1 00:00:01,418 --> 00:00:03,877 In the beginning, there was darkness... 2 00:00:03,920 --> 00:00:06,005 and then, bang... 3 00:00:06,047 --> 00:00:09,216 giving birth to an endless expanding existence... 4 00:00:09,259 --> 00:00:11,802 of time, space, and matter. 5 00:00:11,845 --> 00:00:14,096 Now, see further than we've ever imagined... 6 00:00:14,139 --> 00:00:16,015 beyond the limits of our existence... 7 00:00:16,057 --> 00:00:18,892 in a place we call "The Universe. " 8 00:00:21,938 --> 00:00:25,566 Are there planets beyond our solar system? 9 00:00:25,608 --> 00:00:28,402 It's a question few have dared to probe. 10 00:00:28,445 --> 00:00:31,488 The origin of hunting for planets started, really... 11 00:00:31,531 --> 00:00:34,575 from the lunatic fringe of science. 12 00:00:34,617 --> 00:00:38,412 Now, hundreds of these exotic worlds have been found. 13 00:00:38,455 --> 00:00:41,415 Could any of them be home to alien life? 14 00:00:41,458 --> 00:00:44,960 Right now, the sort of planets we're discovering are kind of monsters. 15 00:00:46,212 --> 00:00:49,548 You would be incinerated immediately before you had a chance... 16 00:00:49,591 --> 00:00:52,259 to really sort of groove on your surroundings. 17 00:00:53,136 --> 00:00:56,096 But some planets hold more promise. 18 00:00:56,139 --> 00:00:58,140 I'm so excited about Gliese 436... 19 00:00:58,183 --> 00:00:59,892 I'm almost jumping out of my clothes. 20 00:01:00,518 --> 00:01:04,104 Could we be on the verge of finding another Earth? 21 00:01:04,147 --> 00:01:06,607 We still don't know whether our Earth... 22 00:01:06,649 --> 00:01:11,111 is a commonly occurring planet or a one-in-a-billion freak. 23 00:01:12,030 --> 00:01:16,158 Cutting-edge science, strange worlds, and wild weather... 24 00:01:16,201 --> 00:01:20,829 as we travel the universe in search of "Alien Planets. " 25 00:01:33,301 --> 00:01:36,178 Lurking in the constellation Pegasus... 26 00:01:36,221 --> 00:01:40,140 fifty light-years from Earth, is a monstrous planet... 27 00:01:41,267 --> 00:01:45,854 a superheated gas giant almost as massive as Jupiter... 28 00:01:45,897 --> 00:01:49,066 whipping around its star in a little over four days. 29 00:01:50,401 --> 00:01:53,112 It's called 51 Pegasi b... 30 00:01:53,154 --> 00:01:54,822 and in 1995... 31 00:01:54,864 --> 00:01:59,785 it became the first planet detected orbiting an alien sun. 32 00:02:01,538 --> 00:02:03,664 It was a landmark discovery... 33 00:02:03,706 --> 00:02:07,167 but just a stepping stone on an even greater quest... 34 00:02:07,210 --> 00:02:10,838 to find a planet that looks more like our own. 35 00:02:10,880 --> 00:02:14,133 The ultimate but elusive goal for astronomers... 36 00:02:14,175 --> 00:02:16,593 is to find another Earth. 37 00:02:16,636 --> 00:02:22,266 What we're after is the appreciation of where our Earth fits in... 38 00:02:22,308 --> 00:02:24,935 in the grand context of our universe... 39 00:02:24,978 --> 00:02:26,812 and we'd love to be able to find other Earths. 40 00:02:27,772 --> 00:02:30,357 But Earths are so undetectable... 41 00:02:30,400 --> 00:02:33,402 little chunks of rock that don't emit much light. 42 00:02:35,196 --> 00:02:38,991 How common might Earthlike planets be in the universe? 43 00:02:39,033 --> 00:02:41,577 Even if only one percent of all stars... 44 00:02:41,619 --> 00:02:43,996 were circled by a planet like our own... 45 00:02:44,038 --> 00:02:47,249 that would still mean there are billions of other Earths... 46 00:02:47,292 --> 00:02:49,209 waiting to be discovered. 47 00:02:50,378 --> 00:02:54,173 We are almost sure that rocky, Earthlike planets... 48 00:02:54,215 --> 00:02:58,385 exist in abundance out there, but how Earthlike? 49 00:02:58,428 --> 00:03:03,182 There are still open questions about the uniqueness of our Earth... 50 00:03:03,224 --> 00:03:06,602 and we don't know whether our Earth is unusual or not. 51 00:03:06,644 --> 00:03:11,815 It's an extremely profound and, I think, disturbing question. 52 00:03:13,526 --> 00:03:15,736 In the realm of alien planets... 53 00:03:15,778 --> 00:03:18,947 there's a wide range of imaginable worlds. 54 00:03:20,283 --> 00:03:25,120 We might find ocean worlds, completely covered in water... 55 00:03:25,163 --> 00:03:26,830 frigid ice planets... 56 00:03:28,041 --> 00:03:29,583 Mars-like worlds... 57 00:03:29,626 --> 00:03:34,588 but perhaps with thick atmospheres, fed by massive active volcanoes... 58 00:03:35,548 --> 00:03:40,510 and even planets with two suns in their skies. 59 00:03:40,553 --> 00:03:44,014 There may be planets that humans would find hospitable... 60 00:03:44,057 --> 00:03:47,517 and others on which humans wouldn't dare tread... 61 00:03:47,560 --> 00:03:50,812 that could still be home to other types of creatures. 62 00:03:52,315 --> 00:03:54,441 Perhaps the major lesson we've learned so far... 63 00:03:54,484 --> 00:03:56,443 from looking for planets around other stars... 64 00:03:56,486 --> 00:03:59,571 is that nature can make a lot more planets than we can dream of. 65 00:04:02,533 --> 00:04:05,702 Finding just one other truly Earthlike planet... 66 00:04:05,745 --> 00:04:09,206 would hint that Earths are common in the universe. 67 00:04:09,249 --> 00:04:14,461 And if Earths are common, then, perhaps, life, too, is widespread. 68 00:04:16,297 --> 00:04:20,842 But of the over two hundred alien planets detected so far... 69 00:04:20,885 --> 00:04:24,888 most of them seem utterly hostile to life as we know it. 70 00:04:26,391 --> 00:04:29,601 So far, we found sort of three kinds of worlds. 71 00:04:29,644 --> 00:04:30,936 One kind are the planets... 72 00:04:30,979 --> 00:04:33,105 that are really close to the star that they orbit... 73 00:04:33,147 --> 00:04:35,148 and they're totally baked to death. 74 00:04:36,651 --> 00:04:38,652 Then there are the ones that are quite far away... 75 00:04:38,695 --> 00:04:40,028 and they're pretty cold. 76 00:04:41,030 --> 00:04:43,365 And then there are the ones in the highly eccentric orbits... 77 00:04:43,408 --> 00:04:45,325 which sometimes get close to the star... 78 00:04:45,368 --> 00:04:46,702 and sometimes far away. 79 00:04:47,704 --> 00:04:50,831 So they're alternately very hot and cold. 80 00:04:52,125 --> 00:04:54,710 So far, we definitely haven't found any worlds... 81 00:04:54,752 --> 00:04:57,045 with jungles and forests. 82 00:04:57,088 --> 00:04:59,214 Indeed, we haven't found any worlds... 83 00:04:59,257 --> 00:05:02,467 that are square smack in the habitable zone... 84 00:05:02,510 --> 00:05:04,511 where there's liquid water on the surface... 85 00:05:04,554 --> 00:05:05,887 and other nice conditions. 86 00:05:07,765 --> 00:05:08,807 Our frame of reference... 87 00:05:08,850 --> 00:05:12,185 for what we consider to be a nice planet is this one. 88 00:05:12,228 --> 00:05:14,229 We like it quite a bit. 89 00:05:14,772 --> 00:05:17,357 We've got breathable air, it's a pleasant temperature... 90 00:05:17,400 --> 00:05:19,192 and there's water. 91 00:05:19,235 --> 00:05:22,112 And even in our own solar system, we don't see a lot of planets like that. 92 00:05:22,155 --> 00:05:24,614 And right now, the sort of planets we're discovering... 93 00:05:24,657 --> 00:05:26,241 are kind of monsters. 94 00:05:27,410 --> 00:05:29,077 In other words, they're extremes. 95 00:05:32,373 --> 00:05:37,502 So is the Earth, with its rocky surface, oceans, and abundant life... 96 00:05:37,545 --> 00:05:41,798 just a planetary wonder with no close kin in the cosmos? 97 00:05:43,092 --> 00:05:47,721 The early discoveries of alien planets have yet to answer that question... 