1 00:00:01,000 --> 00:00:04,000 You’re looking at the night sky in another galaxy. 2 00:00:04,000 --> 00:00:08,500 Hubble’s observations of Messier 31, the Andromeda Galaxy, 3 00:00:08,700 --> 00:00:11,000 show unprecedented detail. 4 00:00:11,300 --> 00:00:15,000 Most of the stars in this image are outside the Milky Way 5 00:00:15,200 --> 00:00:18,000 and lie over two million light-years away. 6 00:00:18,200 --> 00:00:21,500 Its one of the deepest, most detailed images 7 00:00:21,700 --> 00:00:25,000 ever made of a galaxy outside our own. 8 00:00:41,000 --> 00:00:44,000 Episode 48: Deep Observations of the Andromeda Galaxy 9 00:00:47,000 --> 00:00:51,000 Presented by Dr J, aka Dr Joe Liske 10 00:00:53,000 --> 00:00:56,000 Hello and welcome to another episode of the Hubblecast. 11 00:00:56,300 --> 00:00:59,500 Now, astronomers have observed millions and millions of galaxies 12 00:00:59,700 --> 00:01:03,500 across the night sky, but only a tiny fraction of them, 13 00:01:03,700 --> 00:01:07,500 only a few tens, are actually close enough to us that 14 00:01:07,700 --> 00:01:10,500 we can distinguish the individual stars that they are made of. 15 00:01:10,700 --> 00:01:15,500 And that’s what makes this small group of galaxies kind of special for us astronomers. 16 00:01:18,000 --> 00:01:21,000 The Andromeda Galaxy is one of this group. 17 00:01:21,300 --> 00:01:24,500 It is nearer to Earth than any other spiral galaxy, 18 00:01:24,700 --> 00:01:28,000 which means that we have a particularly good view of it. 19 00:01:28,300 --> 00:01:32,500 In fact, the Andromeda Galaxy is the one of the largest objects in the night sky 20 00:01:32,700 --> 00:01:37,000 several times bigger than the full Moon, although of course it’s much fainter. 21 00:01:39,000 --> 00:01:43,500 The relative proximity of the galaxy and the unparalleled quality of Hubble’s images, 22 00:01:43,700 --> 00:01:47,000 thanks to its position above the atmosphere, 23 00:01:47,200 --> 00:01:51,500 combine to give astronomers a unique view right into another galaxy. 24 00:01:57,000 --> 00:02:00,000 Far from being a dense, opaque object, 25 00:02:00,200 --> 00:02:04,000 Hubble’s observations of the Andromeda Galaxy remind us that one of 26 00:02:04,200 --> 00:02:07,000 the dominant features of a galaxy is actually 27 00:02:07,000 --> 00:02:09,000 the huge distances between its stars. 28 00:02:09,200 --> 00:02:13,500 And in these huge gaps we can see right through the Andromeda Galaxy 29 00:02:13,700 --> 00:02:16,500 to the far more distant galaxies in the background. 30 00:02:23,000 --> 00:02:27,000 This observation was made in the Andromeda Galaxy’s halo, 31 00:02:27,200 --> 00:02:31,500 the huge sphere of stars and invisible dark matter that surrounds the galaxy. 32 00:02:32,000 --> 00:02:36,000 Although Hubble is able to spot many thousands of stars here, 33 00:02:36,200 --> 00:02:40,000 this part of the galaxy is in fact very sparsely populated 34 00:02:40,200 --> 00:02:43,500 and so many background galaxies are visible. 35 00:02:47,000 --> 00:02:51,500 This giant stellar stream, is noticeably denser than the rest of the halo. 36 00:02:51,700 --> 00:02:55,000 This swathe of stars was left behind by a dwarf galaxy 37 00:02:55,200 --> 00:02:58,000 that was swallowed by Andromeda. 38 00:03:14,500 --> 00:03:18,500 But the most crowded of these observations is in the galaxy’s disc — 39 00:03:18,700 --> 00:03:22,000 that’s the part that includes the distinctive spiral arms, 40 00:03:22,200 --> 00:03:25,500 as well as the dimmer and less numerous stars in the gaps between them. 41 00:03:30,500 --> 00:03:35,000 Busy as these images look, we’re only in the outskirts of the Andromeda galaxy here. 42 00:03:35,200 --> 00:03:39,000 That’s because these observations were made in order to study 43 00:03:39,200 --> 00:03:43,500 a particular type of variable star that is common in the outer reaches of galaxies. 44 00:03:47,500 --> 00:03:50,500 To the naked eye, the Andromeda Galaxy is just a huge, 45 00:03:50,700 --> 00:03:52,500 grey, faint patch in the sky. 46 00:03:52,700 --> 00:03:56,000 But the Hubble’s observations reveal an entirely different perspective, 47 00:03:56,200 --> 00:04:01,000 where the ethereal shape of the galaxy is resolved into individual stars. 48 00:04:01,200 --> 00:04:04,500 This is Dr J signing off for the Hubblecast. 49 00:04:04,500 --> 00:04:08,000 Once again, nature has surprised us beyond our wildest imagination. 50 00:04:10,000 --> 00:04:13,000 Transcribed by ESA/Hubble 51 00:04:16,000 --> 00:04:17,500 The Hubble mission is a project of international cooperation 52 00:04:17,700 --> 00:04:19,500 between NASA and the European Space Agency.