1 00:00:02,080 --> 00:00:06,000 Finding Life 2 00:00:08,500 --> 00:00:11,470 Have you ever wondered about life in the Universe? 3 00:00:11,470 --> 00:00:14,600 Inhabited planets orbiting distant stars? 4 00:00:14,600 --> 00:00:17,500 Astronomers have — for centuries. 5 00:00:17,500 --> 00:00:21,950 After all, with so many galaxies, and each with so many stars, 6 00:00:21,950 --> 00:00:24,140 how could the Earth be unique? 7 00:00:25,500 --> 00:00:30,110 In 1995, Swiss astronomers Michel Mayor and Didier Queloz 8 00:00:30,110 --> 00:00:34,660 were the first to discover an exoplanet orbiting a normal star. 9 00:00:35,000 --> 00:00:39,490 Since then, planet hunters have found many hundreds of alien worlds. 10 00:00:39,490 --> 00:00:44,780 Large and small, hot and cold, and in a wide variety of orbits. 11 00:00:45,600 --> 00:00:49,800 Now, we’re on the brink of discovering Earth’s twin sisters. 12 00:00:50,290 --> 00:00:56,290 And in the future: a planet with life — the Holy Grail of astrobiologists. 13 00:01:02,590 --> 00:01:06,070 The European Southern Observatory plays an important role 14 00:01:06,070 --> 00:01:08,310 in the search for exoplanets. 15 00:01:09,290 --> 00:01:13,560 Michel Mayor’s team found hundreds of them from Cerro La Silla, 16 00:01:13,560 --> 00:01:16,880 ESO’s first Chilean foothold. 17 00:01:17,890 --> 00:01:19,880 Here’s the CORALIE spectrograph, 18 00:01:19,880 --> 00:01:23,120 mounted on the Swiss Leonhard Euler Telescope. 19 00:01:25,030 --> 00:01:30,940 It measures the tiny wobbles of stars, caused by the gravity of orbiting planets. 20 00:01:30,940 --> 00:01:37,910 ESO’s venerable 3.6-metre telescope is also hunting for exoplanets. 21 00:01:39,200 --> 00:01:42,320 The HARPS spectrograph is the most accurate in the world. 22 00:01:42,320 --> 00:01:46,680 So far, it has discovered more than 150 planets. 23 00:01:51,750 --> 00:01:53,360 Its biggest trophy: 24 00:01:53,360 --> 00:01:59,950 a rich system containing at least five and maybe as many as seven alien worlds. 25 00:02:11,330 --> 00:02:13,960 But there are other ways to find exoplanets. 26 00:02:22,130 --> 00:02:28,350 In 2006, the 1.5-metre Danish telescope helped to discover a distant planet 27 00:02:28,350 --> 00:02:31,350 that is just five times more massive than the Earth. 28 00:02:35,500 --> 00:02:39,200 The trick? Gravitational microlensing. 29 00:02:40,040 --> 00:02:45,150 The planet and its parent star passed in front of a brighter star in the background, 30 00:02:45,150 --> 00:02:47,320 magnifying its image. 31 00:02:49,420 --> 00:02:54,660 And in some cases, you can even capture exoplanets on camera. 32 00:02:57,960 --> 00:03:04,240 In 2004, NACO, the adaptive optics camera on the Very Large Telescope, 33 00:03:04,240 --> 00:03:08,220 took the first image ever of an exoplanet. 34 00:03:08,220 --> 00:03:14,020 The red dot in this image is a giant planet orbiting a brown dwarf star. 35 00:03:17,880 --> 00:03:22,650 In 2010, NACO went one step further. 36 00:03:24,440 --> 00:03:28,330 This star is 130 light-years away from Earth. 37 00:03:28,330 --> 00:03:35,080 It is younger and brighter than the Sun, and four planets circle around it in wide orbits. 38 00:03:36,900 --> 00:03:41,970 NACO’s eagle-eyed vision made it possible to measure the light of planet c 39 00:03:41,970 --> 00:03:46,490 — a gas giant ten times more massive than Jupiter. 40 00:03:48,070 --> 00:03:50,450 Despite the glare of the parent star, 41 00:03:50,450 --> 00:03:54,450 the feeble light of the planet could be stretched out into a spectrum, 42 00:03:54,450 --> 00:03:57,380 revealing details about the atmosphere. 43 00:03:59,270 --> 00:04:05,740 Today, many exoplanets are discovered when they transit across their parent stars. 44 00:04:05,740 --> 00:04:09,020 If we happen to see the planet’s orbit edge-on, 45 00:04:09,020 --> 00:04:12,390 it will pass in front of its star every cycle. 46 00:04:12,390 --> 00:04:16,870 Thus, tiny, regular brightness dips in the light of a star 47 00:04:16,870 --> 00:04:20,310 betray the existence of an orbiting planet. 48 00:04:23,010 --> 00:04:27,600 The TRAPPIST telescope at La Silla will help search for these elusive transits. 49 00:04:28,250 --> 00:04:29,570 Meanwhile, 50 00:04:29,570 --> 00:04:36,120 the Very Large Telescope has studied a transiting planet in exquisite detail. 51 00:04:36,910 --> 00:04:44,820 Meet GJ1214b, a super-Earth 2.6 times larger than our home planet. 52 00:04:47,010 --> 00:04:53,040 During transits, the planet’s atmosphere partly absorbs the light of the parent star. 53 00:04:57,200 --> 00:05:02,740 ESO’s sensitive FORS spectrograph revealed that GJ1214b 54 00:05:02,740 --> 00:05:07,000 might well be a hot and steamy sauna world. 55 00:05:09,920 --> 00:05:14,060 Gas giants and sauna worlds are inhospitable to life. 56 00:05:14,060 --> 00:05:17,060 But the hunt is not over yet. 57 00:05:18,010 --> 00:05:22,420 Soon, the new SPHERE instrument will be installed at the VLT. 58 00:05:22,420 --> 00:05:28,490 SPHERE will be able to spot faint planets in the glare of their host stars. 59 00:05:29,200 --> 00:05:35,140 In 2016, the ESPRESSO spectrograph will arrive at the VLT 60 00:05:35,140 --> 00:05:39,110 and greatly surpass the current HARPS instrument. 61 00:05:41,000 --> 00:05:44,850 And ESO’s Extremely Large Telescope, once completed, 62 00:05:44,850 --> 00:05:49,170 may well find evidence for alien biospheres. 63 00:05:56,480 --> 00:05:59,390 On Earth, life is abundant. 64 00:06:00,960 --> 00:06:09,640 Northern Chile offers its share of condors, vicuñas, vizcachas and giant cacti. 65 00:06:11,910 --> 00:06:16,830 Even the arid soil of the Atacama desert teems with hardy microbes. 66 00:06:20,970 --> 00:06:25,300 We’ve found the building blocks of life in interstellar space. 67 00:06:26,000 --> 00:06:28,790 We’ve learnt that planets are abundant. 68 00:06:33,110 --> 00:06:38,190 Billions of years ago, comets brought water and organic molecules to Earth. 69 00:06:40,540 --> 00:06:44,250 Wouldn’t we expect the same thing to happen elsewhere? 70 00:06:49,500 --> 00:06:51,400 Or are we alone? 71 00:06:53,040 --> 00:06:55,080 It’s the biggest question ever. 72 00:06:56,480 --> 00:06:59,530 And the answer is almost within reach.