98 00:05:47,764 --> 00:05:52,976 but they have brought legitimacy to what once seemed like a futile quest. 99 00:05:54,562 --> 00:05:57,481 While many believed there had to be other worlds out there... 100 00:05:57,523 --> 00:05:59,232 in the vastness of the universe... 101 00:05:59,275 --> 00:06:04,071 locating them was widely considered beyond the reach of modern science. 102 00:06:05,114 --> 00:06:07,032 Only a few decades ago... 103 00:06:07,075 --> 00:06:11,161 an astronomer hunting for these so-called "extrasolar planets"... 104 00:06:11,204 --> 00:06:15,582 was taken about as seriously as someone searching for UFOs. 105 00:06:17,251 --> 00:06:21,588 The search for planets, as it started in the 1980s and 1990s... 106 00:06:21,631 --> 00:06:26,635 was considered off of the beaten track of standard science. 107 00:06:27,929 --> 00:06:29,137 In the early eighties... 108 00:06:29,180 --> 00:06:32,516 astronomer Geoff Marcy's career was going nowhere. 109 00:06:32,558 --> 00:06:36,478 His research into the magnetic fields of stars had reached a dead end... 110 00:06:36,562 --> 00:06:41,108 and he was beginning to question his own abilities as a scientist. 111 00:06:41,150 --> 00:06:44,694 When I first began thinking about looking for planets... 112 00:06:44,737 --> 00:06:48,240 it was in a time in my career when I thought it was over. 113 00:06:48,282 --> 00:06:50,784 I thought there's no hope for me as a scientist... 114 00:06:50,827 --> 00:06:53,745 and I thought the best shot I had... 115 00:06:53,788 --> 00:06:57,290 going out in flames, was to try an experiment... 116 00:06:57,333 --> 00:06:59,418 that everybody thought would never work... 117 00:06:59,460 --> 00:07:02,003 namely, looking for planets around other stars. 118 00:07:02,046 --> 00:07:06,508 And most people thought we would never find any planets. 119 00:07:08,636 --> 00:07:11,972 Before Geoff Marcy, his collaborator, Paul Butler... 120 00:07:12,014 --> 00:07:15,308 and a handful of pioneering astronomers around the globe... 121 00:07:15,351 --> 00:07:18,145 could begin the search for alien planets... 122 00:07:18,187 --> 00:07:21,022 they had to first perfect methods for finding them. 123 00:07:22,191 --> 00:07:25,861 Stars are easy to locate using conventional telescopes... 124 00:07:26,863 --> 00:07:31,533 but to find a planet takes some ingenuity and patience. 125 00:07:32,952 --> 00:07:34,995 Unlike the stars they orbit... 126 00:07:35,037 --> 00:07:38,915 planets are small and emit very little light. 127 00:07:38,958 --> 00:07:42,085 Even the giant of our solar system, Jupiter... 128 00:07:42,128 --> 00:07:45,922 is a thousand times less massive than the Sun... 129 00:07:45,965 --> 00:07:49,009 and ten billion times fainter. 130 00:07:49,051 --> 00:07:53,430 A huge difficulty in taking a picture of a planet around a star... 131 00:07:53,473 --> 00:07:57,559 is that the planet is extremely, extremely faint compared to the star. 132 00:08:00,938 --> 00:08:02,522 The star is so bright... 133 00:08:02,565 --> 00:08:06,776 it almost completely obscures the much, much dimmer planet. 134 00:08:09,071 --> 00:08:12,824 Blinded by starlight, planet hunters realized... 135 00:08:12,867 --> 00:08:15,785 that even if they couldn't see a planet directly... 136 00:08:15,828 --> 00:08:20,248 they should still be able to detect its gravitational effect on the star it orbits. 137 00:08:21,083 --> 00:08:25,670 A star with no planets should drift smoothly through the sky... 138 00:08:25,713 --> 00:08:30,258 while one with planets should exhibit a telltale gravitational wobble. 139 00:08:31,636 --> 00:08:35,472 We often say that planets orbit the Sun or other stars... 140 00:08:35,515 --> 00:08:37,599 but that's not exactly true. 141 00:08:37,642 --> 00:08:42,479 The planets and the stars orbit their common center of mass... 142 00:08:42,522 --> 00:08:44,231 or center of gravity. 143 00:08:45,775 --> 00:08:49,402 And this center of mass isn't halfway between them. 144 00:08:49,445 --> 00:08:52,364 Just like on a seesaw, the more massive object... 145 00:08:52,406 --> 00:08:56,993 must be closer to the center of mass to bring balance to the system. 146 00:08:58,120 --> 00:09:00,622 So consider the Sun and Jupiter. 147 00:09:00,665 --> 00:09:04,626 The Sun is about a thousand times more massive than Jupiter. 148 00:09:04,669 --> 00:09:08,630 So the Sun is here, the fulcrum or balancing point is there... 149 00:09:08,673 --> 00:09:12,842 and Jupiter is way out here a thousand times farther away. 150 00:09:16,681 --> 00:09:20,433 In space, this means that planets trace out large orbits... 151 00:09:20,476 --> 00:09:21,977 around the center of mass... 152 00:09:22,853 --> 00:09:27,023 while stars make much smaller, but still detectable orbits. 153 00:09:28,317 --> 00:09:31,403 Here's a hypothetical planet orbiting a star. 154 00:09:31,445 --> 00:09:34,447 In fact, they're orbiting their common center of mass. 155 00:09:34,490 --> 00:09:38,285 So the planet moves in a relatively large orbit... 156 00:09:38,327 --> 00:09:42,289 but the star also moves, but in a much smaller orbit. 157 00:09:42,331 --> 00:09:46,459 So the star moves only a little bit, and the planet moves a lot. 158 00:09:47,962 --> 00:09:50,463 I have a somewhat unusual hobby for an astronomer. 159 00:09:51,465 --> 00:09:53,383 I'm a belly dancer and fire performer. 160 00:09:54,385 --> 00:09:56,761 But it turns out that spinning fire... 161 00:09:56,804 --> 00:09:59,764 is a great way of simulating the motion of a planet. 162 00:10:00,641 --> 00:10:04,811 The centrifugal motion of your fire on the chain... 163 00:10:04,854 --> 00:10:08,356 is very similar to the motion of a planet under gravity. 164 00:10:09,525 --> 00:10:12,611 The light on my wrist represents the star... 165 00:10:12,653 --> 00:10:15,113 and the spinning ball of fire around that is a planet. 166 00:10:16,157 --> 00:10:19,993 And as you can see, the ball of fire draws out a large circle... 167 00:10:20,036 --> 00:10:23,371 and my wrist is drawing out a smaller circle inside it. 168 00:10:26,250 --> 00:10:28,835 It's this tiny wobble of starlight... 169 00:10:28,878 --> 00:10:33,340 that scientists use to find extrasolar planets. 170 00:10:33,382 --> 00:10:35,925 But even this wobble would be undetectable... 171 00:10:35,968 --> 00:10:38,053 if it wasn't for the Doppler effect... 172 00:10:38,095 --> 00:10:40,096 the fact that wavelengths get shorter... 173 00:10:40,139 --> 00:10:42,515 as the object emitting them moves toward you... 174 00:10:42,558 --> 00:10:44,684 and longer as it moves away from you. 175 00:10:45,686 --> 00:10:47,395 The Doppler effect is very familiar... 176 00:10:47,438 --> 00:10:50,732 if you've ever heard a train going by, blowing its whistle. 177 00:10:53,903 --> 00:10:56,321 So when the train is coming toward you... 178 00:10:56,364 --> 00:10:58,365 you hear a high-pitched whistle... 179 00:11:00,826 --> 00:11:03,828 and as the train recedes into the distance away from you... 180 00:11:07,083 --> 00:11:11,836 you hear the pitch of the whistle get lower and lower in frequency. 181 00:11:13,506 --> 00:11:17,133 Just like sound waves, light waves appear to shift in frequency... 182 00:11:17,176 --> 00:11:20,887 as the object emitting them comes toward or away from you. 183 00:11:20,930 --> 00:11:22,806 Light from an object moving toward you... 184 00:11:22,848 --> 00:11:24,516 will look slightly bluer. 185 00:11:24,558 --> 00:11:26,476 Light from an object moving away from you... 186 00:11:26,519 --> 00:11:28,561 will look slightly redder. 187 00:11:28,604 --> 00:11:31,481 When the light waves shift their wavelength... 