1 00:00:00,010 --> 00:00:04,010 Narrator: In 2011, NASA's Swift satellite 2 00:00:04,030 --> 00:00:08,040 caught an X-ray outburst from a small galaxy 3 00:00:08,060 --> 00:00:12,060 3.8 billion light-years away. Within a couple of days, researchers realized 4 00:00:12,080 --> 00:00:16,130 they were witnessing the aftermath of a tidal disruption event--a star 5 00:00:16,150 --> 00:00:20,180 ripped apart by the monster black hole at the galaxy's center. 6 00:00:20,200 --> 00:00:24,210 Some of the stellar material fell toward the black hole, forming 7 00:00:24,230 --> 00:00:28,260 an accretion disk and a jet pointed in our direction. 8 00:00:28,280 --> 00:00:32,320 Erin Kara: Tidal disruption events offer us this rare view 9 00:00:32,340 --> 00:00:36,420 at the most common kind of supermassive black hole in the universe, these so-called 10 00:00:36,440 --> 00:00:40,550 dormant supermassive black holes. Ninety percent of black holes 11 00:00:40,570 --> 00:00:44,690 in the universe don't have a lot of hot material orbiting around 12 00:00:44,710 --> 00:00:48,850 them, they don't form these accretion disks, and so we can't observe 13 00:00:48,870 --> 00:00:52,890 them. Tidal disruption events, where the stellar debris 14 00:00:52,910 --> 00:00:56,930 causes the formation of a temporary accretion disk, offers 15 00:00:56,950 --> 00:01:00,960 us a way to probe this probe this population of supermassive black holes. 16 00:01:00,980 --> 00:01:05,010 Narrator: Swift monitored the outburst's progress and was joined 17 00:01:05,030 --> 00:01:09,040 by the European Space Agency's XMM-Newton observatory, 18 00:01:09,060 --> 00:01:13,090 and the Japanese Suzaku satellite. Recently, 19 00:01:13,110 --> 00:01:17,210 astronomers introduced a new analysis technique that for the first time allows 20 00:01:17,230 --> 00:01:21,350 them to peer deep into the gravitational well of a normally quiescent black hole. 21 00:01:21,370 --> 00:01:25,450 Called X-ray reverberation mapping, the 22 00:01:25,470 --> 00:01:29,530 method charts the region close to the black hole using light echoes from X-ray flashes, 23 00:01:29,550 --> 00:01:33,630 similar to the way sonar uses sound to map the ocean floor. 24 00:01:33,650 --> 00:01:37,650 Erin: X-ray reverberation mapping has been 25 00:01:37,670 --> 00:01:41,690 very successful at probing the accretion flow in 26 00:01:41,710 --> 00:01:45,720 well-established accretion disk structures, but had never been used 27 00:01:45,740 --> 00:01:49,790 to look at tidal disruption events. My collaborator at the 28 00:01:49,810 --> 00:01:53,840 University of Maryland and I were having lunch one day, and she says 29 00:01:53,860 --> 00:01:57,900 "Has anyone ever looked at tidal disruption events with X-ray 30 00:01:57,920 --> 00:02:01,990 reverberation mapping?" That night I stayed late at the office and 31 00:02:02,010 --> 00:02:06,070 just tried it out on this data from Swift J1644 32 00:02:06,090 --> 00:02:10,180 and much to my surprise the result was 33 00:02:10,200 --> 00:02:14,310 amazing and I could see that we were looking at 34 00:02:14,330 --> 00:02:18,460 the structure of the inner accretion flow around a normally 35 00:02:18,480 --> 00:02:22,530 dormant black hole for the first time. It's not like a normal accretion flow 36 00:02:22,550 --> 00:02:26,600 in an active galaxy that's a flat disk, this is 37 00:02:26,620 --> 00:02:30,710 something that is extremely puffy, very turbulent, and 38 00:02:30,730 --> 00:02:34,830 we are measuring flashes of X-ray emission deep within this 39 00:02:34,850 --> 00:02:38,930 newly formed accretion disk. Narrator: Stellar 40 00:02:38,950 --> 00:02:43,070 material streamed into the developing disk, churning it into a thick, chaotic 41 00:02:43,090 --> 00:02:47,250 whirlpool of X-ray emitting gas, funneling toward the central black hole. 42 00:02:47,270 --> 00:02:51,440 Deep inside this cavity, multiple X-ray flares 43 00:02:51,460 --> 00:02:55,500 erupted, providing a flash that echoed throughout the region. 44 00:02:55,520 --> 00:02:59,580 Erin: Previously, astronomers had thought that the X-ray emission 45 00:02:59,600 --> 00:03:03,640 is coming from far out in a jet, but we're finding 46 00:03:03,660 --> 00:03:07,750 with these observations is that the X-ray emission is coming from 47 00:03:07,770 --> 00:03:11,880 flares very close to the supermassive black hole. And we can 48 00:03:11,900 --> 00:03:16,030 use these observations to probe properties of the black hole 49 00:03:16,050 --> 00:03:20,230 itself. For instance, we found that the mass of the black hole is something 50 00:03:20,250 --> 00:03:24,410 on the order of a million times the mass of the sun. 51 00:03:24,430 --> 00:03:28,450 Narrator: The first observations of X-ray reverberations from deep inside an 52 00:03:28,470 --> 00:03:32,510 accretion disk are providing new insights into a rarely observed class 53 00:03:32,530 --> 00:03:36,580 of black holes. They're also laying the groundwork for a better 54 00:03:36,600 --> 00:03:40,680 understanding of tidal disruption events, and the black holes they illuminate. 55 00:03:40,700 --> 00:03:44,790 [Music] 56 00:03:44,810 --> 00:03:48,900 [Music] 57 00:03:48,920 --> 00:03:53,010 [Beeping] 58 00:03:53,030 --> 00:03:58,550 [Beeping] 59 00:03:58,570 --> 00:04:04,257 [Beeping]