1 00:00:12,090 --> 00:00:04,030 [Music] 2 00:00:12,110 --> 00:00:16,120 Narrator: When it comes to finding planets outside our 3 00:00:16,140 --> 00:00:20,170 solar system, no space mission to date can beat NASA's Kepler 4 00:00:20,190 --> 00:00:24,180 in 5 years it has found more than a thousand confirmed exoplanets, 5 00:00:24,200 --> 00:00:28,220 with thousands more awaiting confirmation. Kepler finds 6 00:00:28,240 --> 00:00:32,260 exoplanets by carefully watching starlight, looking for slight dips in 7 00:00:32,280 --> 00:00:36,300 brightness as a planet passes in front of, or transits, its star. This 8 00:00:36,320 --> 00:00:40,340 technique, called time-series transit photometry, is most effective 9 00:00:40,360 --> 00:00:44,370 for large planets in close orbits. This both maximizes the light 10 00:00:44,390 --> 00:00:48,380 loss during a given transit and the number of transits we observe. 11 00:00:48,400 --> 00:00:52,400 But how far can astronomers go with this technique? Can we 12 00:00:52,420 --> 00:00:56,410 find a twin of Earth? Or even identify whether a planet has moons? 13 00:00:56,430 --> 00:01:00,450 With two transit photometry missions on the horizon--NASA's 14 00:01:00,470 --> 00:01:04,490 TESS and ESA's PLATO--some astronomers have examined the limits 15 00:01:04,510 --> 00:01:08,500 of this technique, with surprising results. Daniel Angerhausen: For our study, 16 00:01:08,520 --> 00:01:12,530 Michael Hippke and I combined the knowledge of the 17 00:01:12,550 --> 00:01:16,580 lessons learned from Kepler with what we know about the future missions like 18 00:01:16,600 --> 00:01:20,610 TESS and PLATO, and we asked ourself the question 'what would we be able 19 00:01:20,630 --> 00:01:24,630 to see if we put these observatories outside our solar system and observed 20 00:01:24,650 --> 00:01:28,650 our solar system.' And the results are that we 21 00:01:28,670 --> 00:01:32,670 probably won't be able to see Mars, or Mercury, but 22 00:01:32,690 --> 00:01:36,690 everything else in our solar system we definitely get a solid detection of 23 00:01:36,710 --> 00:01:40,700 Earth, a solid detection of Venus. Also of the outer planets. 24 00:01:40,720 --> 00:01:44,730 We might even be able to see ring structures like the one around 25 00:01:44,750 --> 00:01:48,750 Saturn, and maybe even moons, Jupiter's moons. 26 00:01:48,770 --> 00:01:52,790 Narrator: In another study, they pushed Kepler to the limit by cleverly 27 00:01:52,810 --> 00:01:56,850 combining almost all extrasolar planet data collected by the telescope 28 00:01:56,870 --> 00:02:00,880 using an understanding of orbital mechanics. Daniel: For example, Jupiter 29 00:02:00,900 --> 00:02:04,930 has so-called trojan asteroids that collect in two 30 00:02:04,950 --> 00:02:08,950 specific areas on its orbit, pretty symmetrically to its orbit. 31 00:02:08,970 --> 00:02:12,990 And in the study that we did on the Kepler data, where we added up 32 00:02:13,010 --> 00:02:17,030 all the phase curves of all 4,000 planets in the Kepler data set, we were even 33 00:02:17,050 --> 00:02:21,050 able to see signatures of asteroids in extrasolar 34 00:02:21,070 --> 00:02:25,090 systems. And with the future missions we might even be able to find that 35 00:02:25,110 --> 00:02:29,130 in individual systems and not just by putting all the data together. 36 00:02:29,150 --> 00:02:33,150 We wanted to figure out what the ultimate limit 37 00:02:33,170 --> 00:02:37,200 is that we can do photometry with, and it turns out 38 00:02:37,220 --> 00:02:41,220 with the next generation of instruments we're already hitting the technical limit and are 39 00:02:41,240 --> 00:02:45,260 mostly limited by the variation of the host stars themselves, 40 00:02:45,280 --> 00:02:49,340 by the huge noise that's coming from the host stars. Narrator: The way to push down 41 00:02:49,360 --> 00:02:53,370 this noise is by observing stars for longer periods to improve 42 00:02:53,390 --> 00:02:57,430 models of the star's behavior, allowing astronomers to tease out the smallest transits. 43 00:02:57,450 --> 00:03:01,440 The work of Hippke and Angerhausen shows 44 00:03:01,460 --> 00:03:05,470 that future missions will be able to detect Earth-size planets orbiting 45 00:03:05,490 --> 00:03:09,510 sun-like stars at distances that would allow liquid water. 46 00:03:09,530 --> 00:03:13,530 These systems will become prime targets for more detailed study, using other 47 00:03:13,550 --> 00:03:17,580 missions, such as NASA's James Webb Space Telescope. Will we 48 00:03:17,600 --> 00:03:21,670 find a copy of our solar system? How common are habitable 49 00:03:21,690 --> 00:03:25,700 worlds, and particularly twins of Earth? The thousands of exoplanets 50 00:03:25,720 --> 00:03:29,740 to be discovered by TESS and PLATO will go a long way to providing answers. 51 00:03:29,760 --> 00:03:33,790 [Music][Beeping]