188 00:11:31,524 --> 00:11:33,441 toward the blue and toward the red... 189 00:11:33,484 --> 00:11:36,736 and back toward the blue again as the star wobbles around... 190 00:11:36,779 --> 00:11:40,073 the shift is excruciatingly tiny... 191 00:11:40,116 --> 00:11:42,242 but it's that difference in the wavelength... 192 00:11:42,284 --> 00:11:45,829 of the light waves coming at you, that is what we measure... 193 00:11:45,871 --> 00:11:49,207 and it's what allows us to detect planets around other stars. 194 00:11:51,001 --> 00:11:52,836 Using this Doppler technique... 195 00:11:52,878 --> 00:11:56,756 Marcy and Butler spent over a decade patiently studying... 196 00:11:56,799 --> 00:12:01,636 one hundred twenty nearby stars for any sign of a wobble. 197 00:12:02,680 --> 00:12:07,058 I went eleven years without finding a single planet, nothing... 198 00:12:07,101 --> 00:12:08,893 and no one was surprised by that. 199 00:12:08,936 --> 00:12:15,608 It seemed logical to everybody else that it was a fruitless, frivolous... 200 00:12:15,651 --> 00:12:20,238 maybe even lunatic exercise to look for planets of any sort. 201 00:12:22,700 --> 00:12:26,536 But then, in 1995, came the surprise announcement... 202 00:12:26,579 --> 00:12:30,457 from Swiss astronomers, Michel Mayor and Diedre Queloz... 203 00:12:30,499 --> 00:12:33,460 that they had discovered a gas giant planet... 204 00:12:33,502 --> 00:12:37,213 circling the star 51 Pegasi. 205 00:12:37,256 --> 00:12:40,258 Marcy and Butler rushed up to Lick Observatory... 206 00:12:40,301 --> 00:12:42,594 on Northern California's Mount Hamilton... 207 00:12:42,636 --> 00:12:45,263 to aim their own telescope at the star... 208 00:12:45,306 --> 00:12:48,308 and see if they could confirm the Swiss team's results. 209 00:12:48,350 --> 00:12:52,395 Yup, there it is. Looks beautiful. 210 00:12:52,438 --> 00:12:56,566 Paul Butler and I were shocked to see that the wobble of the star... 211 00:12:56,609 --> 00:13:00,487 was precisely as the Swiss had said it was. 212 00:13:00,529 --> 00:13:03,656 And I remember driving off Mount Hamilton... 213 00:13:03,699 --> 00:13:06,910 from Lick Observatory in complete silence... 214 00:13:06,952 --> 00:13:08,578 Paul Butler next to me. 215 00:13:08,621 --> 00:13:14,375 We knew that the first extrasolar planet had been discovered. 216 00:13:14,418 --> 00:13:17,754 It was a very moving, you know, personally moving moment. 217 00:13:20,758 --> 00:13:23,843 Despite the monumental nature of the discovery... 218 00:13:23,886 --> 00:13:26,763 this, like all future extrasolar planets... 219 00:13:26,806 --> 00:13:29,724 wouldn't get the name of a Greek or Roman god. 220 00:13:29,767 --> 00:13:32,227 It would take the astronomical catalog name... 221 00:13:32,269 --> 00:13:35,730 of its parent star, 51 Pegasi... 222 00:13:35,773 --> 00:13:38,650 and add to it a lowercase b. 223 00:13:38,692 --> 00:13:40,693 In this standard nomenclature... 224 00:13:40,736 --> 00:13:43,696 if a second planet was found around the same star... 225 00:13:43,739 --> 00:13:47,367 it would get a lowercase c, and so on through the alphabet. 226 00:13:49,203 --> 00:13:54,165 Its name was the only thing unassuming about 51 Pegasi b. 227 00:13:54,750 --> 00:13:59,254 The discovery shook the foundations of our understanding of planets. 228 00:14:03,217 --> 00:14:08,721 In 1995, astrophysicist Alan Boss was asked to review a paper... 229 00:14:08,764 --> 00:14:12,016 announcing the discovery by two Swiss astronomers... 230 00:14:12,059 --> 00:14:14,936 of the first planet orbiting an alien sun. 231 00:14:15,896 --> 00:14:16,896 Reviewing this paper... 232 00:14:16,939 --> 00:14:18,648 caused me a fair number of sleepless nights... 233 00:14:18,691 --> 00:14:20,859 because it was pretty stunning what they had found. 234 00:14:21,819 --> 00:14:23,570 Stunning because the Swiss... 235 00:14:23,612 --> 00:14:26,614 claimed to have found a Jupiter-like planet. 236 00:14:26,657 --> 00:14:29,617 But where Jupiter orbits the Sun in twelve years... 237 00:14:29,660 --> 00:14:33,788 this planet zipped around its star in only four days. 238 00:14:34,623 --> 00:14:35,915 And that also meant that the planet... 239 00:14:35,958 --> 00:14:38,293 had to be much, much closer to its central star... 240 00:14:38,335 --> 00:14:41,546 roughly a hundred times closer than Jupiter is. 241 00:14:41,589 --> 00:14:44,173 And that just was hard to understand. 242 00:14:45,509 --> 00:14:47,051 Jupiter orbits the Sun... 243 00:14:47,094 --> 00:14:50,430 at a comfortable distance of around half a billion miles. 244 00:14:51,932 --> 00:14:57,687 51 Pegasi b is more like five million miles from its star. 245 00:14:57,730 --> 00:15:00,398 If it were dropped into our own solar system... 246 00:15:00,441 --> 00:15:03,902 this alien planet would orbit much closer to the sun... 247 00:15:03,944 --> 00:15:07,530 than Mercury, our innermost planet. 248 00:15:07,573 --> 00:15:09,407 Being so close to the star... 249 00:15:09,450 --> 00:15:12,660 means that the planet is being literally fried. 250 00:15:13,329 --> 00:15:15,914 The radiation from the star is incredible... 251 00:15:15,956 --> 00:15:19,125 compared to what we experience here on Earth... 252 00:15:19,168 --> 00:15:21,461 relatively far from our sun. 253 00:15:21,503 --> 00:15:24,339 So this was a completely unexpected discovery. 254 00:15:25,466 --> 00:15:27,842 It was a planet that could not have formed there. 255 00:15:28,844 --> 00:15:31,137 Astronomers knew it didn't belong there. 256 00:15:34,934 --> 00:15:36,476 In the same way that if we found... 257 00:15:36,518 --> 00:15:38,937 a giant redwood in the middle of Central Park... 258 00:15:38,979 --> 00:15:40,813 we would know that it didn't belong there. 259 00:15:44,693 --> 00:15:46,945 You'd have to ask yourself, how did it get there? 260 00:15:46,987 --> 00:15:49,364 And that's what astronomers were asking themselves... 261 00:15:49,406 --> 00:15:52,200 about these giant planets that they were finding. 262 00:15:53,160 --> 00:15:56,788 51 Pegasi b wasn't just a freak of nature. 263 00:15:56,830 --> 00:15:59,958 It was the first of dozens of so-called "roasters"... 264 00:16:00,000 --> 00:16:05,380 or "hot Jupiters" to be discovered in seemingly impossible close-in orbits. 265 00:16:07,091 --> 00:16:09,592 Impossible because the accepted theory... 266 00:16:09,635 --> 00:16:13,429 for how gas planets form suggests that rock and ice... 267 00:16:13,472 --> 00:16:16,057 in a disk surrounding a young star... 268 00:16:16,100 --> 00:16:21,062 coalesces into a solid core that then accretes gas... 269 00:16:21,105 --> 00:16:24,315 growing larger and larger until it has cleared out... 270 00:16:24,358 --> 00:16:27,402 all the planet-forming material in its area. 271 00:16:28,195 --> 00:16:29,779 This process can only occur... 272 00:16:29,822 --> 00:16:32,240 at a distance far enough from the star... 273 00:16:32,282 --> 00:16:35,201 where it's cold enough for ice to exist. 274 00:16:35,244 --> 00:16:38,705 You can't form something that massive, that close in to a star. 275 00:16:38,747 --> 00:16:43,209 It needs to form past the snow line where ice can form. 276 00:16:44,420 --> 00:16:47,338 And in our solar system, that's about where Jupiter is... 277 00:16:47,381 --> 00:16:50,258 about five times further out from the Sun than the Earth. 278 00:16:52,636 --> 00:16:56,389 So how could a gas giant planet like 51 Pegasi b... 279 00:16:56,432 --> 00:16:59,809 form so scorchingly close to its star? 280 00:16:59,852 --> 00:17:00,893 It was one of these things... 281 00:17:00,936 --> 00:17:02,895 where I woke up in the middle of the night... 