WEBVTT - Can Galaxies Exist Without Dark Matter? 0:00:01.920 --> 0:00:06.520 Welcome to brain Stuff production of I Heart Radio. Hey 0:00:06.519 --> 0:00:10.079 brain Stuff, Lauren vocal bomb here. Dark matter sounds a 0:00:10.080 --> 0:00:13.039 little mysterious because it is. It's stuff we can't see 0:00:13.080 --> 0:00:15.800 with any existing telescopes, but that math and physics tells 0:00:15.840 --> 0:00:17.799 us must exist based on the way that normal matter, 0:00:17.960 --> 0:00:20.880 the stuff we can see, behaves, and there's a lot 0:00:20.920 --> 0:00:24.799 of dark matter out there. Astrophysicists think that about of 0:00:24.840 --> 0:00:27.479 the universe is made up of dark matter compared with 0:00:27.520 --> 0:00:30.400 only five percent normal matter, meaning that the term normal 0:00:30.520 --> 0:00:34.400 probably isn't the most accurate. Dark matter is the bedrock 0:00:34.440 --> 0:00:36.919 that all galaxies are anchored too. You can't get one 0:00:36.960 --> 0:00:40.360 without the other, or so we thought, until astronomers found 0:00:40.440 --> 0:00:43.560 ghostly galaxy that doesn't appear to contain any dark matter. 0:00:44.000 --> 0:00:45.559 It's as if the universe is playing a trick on 0:00:45.640 --> 0:00:47.400 us by flipping the laws of physics on their head. 0:00:47.760 --> 0:00:51.360 Dark matter should be there, but isn't. It's a game 0:00:51.440 --> 0:00:54.080 change your galaxy, astronomers are saying, and it's like nothing 0:00:54.080 --> 0:00:56.400 we've ever seen before. We may not be able to 0:00:56.440 --> 0:00:59.400 spot dark matter, but astronomers can measure its gravitational effects 0:00:59.440 --> 0:01:02.160 acting on normal matter. For example, they can look at 0:01:02.160 --> 0:01:05.200 how fast stars cruise around a galaxy. When dark matter 0:01:05.280 --> 0:01:08.479 is present, that galaxy's gravity will be bulked up, causing 0:01:08.520 --> 0:01:10.800 its stars to move faster than if just normal matter 0:01:10.840 --> 0:01:13.320 were present. But in the case of n g C 0:01:13.640 --> 0:01:16.760 one oh five two dash DF two, an ultra diffuse 0:01:16.800 --> 0:01:20.240 galaxy located sixty five million light years away, astronomers have 0:01:20.240 --> 0:01:22.280 found that its stars are moving in exactly the way 0:01:22.280 --> 0:01:24.440 that would be predicted if only the total mass of 0:01:24.440 --> 0:01:27.399 all the visible stuff is considered. In other words, dark 0:01:27.400 --> 0:01:29.760 matter doesn't seem to be exerting its gravity on normal 0:01:29.760 --> 0:01:34.600 matter in that galaxy, and that's weird, Peter Van Dulkum 0:01:34.680 --> 0:01:37.640 of Yale University said in a statement, finding a galaxy 0:01:37.680 --> 0:01:41.600 without dark matter is unexpected because this invisible, mysterious substance 0:01:41.680 --> 0:01:44.720 is the most dominant aspect of any galaxy. For decades, 0:01:44.760 --> 0:01:46.840 we thought the galaxies start their lives as blobs of 0:01:46.920 --> 0:01:50.600 dark matter. After that everything else happens. Gas falls into 0:01:50.640 --> 0:01:53.280 the dark matter halo's the gas turns into stars. They 0:01:53.320 --> 0:01:55.560 slowly build up. Then you end up with galaxies like 0:01:55.600 --> 0:01:58.920 the Milky Way. This galaxy challenges the standard ideas of 0:01:58.920 --> 0:02:03.400 how we think galaxies form. Ultra diffuse galaxies are oddities 0:02:03.400 --> 0:02:06.280 in their own right, having only been discovered in as 0:02:06.360 --> 0:02:09.480 they are very difficult to detect. However, it appears that 0:02:09.560 --> 0:02:12.000 this class of galaxy is common, but none are like 0:02:12.120 --> 0:02:15.160 the one in question. The galaxy was discovered using the 0:02:15.200 --> 0:02:18.440 Dragonfly Telephoto Array, a telescope in New Mexico that's custom 0:02:18.480 --> 0:02:21.440 made to