1 00:00:02,000 --> 00:00:07,000 Downloaded from YTS.MX 2 00:00:02,520 --> 00:00:04,040 [contemplative music playing] 3 00:00:04,120 --> 00:00:05,520 [narrator] Life. 4 00:00:05,600 --> 00:00:09,040 An unbelievable, perfect combination of elements 5 00:00:08,000 --> 00:00:13,000 Official YIFY movies site: YTS.MX 6 00:00:09,120 --> 00:00:12,400 that is able to create living matter. 7 00:00:12,480 --> 00:00:15,840 Maybe the biggest mystery of nature. 8 00:00:19,920 --> 00:00:24,480 Is life an amazing phenomenon, exclusive to our planet? 9 00:00:28,080 --> 00:00:33,000 In recent years, we have made several amazing discoveries 10 00:00:33,080 --> 00:00:36,960 that suggest that the conditions in our solar system for life 11 00:00:37,040 --> 00:00:40,400 might be more prevalent than ever imagined. 12 00:00:41,640 --> 00:00:45,160 Recent missions are revealing strange worlds. 13 00:00:45,240 --> 00:00:47,680 Moons that could have vast oceans 14 00:00:47,760 --> 00:00:50,480 concealed beneath miles of ice. 15 00:00:50,560 --> 00:00:54,600 Like Europa, which orbits around the giant Jupiter. 16 00:00:55,680 --> 00:00:59,640 Places where jets erupt hundreds of miles into space, 17 00:00:59,720 --> 00:01:03,560 like Enceladus, the tiny Saturn's moon. 18 00:01:05,280 --> 00:01:08,880 Or moons with a very Earthlike landscape, 19 00:01:08,960 --> 00:01:14,520 with mountains, valleys, clouds and lakes of liquid methane or ethane, 20 00:01:14,600 --> 00:01:18,440 like Titan, the largest moon of Saturn. 21 00:01:21,720 --> 00:01:25,440 If life was ever possible or is now a fact 22 00:01:25,520 --> 00:01:29,320 in any of those remote worlds in our solar system, 23 00:01:29,400 --> 00:01:32,320 with very harsh and different conditions from Earth, 24 00:01:34,040 --> 00:01:37,080 that could imply that life could be possible 25 00:01:37,160 --> 00:01:39,600 in any other remote world in outer space. 26 00:01:41,960 --> 00:01:44,480 Second genesis within the same solar system 27 00:01:44,560 --> 00:01:48,080 implies that the origin of life is a likely event. 28 00:01:48,160 --> 00:01:50,000 If it happens twice in the same solar system, 29 00:01:50,080 --> 00:01:52,320 it's likely happening everywhere in the universe. 30 00:01:53,240 --> 00:01:55,680 [narrator] Now scientists are searching for planets 31 00:01:55,760 --> 00:01:58,560 far beyond the boundaries of our solar system, 32 00:01:58,640 --> 00:02:01,760 where we might detect life in the near future. 33 00:02:03,800 --> 00:02:09,160 Thanks to the NASA space telescope Kepler, launched in 2009, 34 00:02:09,240 --> 00:02:12,120 we know that in our galaxy alone, 35 00:02:12,200 --> 00:02:15,440 there are billions of Earthlike exoplanets 36 00:02:15,520 --> 00:02:17,360 orbiting their stars. 37 00:02:18,480 --> 00:02:20,840 Given the vastness of the universe, 38 00:02:20,920 --> 00:02:24,280 with more than a hundred billion galaxies, 39 00:02:24,360 --> 00:02:27,280 it is hard to conceive that somewhere 40 00:02:27,360 --> 00:02:31,520 there is no Earthlike planet that can harbor life. 41 00:02:34,440 --> 00:02:37,080 Unless something very unusual happened here on Earth, 42 00:02:37,160 --> 00:02:41,400 then life has developed on thousands of millions of planets 43 00:02:41,480 --> 00:02:43,000 just in our galaxy, right? 44 00:02:43,560 --> 00:02:46,720 If it's not a miracle, then it's all over the place. 45 00:02:46,800 --> 00:02:48,320 That's the bottom line. 46 00:02:49,680 --> 00:02:52,080 In recent years, thanks to Kepler, 47 00:02:52,160 --> 00:02:56,080 we have confirmed dozens of Earthlike exoplanets 48 00:02:56,160 --> 00:02:58,040 that might harbor life 49 00:02:58,120 --> 00:03:02,400 and even intelligent life waiting to be discovered. 50 00:03:04,240 --> 00:03:07,080 We don't know if the discovery of life will happen first 51 00:03:07,160 --> 00:03:10,720 on one of these moons or planets in our solar system 52 00:03:11,400 --> 00:03:14,160 or on an Earth-like exoplanet. 53 00:03:14,960 --> 00:03:19,200 But what we do know is that we are closer than ever to unveiling 54 00:03:19,280 --> 00:03:21,840 one of the greatest mysteries of nature: 55 00:03:21,920 --> 00:03:25,040 whether there is life in outer space. 56 00:03:32,840 --> 00:03:35,040 Is there life beyond Earth? 57 00:03:37,400 --> 00:03:41,200 Humankind has always asked itself this question, 58 00:03:41,280 --> 00:03:44,240 but no answer has yet been found. 59 00:03:49,720 --> 00:03:53,520 It appears that we are closer to solving this mystery. 60 00:03:54,960 --> 00:03:59,560 Recent discoveries have uncovered planets beyond our solar system 61 00:03:59,640 --> 00:04:03,120 that are believed to be similar in many ways to Earth. 62 00:04:05,240 --> 00:04:10,240 [man] If I got to ride in a spaceship to one planet that we found with Kepler, 63 00:04:10,320 --> 00:04:12,880 the one that I would go to is Kepler-186f. 64 00:04:12,960 --> 00:04:14,520 It's one of the smallest ones. 65 00:04:14,600 --> 00:04:16,640 Uh, it's at the right temperature, 66 00:04:16,720 --> 00:04:20,279 um, that liquid water could exist on its surface. 67 00:04:22,560 --> 00:04:27,600 [narrator] Kepler-186f is the first validated Earth-size planet 68 00:04:27,680 --> 00:04:30,600 to orbit a distant star in the habitable zone 69 00:04:30,680 --> 00:04:34,360 where liquid water might pool on the planet's surface. 70 00:04:37,560 --> 00:04:43,240 The discovery of Kepler-186f confirms that Earth-sized planets exist 71 00:04:43,320 --> 00:04:45,280 in the habitable zones of other stars 72 00:04:45,360 --> 00:04:47,880 and signals a significant step closer 73 00:04:47,960 --> 00:04:50,680 to finding a world similar to Earth. 74 00:04:53,760 --> 00:04:58,840 Kepler-186f orbits its star once every 130 days 75 00:04:58,920 --> 00:05:02,680 and receives one-third the energy that the Earth does from the sun, 76 00:05:02,760 --> 00:05:06,040 placing it near the outer edge of the habitable zone. 77 00:05:08,280 --> 00:05:11,760 If you could stand on the surface of Kepler-186f, 78 00:05:11,840 --> 00:05:14,520 the brightness of its star at nigh noon 79 00:05:14,600 --> 00:05:17,040 would appear as bright as our sun is 80 00:05:17,120 --> 00:05:19,760 about an hour before sunset on Earth. 81 00:05:23,840 --> 00:05:28,600 [woman] Today, when we take a look at what we know 82 00:05:28,680 --> 00:05:31,480 about the origins of life on this planet, 83 00:05:31,560 --> 00:05:33,960 it leads us to think 84 00:05:34,040 --> 00:05:36,880 that the same things that happened here 85 00:05:36,960 --> 00:05:39,440 might well have happened elsewhere, 86 00:05:39,520 --> 00:05:42,440 and so life beyond this planet 87 00:05:42,520 --> 00:05:47,800 is quite plausible in terms of the science that we know today. 88 00:05:48,720 --> 00:05:52,920 [narrator] We now know there are four important candidates in our solar system 89 00:05:53,000 --> 00:05:54,200 to harbor life. 90 00:05:55,200 --> 00:05:56,480 Mars. 91 00:05:59,240 --> 00:06:01,320 Jupiter's moon Europa. 92 00:06:02,800 --> 00:06:07,360 And Saturn's moons Titan and Enceladus. 93 00:06:08,840 --> 00:06:13,760 On every of them, we can find all of the three key ingredients for life: 94 00:06:13,840 --> 00:06:18,200 organic compounds, a liquid, and an energy source. 95 00:06:19,720 --> 00:06:21,600 [wind whistling] 96 00:06:22,640 --> 00:06:25,120 There is water on Mars 97 00:06:25,200 --> 00:06:28,960 in the form of ice at the poles and under the surface, 98 00:06:29,040 --> 00:06:31,360 but it is also flowing 99 00:06:31,440 --> 00:06:35,080 from time to time at the surface during spring and summer. 100 00:06:36,720 --> 00:06:40,680 [narrator] Although there's no evidence of any form of life on Mars yet, 101 00:06:40,760 --> 00:06:43,680 scientists think it might be found soon. 102 00:06:46,720 --> 00:06:48,480 On Jupiter's moon Europa, 103 00:06:48,560 --> 00:06:51,720 two of those key ingredients can also be found. 104 00:06:53,880 --> 00:06:55,760 We do know there is water on Europa. 105 00:06:55,840 --> 00:06:59,080 On the surface of Europa, we have an icy crust. 