282 00:17:02,938 --> 00:17:06,149 and, one night, I said to myself, maybe what this means... 283 00:17:06,191 --> 00:17:08,651 is that this object had to have migrated inwards... 284 00:17:08,694 --> 00:17:10,528 from where it originally formed. 285 00:17:13,741 --> 00:17:16,534 We now, I think, have an understanding... 286 00:17:16,577 --> 00:17:20,288 that planet formation is an almost chaotic process... 287 00:17:20,330 --> 00:17:24,292 a sort of roll of the dice with many planetesimals... 288 00:17:24,334 --> 00:17:26,961 wannabe planets forming, building up... 289 00:17:27,004 --> 00:17:28,379 and a competition... 290 00:17:28,422 --> 00:17:31,883 a sort of gravitational musical chairs takes place... 291 00:17:31,925 --> 00:17:34,802 in which the planets compete for their own space. 292 00:17:36,472 --> 00:17:38,056 In this competition... 293 00:17:38,098 --> 00:17:41,059 some planets are flung out of the solar system... 294 00:17:41,101 --> 00:17:44,103 and some are tossed toward the center. 295 00:17:44,146 --> 00:17:48,066 It's believed some planets crash and burn on their parent star... 296 00:17:49,943 --> 00:17:53,946 while others survive in a close but stable orbit. 297 00:17:53,989 --> 00:17:57,158 These survivors are the hot Jupiters. 298 00:17:57,993 --> 00:18:02,455 The discovery of the hot Jupiter circling 51 Pegasi... 299 00:18:02,498 --> 00:18:05,500 sent planet hunters Geoff Marcy and Paul Butler... 300 00:18:05,542 --> 00:18:08,127 back to analyze the data they had been collecting... 301 00:18:08,170 --> 00:18:09,587 for the past decade. 302 00:18:09,630 --> 00:18:11,214 Their team had been looking... 303 00:18:11,256 --> 00:18:15,426 for the expected long-term wobbles caused by a giant planet. 304 00:18:15,469 --> 00:18:17,595 We ourselves suddenly realized... 305 00:18:17,638 --> 00:18:19,931 we should analyze our data in a slightly different way... 306 00:18:19,973 --> 00:18:21,974 look for the shorter period planets... 307 00:18:22,017 --> 00:18:26,229 not just planets that take a long time to go around their star. 308 00:18:26,271 --> 00:18:30,149 And that led us to discover within existing data... 309 00:18:30,192 --> 00:18:33,319 all of these planets that had been buried there for years. 310 00:18:37,699 --> 00:18:40,535 I remember the day like it was yesterday... 311 00:18:40,577 --> 00:18:43,746 December 30, 1995. 312 00:18:43,789 --> 00:18:46,249 And at 8 A.M., the phone rings. 313 00:18:46,291 --> 00:18:48,167 I pick it up, it's Paul Butler... 314 00:18:48,210 --> 00:18:51,587 my ace collaborator for twenty years now. 315 00:18:51,630 --> 00:18:54,298 And Paul just said, "Geoff, come over here. " 316 00:18:57,761 --> 00:18:59,595 So, of course, I immediately got in my car. 317 00:18:59,638 --> 00:19:02,557 I drove right to this very office, right here where I'm sitting now... 318 00:19:02,599 --> 00:19:05,143 in Campbell Hall at UC Berkeley... 319 00:19:05,185 --> 00:19:07,061 and he showed me his computer screen. 320 00:19:07,104 --> 00:19:11,065 And there on that screen was the unmistakable graph... 321 00:19:11,108 --> 00:19:13,860 of the wobble of the star 70 Virginis... 322 00:19:13,902 --> 00:19:15,695 going up and down and up and down... 323 00:19:15,737 --> 00:19:19,031 the star wobbling to and fro, exactly as we had imagined... 324 00:19:19,074 --> 00:19:22,785 a planet's signature would look in our data. 325 00:19:22,828 --> 00:19:26,831 So that was the moment, with both of our eyes open this wide... 326 00:19:26,874 --> 00:19:29,792 that we knew we had discovered our first planet... 327 00:19:29,835 --> 00:19:31,711 the second planet ever discovered. 328 00:19:33,589 --> 00:19:37,675 70 Virginis b is fifty-nine light-years from Earth... 329 00:19:37,718 --> 00:19:40,386 in the constellation Virgo. 330 00:19:40,429 --> 00:19:43,890 With a mass at least seven times larger than Jupiter... 331 00:19:43,932 --> 00:19:46,392 this world immediately claimed the title... 332 00:19:46,435 --> 00:19:49,937 as the planetary heavyweight of the known universe. 333 00:19:51,940 --> 00:19:54,108 Here, right before our eyes, essentially... 334 00:19:54,151 --> 00:19:58,237 is a planet seven, maybe ten times bigger than our own Jupiter... 335 00:19:58,280 --> 00:20:00,364 telling us immediately that, yes... 336 00:20:00,407 --> 00:20:02,366 nature does make planets even bigger... 337 00:20:02,409 --> 00:20:04,785 than the largest ones we have here in the solar system. 338 00:20:06,747 --> 00:20:08,414 Rather than a hot Jupiter... 339 00:20:08,457 --> 00:20:11,751 this planet was the first of a new class of alien worlds... 340 00:20:11,793 --> 00:20:14,003 called eccentric giants... 341 00:20:14,046 --> 00:20:16,797 because of their eccentric or elongated orbits. 342 00:20:18,133 --> 00:20:20,009 70 Virginis b swings out... 343 00:20:20,052 --> 00:20:23,471 as far as sixty-three million miles from its star... 344 00:20:23,513 --> 00:20:27,725 and passes as close as twenty-seven million miles. 345 00:20:27,768 --> 00:20:31,646 The frightening aspect of the planet around 70 Virginis... 346 00:20:31,688 --> 00:20:34,523 is that we all grew up in kindergarten... 347 00:20:34,566 --> 00:20:37,109 learning that planets go around the sun... 348 00:20:37,152 --> 00:20:39,445 in merely circular orbits... 349 00:20:39,488 --> 00:20:43,282 so what in the world is a planet doing going around its star... 350 00:20:43,325 --> 00:20:45,993 in one of these elongated, wacky orbits? 351 00:20:48,038 --> 00:20:52,041 Already the first two planets discovered around alien suns... 352 00:20:52,084 --> 00:20:55,086 were challenging our view of how planets should behave. 353 00:20:56,588 --> 00:20:58,756 Further discoveries over the next decade... 354 00:20:58,799 --> 00:21:02,760 would show that eccentric orbits are common in the universe... 355 00:21:02,803 --> 00:21:06,806 while the circular orbits of our solar system seem to be rare. 356 00:21:08,558 --> 00:21:12,603 It's embarrassing, frankly, when you think about... 357 00:21:12,646 --> 00:21:16,816 how we humans imagined planets would orbit other stars... 358 00:21:16,858 --> 00:21:19,402 how common they would be, what properties they would have. 359 00:21:19,444 --> 00:21:20,444 Guess what? 360 00:21:20,487 --> 00:21:22,655 We imagined that those planets... 361 00:21:22,698 --> 00:21:25,658 would look just like the planets that orbit our Sun. 362 00:21:25,701 --> 00:21:28,035 Extraordinarily nearsighted in retrospect. 363 00:21:28,078 --> 00:21:30,538 And for a scientist, I find it embarrassing... 364 00:21:30,580 --> 00:21:32,498 that I was a party to this. 365 00:21:33,375 --> 00:21:36,377 But, in fact, what we've learned is that planets around other stars... 366 00:21:36,420 --> 00:21:40,006 are remarkably different from the representatives... 367 00:21:40,048 --> 00:21:42,425 we have around our Sun. 368 00:21:42,467 --> 00:21:45,928 The planet-hunting revolution that began in the 1990s... 369 00:21:45,971 --> 00:21:51,517 has also obliterated any notion that planets are rare in the universe. 370 00:21:51,560 --> 00:21:54,353 With an ever-growing catalog of alien planets... 371 00:21:56,565 --> 00:21:59,191 astronomers are now trying to learn all they can... 372 00:21:59,234 --> 00:22:02,570 about the more than 200 worlds they've already discovered. 373 00:22:05,282 --> 00:22:08,868 The Doppler technique used by Geoff Marcy and other astronomers... 374 00:22:08,910 --> 00:22:11,996 tells them the mass of the planet they found... 