1 00:00:00,000 --> 00:00:03,000 Astronomers using the NASA/ESA Hubble Space Telescope 2 00:00:03,000 --> 00:00:08,000 have seen dramatic changes in the atmosphere of a faraway planet. 3 00:00:08,000 --> 00:00:11,000 Just after a violent stellar flare bathed it 4 00:00:11,000 --> 00:00:14,000 in intense X-ray radiation 5 00:00:14,000 --> 00:00:19,000 the scientists detected the planet’s atmosphere furiously evaporating away. 6 00:00:19,000 --> 00:00:25,000 These violent events 63 light-years from Earth have given astronomers 7 00:00:25,000 --> 00:00:29,000 their first ever glimpse of the changing weather and climate 8 00:00:29,000 --> 00:00:32,000 on a planet outside our own Solar System. 9 00:00:39,000 --> 00:00:45,000 Brought to you by the European Space Agency and NASA 10 00:00:49,000 --> 00:00:52,000 Hubblecast episode 56: Dramatic change spotted on a faraway planet 11 00:00:57,000 --> 00:01:00,000 Presented by Dr J, aka Dr Joe Liske 12 00:01:02,000 --> 00:01:09,000 Planet HD 189733b has a blue sky, but that’s where the similarities with Earth end. 13 00:01:09,000 --> 00:01:15,000 It’s a huge gas giant similar to Jupiter, but it lies extremely close to its star 14 00:01:15,000 --> 00:01:19,000 much closer than any planet in the Solar System lies to the Sun. 15 00:01:19,000 --> 00:01:26,000 This makes its climate exceptionally hot, with temperatures exceeding 1000ºC. 16 00:01:29,000 --> 00:01:34,000 A team of scientists used Hubble to observe the planet in 2010 17 00:01:34,000 --> 00:01:39,000 and again in 2011, as it was silhouetted against its parent star. 18 00:01:39,000 --> 00:01:44,000 While backlit in this way, a planet’s atmosphere imprints its signature 19 00:01:44,000 --> 00:01:48,000 on the starlight, allowing astronomers to decode what is happening 20 00:01:48,000 --> 00:01:53,000 on scales that would be far too tiny to image directly. 21 00:01:55,000 --> 00:01:59,000 The first set of observations actually… didn’t show much at all. 22 00:01:59,000 --> 00:02:03,000 The scientists had hoped to confirm what they had seen once before 23 00:02:03,000 --> 00:02:04,000 on another planet 24 00:02:04,000 --> 00:02:08,000 the upper layers of the atmosphere gradually boiling off 25 00:02:08,000 --> 00:02:10,000 under the intense assault of the starlight. 26 00:02:10,000 --> 00:02:15,000 But Hubble’s first observations of HD 189733b 27 00:02:15,000 --> 00:02:19,000 showed no trace of the atmosphere escaping. 28 00:02:20,000 --> 00:02:23,000 But if the first set of observations was pretty boring, 29 00:02:23,000 --> 00:02:26,000 the second set was anything but. 30 00:02:26,000 --> 00:02:30,000 Just before they began to observe with Hubble for the second time, 31 00:02:30,000 --> 00:02:35,000 the Swift satellite detected a huge flare coming from the surface of the star 32 00:02:35,000 --> 00:02:40,000 giving off powerful radiation including atmosphere-frying X-rays. 33 00:02:40,000 --> 00:02:44,000 This was like a more violent version of the solar flares 34 00:02:44,000 --> 00:02:47,000 that disrupt communication satellites here on Earth. 35 00:02:47,000 --> 00:02:53,000 When the planet slid into view a few hours later, the changes were startling. 36 00:02:53,000 --> 00:02:57,000 Where they had seen a slumbering planet in 2010 37 00:02:57,000 --> 00:03:03,000 they saw its atmosphere furiously boiling away in 2011. 38 00:03:03,000 --> 00:03:05,000 A plume of gas was evaporating off the planet 39 00:03:05,000 --> 00:03:11,000 which was losing at least 1000 tonnes of gas from its atmosphere every second. 40 00:03:11,000 --> 00:03:14,000 The team believes that the spike in X-rays from the flare 41 00:03:14,000 --> 00:03:18,000 can probably explain the atmospheric evaporation spotted with Hubble. 42 00:03:18,000 --> 00:03:22,000 This type of radiation has enough energy to accelerate 43 00:03:22,000 --> 00:03:26,000 the particles in the atmosphere, which would drive them off the planet. 44 00:03:28,000 --> 00:03:32,000 There are other intriguing possibilities, though, 45 00:03:32,000 --> 00:03:34,000 which are all linked to the star’s activity. 46 00:03:36,000 --> 00:03:42,000 For example it might be gradual seasonal variations in X-rays from the star 47 00:03:42,000 --> 00:03:44,000 rather than the sudden effect of the flare 48 00:03:44,000 --> 00:03:49,000 which drove the change between 2010 and 2011. 49 00:03:49,000 --> 00:03:53,000 This would be similar to the Sun’s 11-year sunspot cycle. 50 00:03:57,000 --> 00:03:59,000 The team have fresh observations planned with Hubble 51 00:03:59,000 --> 00:04:03,000 Hubble and ESA’s XMM-Newton X-ray space telescope 52 00:04:03,000 --> 00:04:08,000 to help nail down exactly what triggered the atmosphere’s evaporation. 53 00:04:10,000 --> 00:04:14,000 But regardless of the cause, this is the first time ever scientists have observed 54 00:04:14,000 --> 00:04:17,000 a clear change in an exoplanet’s atmosphere. 55 00:04:25,000 --> 00:04:30,000 Transcribed by ESA/Hubble