplanets. Josh, 9 00:00:29,120 --> 00:00:32,240 Speaker 2: it's a great book, by the way, Welcome to the program. 10 00:00:32,479 --> 00:00:34,640 Speaker 3: Thank you very much, and I've been looking forward to 11 00:00:34,680 --> 00:00:35,960 Speaker 3: this conversation. 12 00:00:35,880 --> 00:00:38,480 Speaker 2: These exo planets. How many have been discovered so far? 13 00:00:39,440 --> 00:00:42,879 Speaker 3: Well, NASA maintains the closest thing we have to an 14 00:00:42,920 --> 00:00:46,640 Speaker 3: official list of exoplanets, and I checked just before the 15 00:00:46,680 --> 00:00:50,520 Speaker 3: program and the official number is five thousand, five hundred 16 00:00:50,560 --> 00:00:50,880 Speaker 3: to two. 17 00:00:52,159 --> 00:00:54,000 Speaker 2: That's amazing, it is. 18 00:00:54,200 --> 00:00:58,920 Speaker 3: Yes, it's one of the most rapidly advancing fields of astrophysics. 19 00:00:58,480 --> 00:01:01,240 Speaker 2: Considering thirty years ago. Do you know any of them? 20 00:01:01,320 --> 00:01:02,560 Speaker 1: Right? That's right. 21 00:01:02,640 --> 00:01:06,240 Speaker 3: Yes, it's a new field. It's very much technology driven 22 00:01:06,920 --> 00:01:09,479 Speaker 3: and it was only in the mid nineteen nineties, when 23 00:01:09,640 --> 00:01:12,920 Speaker 3: technology advanced to the point that we could start discovering 24 00:01:13,000 --> 00:01:16,840 Speaker 3: planets around distant stars, well outside the Solar System. 25 00:01:17,080 --> 00:01:20,320 Speaker 2: What percent would you guess that a star, wherever it 26 00:01:20,360 --> 00:01:22,959 Speaker 2: may be, would support planets. 27 00:01:23,520 --> 00:01:27,080 Speaker 3: Yeah, that's a good question. So there are too many 28 00:01:27,080 --> 00:01:29,480 Speaker 3: stars for us to search them all, right, there's maybe 29 00:01:29,520 --> 00:01:32,640 Speaker 3: one hundred billion stars in the Milky Way. So what 30 00:01:32,680 --> 00:01:37,040 Speaker 3: we do is we search the nearest brightest stars, those 31 00:01:37,040 --> 00:01:41,200 Speaker 3: are the ones where it's easiest to find planets, and 32 00:01:41,240 --> 00:01:44,240 Speaker 3: we do it kind of a census, and based on 33 00:01:44,319 --> 00:01:48,240 Speaker 3: what we've seen so far, it seems likely that at 34 00:01:48,320 --> 00:01:51,720 Speaker 3: least for Sun like stars, most or all of them 35 00:01:52,120 --> 00:01:56,080 Speaker 3: have some kind of planets. To be a little more specific, 36 00:01:56,360 --> 00:02:00,520 Speaker 3: if you pick a random sun like star, there's at 37 00:02:00,600 --> 00:02:04,120 Speaker 3: least a thirty percent chance that it has one of 38 00:02:04,120 --> 00:02:08,120 Speaker 3: the types of planets that we can detect today. And 39 00:02:08,160 --> 00:02:10,400 Speaker 3: we can't detect all kinds of planets. Some planets are 40 00:02:10,480 --> 00:02:13,760 Speaker 3: much harder to find than others. Planets that are very 41 00:02:13,800 --> 00:02:17,000 Speaker 3: small are difficult for us to find. Planets that are 42 00:02:17,320 --> 00:02:20,000 Speaker 3: in very wide orbits are difficult for us to find. 43 00:02:20,400 --> 00:02:22,520 Speaker 3: So there's like a one in three chance that it 44 00:02:22,520 --> 00:02:25,480 Speaker 3: will have a detectable kind of planet, and that leaves 45 00:02:25,480 --> 00:02:29,160 Speaker 3: plenty of room for the others that probably have the 46 00:02:29,200 --> 00:02:31,640 Speaker 3: types of planets we're only just beginning to be able 47 00:02:31,639 --> 00:02:32,200 Speaker 3: to detect. 