375 00:22:12,039 --> 00:22:14,206 but it doesn't tell them the size. 376 00:22:15,792 --> 00:22:19,253 To figure out just how big an alien planet is... 377 00:22:19,296 --> 00:22:21,088 requires a bit of good luck. 378 00:22:22,090 --> 00:22:25,134 The orbit of the planet has to be aligned in such a way... 379 00:22:25,177 --> 00:22:29,555 that from Earth, we can see it pass directly in front of its star. 380 00:22:29,598 --> 00:22:32,558 This is called transiting. 381 00:22:32,601 --> 00:22:36,729 By measuring how much the starlight dims during this transit... 382 00:22:36,772 --> 00:22:40,191 astronomers can actually determine the size of the planet. 383 00:22:41,985 --> 00:22:45,237 In the fall of 2007, astronomers were watching... 384 00:22:45,280 --> 00:22:49,283 when a hot Jupiter called Tres-4 transited its star. 385 00:22:50,285 --> 00:22:53,454 The planet was about the same mass as Jupiter... 386 00:22:53,497 --> 00:22:56,415 and, therefore, should have been roughly the same size. 387 00:22:56,458 --> 00:22:59,335 But astronomers were in for a surprise. 388 00:22:59,378 --> 00:23:03,089 Tres-4 turned out to be almost twice as big as Jupiter. 389 00:23:03,882 --> 00:23:07,676 It was, in fact, the largest planet ever discovered... 390 00:23:07,719 --> 00:23:10,388 sort of a Jupiter on steroids. 391 00:23:10,430 --> 00:23:13,933 Some of these extrasolar planets are really fluffy. 392 00:23:13,975 --> 00:23:16,602 They're really expanded in size. 393 00:23:16,645 --> 00:23:18,938 And we think that the reason why that's happening... 394 00:23:18,980 --> 00:23:21,065 is because they have an internal source of heat... 395 00:23:21,108 --> 00:23:23,442 which is raising the pressure inside the planet... 396 00:23:23,485 --> 00:23:25,444 causing it to expand. 397 00:23:25,487 --> 00:23:29,698 That's very similar to a steam boiler on a steam train. 398 00:23:35,747 --> 00:23:37,456 In a steam boiler, you have water... 399 00:23:37,499 --> 00:23:39,917 which is being heated by a heat source. 400 00:23:39,960 --> 00:23:41,585 That water is turning to steam. 401 00:23:41,628 --> 00:23:43,379 The pressure is increasing... 402 00:23:43,422 --> 00:23:45,631 and that's causing the piston of the boiler... 403 00:23:45,674 --> 00:23:47,341 to move out, to expand. 404 00:23:55,684 --> 00:23:59,061 If you didn't have the gases' ability to expand... 405 00:23:59,104 --> 00:24:00,312 the planets wouldn't inflate. 406 00:24:00,355 --> 00:24:01,522 Steam trains wouldn't work. 407 00:24:01,565 --> 00:24:03,566 We wouldn't be climbing up this mountain. 408 00:24:04,734 --> 00:24:06,819 While internal heating is the likely cause... 409 00:24:06,862 --> 00:24:09,488 of the so-called fluffy Jupiters... 410 00:24:09,531 --> 00:24:13,534 something much stranger is happening on this alien world. 411 00:24:16,329 --> 00:24:21,000 In the field of extrasolar planets, it seems each new discovery... 412 00:24:21,042 --> 00:24:24,545 creates a brand-new world of scientific intrigue. 413 00:24:31,303 --> 00:24:36,223 At the University of Arizona, planetary scientist Adam Showman... 414 00:24:36,266 --> 00:24:38,392 ponders the weather on other planets. 415 00:24:48,487 --> 00:24:51,864 Recently, Showman helped generate the first-ever forecast... 416 00:24:51,907 --> 00:24:54,700 for a planet beyond our solar system. 417 00:24:54,743 --> 00:24:59,497 And what he found was weather truly befitting an alien world. 418 00:25:00,415 --> 00:25:01,749 We think that the winds are probably... 419 00:25:01,791 --> 00:25:04,877 about 6,000 miles per hour, possibly even more. 420 00:25:04,920 --> 00:25:06,712 This is huge compared to the wind speed... 421 00:25:06,755 --> 00:25:08,547 on any planet in our solar system. 422 00:25:11,051 --> 00:25:14,929 This is HD 189733 b. 423 00:25:14,971 --> 00:25:18,724 It's a hot Jupiter, more than sixty light-years from Earth... 424 00:25:18,767 --> 00:25:22,978 that races around its Sunlike star in a little over two days... 425 00:25:23,021 --> 00:25:25,689 at a distance of only three million miles. 426 00:25:28,151 --> 00:25:30,361 How is it possible to divine the weather... 427 00:25:30,403 --> 00:25:33,405 on a planet 370 trillion miles away? 428 00:25:35,325 --> 00:25:37,993 First, you have to take the planet's temperature. 429 00:25:39,079 --> 00:25:43,415 Scientists knew that, since the planet orbits so close to its star... 430 00:25:43,458 --> 00:25:45,251 it would be tidally locked... 431 00:25:45,293 --> 00:25:47,294 a gravitational effect that would cause it... 432 00:25:47,337 --> 00:25:50,881 to show the same face to the star at all times. 433 00:25:50,924 --> 00:25:53,842 One side would always be bathed in the burning hot light... 434 00:25:53,885 --> 00:25:55,594 of the alien sun... 435 00:25:55,637 --> 00:25:59,223 while the other would be cloaked in perpetual darkness. 436 00:25:59,266 --> 00:26:00,975 If there was no wind on these planets... 437 00:26:01,017 --> 00:26:02,351 then that would mean that the day side... 438 00:26:02,394 --> 00:26:04,061 would then be very, very hot... 439 00:26:04,104 --> 00:26:06,397 and the night side would be very, very cold. 440 00:26:10,485 --> 00:26:12,695 In the spring of 2007... 441 00:26:12,737 --> 00:26:15,781 scientists used the Spitzer Space Telescope... 442 00:26:15,824 --> 00:26:19,368 which sees in infrared wavelengths associated with heat... 443 00:26:19,411 --> 00:26:21,954 to generate a crude map of the temperature... 444 00:26:21,997 --> 00:26:25,291 on both the day and night side of the planet. 445 00:26:27,002 --> 00:26:30,504 You are actually looking at the first map of any kind... 446 00:26:30,547 --> 00:26:33,382 made of an alien world. 447 00:26:33,425 --> 00:26:34,675 What the map shows... 448 00:26:34,718 --> 00:26:37,136 is that the day side of the planet is roasting... 449 00:26:37,178 --> 00:26:41,056 at an otherworldly 1,500 degrees Fahrenheit. 450 00:26:41,099 --> 00:26:45,185 No surprise, given how close the planet orbits to its star. 451 00:26:46,229 --> 00:26:47,563 What was surprising... 452 00:26:47,606 --> 00:26:50,858 was how hot the night side of the planet turned out to be. 453 00:26:52,319 --> 00:26:58,324 Despite being in total darkness, it swelters at around 1,000 degrees. 454 00:26:58,366 --> 00:27:00,826 Clearly, something was distributing heat... 455 00:27:00,869 --> 00:27:02,828 throughout the planet's atmosphere... 456 00:27:02,871 --> 00:27:05,497 carrying thermal energy from the day side... 457 00:27:05,540 --> 00:27:07,958 clear around the other side of the planet. 458 00:27:09,669 --> 00:27:12,588 From his knowledge of weather in our own solar system... 459 00:27:12,631 --> 00:27:14,798 Showman knew what the culprit was. 460 00:27:18,595 --> 00:27:19,970 He ran the numbers... 461 00:27:20,013 --> 00:27:23,015 and that's when he figured out that this alien world... 462 00:27:23,058 --> 00:27:26,393 had jet streams of unprecedented magnitude. 463 00:27:28,855 --> 00:27:32,608 Their 6,000 mile-per-hour winds dwarf anything... 464 00:27:32,651 --> 00:27:35,361 in our own solar system. 465 00:27:35,403 --> 00:27:37,196 Earth, actually, has the slowest speeds... 466 00:27:37,238 --> 00:27:38,989 of any planet in our solar system... 467 00:27:39,032 --> 00:27:41,909 with a typical speed of about twenty miles per hour. 468 00:27:42,744 --> 00:27:44,536 The gas giants in our solar system... 469 00:27:44,579 --> 00:27:47,039 actually have somewhat faster winds than the Earth... 470 00:27:47,082 --> 00:27:48,707 simply because there's no surface... 471 00:27:48,750 --> 00:27:51,251 to have friction to slow down the winds. 472 00:27:52,295 --> 00:27:53,837 On Jupiter and Saturn, for example... 