106 00:07:00,320 --> 00:07:03,840 This icy crust has been observed using Voyager spacecraft 107 00:07:03,920 --> 00:07:07,760 but also the Canadian spacecraft in the '90s. 108 00:07:08,440 --> 00:07:13,200 [narrator] Under an eerie water-ice crust 10- to 30-kilometers thick 109 00:07:13,280 --> 00:07:15,080 that covers this tiny moon, 110 00:07:15,160 --> 00:07:17,360 there's supposed to be a liquid ocean, 111 00:07:17,440 --> 00:07:20,600 which may be about 100 kilometers deep. 112 00:07:26,560 --> 00:07:30,160 The Saturn's moons Titan and Enceladus 113 00:07:30,240 --> 00:07:33,440 have become the search-for-life priority top spots 114 00:07:33,520 --> 00:07:35,200 in the recent years. 115 00:07:36,760 --> 00:07:40,680 Titan is the only moon in the solar system that is known to have an atmosphere. 116 00:07:40,760 --> 00:07:43,120 It's also the only place in the solar system 117 00:07:43,200 --> 00:07:46,160 that has an atmosphere made primarily of nitrogen, 118 00:07:46,240 --> 00:07:47,720 except for the Earth, 119 00:07:47,800 --> 00:07:52,080 so Titan and Earth are closely linked in that way. 120 00:07:52,160 --> 00:07:55,040 Titan is a fascinating world. 121 00:07:55,120 --> 00:07:59,440 It's the most alien place in the solar system, so to speak, 122 00:07:59,520 --> 00:08:01,880 because it, in fact, other than the Earth, 123 00:08:01,960 --> 00:08:03,480 is the only place we know of 124 00:08:03,560 --> 00:08:06,640 that has seas of liquid on its surface, 125 00:08:06,720 --> 00:08:08,240 but those seas are not made of water, 126 00:08:08,320 --> 00:08:10,920 they're made of liquid methane and liquid ethane. 127 00:08:12,640 --> 00:08:16,280 [narrator] Titan is the only place in the solar system outside Earth 128 00:08:16,360 --> 00:08:19,480 where there are stable bodies of surface liquid, 129 00:08:19,560 --> 00:08:22,640 but at minus 180° Celsius, 130 00:08:22,720 --> 00:08:24,680 this liquid can't be water. 131 00:08:24,760 --> 00:08:26,320 We know there are lakes 132 00:08:26,400 --> 00:08:30,560 filled with super-chilled liquid methane and ethane. 133 00:08:31,560 --> 00:08:36,200 In recent years, Enceladus, a tiny moon orbiting Saturn, 134 00:08:36,280 --> 00:08:40,640 has become one of the main goals for exobiology. 135 00:08:42,240 --> 00:08:46,560 Enceladus is a small, icy moon, quite similar to Europa 136 00:08:46,640 --> 00:08:50,840 as it has a thick icy crust and an ocean beneath. 137 00:08:53,680 --> 00:08:56,160 We know there are vast jets of water ice 138 00:08:56,240 --> 00:08:58,920 erupting several miles into space. 139 00:09:00,040 --> 00:09:04,160 Enceladus is one of the most interesting places in the solar system 140 00:09:04,240 --> 00:09:07,480 because of the presence of this activity, 141 00:09:07,560 --> 00:09:09,800 this geyser-like activity. 142 00:09:10,480 --> 00:09:14,560 If we have geyser-like activity, people expect to have water, liquid water. 143 00:09:17,200 --> 00:09:19,080 [narrator] Recently, in those jets, 144 00:09:19,160 --> 00:09:23,040 some of the basic chemical building blocks of life have been detected, 145 00:09:23,120 --> 00:09:26,160 so we can be sure that we have on Enceladus 146 00:09:26,240 --> 00:09:28,840 the trifecta to harbor life: 147 00:09:28,920 --> 00:09:33,320 liquid, organic compounds and an energy source. 148 00:09:39,720 --> 00:09:44,800 But if life was able to emerge in any of those remote and harsh worlds, 149 00:09:44,880 --> 00:09:47,680 why couldn't it also arise on any other planet 150 00:09:47,760 --> 00:09:50,440 far beyond the boundaries of our solar system? 151 00:09:51,520 --> 00:09:54,200 Second genesis within the same solar system 152 00:09:54,280 --> 00:09:57,760 implies that the origin of life is a likely event. 153 00:09:57,840 --> 00:09:59,800 If it happens twice in the same solar system, 154 00:09:59,880 --> 00:10:02,320 it's likely happening everywhere in the universe. 155 00:10:03,320 --> 00:10:06,840 [man] If we were able to find life within our own solar system 156 00:10:06,920 --> 00:10:08,240 on another place, 157 00:10:08,320 --> 00:10:11,920 and furthermore be able to say that it developed, 158 00:10:12,000 --> 00:10:13,840 you know, independently, 159 00:10:13,920 --> 00:10:18,680 then you're saying, within the same stellar system, 160 00:10:18,760 --> 00:10:20,840 you had life evolve twice. 161 00:10:20,920 --> 00:10:24,400 And the conclusion from that is that life forms very easily. 162 00:10:26,960 --> 00:10:28,560 [narrator] A generation ago, 163 00:10:28,640 --> 00:10:32,360 just the idea of a planet orbiting a distant star 164 00:10:32,440 --> 00:10:35,200 was still in the realm of science fiction. 165 00:10:37,840 --> 00:10:42,080 So, to think of the possibility of life on a planet like that 166 00:10:42,160 --> 00:10:44,280 was simply unimaginable. 167 00:10:46,080 --> 00:10:51,680 In fact, the first exoplanets weren't discovered till 1992. 168 00:10:53,440 --> 00:10:57,160 That very year, two super-Earth exoplanets were found 169 00:10:57,240 --> 00:11:00,920 around pulsar PSR 1257+12 170 00:11:01,000 --> 00:11:06,040 at a remote distance of 2,300 light-years away. 171 00:11:06,600 --> 00:11:10,200 This announcement shocked the scientific community at that time, 172 00:11:10,280 --> 00:11:15,440 as it was the first multi-planet, extra-solar system ever discovered. 173 00:11:16,480 --> 00:11:19,720 Could any of these super-Earth harbor life? 174 00:11:22,240 --> 00:11:25,800 Unfortunately, a pulsar is a very different kind of star 175 00:11:25,880 --> 00:11:27,160 from the sun. 176 00:11:28,960 --> 00:11:31,360 In fact, it's a dead star 177 00:11:31,440 --> 00:11:34,040 formed when some of the largest stars in the universe 178 00:11:34,120 --> 00:11:36,600 exploded as super novae. 179 00:11:38,200 --> 00:11:40,760 The pulsar, which is what's left after a star, 180 00:11:40,840 --> 00:11:42,720 a really massive star, explodes, 181 00:11:42,800 --> 00:11:45,560 then you've got this thing which is one step away from being a black hole. 182 00:11:45,640 --> 00:11:47,600 While this was really exciting, 183 00:11:47,680 --> 00:11:49,040 it was hard to tell what it meant 184 00:11:49,120 --> 00:11:52,000 because pulsars are so much different from normal stars. 185 00:11:52,080 --> 00:11:54,960 [narrator] These may not seem at first to be good places 186 00:11:55,040 --> 00:11:56,800 to look for habitable planets. 187 00:11:57,720 --> 00:12:01,680 Super novae are, frankly, quite apocalyptic events 188 00:12:01,760 --> 00:12:05,520 that would easily vaporize any ill-fated planets 189 00:12:05,600 --> 00:12:07,960 in orbit around the exploding star. 190 00:12:09,520 --> 00:12:13,120 That distant world would be bathed in a lethal cocktail 191 00:12:13,200 --> 00:12:15,760 of X-rays and charged particles 192 00:12:15,840 --> 00:12:18,760 emitted by a star so faint in visible light 193 00:12:18,840 --> 00:12:22,840 that it would scarcely cast a shadow on this world's surface. 194 00:12:22,920 --> 00:12:24,960 So the chances of life arising 195 00:12:25,040 --> 00:12:28,920 in such a weird and hostile environment would be remote. 196 00:12:31,360 --> 00:12:34,400 However, the real importance of this discovery 197 00:12:34,480 --> 00:12:36,080 was that for the first time ever, 198 00:12:36,160 --> 00:12:40,400 the existence of planetary systems beyond the limits of our solar system 199 00:12:40,480 --> 00:12:41,680 was confirmed. 200 00:12:45,120 --> 00:12:50,120 If we found two exoplanets out there, why couldn't there be many more? 201 00:12:53,440 --> 00:12:56,880 We had to wait three more years to find an exoplanet 202 00:12:56,960 --> 00:12:58,880 orbiting a sunlike star, 203 00:12:58,960 --> 00:13:02,600 which was far more important, because the conditions of such a planet 204 00:13:02,680 --> 00:13:06,760 would be potentially similar to any of the planets in the solar system. 205 00:13:07,960 --> 00:13:12,520 On October 6th, 1995, was the announcement of the discovery 206 00:13:12,600 --> 00:13:17,280 of the first planet orbiting a sunlike star in the journal Nature. 207 00:13:17,360 --> 00:13:23,880 That star was 51 Pegasi, a sunlike star located 51 light-years away, 208 00:13:23,960 --> 00:13:27,360 and the exoplanet was a giant planet. 209 00:13:28,000 --> 00:13:30,960 The first exoplanet found around a star like our own 210 00:13:31,040 --> 00:13:33,160 was called 51 Pegasi b. 211 00:13:33,240 --> 00:13:35,160 It's very unusual. It's a very large planet. 