48 00:02:32,600 --> 00:02:35,200 Speaker 2: And Josh, of those planets that might be out there, 49 00:02:35,440 --> 00:02:39,920 Speaker 2: what percent do you think might be earth like, Well. 50 00:02:39,720 --> 00:02:41,960 Speaker 3: It kind of depends on what you mean by earth like. 51 00:02:43,280 --> 00:02:46,400 Speaker 3: The one thing you need to know about exoplanet science 52 00:02:47,160 --> 00:02:49,960 Speaker 3: is that we can only learn a very limited amount 53 00:02:50,080 --> 00:02:54,320 Speaker 3: of information about each planet. So if we have a 54 00:02:54,320 --> 00:02:57,000 Speaker 3: planet in the Solar System like Mars, I can show 55 00:02:57,040 --> 00:03:00,240 Speaker 3: you beautiful images of the surface of Mars and it'd 56 00:03:00,280 --> 00:03:04,079 Speaker 3: see mountains and valleys, and you can look for water 57 00:03:04,280 --> 00:03:08,079 Speaker 3: at the ice caps and so forth. For exoplanets, they're 58 00:03:08,160 --> 00:03:11,040 Speaker 3: so hard to detect that we have none of that 59 00:03:11,200 --> 00:03:14,640 Speaker 3: kind of detailed information. Most of the time. All we 60 00:03:14,720 --> 00:03:18,600 Speaker 3: know is the size of the planet, the overall size, 61 00:03:19,160 --> 00:03:22,600 Speaker 3: the mass, and we know how far away it is 62 00:03:23,240 --> 00:03:25,799 Speaker 3: from the star that it's orbiting, We know how fast 63 00:03:25,840 --> 00:03:28,239 Speaker 3: it's moving in its orbit, and we might be able 64 00:03:28,240 --> 00:03:30,960 Speaker 3: to measure the shape of its orbit. That's about it. 65 00:03:32,080 --> 00:03:35,120 Speaker 3: So when you say earth like planet, many of your 66 00:03:35,160 --> 00:03:38,880 Speaker 3: listeners are probably thinking about a planet that has continents 67 00:03:39,160 --> 00:03:43,640 Speaker 3: and oceans, maybe breathable air, that sort of thing. We 68 00:03:43,720 --> 00:03:48,040 Speaker 3: have no way at the moment of knowing whether those 69 00:03:48,080 --> 00:03:53,720 Speaker 3: things are true for any exoplanet. But if we just ask, okay, well, 70 00:03:54,040 --> 00:03:56,760 Speaker 3: what about planets that are the same size as the 71 00:03:56,800 --> 00:04:01,400 Speaker 3: Earth and that orbit a star like the Sun and 72 00:04:01,760 --> 00:04:04,040 Speaker 3: are about the right distance from the star to have 73 00:04:04,160 --> 00:04:07,560 Speaker 3: the same surface temperature as the Earth. That's kind of 74 00:04:07,560 --> 00:04:11,160 Speaker 3: a working definition of Earth like based on things that 75 00:04:11,200 --> 00:04:14,640 Speaker 3: we can measure today, And the answer is that they're 76 00:04:14,720 --> 00:04:18,240 Speaker 3: probably not. We actually struggle to detect such planets. That's 77 00:04:18,320 --> 00:04:20,600 Speaker 3: kind of right on the limit of our technology right 78 00:04:20,640 --> 00:04:25,599 Speaker 3: now to detect planets as small as the Earth. But 79 00:04:25,680 --> 00:04:30,200 Speaker 3: it seems to be that maybe ten of Sun like 80 00:04:30,279 --> 00:04:32,679 Speaker 3: stars have such a planet. 