473 00:27:53,880 --> 00:27:56,590 the winds are a few hundred miles per hour. 474 00:27:56,633 --> 00:27:59,176 So you're still about almost a factor of ten lower... 475 00:27:59,219 --> 00:28:00,761 than on these hot Jupiters. 476 00:28:02,138 --> 00:28:05,557 The weather on hot Jupiters may be extreme... 477 00:28:05,600 --> 00:28:08,602 but the forecast for another class of alien planets... 478 00:28:08,645 --> 00:28:13,315 the eccentric giants, is tailor-made for a disaster movie. 479 00:28:15,652 --> 00:28:21,156 This is HD 80606 b, a gas-giant planet... 480 00:28:21,199 --> 00:28:24,410 located roughly two hundred light-years from Earth... 481 00:28:24,452 --> 00:28:28,080 orbiting a star in the constellation Ursa Major. 482 00:28:28,123 --> 00:28:32,501 A year on this bizarre world lasts 111 days... 483 00:28:32,544 --> 00:28:37,673 and it has the most eccentric orbit of any known planet. 484 00:28:37,716 --> 00:28:39,758 With its nearly circular orbit... 485 00:28:39,801 --> 00:28:44,304 Earth's distance from the Sun changes relatively little throughout the year... 486 00:28:44,347 --> 00:28:46,974 varying by only about four million miles. 487 00:28:47,767 --> 00:28:49,101 But during its year... 488 00:28:49,144 --> 00:28:54,314 HD 80606 b comes as close as three million miles to its sun... 489 00:28:54,357 --> 00:28:57,067 and as far as seventy-eight million... 490 00:28:57,110 --> 00:28:59,987 a difference of seventy-five million miles. 491 00:29:00,905 --> 00:29:05,951 This crazy orbit leads to completely crazy weather. 492 00:29:05,994 --> 00:29:09,288 The planet heats up by hundreds and hundreds of degrees... 493 00:29:09,330 --> 00:29:10,956 in a matter of a few hours... 494 00:29:10,999 --> 00:29:13,917 and that drives just absolutely tremendous storms. 495 00:29:15,754 --> 00:29:18,714 As the planet swings in close to its star... 496 00:29:18,757 --> 00:29:23,260 the alien sun looms ever larger in the sky. 497 00:29:23,303 --> 00:29:25,220 And so you get a huge amount of heating... 498 00:29:25,263 --> 00:29:26,805 on one side of the planet. 499 00:29:26,848 --> 00:29:28,724 The other side of the planet is in the night. 500 00:29:28,767 --> 00:29:32,436 What that does is it drives an intense storm. 501 00:29:32,479 --> 00:29:35,439 It's basically a shockwave around both sides of the planet... 502 00:29:35,482 --> 00:29:39,067 that is moving roughly at the speed of a supersonic jet. 503 00:29:40,320 --> 00:29:45,657 This fiery hurricane rips around the planet in only twelve hours. 504 00:29:45,700 --> 00:29:48,285 As the shockwave slowly dies down... 505 00:29:48,328 --> 00:29:52,790 the superheated atmosphere churns into a giant vortex... 506 00:29:52,832 --> 00:29:57,795 that engulfs an entire hemisphere, a sort of greater red spot. 507 00:29:59,380 --> 00:30:02,591 As the planet moves away from the heat of its star... 508 00:30:02,634 --> 00:30:06,220 the storm gradually loses energy and intensity. 509 00:30:06,262 --> 00:30:11,183 But on this eccentric giant, the calm never lasts for long. 510 00:30:11,226 --> 00:30:15,437 Every 111 days, the shockwave is reignited... 511 00:30:15,480 --> 00:30:19,024 and the violent cycle begins anew. 512 00:30:19,067 --> 00:30:21,443 It's much stranger than anything that we have... 513 00:30:21,486 --> 00:30:23,821 in our own solar system. 514 00:30:23,863 --> 00:30:27,449 If you were there, you would be incinerated immediately... 515 00:30:27,492 --> 00:30:29,326 before you had a chance to really, sort of... 516 00:30:29,369 --> 00:30:31,078 groove on your surroundings. 517 00:30:38,461 --> 00:30:42,714 The universe seems adept at creating strange worlds... 518 00:30:42,757 --> 00:30:45,592 even in the most unlikely of places. 519 00:30:47,428 --> 00:30:49,221 This is a pulsar... 520 00:30:49,264 --> 00:30:52,850 a rapidly spinning variety of an exotic stellar object... 521 00:30:52,892 --> 00:30:54,601 called a neutron star. 522 00:30:56,646 --> 00:30:59,314 Neutron stars are the remnants left behind... 523 00:30:59,357 --> 00:31:03,151 after a massive star explodes in a supernova. 524 00:31:06,739 --> 00:31:09,324 No one expected to find planets circling... 525 00:31:09,367 --> 00:31:13,078 in such a treacherous cosmic neighborhood. 526 00:31:13,121 --> 00:31:14,663 Never in my wildest dreams... 527 00:31:14,706 --> 00:31:16,999 did I think we would ever find planets... 528 00:31:17,041 --> 00:31:19,751 orbiting a neutron star, a pulsar. 529 00:31:19,794 --> 00:31:21,837 I mean, after all, neutron stars are formed... 530 00:31:21,880 --> 00:31:25,883 as a result of supernova explosions, where the starjust blows up. 531 00:31:30,763 --> 00:31:34,766 So certainly any planets that might have been there to begin with... 532 00:31:36,644 --> 00:31:38,312 would have been blown away. 533 00:31:39,689 --> 00:31:43,191 And yet, in the early 1990s... 534 00:31:43,234 --> 00:31:45,777 astronomers discovered two rocky planets... 535 00:31:45,820 --> 00:31:50,115 around a pulsar 7,000 trillion miles from Earth. 536 00:31:51,492 --> 00:31:55,746 Their discovery, in fact, predates 51 Pegasi b... 537 00:31:55,788 --> 00:32:00,876 making them, technically, the first alien worlds ever detected. 538 00:32:00,919 --> 00:32:03,503 But since they orbit such strange stars... 539 00:32:03,546 --> 00:32:06,256 many astronomers consider pulsar planets... 540 00:32:06,299 --> 00:32:08,759 to be in a category of their own. 541 00:32:08,801 --> 00:32:12,095 The pulsar planets were very interesting. 542 00:32:12,138 --> 00:32:14,389 They're actually very low in mass... 543 00:32:14,432 --> 00:32:17,809 and more similar to the Earth's mass. 544 00:32:19,520 --> 00:32:22,439 They form an interesting, exotic classification... 545 00:32:22,482 --> 00:32:23,857 or family of planets... 546 00:32:23,900 --> 00:32:26,234 but it's by no means the mainstream. 547 00:32:28,279 --> 00:32:30,405 While most planets are believed to have formed... 548 00:32:30,448 --> 00:32:34,701 out of the same disk of gas and dust as their parent stars... 549 00:32:34,744 --> 00:32:39,665 clearly these pulsar planets formed a different way. 550 00:32:39,707 --> 00:32:41,750 The planets that have been found... 551 00:32:41,793 --> 00:32:44,836 must have formed after the supernova explosion. 552 00:32:48,633 --> 00:32:50,926 And that's really bizarre because we would think... 553 00:32:50,969 --> 00:32:53,553 that all of the material was blown away... 554 00:32:53,596 --> 00:32:55,514 but apparently some of that debris... 555 00:32:55,556 --> 00:32:57,891 must have somehow been in a disk... 556 00:32:57,934 --> 00:33:01,561 and parts of that disk coalesced into planets. 557 00:33:02,730 --> 00:33:04,481 But that's extremely surprising. 558 00:33:04,524 --> 00:33:07,609 I don't know that anyone really understands that process yet. 559 00:33:09,070 --> 00:33:10,654 Although the pulsar planets... 560 00:33:10,697 --> 00:33:13,156 are believed to have rocky surfaces... 561 00:33:13,199 --> 00:33:16,034 it's unlikely they would be a platform for life... 562 00:33:16,077 --> 00:33:19,371 and any visit by humans would be short-lived. 563 00:33:20,623 --> 00:33:22,374 As the pulsar rotates... 564 00:33:22,417 --> 00:33:26,920 it emits well-focused beams of charged particles from its poles... 565 00:33:26,963 --> 00:33:31,425 creating a rotating spotlight of horrific radiation. 566 00:33:32,593 --> 00:33:34,469 Standing on a pulsar planet... 567 00:33:34,512 --> 00:33:36,596 would be a very dangerous proposition. 568 00:33:37,640 --> 00:33:40,934 There would be high-energy radiation all around you... 569 00:33:40,977 --> 00:33:44,855 just an onslaught of particles and waves... 