212 00:13:35,240 --> 00:13:37,520 It's bigger than Jupiter, it's more massive than Jupiter. 213 00:13:37,600 --> 00:13:40,840 And it's on a very short period orbit. It goes around its star. 214 00:13:40,920 --> 00:13:43,720 One year on this planet takes four days. 215 00:13:43,800 --> 00:13:45,760 It is a very short amount of time. 216 00:13:47,560 --> 00:13:49,880 [narrator] That discovery marked a turning point 217 00:13:49,960 --> 00:13:51,960 in the search for exoplanets. 218 00:13:54,520 --> 00:13:58,200 From that moment on, many new ones were found. 219 00:14:06,640 --> 00:14:12,720 Nevertheless, what radically revolutionized the search for exoplanets 220 00:14:12,800 --> 00:14:15,960 was the NASA space telescope Kepler. 221 00:14:18,200 --> 00:14:19,920 Before Kepler was launched, 222 00:14:20,000 --> 00:14:23,840 there was hundreds of planets that we knew of 223 00:14:23,920 --> 00:14:25,720 in systems around other stars, 224 00:14:25,800 --> 00:14:27,680 and now we know of thousands. 225 00:14:27,760 --> 00:14:30,520 And that's why Kepler was so revolutionary. 226 00:14:31,880 --> 00:14:34,000 [narrator] The Kepler was a space telescope 227 00:14:34,080 --> 00:14:37,680 specifically designed to survey our region of the Milky Way galaxy 228 00:14:37,760 --> 00:14:41,120 to discover hundreds of Earth-sized and smaller planets 229 00:14:41,200 --> 00:14:44,560 in or near the habitable zone of their respective stars 230 00:14:44,640 --> 00:14:45,920 and determine the fraction 231 00:14:46,000 --> 00:14:49,040 of the hundreds of billions of stars in our galaxy 232 00:14:49,120 --> 00:14:50,840 that might have such planets. 233 00:14:52,560 --> 00:14:54,720 It works very simply. Anybody can understand this. 234 00:14:54,800 --> 00:14:58,600 It's just staring at one spot on the sky, all the time, never blinks. 235 00:14:58,680 --> 00:15:03,080 And it's looking at 150,000 stars, and it just monitors how bright they are. 236 00:15:03,160 --> 00:15:05,720 Kind of like a camera light meter, really. 237 00:15:05,800 --> 00:15:09,360 And occasionally they'll see a… this star over here, for example, 238 00:15:09,440 --> 00:15:10,720 it'll get a little bit dimmer, 239 00:15:10,800 --> 00:15:14,200 a very fraction of a percent dimmer, for a few hours, 240 00:15:14,280 --> 00:15:15,560 and then it will get bright again. 241 00:15:15,640 --> 00:15:19,440 Well, that happens if a planet passes in front of that star. 242 00:15:20,320 --> 00:15:23,920 We've gone from finding a hundred planets to over a thousand planets with Kepler, 243 00:15:24,000 --> 00:15:25,400 those that have been confirmed. 244 00:15:25,480 --> 00:15:29,760 And there's about 3,000 or 4,000 more which we have strong evidence for 245 00:15:29,840 --> 00:15:32,280 but we wouldn't consider confirmed planets just yet. 246 00:15:33,840 --> 00:15:36,080 [Seth] Kepler is on the hunt for planets. 247 00:15:36,160 --> 00:15:40,920 Kepler has found literally thousands of planets or planetary candidates. 248 00:15:41,000 --> 00:15:43,720 It's… it's a planet-finding machine. 249 00:15:45,960 --> 00:15:49,080 [narrator] In 2011, for the first time ever, 250 00:15:49,160 --> 00:15:52,880 Kepler provided scientists with a census of the Milky Way, 251 00:15:52,960 --> 00:15:56,120 so we could calculate how many stars in the Milky Way 252 00:15:56,200 --> 00:15:58,440 could have a planet like ours. 253 00:15:58,520 --> 00:16:00,200 Around a billion. 254 00:16:03,920 --> 00:16:05,680 Maybe there are a million, maybe there are a billion, 255 00:16:05,760 --> 00:16:09,280 maybe there are a hundred billion planets in the Milky Way galaxy 256 00:16:09,360 --> 00:16:10,600 that could support life, 257 00:16:10,680 --> 00:16:13,840 the kind of planets that Earthly life could survive on. 258 00:16:13,920 --> 00:16:16,560 How many of them have cooked up their own life? 259 00:16:16,640 --> 00:16:18,840 And we don't know the answer to that, okay? 260 00:16:18,920 --> 00:16:21,680 Because that depends on how hard it is to get life started. 261 00:16:21,760 --> 00:16:24,560 Just 'cause I give you all these, you know, these worlds 262 00:16:24,640 --> 00:16:28,320 doesn't mean that life will get started, but, on the other hand, 263 00:16:28,400 --> 00:16:32,200 those planets are all made out of the same stuff that Earth is. 264 00:16:32,280 --> 00:16:36,920 So, again, unless something very unusual happened here and nowhere else, 265 00:16:37,000 --> 00:16:39,480 there's gonna be biology all over the place. 266 00:16:45,760 --> 00:16:48,000 [narrator] Just four years after its launch, 267 00:16:48,080 --> 00:16:50,440 on April 2013, 268 00:16:50,520 --> 00:16:54,480 the Kepler team reported one of their first great triumphs. 269 00:16:54,560 --> 00:16:58,800 The discovery for the first time ever of two exoplanets 270 00:16:58,880 --> 00:17:00,680 very similar to the Earth. 271 00:17:00,760 --> 00:17:04,480 Kepler-62e and Kepler-62f. 272 00:17:04,560 --> 00:17:06,160 [wind whistling] 273 00:17:06,240 --> 00:17:09,119 This discovery created great enthusiasm, 274 00:17:09,200 --> 00:17:12,440 as it implied the confirmation of Earthlike planets, 275 00:17:12,520 --> 00:17:14,800 where life might be possible. 276 00:17:16,480 --> 00:17:22,400 Each of these planets have a radius 1.6 and 1.4 times of Earth 277 00:17:22,480 --> 00:17:26,520 and orbits Kepler-62, an orange dwarf star, 278 00:17:26,599 --> 00:17:29,240 in its circumstellar habitable zone. 279 00:17:31,320 --> 00:17:37,080 A modeling study also concluded that Kepler-62e and Kepler-62f 280 00:17:37,160 --> 00:17:42,080 are likely covered mostly, perhaps completely, in water. 281 00:17:42,160 --> 00:17:45,920 Kepler-62e probably has a very cloudy sky 282 00:17:46,000 --> 00:17:49,040 and is warm and humid all the way to the polar regions. 283 00:17:49,800 --> 00:17:52,200 Kepler-62f would be cooler, 284 00:17:52,280 --> 00:17:55,160 but still potentially life friendly. 285 00:17:58,800 --> 00:18:03,960 Unfortunately, they are at a huge distance of 1,200 light-years away 286 00:18:04,040 --> 00:18:05,960 in the constellation of Lyra. 287 00:18:08,360 --> 00:18:10,040 Thanks to the Kepler mission, 288 00:18:10,120 --> 00:18:14,400 we now know that there are tens of billions of planets orbiting stars 289 00:18:14,480 --> 00:18:17,640 just in our galaxy, the Milky Way, 290 00:18:17,720 --> 00:18:21,560 and we know there are billions of galaxies across the universe. 291 00:18:21,640 --> 00:18:24,920 So if, in just one planetary system like ours, 292 00:18:25,000 --> 00:18:26,720 life arose on one planet, 293 00:18:26,800 --> 00:18:29,360 and there are at least four more candidates, 294 00:18:29,440 --> 00:18:34,000 the likelihood of finding a planet in outer space that could harbor life 295 00:18:34,080 --> 00:18:35,600 should be very high. 296 00:18:42,960 --> 00:18:44,800 But Kepler has discovered for us, 297 00:18:44,880 --> 00:18:47,760 not only the existence of Earthlike planets, 298 00:18:47,840 --> 00:18:52,080 but also has provided us with amazing data about the universe, 299 00:18:52,160 --> 00:18:55,120 such as the confirmation of the existence of planets 300 00:18:55,200 --> 00:18:59,160 that orbit around not only one but two stars, 301 00:18:59,240 --> 00:19:01,280 like Kepler-16b. 302 00:19:02,000 --> 00:19:05,080 This planet was Kepler's first discovery of a planet 303 00:19:05,160 --> 00:19:10,080 that orbits two stars, what is known as a circumbinary planet. 304 00:19:11,360 --> 00:19:15,120 So, one of the most exciting discoveries from Kepler 305 00:19:15,200 --> 00:19:19,520 was that we were actually able to find planets around binary stars, 306 00:19:19,600 --> 00:19:23,080 and the first one that was found was Kepler-16b. 307 00:19:24,360 --> 00:19:26,960 [Fergal] Kepler-16b is many people's favorite planet 308 00:19:27,040 --> 00:19:28,560 that was discovered with Kepler. 309 00:19:28,640 --> 00:19:32,480 Uh, it orbits around not one but two stars at the same time. 310 00:19:34,960 --> 00:19:37,280 This was something which was predicted not to exist. 311 00:19:37,360 --> 00:19:41,560 Two stars setting at the same time was just a piece of science fiction. 