81 00:04:34,000 --> 00:04:36,680 Speaker 2: Josh, how does a planet even form? 82 00:04:37,240 --> 00:04:39,159 Speaker 3: That's a great question, and that is one of the 83 00:04:39,200 --> 00:04:46,120 Speaker 3: big questions that motivates this field. Planets and stars. They 84 00:04:46,160 --> 00:04:50,320 Speaker 3: didn't just pop into existence with the Big Bang. They 85 00:04:50,320 --> 00:04:53,880 Speaker 3: had to form the universe. The early universe was just 86 00:04:53,920 --> 00:04:59,800 Speaker 3: a kind of formless sea of atoms, and somehow, in 87 00:04:59,839 --> 00:05:03,120 Speaker 3: a there some process must have created the Sun and 88 00:05:03,160 --> 00:05:07,200 Speaker 3: the planets and other stars and their planets. And the 89 00:05:07,279 --> 00:05:11,920 Speaker 3: current theory is that This happens mainly due to gravity. 90 00:05:12,839 --> 00:05:15,359 Speaker 3: When we look around the galaxy, we see lots of 91 00:05:15,760 --> 00:05:20,159 Speaker 3: clouds of material, mostly hydrogen gas, but all kinds of 92 00:05:20,160 --> 00:05:23,400 Speaker 3: other stuff is mixed in there too, And every now 93 00:05:23,440 --> 00:05:29,080 Speaker 3: and then, one of those gigantic clouds of gas starts 94 00:05:29,160 --> 00:05:34,200 Speaker 3: contracting under its own gravity. Gravity, as you know, is 95 00:05:34,520 --> 00:05:37,880 Speaker 3: an attractive force. Everything attracts everything else with the force 96 00:05:37,920 --> 00:05:38,920 Speaker 3: of gravity. 97 00:05:38,640 --> 00:05:40,360 Speaker 2: And it's universal, right, and. 98 00:05:40,279 --> 00:05:44,000 Speaker 3: It's universal as far as we can see, And so 99 00:05:44,080 --> 00:05:47,640 Speaker 3: that will cause the cloud to start shrinking under its 100 00:05:47,680 --> 00:05:52,400 Speaker 3: own gravity. And what happens is that if it contracts 101 00:05:53,240 --> 00:05:56,919 Speaker 3: strong enough and gets to be small enough and dense enough, 102 00:05:57,520 --> 00:06:01,200 Speaker 3: then the material can ignite and become a star. It 103 00:06:01,200 --> 00:06:06,640 Speaker 3: can start nuclear fusion reactions that give stars their power sources. 104 00:06:07,760 --> 00:06:11,159 Speaker 3: But it doesn't just all collapse into a point like 105 00:06:11,200 --> 00:06:16,000 Speaker 3: a star. Instead, what happens is the material ends up 106 00:06:16,080 --> 00:06:22,400 Speaker 3: swirling around this new born star like a vortex. And 107 00:06:22,440 --> 00:06:27,120 Speaker 3: that spinning pattern of material, that disk of material that 108 00:06:27,200 --> 00:06:29,920 Speaker 3: surrounds a young star that is supposed to be where 109 00:06:29,920 --> 00:06:34,680 Speaker 3: the planet's formed. The planets kind of congeal out of 110 00:06:34,720 --> 00:06:39,320 Speaker 3: this material that swirls around a newborn star for several 111 00:06:39,360 --> 00:06:44,560 Speaker 3: million years, so that is the essence of the modern 112 00:06:44,600 --> 00:06:48,880 Speaker 3: theory of planet formation. You form a star by contracting 113 00:06:49,160 --> 00:06:52,839 Speaker 3: a giant cloud of gas under its own gravity, and 114 00:06:52,880 --> 00:06:55,560 Speaker 3: then the material that doesn't quite make it down all 115 00:06:55,560 --> 00:06:58,080 Speaker 3: the way to the star swirls around for a long time, 116 00:06:58,360 --> 00:07:01,400 Speaker 3: brillions of years in fact, and that gives enough time 117 00:07:01,560 --> 00:07:08,240 Speaker 3: for small objects within that spinning disk to conglomerate and 118 00:07:08,440 --> 00:07:11,920 Speaker 3: join together and get larger and larger and become planets. 