1 00:00:00,320 --> 00:00:04,680 Our knowledge of exoplanets is growing rapidly. 2 00:00:04,680 --> 00:00:11,440 In recent years astronomers have discovered myriad worlds beyond our solar system 3 00:00:11,440 --> 00:00:16,880 even deducing information about their sizes, temperatures and atmospheres 4 00:00:17,800 --> 00:00:24,260 But how can scientists know these details about planets that exist at such a vast distances from us? 5 00:00:32,060 --> 00:00:36,280 Discovering Exoplanets from Transits. 6 00:00:37,200 --> 00:00:40,500 Exoplanets raise some tantalizing questions 7 00:00:41,600 --> 00:00:45,900 from the possibility of other Earth-like worlds to alien life. 8 00:00:48,420 --> 00:00:52,300 But pursuing answers to these questions is not an easy task 9 00:00:53,300 --> 00:00:56,860 Exoplanets emit almost no visible light of their own 10 00:00:57,460 --> 00:01:03,440 and orbit stars at great distances from Earth, making them very difficult to observe. 11 00:01:07,000 --> 00:01:11,320 Transits offer one of the best chances to study exoplanets. 12 00:01:12,580 --> 00:01:16,020 This is when a planet crosses between its host star and Earth, 13 00:01:16,540 --> 00:01:20,200 temporarily reducing the star's apparent brightness. 14 00:01:21,100 --> 00:01:24,660 The duration and change in intensity of the light curve 15 00:01:24,760 --> 00:01:28,300 give astronomers clues about the planet's size and orbit. 16 00:01:29,900 --> 00:01:35,000 Additional smaller dips in light levels just before or after the transit 17 00:01:35,220 --> 00:01:39,120 can indicate a satellite; an exomoon. 18 00:01:42,480 --> 00:01:45,760 Transits can even tell us what a planet is made of. 19 00:01:48,760 --> 00:01:52,440 The tiny fraction of light that passes through its atmosphere 20 00:01:53,020 --> 00:01:56,180 interacts with atoms and molecules there. 21 00:01:59,440 --> 00:02:01,980 The light then carries information about them, 22 00:02:02,360 --> 00:02:05,080 which scientists use to infer conditions 23 00:02:05,660 --> 00:02:09,640 like temperature, chemical composition and formation history. 24 00:02:12,780 --> 00:02:16,100 However, this method has limits. 25 00:02:16,600 --> 00:02:22,160 Transits only happen if a planet's orbit actually crosses between its host star and Earth 26 00:02:22,940 --> 00:02:25,920 so its orbit must be edge-on towards us. 27 00:02:27,520 --> 00:02:32,660 This is the case for just a small fraction of planetary systems 28 00:02:34,080 --> 00:02:40,400 Where they do occur, transits happen infrequently and last for a relatively short time 29 00:02:40,820 --> 00:02:43,700 so chance observations are unlikely. 30 00:02:47,580 --> 00:02:53,980 Transits are also bias towards finding larger exoplanets that are closer to their host star. 31 00:02:55,380 --> 00:03:01,980 These planets block out more light, producing a larger dip in brightness that is easier to detect. 32 00:03:02,520 --> 00:03:06,600 So transits don't represents the full diversity of worlds out there. 33 00:03:09,780 --> 00:03:12,720 There can even be false positives. 34 00:03:13,660 --> 00:03:19,780 Sometimes a dip in brightness is caused by something else such as one star passing in front of another 35 00:03:20,060 --> 00:03:21,500 in a binary system. 36 00:03:25,000 --> 00:03:30,420 Despite these limitations, transits have revealed scores of other worlds 37 00:03:30,660 --> 00:03:34,440 thanks to the sheer number of stars and planets in the universe 38 00:03:35,260 --> 00:03:38,660 and the sophisticated technology that looks for them. 39 00:03:40,820 --> 00:03:44,620 The Hubble Space Telescope is a major milestone in this field. 40 00:03:46,220 --> 00:03:51,600 Hubble has made the first atmospheric study of Earth-sized exoplanets, 41 00:03:53,680 --> 00:03:57,760 captured the first image of an exoplanet in visible light, 42 00:03:59,120 --> 00:04:04,500 and discovered the first organic molecule in the atmosphere of an exoplanet. 43 00:04:06,380 --> 00:04:11,180 However, these remarkable discoveries push Hubble to its very limits. 44 00:04:11,720 --> 00:04:15,000 To delve even deeper into these distant worlds, 45 00:04:15,280 --> 00:04:17,720 we need even more powerful telescopes. 46 00:04:19,540 --> 00:04:25,480 The upcoming James Webb Space Telescope will take this technology to the next level. 47 00:04:26,660 --> 00:04:32,880 James Webb will observe the universe at infrared wavelengths with unprecedented sensitivity. 48 00:04:33,960 --> 00:04:38,080 This is especially advantageous for studying exoplanets 49 00:04:38,780 --> 00:04:44,800 because molecules in exoplanet atmospheres leave most clues in the infrared range. 50 00:04:47,360 --> 00:04:52,100 Specifically, these wavelengths could help us find habitable planets. 51 00:04:52,680 --> 00:05:00,320 Planets with the right conditions to sustain liquid water emit heat radiation that peaks in the infrared. 52 00:05:02,140 --> 00:05:09,260 James Webb's sensitivity to these crucial wavelengths is bound to uncover more secrets of exoplanets 53 00:05:09,500 --> 00:05:13,900 and might even find life elsewhere in the Universe. 54 00:05:15,660 --> 00:05:18,040 This Hubblecast script was translated by Bethany Downer.