570 00:33:44,897 --> 00:33:48,066 and the radiation field would be so strong... 571 00:33:48,109 --> 00:33:51,570 that it would probably destroy your living tissue... 572 00:33:51,612 --> 00:33:54,781 and it would certainly cause cancer and mutations very quickly. 573 00:33:54,824 --> 00:33:56,575 But it would probably kill you. 574 00:33:56,617 --> 00:33:59,453 If you were really unlucky- or lucky, I suppose. 575 00:33:59,495 --> 00:34:00,495 If you're gonna die anyway... 576 00:34:00,538 --> 00:34:02,622 you might as well die in a spectacular way. 577 00:34:02,665 --> 00:34:04,624 You would be in the beam of the pulsar. 578 00:34:04,667 --> 00:34:09,171 So, every rotation, the beam would flash past you... 579 00:34:09,213 --> 00:34:12,049 and you would see this incredibly bright beacon... 580 00:34:12,091 --> 00:34:15,469 like a lighthouse really close to you just flashing in your face. 581 00:34:16,804 --> 00:34:19,097 It would not be a very hospitable environment. 582 00:34:19,140 --> 00:34:20,140 No way. 583 00:34:21,434 --> 00:34:24,936 While the pulsar planets might not be nice places to visit... 584 00:34:24,979 --> 00:34:27,189 they have taught us something fundamental... 585 00:34:27,231 --> 00:34:30,942 about planet formation in the universe. 586 00:34:30,985 --> 00:34:34,529 These planets, weird planets, around a neutron star... 587 00:34:34,572 --> 00:34:37,532 have taught us that planetary formation... 588 00:34:37,575 --> 00:34:39,993 appears to be relatively easy. 589 00:34:41,162 --> 00:34:43,997 Gravity appears to like to pull stuff together... 590 00:34:44,040 --> 00:34:46,500 when there's enough stuff in a given region. 591 00:34:49,504 --> 00:34:51,838 If nature is so good at making planets... 592 00:34:51,881 --> 00:34:54,466 even under difficult circumstances... 593 00:34:54,509 --> 00:34:59,304 then the odds are fairly high that the universe is full of planets... 594 00:34:59,347 --> 00:35:01,932 and that somewhere out there in the cosmos... 595 00:35:01,974 --> 00:35:04,184 other Earths are waiting to be discovered. 596 00:35:06,813 --> 00:35:09,940 But if that's the case, then where are the Earths? 597 00:35:10,942 --> 00:35:12,943 Why haven't we found them yet? 598 00:35:14,237 --> 00:35:17,155 The first planets that were found in the late 1990s... 599 00:35:17,198 --> 00:35:21,118 were massive planets, 300 times the mass of our Earth. 600 00:35:25,206 --> 00:35:27,499 And it's really not a surprise... 601 00:35:27,542 --> 00:35:30,001 that we found the most massive ones first. 602 00:35:31,254 --> 00:35:33,797 Like the giant redwood trees behind me... 603 00:35:33,840 --> 00:35:35,340 they were the easiest to see... 604 00:35:35,383 --> 00:35:38,844 from the enormous distances that we were looking. 605 00:35:38,886 --> 00:35:40,846 So when we find stars, where we say... 606 00:35:40,888 --> 00:35:43,431 "Ah, there's just one single massive planet... 607 00:35:43,474 --> 00:35:47,435 "one giant redwood," that's almost certain to not be true. 608 00:35:47,478 --> 00:35:50,355 There's almost certainly a forest of planets... 609 00:35:50,398 --> 00:35:53,984 and asteroids and comets also orbiting that star. 610 00:35:56,571 --> 00:36:00,448 As astronomers continue to scrutinize alien solar systems... 611 00:36:00,491 --> 00:36:03,952 they are edging ever closer to finding Earthlike planets. 612 00:36:06,581 --> 00:36:10,125 This is Gliese 436 b. 613 00:36:10,168 --> 00:36:13,712 It's a world roughly twenty times the mass of Earth... 614 00:36:13,754 --> 00:36:16,756 similar in mass and size to Neptune. 615 00:36:16,799 --> 00:36:22,512 It orbits a star thirty light-years away in the constellation Leo. 616 00:36:22,555 --> 00:36:24,222 I'm so excited about Gliese 436... 617 00:36:24,265 --> 00:36:26,016 I'm almost jumping out of my clothes. 618 00:36:26,058 --> 00:36:30,645 It's the most important discovery since 51 Pegasi... 619 00:36:30,688 --> 00:36:32,772 maybe even more important. 620 00:36:33,774 --> 00:36:37,110 What has Geoff Marcy so excited is that this planet... 621 00:36:37,153 --> 00:36:41,239 was found to have a density of 2. 1 grams per cubic centimeter. 622 00:36:42,575 --> 00:36:43,575 What does that mean? 623 00:36:43,618 --> 00:36:45,202 It's a spectacular number... 624 00:36:45,244 --> 00:36:49,331 because every schoolchild knows that the density of water... 625 00:36:49,373 --> 00:36:51,541 is one gram per cubic centimeter... 626 00:36:51,584 --> 00:36:54,669 and we also know that rocks that you pick up on the street... 627 00:36:54,712 --> 00:36:57,464 the density of our Earth, for example, as a rock... 628 00:36:57,506 --> 00:37:00,759 is about five grams per cubic centimeter. 629 00:37:00,801 --> 00:37:03,428 And therefore, this planet, around 436... 630 00:37:03,471 --> 00:37:07,599 is composed of a mixture of rock and water. 631 00:37:09,644 --> 00:37:14,022 A planet made of rock and water sounds tantalizingly Earthlike... 632 00:37:14,065 --> 00:37:16,900 but Gliese 436 b has so much water... 633 00:37:16,943 --> 00:37:19,694 there would be no landmasses exposed at all. 634 00:37:20,988 --> 00:37:22,405 And you wouldn't want to take a swim... 635 00:37:22,448 --> 00:37:25,116 in the oceans of this watery alien world. 636 00:37:26,077 --> 00:37:29,621 There may be a layer of liquid water on the surface... 637 00:37:29,664 --> 00:37:32,832 but below that, things begin to get a little weird. 638 00:37:33,834 --> 00:37:37,671 There's so much water that the sheer gravitational force... 639 00:37:37,713 --> 00:37:41,424 of the water molecules pressing down toward the center... 640 00:37:41,467 --> 00:37:44,010 will crush the water so tightly... 641 00:37:44,053 --> 00:37:47,472 that the water molecules are almost touching each other. 642 00:37:47,515 --> 00:37:49,182 It's a very odd type of water. 643 00:37:49,225 --> 00:37:52,102 In fact, we call it ice, even though it's not cold... 644 00:37:52,144 --> 00:37:53,561 because the water molecules... 645 00:37:53,604 --> 00:37:57,440 will be arranged in a structure like ice... 646 00:37:57,483 --> 00:38:00,110 but only due to its high pressure. 647 00:38:01,195 --> 00:38:07,033 Clearly, Gliese 436 b isn't quite an Earthlike planet... 648 00:38:07,076 --> 00:38:09,703 but what about this alien world? 649 00:38:11,122 --> 00:38:15,750 What would make an alien planet truly Earthlike? 650 00:38:15,793 --> 00:38:20,505 It should be made primarily of rock with enough water for oceans... 651 00:38:20,548 --> 00:38:22,007 but not so much water... 652 00:38:22,049 --> 00:38:25,927 that the land masses are completely submerged. 653 00:38:25,970 --> 00:38:30,348 It would also have to be in its star's habitable zone. 654 00:38:30,391 --> 00:38:32,392 The typical idea for a habitable zone... 655 00:38:32,435 --> 00:38:34,602 is the range of distances from a star... 656 00:38:34,645 --> 00:38:37,814 where an Earthlike planet could have liquid water at its surface. 657 00:38:37,857 --> 00:38:41,526 The idea would be that if you took Earth and pushed it in too far... 658 00:38:41,569 --> 00:38:45,071 the oceans would all boil away, and that's bad for life. 659 00:38:45,114 --> 00:38:47,032 Or if you took the Earth and pushed it out too far... 660 00:38:47,074 --> 00:38:49,617 the oceans would all freeze, and that's bad for life. 661 00:38:52,246 --> 00:38:54,039 In our own solar system... 662 00:38:54,081 --> 00:38:57,375 the habitable zone ranges from Mars' orbit... 663 00:38:57,418 --> 00:39:00,879 into as close as to where Venus orbits. 664 00:39:00,921 --> 00:39:05,216 But the habitable zone in alien solar systems varies... 