119 00:07:12,600 --> 00:07:15,840 Speaker 2: And in our Solar system, Josh, the one planet that 120 00:07:15,880 --> 00:07:19,440 Speaker 2: didn't get its act together and form is probably what 121 00:07:19,480 --> 00:07:21,600 Speaker 2: they call the asteroid belt, now right. 122 00:07:21,880 --> 00:07:24,760 Speaker 3: Yeah, that's right. So there are actually two places in 123 00:07:24,760 --> 00:07:27,840 Speaker 3: the Solar System where we see a lot of small debris, 124 00:07:28,640 --> 00:07:33,640 Speaker 3: asteroids and other objects of similar size. One of them 125 00:07:33,720 --> 00:07:37,720 Speaker 3: is between Mars and Jupiter. That's the asteroid belt that 126 00:07:37,800 --> 00:07:40,840 Speaker 3: you just referred to. Probably what happened there is we're 127 00:07:40,880 --> 00:07:45,880 Speaker 3: looking at the material that would have come together under 128 00:07:46,360 --> 00:07:50,520 Speaker 3: its own gravity to become a planet. But Jupiter is 129 00:07:50,600 --> 00:07:54,280 Speaker 3: right next door, and Jupiter is a very massive planet, 130 00:07:55,040 --> 00:07:58,920 Speaker 3: and that means that its gravity stirs up the material 131 00:07:59,200 --> 00:08:03,400 Speaker 3: in the asteroid belt and probably prevented it from forming 132 00:08:03,920 --> 00:08:07,880 Speaker 3: a full fledged planet. The other region that's like that 133 00:08:08,040 --> 00:08:12,120 Speaker 3: is out beyond Neptune. There's another zone where we find 134 00:08:12,600 --> 00:08:16,600 Speaker 3: lots of small, rocky and icy bodies. That's called the 135 00:08:16,680 --> 00:08:21,760 Speaker 3: Kuiper Belt. That's right. Probably what happened there is that 136 00:08:21,760 --> 00:08:25,920 Speaker 3: that material might have become a planet eventually too. But 137 00:08:26,440 --> 00:08:29,920 Speaker 3: everything happens so slowly out there. The further you are 138 00:08:30,280 --> 00:08:34,520 Speaker 3: from the Sun, the weaker the Sun's gravity, and the 139 00:08:34,640 --> 00:08:37,840 Speaker 3: slower all of the motions are out there, and so 140 00:08:38,120 --> 00:08:41,480 Speaker 3: they're just they couldn't get it together quickly enough to 141 00:08:41,600 --> 00:08:42,640 Speaker 3: form a planet. 142 00:08:44,000 --> 00:08:46,959 Speaker 2: Josh, you mentioned the Big Bang, and I got to 143 00:08:47,000 --> 00:08:49,679 Speaker 2: tell you, I have interviewed so many scientists on this 144 00:08:49,760 --> 00:08:53,800 Speaker 2: program over the years. I still don't understand the Big Bang. 145 00:08:53,920 --> 00:08:57,160 Speaker 2: How something would start from nothing? Have you come up 146 00:08:57,200 --> 00:08:58,640 Speaker 2: with your own thoughts about that? 147 00:08:59,200 --> 00:09:04,120 Speaker 3: Yeah, I don't know what came, why something started from nothing. 148 00:09:04,160 --> 00:09:08,360 Speaker 3: I think that's one of the large kind of imponderable 149 00:09:08,640 --> 00:09:12,720 Speaker 3: questions that we have today. But I do know the 150 00:09:13,000 --> 00:09:17,760 Speaker 3: evidence for the Big Bang, the fact that we have 151 00:09:18,360 --> 00:09:22,640 Speaker 3: pretty good reason to think that the universe is expanding. 