312 00:19:41,640 --> 00:19:44,400 But the universe is stranger than what scientists can imagine, 313 00:19:44,480 --> 00:19:46,680 and it turns out that this sort of thing is true. 314 00:19:51,560 --> 00:19:53,120 [narrator] Since 1992, 315 00:19:53,200 --> 00:19:56,520 over 2,000 exoplanets have been discovered. 316 00:19:58,760 --> 00:20:02,720 Thanks to future space telescope missions planned for launch, 317 00:20:02,800 --> 00:20:06,920 the number of observed exoplanets is expected to increase greatly 318 00:20:07,000 --> 00:20:08,640 in the coming years. 319 00:20:11,680 --> 00:20:13,960 Despite having discovered just a tiny fraction 320 00:20:14,040 --> 00:20:17,960 of all of those billions of exoplanets that we think that exist, 321 00:20:18,040 --> 00:20:21,560 how could we know how many of them could harbor life? 322 00:20:25,920 --> 00:20:28,440 In astronomy and astrobiology, 323 00:20:28,520 --> 00:20:32,880 the region around a star where a planet with sufficient atmospheric pressure 324 00:20:32,960 --> 00:20:35,480 can maintain liquid water on its surface 325 00:20:35,560 --> 00:20:39,280 is known as the circumstellar habitable zone. 326 00:20:39,360 --> 00:20:41,400 [Fergal] The habitable zone is a place, 327 00:20:41,480 --> 00:20:43,960 it's kind of a way of thinking about the right way to go look 328 00:20:44,040 --> 00:20:45,960 for planets like our own. 329 00:20:46,960 --> 00:20:50,320 [narrator] The Earth is obviously in the circumstellar habitable zone 330 00:20:50,400 --> 00:20:51,920 of our solar system. 331 00:20:52,600 --> 00:20:53,600 [wind whistling] 332 00:20:53,680 --> 00:20:57,600 A potentially habitable planet implies a terrestrial planet 333 00:20:57,680 --> 00:21:00,680 with conditions roughly comparable to those of Earth, 334 00:21:00,760 --> 00:21:04,040 and thus potentially favorable to life. 335 00:21:04,120 --> 00:21:05,640 There's a sweet spot, 336 00:21:05,720 --> 00:21:08,760 an area where it's not too hot and not too cold, 337 00:21:08,840 --> 00:21:10,480 and we call that the habitable zone, 338 00:21:10,560 --> 00:21:13,040 or some people call that the Goldilocks zone. 339 00:21:14,080 --> 00:21:17,120 If you've got a planet in that region, if it's small, if it's rocky enough, 340 00:21:17,200 --> 00:21:20,480 and it had water, that water would be in a liquid state, more than likely, 341 00:21:20,560 --> 00:21:22,520 so that would be a good place to go looking. 342 00:21:27,200 --> 00:21:31,560 [narrator] On November 2013, astronomers reported, 343 00:21:31,640 --> 00:21:34,160 based on Kepler space mission data, 344 00:21:34,240 --> 00:21:39,200 that there could be as many as 40 billion Earth-sized planets 345 00:21:39,280 --> 00:21:44,160 orbiting in the habitable zones of sunlike stars and red dwarfs, 346 00:21:44,240 --> 00:21:47,280 just in our galaxy, the Milky Way, 347 00:21:47,360 --> 00:21:51,520 11 billion of which may be orbiting sunlike stars. 348 00:21:54,720 --> 00:21:59,240 Those 11 billion exoplanets orbiting stars like our sun 349 00:21:59,320 --> 00:22:04,040 really are a huge number of potential Earthlike worlds. 350 00:22:05,480 --> 00:22:09,840 However, now we know that stars very different from our sun 351 00:22:09,920 --> 00:22:12,760 may be a good place to look for life. 352 00:22:15,640 --> 00:22:20,760 In May 2016, a team of astronomers announced, 353 00:22:20,840 --> 00:22:22,520 for the first time ever, 354 00:22:22,600 --> 00:22:26,480 the finding of three habitable planets orbiting a star 355 00:22:26,560 --> 00:22:30,680 completely different from ours, an ultracool dwarf star. 356 00:22:32,480 --> 00:22:37,160 It's the first planetary system found around a star like this. 357 00:22:37,240 --> 00:22:40,360 The star, named Trappist-1, 358 00:22:40,440 --> 00:22:42,880 is just 40 light-years away 359 00:22:42,960 --> 00:22:45,360 and is much cooler and redder than the sun 360 00:22:45,440 --> 00:22:47,880 and barely larger than Jupiter. 361 00:22:49,880 --> 00:22:53,840 In fact, stars like this are very common in the Milky Way, 362 00:22:53,920 --> 00:22:56,000 and they are very long-lived. 363 00:22:57,680 --> 00:23:01,040 The three planets are very similar in size to the Earth 364 00:23:01,120 --> 00:23:04,560 and might have habitable regions on their surfaces. 365 00:23:04,640 --> 00:23:07,600 So the answer to what the best place in the universe is 366 00:23:07,680 --> 00:23:09,520 to find life nowadays 367 00:23:09,600 --> 00:23:11,600 has radically changed. 368 00:23:15,720 --> 00:23:20,080 To date, among all of the more than 1,000 confirmed exoplanets, 369 00:23:21,080 --> 00:23:22,760 there are around 50 370 00:23:22,840 --> 00:23:25,000 that are in the circumstellar habitable zone 371 00:23:25,080 --> 00:23:26,920 of the star they orbit around. 372 00:23:27,920 --> 00:23:32,440 And therefore they could be potentially considered Earthlike planets, 373 00:23:32,520 --> 00:23:36,320 which does not imply these distant worlds may harbor life. 374 00:23:37,480 --> 00:23:42,800 However, could life be possible outside those habitable zones? 375 00:23:43,960 --> 00:23:45,640 [wind whistling] 376 00:23:45,720 --> 00:23:49,520 The discovery of hydrocarbon lakes on Saturn's moon Titan 377 00:23:49,600 --> 00:23:52,840 has begun to call into question the carbon chauvinism 378 00:23:52,920 --> 00:23:56,480 that underpins circumstellar habitable zone theory. 379 00:23:58,880 --> 00:24:01,960 Liquid water environments have been found to exist 380 00:24:02,040 --> 00:24:04,320 in the absence of atmospheric pressure 381 00:24:04,400 --> 00:24:06,280 and at temperatures outside 382 00:24:06,360 --> 00:24:09,560 the circumstellar habitable zone temperature range. 383 00:24:11,160 --> 00:24:13,600 Just because a planet is outside the habitable zone 384 00:24:13,680 --> 00:24:15,840 doesn't mean that it couldn't have life. 385 00:24:15,920 --> 00:24:18,760 [narrator] For example, Saturn's moon Enceladus 386 00:24:18,840 --> 00:24:20,440 and Jupiter's Europa, 387 00:24:20,520 --> 00:24:23,960 both outside the habitable zone of our solar system, 388 00:24:24,040 --> 00:24:26,840 may hold large volumes of liquid water 389 00:24:26,920 --> 00:24:28,800 in subsurface oceans. 390 00:24:31,800 --> 00:24:34,960 If we are considering the possibility that life could arise 391 00:24:35,040 --> 00:24:36,800 in such harsh environments, 392 00:24:36,880 --> 00:24:39,720 which are not in the circumstellar habitable zone, 393 00:24:39,800 --> 00:24:42,680 that implies that we should look for exoplanets 394 00:24:42,760 --> 00:24:44,560 far beyond those zones. 395 00:24:45,880 --> 00:24:48,240 So the chances of finding an exoplanet 396 00:24:48,320 --> 00:24:52,200 with conditions to support life are much higher. 397 00:24:57,160 --> 00:24:59,160 We know that it's not an easy task 398 00:24:59,240 --> 00:25:03,200 to study and analyze the planets and moons of our own solar system, 399 00:25:03,280 --> 00:25:06,840 as they are millions of kilometers away from Earth. 400 00:25:08,600 --> 00:25:12,600 However, exoplanets are not just millions of kilometers away 401 00:25:12,680 --> 00:25:16,200 but many light-years away from Earth. 402 00:25:16,280 --> 00:25:19,640 How can astronomers manage to study exoplanets 403 00:25:19,720 --> 00:25:22,760 if they are trillions of kilometers away? 404 00:25:25,960 --> 00:25:30,120 There are several methods used by astronomers and astrobiologists 405 00:25:30,200 --> 00:25:31,760 to discover and to study 406 00:25:31,840 --> 00:25:35,120 these extremely distant, mysterious worlds. 407 00:25:38,680 --> 00:25:42,320 Before the launching of the Kepler mission in 2009, 408 00:25:42,400 --> 00:25:45,720 the most successful technique for detecting exoplanets 409 00:25:45,800 --> 00:25:47,720 was the Doppler spectroscopy, 410 00:25:47,800 --> 00:25:50,800 also known as the radial velocity method. 411 00:25:52,080 --> 00:25:54,680 The radial velocity method relies on the fact 412 00:25:54,760 --> 00:25:57,560 that a star does not remain completely stationary 413 00:25:57,640 --> 00:25:59,880 when it is orbited by a planet. 