665 00:39:05,259 --> 00:39:08,219 depending on how hot the star is. 666 00:39:08,262 --> 00:39:12,432 Currently, our best hope for finding habitable Earthlike planets... 667 00:39:12,475 --> 00:39:18,772 is to look around cool, dim stars called red dwarfs or M dwarfs. 668 00:39:18,814 --> 00:39:21,608 The M dwarfs themselves are very special stars. 669 00:39:22,777 --> 00:39:25,362 So our Sun might be a hundred-watt light bulb. 670 00:39:25,404 --> 00:39:29,240 An M dwarf is perhaps a ten-watt light bulb. 671 00:39:29,283 --> 00:39:30,575 And so what that means is... 672 00:39:30,618 --> 00:39:33,578 that to stay warm enough so that you have liquid water... 673 00:39:33,621 --> 00:39:36,122 not ice, but still not too hot... 674 00:39:36,165 --> 00:39:38,833 you move the planet in much closer. 675 00:39:38,876 --> 00:39:42,337 And those close planets are easier for us to detect with our technique... 676 00:39:42,380 --> 00:39:44,756 because they tug on the star more. 677 00:39:47,843 --> 00:39:51,304 One of these M dwarfs, called Gliese 876... 678 00:39:51,347 --> 00:39:55,225 has been found to have at least three planets orbiting it. 679 00:39:55,267 --> 00:40:00,271 Two of them are gas giants, but the third, Gliese 876 d... 680 00:40:00,314 --> 00:40:03,775 is one of the smallest planets discovered so far... 681 00:40:03,818 --> 00:40:07,153 at roughly six or seven times the mass of the Earth. 682 00:40:07,196 --> 00:40:11,324 It's also just on the edge of its star's habitable zone. 683 00:40:11,367 --> 00:40:15,370 The planet orbits in just 1.9 days around its host star... 684 00:40:15,413 --> 00:40:18,248 but because the host star is so low in luminosity... 685 00:40:18,290 --> 00:40:20,250 it puts it on the edge... 686 00:40:20,292 --> 00:40:22,961 of what you might imagine a habitable zone to be. 687 00:40:23,003 --> 00:40:24,087 There could be some region... 688 00:40:24,130 --> 00:40:27,173 a ring around the planet towards the backside... 689 00:40:27,216 --> 00:40:28,883 where the temperature's actually just right... 690 00:40:28,926 --> 00:40:30,468 for liquid water to exist. 691 00:40:33,055 --> 00:40:36,641 When it was first discovered, scientists hailed this planet... 692 00:40:36,684 --> 00:40:39,477 as the first of the super Earths. 693 00:40:39,520 --> 00:40:41,271 Seven times the mass of the Earth... 694 00:40:41,313 --> 00:40:44,858 sounds so close to the size of our Earth... 695 00:40:44,900 --> 00:40:47,777 that you wonder whether or not it's a rocky planet... 696 00:40:47,820 --> 00:40:49,529 maybe with a thick atmosphere. 697 00:40:52,575 --> 00:40:54,659 But today, the experts are unsure... 698 00:40:54,702 --> 00:40:57,537 whether this is a large, rocky planet at all. 699 00:40:57,580 --> 00:41:00,248 Like Gliese 436 b, it may be... 700 00:41:00,291 --> 00:41:03,710 completely covered in an ocean of super dense water. 701 00:41:04,545 --> 00:41:07,547 To call it a super Earth is to suggest... 702 00:41:07,590 --> 00:41:11,134 that we've found a planet that's a close cousin of our Earth. 703 00:41:11,177 --> 00:41:14,429 I would now rather think of it as a distant cousin... 704 00:41:14,472 --> 00:41:19,267 not unrelated to our Earth, but far enough away... 705 00:41:19,310 --> 00:41:22,353 indeed, more like Neptune in our own solar system... 706 00:41:22,396 --> 00:41:24,147 that has a big, rocky core... 707 00:41:24,190 --> 00:41:27,525 but surrounded by a big envelope of water. 708 00:41:29,570 --> 00:41:31,362 So the race continues... 709 00:41:31,405 --> 00:41:34,991 to discover the first truly Earthlike planet. 710 00:41:35,034 --> 00:41:38,912 At the University of Arizona, astronomer Laird Close... 711 00:41:38,954 --> 00:41:43,416 is hoping to capture the first picture of an alien Earth. 712 00:41:43,459 --> 00:41:47,462 But to do that will take a giant leap in telescope technology. 713 00:41:48,547 --> 00:41:51,007 Here at the Steward Observatory Mirror Lab... 714 00:41:51,050 --> 00:41:54,385 in a cavernous space underneath the bleachers... 715 00:41:54,428 --> 00:41:57,305 of the university's football stadium... 716 00:41:57,348 --> 00:42:00,183 engineers are working on the next generation... 717 00:42:00,226 --> 00:42:02,602 of super telescopes. 718 00:42:07,858 --> 00:42:10,193 This is the largest mirror that's ever been made. 719 00:42:10,236 --> 00:42:13,071 This mirror is 8.4 meters across... 720 00:42:13,113 --> 00:42:16,866 but it's just 1/7 of the size that's needed... 721 00:42:16,909 --> 00:42:18,826 for the Giant Magellan Telescope. 722 00:42:18,869 --> 00:42:22,247 And together, when combined with seven other mirrors like it... 723 00:42:22,289 --> 00:42:24,249 in the Giant Magellan telescope... 724 00:42:24,291 --> 00:42:27,752 we will be able to actually directly image extrasolar planets... 725 00:42:27,795 --> 00:42:31,256 and maybe even Earthlike planets around alien suns. 726 00:42:33,259 --> 00:42:36,553 Scheduled for completion in 2016... 727 00:42:36,595 --> 00:42:38,972 this telescope will be able to make images... 728 00:42:39,014 --> 00:42:43,726 up to ten times sharper than the Hubble space telescope. 729 00:42:44,770 --> 00:42:49,315 NASA and the European Space Agency are also developing several missions... 730 00:42:49,358 --> 00:42:51,693 that will use space-based telescopes... 731 00:42:51,735 --> 00:42:55,113 to search the stars for our planetary kin. 732 00:42:55,155 --> 00:42:59,284 This will be incredibly exciting for humankind... 733 00:42:59,326 --> 00:43:03,288 to know whether or not around those little points of light... 734 00:43:03,330 --> 00:43:04,622 that we see in the night sky... 735 00:43:04,665 --> 00:43:06,666 whether there's Earthlike planets tied in... 736 00:43:06,709 --> 00:43:08,459 in orbit around those stars. 737 00:43:13,507 --> 00:43:17,635 As technology improves, we're gonna be able to find planets... 738 00:43:17,678 --> 00:43:19,721 that look much more like the Earth... 739 00:43:19,763 --> 00:43:22,348 planets that, perhaps, have life on them... 740 00:43:22,391 --> 00:43:25,893 and maybe even planets that have forests and steam trains. 741 00:43:30,232 --> 00:43:33,610 The astronomers who have dedicated their lives to this quest... 742 00:43:33,652 --> 00:43:36,029 all believe it's only a matter of time... 743 00:43:36,071 --> 00:43:39,657 before we find the first truly Earthlike planet. 744 00:43:41,076 --> 00:43:43,244 The most exciting thing I can tell you... 745 00:43:43,287 --> 00:43:46,331 is that we are now routinely discovering... 746 00:43:46,373 --> 00:43:48,416 commonly discovering planets... 747 00:43:48,459 --> 00:43:52,503 that are a mere five or ten times the mass of our Earth. 748 00:43:52,546 --> 00:43:55,340 We're not quite to the point where we're finding Earths... 749 00:43:55,382 --> 00:43:57,050 and that's where we really want to be. 750 00:43:58,218 --> 00:43:59,344 But we're finding planets... 751 00:43:59,386 --> 00:44:02,388 that are ever so close to our home planet. 752 00:44:04,141 --> 00:44:07,018 So when we actually do cross that final threshold... 753 00:44:07,061 --> 00:44:10,229 and do find evidence that there's a habitable planet out there... 754 00:44:10,272 --> 00:44:13,858 this is gonna be a quite an epochal event for humanity. 755 00:44:13,901 --> 00:44:15,526 People should not worry too much yet... 756 00:44:15,569 --> 00:44:17,612 that we haven't found any Earthlike planets... 757 00:44:17,655 --> 00:44:21,532 because, well, a lot of effort is going into it right now... 758 00:44:21,575 --> 00:44:23,743 and I think it will be done in the next ten years. 759 00:44:23,786 --> 00:44:25,495 Yeah, stay tuned.