152 00:09:23,000 --> 00:09:26,920 Speaker 3: That is the when we look at distant galaxies, we 153 00:09:27,040 --> 00:09:31,200 Speaker 3: see that the distances between galaxies are growing with time, 154 00:09:32,440 --> 00:09:35,280 Speaker 3: and that means that if we trace back the clock 155 00:09:36,080 --> 00:09:40,280 Speaker 3: about thirteen point seven billion years I think is the 156 00:09:40,320 --> 00:09:42,760 Speaker 3: current estimate for the age of the universe, that the 157 00:09:42,880 --> 00:09:47,520 Speaker 3: universe was an extremely dense state, that all of the 158 00:09:47,600 --> 00:09:52,040 Speaker 3: matter that we see and spread all over in distant 159 00:09:52,040 --> 00:09:56,040 Speaker 3: galaxies was actually quite close to each other. So it 160 00:09:56,080 --> 00:09:59,920 Speaker 3: was a very hot, dense sea, as I call it 161 00:10:00,040 --> 00:10:03,320 Speaker 3: before of atoms. There's actually a lot of very solid 162 00:10:03,360 --> 00:10:06,920 Speaker 3: evidence for that, and the evidence can take us all 163 00:10:06,960 --> 00:10:10,880 Speaker 3: the way back to the first few seconds after the 164 00:10:10,880 --> 00:10:17,400 Speaker 3: Big Bang. We understand we think the conditions at that 165 00:10:17,640 --> 00:10:21,000 Speaker 3: moment in the early universe's history, and the reason is 166 00:10:21,040 --> 00:10:23,760 Speaker 3: that when we look around the universe, we see it's 167 00:10:23,760 --> 00:10:28,920 Speaker 3: mostly hydrogen, but there's also some helium. Hydrogen and helium 168 00:10:28,960 --> 00:10:33,240 Speaker 3: are the simplest kind of atoms that there are, and 169 00:10:33,320 --> 00:10:36,800 Speaker 3: so there's three quarters of the universe is hydrogen and 170 00:10:36,840 --> 00:10:40,199 Speaker 3: the other quarter is mostly helium. And the only way 171 00:10:40,240 --> 00:10:43,240 Speaker 3: to make sense of that is to suppose that these 172 00:10:43,320 --> 00:10:48,400 Speaker 3: elements formed in that early, hot, dense phase of the universe. 173 00:10:49,520 --> 00:10:53,120 Speaker 3: And if you calculate, well, what would be the elements 174 00:10:53,120 --> 00:10:57,800 Speaker 3: that formed from a hot, expanding fireball with the conditions 175 00:10:57,840 --> 00:11:01,160 Speaker 3: that we think existed in yearly Universe. You get the 176 00:11:01,200 --> 00:11:03,520 Speaker 3: right answer, You get that, well, there should be about 177 00:11:03,720 --> 00:11:07,720 Speaker 3: three quarters hydrogen and most of the rest is helium, 178 00:11:07,720 --> 00:11:11,360 Speaker 3: with a little bit of lithium and so forth. So 179 00:11:11,400 --> 00:11:14,040 Speaker 3: the evidence can take us back to the first few seconds. 180 00:11:14,920 --> 00:11:17,240 Speaker 3: But then if you ask me, well, what about beforehand, 181 00:11:17,720 --> 00:11:20,600 Speaker 3: that's where we have to go off of the path 182 00:11:20,760 --> 00:11:22,920 Speaker 3: of the evidence and start speculation. 183 00:11:23,320 --> 00:11:26,560 Speaker 1: Listen to more Coast to Coast AM every weeknight at 184 00:11:26,600 --> 00:11:29,840 Speaker 1: one am Eastern and go to Coast to coastam dot 185 00:11:29,880 --> 00:11:30,680 Speaker 1: com for more