414 00:25:59,960 --> 00:26:02,800 The planet is much smaller than its star, 415 00:26:02,880 --> 00:26:05,960 but it still exerts a tiny gravitational pull 416 00:26:06,040 --> 00:26:08,760 or tug on the star as it orbits. 417 00:26:09,520 --> 00:26:12,800 When a planet is behind the star, from our point of view, 418 00:26:12,880 --> 00:26:15,520 it pulls the star slightly away from us. 419 00:26:16,720 --> 00:26:20,440 When it's in front, it pulls the star slightly toward us. 420 00:26:20,520 --> 00:26:23,920 This causes the star to wobble back and forth. 421 00:26:24,000 --> 00:26:27,400 Astronomers look for this wobbling to find planets. 422 00:26:29,360 --> 00:26:33,480 They use something called a spectrograph and powerful telescopes 423 00:26:33,560 --> 00:26:36,360 to examine the light coming from a star. 424 00:26:36,440 --> 00:26:40,360 A spectrograph, like a prism, splits the light from the star 425 00:26:40,440 --> 00:26:43,560 into its component colors, producing a spectrum. 426 00:26:43,640 --> 00:26:45,400 Some of the starlight gets absorbed 427 00:26:45,480 --> 00:26:48,080 as it passes through the star's atmosphere, 428 00:26:48,160 --> 00:26:52,760 and this produces small dark gaps, or lines, in the spectrum. 429 00:26:54,840 --> 00:26:56,920 As the star moves closer to us, 430 00:26:57,000 --> 00:27:00,280 these lines shift toward the blue end of the spectrum. 431 00:27:00,360 --> 00:27:03,320 As the star moves away, the lines shift back 432 00:27:03,400 --> 00:27:05,400 toward the red end of the spectrum. 433 00:27:05,480 --> 00:27:09,200 So the spectrum appears first slightly blue shifted 434 00:27:09,280 --> 00:27:11,880 and then slightly red shifted. 435 00:27:12,640 --> 00:27:15,760 Therefore, astronomers can look for orbiting planets 436 00:27:15,840 --> 00:27:19,360 by looking for these back and forth motions of the lines 437 00:27:19,440 --> 00:27:21,120 in a star's spectrum. 438 00:27:22,200 --> 00:27:24,400 From the speed it's being pulled toward you 439 00:27:24,480 --> 00:27:26,440 and how long it takes to go around in that circle, 440 00:27:26,520 --> 00:27:27,920 you can work out the mass of the planet, 441 00:27:28,000 --> 00:27:30,640 or the companion thing which is pulling it around. 442 00:27:30,720 --> 00:27:33,280 If that mass is very small, the thing is a planet. 443 00:27:33,920 --> 00:27:35,400 That method has been very successful. 444 00:27:35,480 --> 00:27:38,160 It found most of the planets which were discovered early on. 445 00:27:39,520 --> 00:27:43,760 [narrator] However, the Kepler technique was based on the planet's transit. 446 00:27:43,840 --> 00:27:46,680 The transit method is based on the observation 447 00:27:46,760 --> 00:27:49,760 of a star's small drop in brightness that occurs 448 00:27:49,840 --> 00:27:53,200 when the orbit of one of the star's planets passes, 449 00:27:53,280 --> 00:27:56,120 "transits," in front of the star. 450 00:27:56,200 --> 00:28:00,920 The amount of light lost depends on the sizes of the star and the planet, 451 00:28:01,000 --> 00:28:05,440 and the duration of the transit depends on the planet's distance from the star 452 00:28:05,520 --> 00:28:07,800 and the star's mass. 453 00:28:07,880 --> 00:28:11,080 With the Kepler space telescope, when we look at a star, 454 00:28:11,160 --> 00:28:12,760 we don't see the planet directly. 455 00:28:12,840 --> 00:28:15,720 All we see is a tiny dip in the brightness of the star 456 00:28:15,800 --> 00:28:18,160 when the planet passes in front of it. 457 00:28:18,240 --> 00:28:20,800 From the size of the dip, we work out the relative size of the planet. 458 00:28:20,880 --> 00:28:22,880 Is it a big planet or a small planet? 459 00:28:24,160 --> 00:28:26,560 [narrator] The combination of transit photometry 460 00:28:26,640 --> 00:28:28,360 and Doppler velocimetry 461 00:28:28,440 --> 00:28:31,760 reveals planetary radius, mass and density, 462 00:28:31,840 --> 00:28:33,800 which are some of the main parameters 463 00:28:33,880 --> 00:28:36,680 to evaluate the potentiality of the exoplanet 464 00:28:36,760 --> 00:28:40,720 as an Earthlike candidate, and so to harbor life. 465 00:28:43,720 --> 00:28:45,400 Once you know the distance from the star, 466 00:28:45,480 --> 00:28:46,960 you know how hot the star is, 467 00:28:47,040 --> 00:28:51,000 you can estimate what the temperature on the surface of the planet 468 00:28:51,080 --> 00:28:52,440 would be like. 469 00:28:52,520 --> 00:28:54,000 [narrator] Another of the main parameters 470 00:28:54,080 --> 00:28:57,400 to analyze the Earthlike potential of an exoplanet 471 00:28:57,480 --> 00:28:59,640 is its atmospheric composition. 472 00:29:01,320 --> 00:29:04,400 Atmospheric studies of exoplanets might be performed 473 00:29:04,480 --> 00:29:07,480 with spectroscopy during planetary transit. 474 00:29:09,000 --> 00:29:11,320 During the transit, the stellar light 475 00:29:11,400 --> 00:29:14,440 passes through the atmospheric limb of the planet. 476 00:29:14,520 --> 00:29:17,320 Spectral analysis of this filtered light 477 00:29:17,400 --> 00:29:20,480 reveals the structure and composition of the atmosphere. 478 00:29:23,600 --> 00:29:27,360 Astronomers could identify the most Earthlike exoplanets 479 00:29:27,440 --> 00:29:30,720 by detecting the biomarkers, which are the imprints 480 00:29:30,800 --> 00:29:34,240 that life forms have on their host planet atmosphere. 481 00:29:35,440 --> 00:29:39,000 For instance, the molecular oxygen that we are breathing 482 00:29:39,080 --> 00:29:41,960 results from the presence of life on Earth. 483 00:29:42,960 --> 00:29:45,720 Unfortunately, with present-day technology, 484 00:29:45,800 --> 00:29:48,360 it's extremely hard to closely study 485 00:29:48,440 --> 00:29:51,640 the atmospheric composition of those remote planets. 486 00:29:51,720 --> 00:29:54,720 The main thing that's keeping us from being able to do that now is technology. 487 00:29:54,800 --> 00:29:59,240 We don't have the technology, you know, in functioning instruments 488 00:29:59,320 --> 00:30:02,120 at the moment to be able to do that effectively. 489 00:30:02,200 --> 00:30:05,240 But that's something that will change with other missions in the pipeline, 490 00:30:05,320 --> 00:30:10,160 like Jack Webb Space Telescope and other missions that are happening. 491 00:30:11,400 --> 00:30:16,440 [narrator] Kepler continuously monitors over 100,000 stars similar to our sun 492 00:30:16,520 --> 00:30:20,320 for brightness changes produced by planetary transits. 493 00:30:20,400 --> 00:30:23,040 Thanks to this ingenious technique, 494 00:30:23,120 --> 00:30:28,360 Kepler has confirmed to date more than 1,000 exoplanets. 495 00:30:29,080 --> 00:30:31,560 Scientists think that about a few dozen of them 496 00:30:31,640 --> 00:30:34,080 can be labeled as Earthlike. 497 00:30:38,880 --> 00:30:42,520 Considering the possibilities of finding an Earthlike exoplanet 498 00:30:42,600 --> 00:30:45,160 are much higher in the circumstellar habitable zone 499 00:30:45,240 --> 00:30:46,880 of its planetary system, 500 00:30:46,960 --> 00:30:51,400 the planet hunting then started to focus on those areas. 501 00:30:54,840 --> 00:30:59,320 One of the first discoveries was 70 Virginis b, 502 00:30:59,400 --> 00:31:04,120 an exoplanet located approximately 60 light-years away 503 00:31:04,200 --> 00:31:06,200 in the constellation of Virgo. 504 00:31:06,840 --> 00:31:11,080 70 Virginis b was located exactly in the middle 505 00:31:11,160 --> 00:31:14,400 of the circumstellar habitable zone of its planetary system, 506 00:31:14,480 --> 00:31:17,960 so it was supposed not to be too hot or too cold. 507 00:31:20,440 --> 00:31:24,520 Unfortunately, further studies reported that this remote world 508 00:31:24,600 --> 00:31:27,800 was a gas giant with very high temperatures, 509 00:31:27,880 --> 00:31:31,080 which ruled out any potential for liquid water, 510 00:31:31,160 --> 00:31:33,120 and therefore of life. 511 00:31:37,360 --> 00:31:42,000 The early findings were discouraging in terms of detecting an Earth analog. 512 00:31:43,240 --> 00:31:45,200 But this was just the beginning. 513 00:31:48,640 --> 00:31:55,120 In 1998, a discovery made in the star Gliese 876, 514 00:31:55,200 --> 00:31:58,880 a red dwarf located in the constellation of Aquarius 515 00:31:58,960 --> 00:32:02,120 at a distance of 15 light-years away from Earth, 516 00:32:02,200 --> 00:32:04,440 really encouraged astronomers. 