1 00:00:01,500 --> 00:00:07,000 Astronomers have used the Hubble Space Telescope to forecast a future cosmic pile up: 2 00:00:07,200 --> 00:00:11,500 the titanic collision of the Milky Way and the Andromeda galaxy 3 00:00:11,700 --> 00:00:14,500 in about four billion years time. 4 00:00:20,220 --> 00:00:28,230 Brought to you by the European Space Agency and NASA 5 00:00:31,500 --> 00:00:35,000 Hubblecast Episode 55: Crash of the Titans 6 00:00:38,000 --> 00:00:41,000 Presented by Dr J, aka Dr Joe Liske 7 00:00:44,000 --> 00:00:48,500 The Andromeda Galaxy, some 2.2 million light-years away, 8 00:00:48,700 --> 00:00:52,500 is the closest spiral galaxy to our home, the Milky Way. 9 00:00:53,000 --> 00:00:57,000 For around a century, astronomers have known that it's moving towards us, 10 00:00:57,200 --> 00:01:00,500 but whether or not the two galaxies would actually collide, 11 00:01:00,700 --> 00:01:03,500 or simply fly past each other, remained unclear. 12 00:01:04,000 --> 00:01:09,500 Now, a team of astronomers has used the Hubble Space Telescope to shed light on this question, 13 00:01:09,700 --> 00:01:13,000 by looking at the motion of stars in the Andromeda Galaxy. 14 00:01:14,500 --> 00:01:18,000 We wanted to figure out how Andromeda was moving through space. 15 00:01:18,200 --> 00:01:22,500 So in order to do that we measured the location of the Andromeda stars 16 00:01:22,700 --> 00:01:24,500 relative to the background galaxies. 17 00:01:24,700 --> 00:01:29,500 In 2002 they were in one place, and in 2010 they were in a slightly different place. 18 00:01:29,700 --> 00:01:33,700 And that allowed us to measure the motion over a period of eight years. 19 00:01:37,000 --> 00:01:41,500 The motion is actually incredibly subtle, and not obvious to the human eye, 20 00:01:41,700 --> 00:01:44,000 even when looking at Hubble’s sharp images. 21 00:01:44,200 --> 00:01:48,500 However, sophisticated image analysis revealed tiny movements 22 00:01:48,700 --> 00:01:52,000 that the scientists were able to project into the future. 23 00:01:58,000 --> 00:02:02,000 Based on these findings, it is finally possible to show 24 00:02:02,200 --> 00:02:05,700 what will happen to the Milky Way over the next eight billion years, 25 00:02:05,780 --> 00:02:07,850 as the galaxies drift closer, 26 00:02:15,000 --> 00:02:16,300 and then collide 27 00:02:16,500 --> 00:02:22,000 and gradually merge into a single, larger, elliptical galaxy with reddish stars. 28 00:02:23,500 --> 00:02:28,000 And yet the Solar System should in fact survive this huge crash. 29 00:02:30,000 --> 00:02:35,000 The reason we think that our Solar System will not be much affected by this collision 30 00:02:35,200 --> 00:02:41,000 between the Milky Way and Andromeda is that galaxies are actually mostly empty space. 31 00:02:41,200 --> 00:02:44,500 Even though our galaxy, as well as the Andromeda Galaxy, 32 00:02:44,500 --> 00:02:47,000 has a hundred billion stars in it, they are very far apart. 33 00:02:47,200 --> 00:02:50,500 So if two galaxies actually collide with each other, 34 00:02:50,700 --> 00:02:53,500 the stars basically pass right between each other 35 00:02:53,700 --> 00:02:57,500 and the chance of two stars directly hitting each other is really, really small. 36 00:02:57,700 --> 00:03:03,500 So the likelihood that our Solar System will be directly impacted by another star, 37 00:03:03,700 --> 00:03:07,000 for example, in Andromeda as we collide with it is really, really small. 38 00:03:07,200 --> 00:03:13,000 Well, if life is still present on Earth when this happens, the changes in the sky will be quite spectacular. 39 00:03:13,200 --> 00:03:18,500 Now they will be very very slow because the timescales on the scales of galaxies in the Universe 40 00:03:18,700 --> 00:03:20,000 are very very long. 41 00:03:20,200 --> 00:03:25,500 So you have to think, millions of years but even then over these timescales over millions of years, 42 00:03:25,700 --> 00:03:27,500 people will see big changes. 43 00:03:28,000 --> 00:03:31,500 If we wait a few billion years, Andromeda will be huge on the sky. 44 00:03:31,700 --> 00:03:35,000 It will be as big as our Milky Way because we’ll be very close to it. 45 00:03:35,200 --> 00:03:38,500 And then later, when the galaxies merge, 46 00:03:38,700 --> 00:03:43,000 the merged remnant of the Milky Way Galaxy and Andromeda 47 00:03:43,000 --> 00:03:46,000 will look more like an elliptical galaxy and we’ll be sitting right in it. 48 00:03:46,200 --> 00:03:51,000 So the view of the Milky Way on the night sky will be completely gone and 49 00:03:51,200 --> 00:03:56,700 this band of light will be replaced by a more spheroidal distribution of light. 50 00:04:00,000 --> 00:04:04,500 And so, the Sun, born in the Milky Way almost 5 billion years ago 51 00:04:04,700 --> 00:04:09,500 will end its life in a new orbit, as part of a new galaxy. 52 00:04:12,700 --> 00:04:16,829 Hubblecast is produced by ESA/Hubble at the European Southern Observatory in Germany. 53 00:04:17,730 --> 00:04:22,060 The Hubble mission is a project of international cooperation between NASA and the European Space Agency. 54 00:04:22,900 --> 00:04:27,220 Transcribed by ESA/Hubble. Translated by — 55 00:04:30,550 --> 00:04:32,560 Stay in touch with Hubble Space Telescope 56 00:04:34,750 --> 00:04:39,300 Hubble Top100: Best astronomical images from the Hubble Space Telescope on the iPad 57 00:04:40,080 --> 00:04:42,460 Don't miss 58 00:04:46,320 --> 00:04:50,420 Now that you've caught up with Hubble, make sure to get the latest from the ground too! 59 00:04:50,870 --> 00:04:55,580 The ESOcast highlights the best of the European Southern Observatory and its powerful telescopes, 60 00:04:56,060 --> 00:04:58,810 that observe from high in the Chilean Andes, 61 00:04:58,910 --> 00:05:03,390 at the southern hemisphere's best known sites for astronomical observations.