1 00:00:02,000 --> 00:00:06,000 Space is a pretty violent place, 2 00:00:06,000 --> 00:00:14,000 full of characters like monster black holes, colliding galaxies and exploding stars 3 00:00:14,000 --> 00:00:19,000 However, sometimes these bullies are more elusive. 4 00:00:20,000 --> 00:00:25,000 Take this new Hubble image of ESO 137-001. 5 00:00:25,000 --> 00:00:35,000 Bright blue streaks are being ripped away from the galaxy — but where is the cosmic culprit? 6 00:00:52,000 --> 00:00:57,000 Episode 72: Clues to a cosmic crime 7 00:00:57,000 --> 00:01:03,000 Presented by Dr. J, aka Dr Joe Liske 8 00:01:05,000 --> 00:01:08,000 Hello, and welcome to another episode of the Hubblecast! 9 00:01:08,000 --> 00:01:13,000 Now galaxies exist in a range of different environments. 10 00:01:13,000 --> 00:01:15,000 Some live their lives in isolation, 11 00:01:15,000 --> 00:01:23,000 while others clump together to form groups and even clusters of galaxies — large gatherings bound together by gravity. 12 00:01:23,000 --> 00:01:31,000 The subject of this new Hubble image is a spiral galaxy called ESO 137-001. 13 00:01:31,000 --> 00:01:38,000 It is travelling through one of these clusters, the Norma cluster, and it’s a journey that will change it forever. 14 00:01:40,000 --> 00:01:45,000 As the intrepid spiral ploughs onwards through this cluster, 15 00:01:45,000 --> 00:01:52,000 it encounters a severe drag, a force felt by any object moving through a fluid. 16 00:01:52,000 --> 00:01:58,000 In this case, the fluid is superheated gas, which lurks within galaxy clusters. 17 00:01:58,000 --> 00:02:03,000 The stars in the galaxy aren’t much bothered by this drag, 18 00:02:03,000 --> 00:02:14,000 but gas is stripped away, creating tattered threads and electric blue jellyfish tendrils, as seen in this new image. 19 00:02:18,000 --> 00:02:22,000 This process is known as ram pressure stripping. 20 00:02:22,000 --> 00:02:24,000 Here’s a rough and ready analogy 21 00:02:24,000 --> 00:02:31,000 it’s a little bit as if the galaxy had leaned out of the window of a car that is travelling down a motorway at very high speed, 22 00:02:31,000 --> 00:02:34,000 and wisps of gas are being torn away by the headwind. 23 00:02:41,000 --> 00:02:46,000 Hubble has spotted a number of other galaxies that undergo this violent stripping 24 00:02:46,000 --> 00:02:51,000 for example, the “comet galaxy”, which looks like a spiral galaxy with a knotty tail, 25 00:02:51,000 --> 00:02:59,000 or the mangled cosmic duo NGC 4402 and 4522. 26 00:03:04,000 --> 00:03:12,000 Streams of murky dust are also being pulled away from ESO 137-001, 27 00:03:12,000 --> 00:03:17,000 visible as the dark brown tangled region around the galaxy’s centre. 28 00:03:17,000 --> 00:03:23,000 This image also shows other telltale signs of this process, 29 00:03:23,000 --> 00:03:27,000 such as the curved appearance of the galaxy’s disc — 30 00:03:27,000 --> 00:03:30,000 a result of the forces exerted by the heated gas. 31 00:03:36,000 --> 00:03:44,000 When these Hubble observations are combined with X-ray images from the Chandra X-ray Observatory, 32 00:03:44,000 --> 00:03:51,000 a bright, extended fog can be seen enveloping the galaxy and streaming off into space. 33 00:03:51,000 --> 00:04:00,000 These X-ray tails are formed from the cool gas stripped from ESO 137-001, 34 00:04:00,000 --> 00:04:07,000 which has since been heated to many millions of degrees Celsius by the hot gas in the cluster. 35 00:04:09,000 --> 00:04:15,000 Studying ram pressure stripping helps astronomers to better understand how galaxies evolve. 36 00:04:15,000 --> 00:04:21,000 ESO 137-001’s trip through the Norma cluster will leave it with very little gas, 37 00:04:21,000 --> 00:04:25,000 rendering it pretty much incapable of forming any new stars. 38 00:04:25,000 --> 00:04:33,000 And that is precisely one of the things that you have to do in order to transform spiral galaxies into elliptical galaxies, 39 00:04:33,000 --> 00:04:36,000 which are typically found in galaxy clusters. 40 00:04:37,000 --> 00:04:44,000 This is Dr. J, signing off for the Hubblecast. Once again, nature has surprised us beyond our wildest imagination. 41 00:04:47,000 --> 00:04:50,000 Hubblecast is produced by ESA/Hubble at the European Southern Observatory in Germany. 42 00:04:50,000 --> 00:04:54,000 The Hubble mission is a project of international cooperation between NASA and the European Space Agency. 43 00:04:55,000 --> 00:04:59,000 www.spacetelescope.org 44 00:05:02,000 --> 00:05:04,000 Transcribed by ESA/Hubble. Translation --