517 00:32:09,280 --> 00:32:13,000 A gas giant was detected in its habitable zone. 518 00:32:13,080 --> 00:32:15,240 Gliese 876 b. 519 00:32:21,080 --> 00:32:26,040 Three years later, another gas giant closer to this one was found. 520 00:32:26,120 --> 00:32:28,320 Gliese 876 c. 521 00:32:30,960 --> 00:32:32,920 We know that life as we know it 522 00:32:33,000 --> 00:32:37,360 is not possible on gas giant planets such as Jupiter or Saturn. 523 00:32:38,960 --> 00:32:41,960 But the big surprise was that both exoplanets 524 00:32:42,040 --> 00:32:45,000 may have habitable moons orbiting around them, 525 00:32:45,080 --> 00:32:47,200 as Jupiter and Saturn have. 526 00:32:48,160 --> 00:32:51,200 [Fergal] This was one of the first planets to be discovered in the habitable zone, 527 00:32:51,280 --> 00:32:53,800 and people theorized that, if it had a moon around it, 528 00:32:53,880 --> 00:32:55,160 the moon would be rocky 529 00:32:55,240 --> 00:32:58,000 and the moon would be at the right temperature to have liquid water. 530 00:32:58,840 --> 00:33:01,240 [narrator] Why couldn't any of these hypothetical moons 531 00:33:01,320 --> 00:33:05,520 around Gliese 876 b and c harbor life, 532 00:33:05,600 --> 00:33:07,960 as we hope Jupiter's moon Europa 533 00:33:08,040 --> 00:33:11,760 or Saturn's moons Titan and Enceladus might? 534 00:33:14,120 --> 00:33:17,480 So it's an exciting place to think about and maybe to look for in the future. 535 00:33:19,000 --> 00:33:21,200 [narrator] After the discovery of these exoplanets 536 00:33:21,280 --> 00:33:23,440 with potential Earthlike moons, 537 00:33:23,520 --> 00:33:28,080 several similar exoplanets with moons orbiting around them were discovered. 538 00:33:28,720 --> 00:33:32,840 Maybe on any of those remote moons, life arose in the past, 539 00:33:32,920 --> 00:33:36,640 or exists in the present, or might appear in the future. 540 00:33:39,680 --> 00:33:44,680 After all these early discoveries, we started to approach to the main goal, 541 00:33:44,760 --> 00:33:48,080 to find the most Earthlike world. 542 00:33:49,280 --> 00:33:52,760 An Earth analog, also referred to as a twin Earth, 543 00:33:52,840 --> 00:33:54,400 or Earthlike planet, 544 00:33:54,480 --> 00:33:57,520 is a planet or moon with environmental conditions 545 00:33:57,600 --> 00:33:59,880 similar to those found on the planet Earth. 546 00:34:04,000 --> 00:34:07,520 If life could arise on Earth millions of years ago 547 00:34:07,600 --> 00:34:10,639 and if we look for exoplanets similar to our planet, 548 00:34:10,719 --> 00:34:14,600 the chances of finding habitable planets skyrocket. 549 00:34:17,280 --> 00:34:19,639 Recent discoveries have uncovered planets 550 00:34:19,719 --> 00:34:23,080 that are believed to be similar in many ways to Earth, 551 00:34:23,159 --> 00:34:26,639 with relatively high Earth similarity indexes. 552 00:34:29,400 --> 00:34:32,600 The size is often thought to be a significant factor, 553 00:34:32,679 --> 00:34:37,560 as planets of Earth size are thought more likely to be terrestrial in nature 554 00:34:37,639 --> 00:34:41,239 and be capable of retaining an Earthlike atmosphere. 555 00:34:51,960 --> 00:34:54,199 From the point of view of Kepler, a planet is Earthlike 556 00:34:54,280 --> 00:34:56,080 if it's small enough that it's probably rocky, 557 00:34:56,159 --> 00:34:58,560 it's not a gas giant like Jupiter or Saturn. 558 00:34:59,560 --> 00:35:02,080 [narrator] But size alone is a poor measure, 559 00:35:02,160 --> 00:35:04,680 particularly in terms of habitability, 560 00:35:04,760 --> 00:35:09,560 because next to us, there is a planet with a very similar size and mass, 561 00:35:09,640 --> 00:35:13,760 Venus, where it is almost impossible for life to arise. 562 00:35:19,680 --> 00:35:22,200 There are other criteria to be considered, 563 00:35:22,280 --> 00:35:25,720 like the surface gravity or the star size and type. 564 00:35:26,880 --> 00:35:29,920 A planet is Earthlike if it's the right distance away from a star 565 00:35:30,000 --> 00:35:33,280 that it's in the habitable zone, that it's not too close that it's too hot 566 00:35:33,360 --> 00:35:35,480 and all the water it would have has boiled away, 567 00:35:35,560 --> 00:35:38,920 and not so cold that if there was any water, it would all freeze to ice. 568 00:35:40,240 --> 00:35:44,320 [narrator] If we are able to examine all of these parameters of an exoplanet, 569 00:35:44,400 --> 00:35:48,720 we would be able to know if it is or not a real twin Earth. 570 00:35:49,600 --> 00:35:53,000 So, when we say Earthlike for Kepler, we usually just mean 571 00:35:53,080 --> 00:35:56,520 that it's small enough that we think that it's solid enough 572 00:35:56,600 --> 00:35:58,840 that you could stand on it, but that doesn't mean 573 00:35:58,920 --> 00:36:02,080 that it has an atmosphere or that it has an ocean. 574 00:36:03,520 --> 00:36:07,560 [narrator] It's also often cited that an Earth analog must be terrestrial, 575 00:36:07,640 --> 00:36:10,360 that is, it should possess a planetary surface 576 00:36:10,440 --> 00:36:13,520 composed of materials similar to Earth's. 577 00:36:15,080 --> 00:36:19,440 The conclusion would be that extrasolar planets or moons 578 00:36:19,520 --> 00:36:22,360 in the center of its circumstellar habitable zone, 579 00:36:22,440 --> 00:36:24,880 the so-called Goldilocks position, 580 00:36:24,960 --> 00:36:26,960 with substantial atmospheres, 581 00:36:27,040 --> 00:36:31,440 may possess oceans and water clouds like those on Earth. 582 00:36:33,000 --> 00:36:36,200 In addition to surface water, a true Earth analog 583 00:36:36,280 --> 00:36:39,080 would require a mix of oceans or lakes 584 00:36:39,160 --> 00:36:41,200 and areas not covered by water. 585 00:36:43,520 --> 00:36:45,640 [Fergal] We believe that water is essential, 586 00:36:45,720 --> 00:36:49,080 but just about everything else you can think about which is important for life, 587 00:36:49,160 --> 00:36:52,520 uh, there seems to be life on the Earth that doesn't need it. 588 00:36:52,600 --> 00:36:54,360 There is life that survives without sunlight. 589 00:36:54,440 --> 00:36:56,120 There's life that survives without oxygen. 590 00:36:56,200 --> 00:36:59,840 There's life that survives deep down underneath the ice in Antarctica. 591 00:37:01,120 --> 00:37:03,640 [narrator] Unfortunately, with the present technology, 592 00:37:03,720 --> 00:37:06,720 we can't properly evaluate most of the parameters, 593 00:37:06,800 --> 00:37:09,640 like the temperature, the atmospheric composition, 594 00:37:09,720 --> 00:37:12,080 or the surface of the exoplanets. 595 00:37:15,720 --> 00:37:20,080 Nevertheless, considering we have already discovered hundreds of exoplanets, 596 00:37:20,160 --> 00:37:21,560 we can't help but wonder 597 00:37:21,640 --> 00:37:25,160 if a real Earth analog has already been discovered. 598 00:37:35,080 --> 00:37:38,720 On 18th April 2013, 599 00:37:38,800 --> 00:37:41,720 astronomers from the Kepler team announced a discovery 600 00:37:41,800 --> 00:37:44,880 that created great expectation. 601 00:37:46,120 --> 00:37:52,320 For the first time ever, two very Earthlike exoplanets were found. 602 00:37:54,000 --> 00:37:56,640 They were the Kepler-62e 603 00:37:59,040 --> 00:38:01,760 and the Kepler-62f. 604 00:38:04,880 --> 00:38:08,640 And orbits Kepler-62, an orange dwarf star, 605 00:38:08,720 --> 00:38:11,160 in its circumstellar habitable zone. 606 00:38:14,040 --> 00:38:19,680 They immediately became prime candidates to host alien life. 607 00:38:21,040 --> 00:38:26,960 A modeling study also concluded that Kepler-62e and Kepler-62f 608 00:38:27,040 --> 00:38:31,440 are likely covered mostly, perhaps completely, in water. 609 00:38:31,520 --> 00:38:36,320 Kepler-62e probably has a very cloudy sky and is warm and humid 610 00:38:36,400 --> 00:38:38,480 all the way to the polar regions. 611 00:38:42,040 --> 00:38:47,200 Kepler-62f would be cooler, but still potentially life-friendly. 