seek out these elusive targets. Then, using a 0:02:21.440 --> 0:02:24.600 set of twin ten meter optical and infrared telescopes in Hawaii, 0:02:24.800 --> 0:02:28.680 the astronomers signaled out ten bright globular clusters, which are large, 0:02:28.680 --> 0:02:32.000 compact groups of stars orbiting the galaxy's core. They then 0:02:32.080 --> 0:02:35.240 use spectral data to measure their motions. These clusters were 0:02:35.240 --> 0:02:38.040 found to be plotting along more slowly than expected, meaning 0:02:38.080 --> 0:02:40.840 there's far less mass in that galaxy then would be predicted. 0:02:41.200 --> 0:02:43.560 In fact, there's so little mass that the researchers have 0:02:43.639 --> 0:02:46.400 come to the astonishing conclusion that there's little, if any 0:02:46.600 --> 0:02:49.880 dark matter there. Follow Up observations were made with the 0:02:49.880 --> 0:02:53.440 Gemini North Telescope, also in Hawaii, so the galaxy structure 0:02:53.440 --> 0:02:56.680 could be studied. With Gemini's help. The researchers ruled out 0:02:56.720 --> 0:02:59.280 interactions with other galaxies as being the cause of its 0:02:59.280 --> 0:03:03.240 weird dark matter deficit, Ben Docom said in the press release, 0:03:03.480 --> 0:03:05.680 if there's any dark matter at all, it's very little. 0:03:05.960 --> 0:03:07.880 The stars in the galaxy can account for all of 0:03:07.919 --> 0:03:10.079 the mass, and there doesn't seem to be any room 0:03:10.120 --> 0:03:13.959 for dark matter. This finding seems to suggest the dark 0:03:13.960 --> 0:03:16.920 matter has quote its own separate existence apart from other 0:03:16.960 --> 0:03:20.440 components of galaxies. He added, and this makes the very 0:03:20.480 --> 0:03:23.040 existence of this galaxy and mystery. If it has no 0:03:23.160 --> 0:03:27.040 dark matter, how did even evolve into a galaxy. In 0:03:27.080 --> 0:03:29.600 their study published in March in the journal Nature, Ben 0:03:29.680 --> 0:03:32.680 Ducom's team speculates that some cataclysmic event in the galaxy 0:03:32.840 --> 0:03:35.080 may have cleared out all the dark matter and blasted 0:03:35.120 --> 0:03:39.120 away all the star forming gases. Alternatively, a nearby massive 0:03:39.120 --> 0:03:41.520 elliptical galaxy may have played a role in the current 0:03:41.520 --> 0:03:44.200 galaxies lack of dark matter billions of years ago when 0:03:44.200 --> 0:03:48.200 it was undergoing its early and violent stages of evolution. Now, 0:03:48.240 --> 0:03:51.280 the researchers are pouring over Hubble space telescopes observations of 0:03:51.320 --> 0:03:54.400 similar galaxies to perhaps find more that lack dark matter. 0:03:55.000 --> 0:03:57.880 If they find more, then altered, diffuse, and faint galaxies 0:03:57.960 --> 0:04:00.040 might be the norm when dark matter isn't press it, 0:04:00.560 --> 0:04:03.040 and that's a fascinating development in our understanding of how 0:04:03.080 --> 0:04:07.800 galaxies evolve. Ben Docom concluded, every galaxy we do about 0:04:07.840 --> 0:04:10.560 before has dark matter, and they all fall in familiar 0:04:10.600 --> 0:04:13.920 categories like spiral or elliptical galaxies. But what would you 0:04:13.920 --> 0:04:16.000 get if there was no dark matter at all? Maybe 0:04:16.040 --> 0:04:23.520 this is what you would get. Today's episode was written 0:04:23.520 --> 0:04:26.200 by dr Ian O'Neill and produced by Tyler Clang. Brain 0:04:26.240 --> 0:04:28.440 Stuff is a production of iHeart Radio's How Stuff Works. 0:04:28.680 --> 0:04:30.560 For more on this and lots of other dark topics, 0:04:30.680 --> 0:04:33.120 visit our home planet, how stuff Works dot com, and 0:04:33.200 --> 0:04:35.440 for more podcasts from my heart Radio, visit the iHeart 0:04:35.520 --> 0:04:37.919 Radio app, Apple Podcasts, or wherever you listen to your 0:04:37.960 --> 0:04:38.599 favorite shows.