612 00:38:47,280 --> 00:38:52,280 Unfortunately, they are at a huge distance of 1,200 light-years away 613 00:38:52,360 --> 00:38:54,400 in the constellation of Lyra. 614 00:39:00,000 --> 00:39:06,080 Soon after, it was discovered, an exoplanet even more similar to Earth, 615 00:39:06,160 --> 00:39:08,560 Kepler-186f. 616 00:39:08,640 --> 00:39:13,400 This finding was a milestone as it was the first rocky planet 617 00:39:13,480 --> 00:39:16,520 found in the habitable zone of its system. 618 00:39:16,600 --> 00:39:20,960 It is 492 light-years away from the Earth. 619 00:39:22,400 --> 00:39:25,160 [Fergal] Kepler-186f is possibly my favorite planet 620 00:39:25,240 --> 00:39:26,920 to come out of the Kepler mission. 621 00:39:27,000 --> 00:39:28,080 It's a small planet. 622 00:39:28,160 --> 00:39:31,200 It's maybe 10% to 20% bigger than the Earth. 623 00:39:31,280 --> 00:39:34,600 Based on everything we know, it's almost certain to be rocky, 624 00:39:34,680 --> 00:39:36,880 and it's the right distance away from its parent star 625 00:39:36,960 --> 00:39:39,760 that, if the atmosphere is right, if the greenhouse effect is right, 626 00:39:39,840 --> 00:39:41,720 it could have liquid water on the surface. 627 00:39:43,200 --> 00:39:44,680 [narrator] After that discovery, 628 00:39:44,760 --> 00:39:48,240 several more Earthlike candidates started to arise. 629 00:39:48,320 --> 00:39:50,920 Like Kepler-438b, 630 00:39:51,000 --> 00:39:53,040 Kepler-442b, 631 00:39:54,280 --> 00:39:56,960 or Kepler-440b. 632 00:39:57,040 --> 00:40:00,040 All of them were very similar to our planet, 633 00:40:00,120 --> 00:40:02,880 but none of them was a real twin Earth. 634 00:40:04,800 --> 00:40:10,080 But everything changed on July 23rd, 2015. 635 00:40:10,160 --> 00:40:14,480 That day, NASA's Kepler space telescope science team 636 00:40:14,560 --> 00:40:19,160 shocked the scientific community with an amazing finding. 637 00:40:20,280 --> 00:40:24,080 The most Earthlike planet ever was discovered. 638 00:40:24,160 --> 00:40:27,200 Its name, Kepler-452b. 639 00:40:28,320 --> 00:40:30,040 What made different this one 640 00:40:30,120 --> 00:40:32,920 to the other previous Earth analog candidates? 641 00:40:34,200 --> 00:40:39,520 Kepler-452b is the very first apparently rocky planet 642 00:40:39,600 --> 00:40:43,400 that orbits a G-type star like our sun. 643 00:40:44,440 --> 00:40:46,520 It's a planet in a habitable zone around a star 644 00:40:46,600 --> 00:40:49,160 which is almost a clone of our own sun. 645 00:40:50,800 --> 00:40:53,920 [narrator] After this discovery, the Earth is a little less lonely 646 00:40:54,000 --> 00:40:55,640 in the universe. 647 00:40:59,960 --> 00:41:03,240 Kepler-452b circles its star, 648 00:41:03,320 --> 00:41:05,480 which is about as hot as our sun, 649 00:41:05,560 --> 00:41:08,720 10% brighter, and 20% larger, 650 00:41:08,800 --> 00:41:13,760 at an orbital radius just 5% larger than that of the Earth. 651 00:41:13,840 --> 00:41:18,440 A year on this planet is 385 Earth days long, 652 00:41:18,520 --> 00:41:21,240 just 20 days longer than Earth's. 653 00:41:23,760 --> 00:41:25,440 What makes this slightly less exciting 654 00:41:25,520 --> 00:41:28,360 from the point of view of could it be habitable is its size. 655 00:41:28,440 --> 00:41:32,320 Our best guess at the size is that it's about 60% bigger 656 00:41:32,400 --> 00:41:34,400 than our own Earth. 657 00:41:35,240 --> 00:41:38,760 [narrator] It is the smallest Earth analog planet ever found 658 00:41:38,840 --> 00:41:42,640 in the habitable zone of a G-type star like our sun. 659 00:41:42,720 --> 00:41:47,320 Previous research on super-Earth size planets like 452b 660 00:41:47,400 --> 00:41:51,240 suggests this one has a good chance of being rocky. 661 00:41:53,320 --> 00:41:54,720 If it is a rocky world, 662 00:41:54,800 --> 00:41:57,440 it would weigh in at about five Earth masses, 663 00:41:57,520 --> 00:42:00,600 giving it a surface gravity of roughly two grams, 664 00:42:00,680 --> 00:42:04,440 which would mean that our weight would be double on its surface. 665 00:42:06,680 --> 00:42:10,560 Kepler-452b could have a thick, cloudy atmosphere 666 00:42:10,640 --> 00:42:12,520 and volcanic activity. 667 00:42:15,360 --> 00:42:19,640 Even more exciting than Kepler-452b's Earthlike demeanor 668 00:42:19,720 --> 00:42:23,440 is the fact that this world has spent around six billion years 669 00:42:23,520 --> 00:42:25,800 in the habitable zone of its star. 670 00:42:26,480 --> 00:42:29,000 That's considerable time for life to arise 671 00:42:29,080 --> 00:42:31,840 somewhere on its surface or in its oceans 672 00:42:31,920 --> 00:42:34,000 should the conditions for life exist. 673 00:42:35,360 --> 00:42:41,120 Kepler-452b is about 1.5 billion years older than the Earth. 674 00:42:41,200 --> 00:42:45,720 If it was Earth-sized, the planet and its aging, brightening star 675 00:42:45,800 --> 00:42:48,000 might be at a point in their evolution 676 00:42:48,080 --> 00:42:51,720 where liquid water would be rapidly evaporating from the surface. 677 00:42:51,800 --> 00:42:53,200 [thunder rumbling] 678 00:42:53,920 --> 00:42:58,840 But because of its higher mass, astronomers believe Kepler-452b 679 00:42:58,920 --> 00:43:04,440 could continue to hold liquid water for the next 500 million years or so. 680 00:43:07,960 --> 00:43:11,320 So far, it's the only known world in the system 681 00:43:11,400 --> 00:43:17,080 which lies some 1,400 light-years away in the Cygnus constellation. 682 00:43:19,360 --> 00:43:22,480 Obviously, we're not going to get there anytime soon, 683 00:43:22,560 --> 00:43:24,280 but it's fascinating to imagine 684 00:43:24,360 --> 00:43:27,160 that far off in the distant reaches of space, 685 00:43:27,240 --> 00:43:31,160 a world very much like our own might already exist. 686 00:43:33,320 --> 00:43:38,880 If this twin Earth exists, why couldn't thousands more like it exist? 687 00:43:45,120 --> 00:43:50,760 Less than a year after the amazing finding of Kepler-452b, 688 00:43:50,840 --> 00:43:53,600 on May 2016, 689 00:43:53,680 --> 00:43:57,040 a new discovery shocked the scientific community. 690 00:43:59,000 --> 00:44:00,960 Astronomers using telescopes 691 00:44:01,040 --> 00:44:03,640 at European Southern Observatory in Chile 692 00:44:03,720 --> 00:44:07,680 discovered three planets around a dim dwarf star 693 00:44:07,760 --> 00:44:12,480 just 40 light-years from Earth in the constellation of Aquarius. 694 00:44:14,240 --> 00:44:19,040 These worlds may be the best targets so far found in the hunt for life 695 00:44:19,120 --> 00:44:20,720 elsewhere in the universe. 696 00:44:21,600 --> 00:44:24,920 They used the Trappist telescope to monitor the brightness 697 00:44:25,000 --> 00:44:29,280 of an ultracool dwarf star in the constellation of Aquarius, 698 00:44:29,360 --> 00:44:32,080 which has been named Trappist-1. 699 00:44:34,520 --> 00:44:37,720 Trappist-1 is much cooler and redder than the sun 700 00:44:37,800 --> 00:44:40,040 and barely larger than Jupiter. 701 00:44:42,000 --> 00:44:44,920 Stars like this are very common in the Milky Way 702 00:44:45,000 --> 00:44:47,080 and they are very long lived. 703 00:44:49,200 --> 00:44:53,240 This was the first time that planets have been found around one of them. 704 00:44:54,320 --> 00:44:57,440 The three planets are very similar in size to the Earth 705 00:44:57,520 --> 00:45:00,760 and might have habitable regions on their surfaces. 706 00:45:04,080 --> 00:45:08,200 But the really exciting result is that these are the first Earth-like planets 707 00:45:08,280 --> 00:45:11,120 that are well suited for the detection of life. 708 00:45:11,960 --> 00:45:14,680 The ultracool dwarf stars are the only places 709 00:45:14,760 --> 00:45:18,160 where life could be detected on an Earth-sized exoplanet 710 00:45:18,240 --> 00:45:20,120 using our current technology. 711 00:45:21,160 --> 00:45:25,680 The light from a much brighter star, like the sun for example, 712 00:45:25,760 --> 00:45:28,240 would swamp vital measurements of the atmospheres 713 00:45:28,320 --> 00:45:30,240 of any candidate planets. 714 00:45:31,480 --> 00:45:34,960 The next step is to make more detailed observations 715 00:45:35,040 --> 00:45:37,440 using the next generation of telescopes, 716 00:45:37,520 --> 00:45:41,560 such as ESO's European Extremely Large Telescope 717 00:45:41,640 --> 00:45:44,400 and the James Webb Space Telescope. 718 00:45:45,360 --> 00:45:49,720 That will allow astronomers to study the atmospheres of planets like this 719 00:45:49,800 --> 00:45:53,440 and to search for molecules related to biological activity, 720 00:45:53,520 --> 00:45:56,280 like ozone, methane or water. 721 00:45:59,640 --> 00:46:02,720 Although there is not yet any proof of the existence of life 722 00:46:02,800 --> 00:46:05,640 on all of these exoplanets that we've already found, 723 00:46:05,720 --> 00:46:09,760 even in the most Earthlike of them, like Kepler-452b, 724 00:46:11,760 --> 00:46:15,760 we can't help but wonder if any of those potential forms of life 725 00:46:15,840 --> 00:46:19,280 that might have arisen there were, or will be, able to evolve 726 00:46:19,360 --> 00:46:21,000 into intelligent life. 727 00:46:24,040 --> 00:46:28,400 If any of those extremely remote worlds was formed billions of years ago, 728 00:46:28,480 --> 00:46:31,760 as Earth did, and it became into a habitable planet, 729 00:46:31,840 --> 00:46:34,360 then the organic compound had time enough 730 00:46:34,440 --> 00:46:37,680 to mix up and organize into living forms. 731 00:46:38,400 --> 00:46:41,440 Perhaps any of those living forms might have evolved 732 00:46:41,520 --> 00:46:43,600 into complex forms of life, 733 00:46:43,680 --> 00:46:46,080 and some of those complex forms of life 734 00:46:46,160 --> 00:46:50,160 might evolve into intelligent beings with consciousness. 735 00:46:51,880 --> 00:46:53,800 Thanks to Kepler mission research, 736 00:46:53,880 --> 00:46:57,640 it's known that just in our galaxy, the Milky Way, 737 00:46:57,720 --> 00:47:00,640 there might be millions of Earth analogs, 738 00:47:00,720 --> 00:47:03,800 and there are billions of galaxies across the universe. 739 00:47:05,840 --> 00:47:09,920 So the chances are much higher than we could have ever imagined. 740 00:47:12,320 --> 00:47:17,520 For that reason, science is carrying out an intense search for intelligent life. 741 00:47:19,240 --> 00:47:22,400 The SETI Institute in California is nowadays 742 00:47:22,480 --> 00:47:25,360 the main world institution devoted to the search 743 00:47:25,440 --> 00:47:27,600 for extraterrestrial intelligence. 744 00:47:27,680 --> 00:47:28,960 Its name, "SETI," 745 00:47:29,040 --> 00:47:32,880 stands for "search for extraterrestrial intelligence." 746 00:47:34,160 --> 00:47:37,480 This search is based on the use of radio telescopes. 747 00:47:37,560 --> 00:47:40,240 Radio telescopes receive radio waves. 748 00:47:40,320 --> 00:47:44,720 As we can't go to space aboard spacecraft to find that intelligent life, 749 00:47:44,800 --> 00:47:47,640 what we look for are radio signals. 750 00:47:48,960 --> 00:47:53,240 What we're looking for is a signal that's at one spot on the radio dial. 751 00:47:53,320 --> 00:47:56,640 Just like when you're listening to the radio in your car, 752 00:47:56,720 --> 00:47:59,360 you know, you tune across the dial, you hear static everywhere, 753 00:47:59,440 --> 00:48:01,400 and then at one spot you hear… [imitates signal] 754 00:48:01,480 --> 00:48:02,640 …and there's a station. 755 00:48:02,720 --> 00:48:07,120 Okay, that's the signal that's produced by a transmitter somewhere. 756 00:48:07,200 --> 00:48:09,080 It's not natural static. 757 00:48:09,160 --> 00:48:13,720 It's not like a quasar or a pulsar or galaxies or hot gas/cold gas. 758 00:48:13,800 --> 00:48:16,440 All those things in space make radio noise, 759 00:48:16,520 --> 00:48:17,760 but it's all over the dial. 760 00:48:17,840 --> 00:48:20,400 So we look for signals that are at one spot on the dial, 761 00:48:20,480 --> 00:48:23,600 and, of course, the source of the signal has to be up in the sky. 762 00:48:23,680 --> 00:48:27,040 Those are the kinds of criteria we use to know that, 763 00:48:27,120 --> 00:48:30,560 even if we don't know what it means, we at least know they're there, 764 00:48:30,640 --> 00:48:32,560 they're on the air. 765 00:48:34,760 --> 00:48:38,000 [narrator] Unfortunately, till now, we haven't received a signal 766 00:48:38,080 --> 00:48:42,000 that can be really attributed to extraterrestrial intelligence. 767 00:48:45,680 --> 00:48:47,560 [dramatic music playing] 768 00:48:47,640 --> 00:48:53,560 In the coming years, NASA and ESA, the European Space Agency, 769 00:48:53,640 --> 00:48:56,440 have planned to launch several space telescopes 770 00:48:56,520 --> 00:48:59,680 that will surely help to unveil the mystery of life 771 00:48:59,760 --> 00:49:02,120 beyond the boundaries of our solar system. 772 00:49:05,800 --> 00:49:09,320 The most ambitious one is the James Webb Space Telescope. 773 00:49:09,400 --> 00:49:12,360 This project is an international collaboration 774 00:49:12,440 --> 00:49:16,920 between NASA, ESA and the Canadian Space Agency, CSA. 775 00:49:19,480 --> 00:49:22,560 It will be the premier observatory of the next decade, 776 00:49:22,640 --> 00:49:25,400 serving thousands of astronomers worldwide. 777 00:49:25,480 --> 00:49:28,680 It will study every phase in the history of our universe, 778 00:49:28,760 --> 00:49:32,160 ranging from the first luminous glows after the big bang 779 00:49:32,240 --> 00:49:35,560 to the formation of solar systems capable of supporting life 780 00:49:35,640 --> 00:49:37,240 on planets like Earth, 781 00:49:37,320 --> 00:49:39,560 to the evolution of our own solar system. 782 00:49:42,880 --> 00:49:47,120 This new telescope, three times more powerful than Hubble, 783 00:49:47,200 --> 00:49:50,160 will be able to analyze starlight passing through the atmospheres 784 00:49:50,240 --> 00:49:52,600 of the closest Earthlike worlds, 785 00:49:52,680 --> 00:49:56,000 looking for the telltale signs of life itself, 786 00:49:56,080 --> 00:49:59,320 like, for instance, detecting gasses in its atmosphere 787 00:49:59,400 --> 00:50:04,880 usually linked to life processes, such as oxygen, methane, carbon dioxide, 788 00:50:04,960 --> 00:50:06,360 or nitrogen. 789 00:50:07,520 --> 00:50:09,680 JWST is really going to help us understand 790 00:50:09,760 --> 00:50:12,320 what atmospheres of planets are like under different conditions, 791 00:50:12,400 --> 00:50:14,240 and that's going to be a really exciting result. 792 00:50:15,960 --> 00:50:19,880 [narrator] There is another mission. The CHEOPS mission. 793 00:50:19,960 --> 00:50:24,760 "CHEOPS" comes from "characterizing exoplanet satellite." 794 00:50:26,760 --> 00:50:32,440 This is an ESA mission, dedicated to searching for exoplanetary transits 795 00:50:32,520 --> 00:50:35,440 by performing ultra-high-precision photometry 796 00:50:35,520 --> 00:50:39,680 on bright stars already known to host planets. 797 00:50:43,520 --> 00:50:45,480 With all of these new space telescopes 798 00:50:45,560 --> 00:50:48,040 programmed to be launched in the coming years, 799 00:50:48,120 --> 00:50:51,400 we are sure that finding a habitable exoplanet 800 00:50:52,560 --> 00:50:57,080 and any consistent biosignature will be just a matter of time. 801 00:51:02,840 --> 00:51:04,600 [peaceful music playing] 802 00:51:07,160 --> 00:51:10,200 If we are ever able to find evidence of the existence 803 00:51:10,280 --> 00:51:14,640 of any form of life among one of those billions of exoplanets 804 00:51:14,720 --> 00:51:18,080 we know are across the observable universe, 805 00:51:18,160 --> 00:51:20,840 it would be undoubtedly shocking. 806 00:51:22,160 --> 00:51:25,320 If we did find life somewhere else in the solar system 807 00:51:25,400 --> 00:51:29,200 and we were able to do, for example, a genetic analysis to determine 808 00:51:29,280 --> 00:51:31,600 that it was distinct from life on Earth, 809 00:51:31,680 --> 00:51:34,600 that would be a really earth-shaking discovery. 810 00:51:36,120 --> 00:51:39,480 [narrator] Living generation might be witness 811 00:51:39,560 --> 00:51:43,680 of a finding that would undoubtedly be a turning point 812 00:51:43,760 --> 00:51:46,080 in the history of humankind, 813 00:51:47,320 --> 00:51:51,600 the discovery of life in outer space. 814 00:51:54,560 --> 00:51:56,560 [contemplative symphonic music playing]