1 00:00:00,010 --> 00:00:04,010 [Music] 2 00:00:04,030 --> 00:00:08,040 [Music] 3 00:00:08,060 --> 00:00:12,050 [Music] Narrator: Eta Carinae 4 00:00:12,070 --> 00:00:16,080 is the most massive star within 10,000 light-years. 5 00:00:16,100 --> 00:00:20,130 In the mid-nineteenth century, a tremendous eruption hurled 6 00:00:20,150 --> 00:00:24,150 enough gas into space to make at least 10 copies of the sun, creating 7 00:00:24,170 --> 00:00:28,180 an expanding nebula still visible today. New results from 8 00:00:28,200 --> 00:00:32,250 NASA satellites, ground-based telescopes, and theoretical models are 9 00:00:32,270 --> 00:00:36,260 providing astronomers with an improved understanding of the system. 10 00:00:36,280 --> 00:00:40,280 At the nebula's heart lie two giant stars. The smaller of the two 11 00:00:40,300 --> 00:00:44,340 is 30 times the mass of the sun and a million times brighter. 12 00:00:44,360 --> 00:00:48,360 The primary weighs 90 suns and shines 5 times brighter than 13 00:00:48,380 --> 00:00:52,400 its companion. Both stars produce powerful outflows called 14 00:00:52,420 --> 00:00:56,470 stellar winds, but the primary's is so dense it prevents astronomers 15 00:00:56,490 --> 00:01:00,500 from directly observing the star. The secondary's orbit 16 00:01:00,520 --> 00:01:04,520 is among the most eccentric known. Every five and a half years, when the 17 00:01:04,540 --> 00:01:08,530 two stars swing toward closest approach, or periastron, the come about 18 00:01:08,550 --> 00:01:12,550 as close to each other as Mars is from the sun. 19 00:01:12,570 --> 00:01:16,560 Eta Carinae's most recent periastron occurred in August 2014, 20 00:01:16,580 --> 00:01:20,590 and many of NASA's space-based telescopes, as well as ground-based 21 00:01:20,610 --> 00:01:24,620 observatories, looked on. Where the stellar winds collide, 22 00:01:24,640 --> 00:01:28,640 temperatures reach hundreds of degrees - hot enough to emit 23 00:01:28,660 --> 00:01:32,680 X-rays. But the X-ray emission shuts down near periastron, 24 00:01:32,700 --> 00:01:36,720 when the smaller star is swallowed up by the dense wind of its larger companion. 25 00:01:36,740 --> 00:01:40,730 The X-rays gradually recover after periastron, 26 00:01:40,750 --> 00:01:44,760 but they do so a bit differently each time, suggesting structural 27 00:01:44,780 --> 00:01:48,790 changes in the dueling winds. Recent observations have 28 00:01:48,810 --> 00:01:52,840 helped theorists refine computer models of this interaction. Here, 29 00:01:52,860 --> 00:01:56,860 darker colors indicate lower gas densities around the stars, 30 00:01:56,880 --> 00:02:00,880 while the stars themselves appear as black circles. When the stars are 31 00:02:00,900 --> 00:02:04,940 far apart, the winds collide head-on, creating a huge cavity 32 00:02:04,960 --> 00:02:08,950 surrounded by 50-million-degree gas. But near periastron, 33 00:02:08,970 --> 00:02:12,990 the secondary whips around the larger star, carving a tunnel though the primary's 34 00:02:13,010 --> 00:02:17,050 dense wind. The secondary star's rapid motion changes the 35 00:02:17,070 --> 00:02:21,070 collision zone from head...to tail. The smaller star's 36 00:02:21,090 --> 00:02:25,100 faster wind flows out along the cavity it created and then crashes into the 37 00:02:25,120 --> 00:02:29,150 outward-moving wind of its companion. From out perspective on Earth, 38 00:02:29,170 --> 00:02:33,170 the X-rays fade, then recover, as the stars move apart. 39 00:02:33,190 --> 00:02:37,210 New 3-D models of these simulations reveal the formation 40 00:02:37,230 --> 00:02:41,320 of finger-like protrusions along the cavity near periastron, 41 00:02:41,340 --> 00:02:45,370 features never before identified. Theorists now investigating 42 00:02:45,390 --> 00:02:49,430 the phenomenon suggest they may arise from instabilities developing in gas as 43 00:02:49,450 --> 00:02:53,510 it flows along the cavity wall. Astronomers also 44 00:02:53,530 --> 00:02:57,530 keep an eye on Eta Carinae with the Hubble Space Telescope. 45 00:02:57,550 --> 00:03:01,560 These images show a structure resembling a crab, formed by gas 46 00:03:01,580 --> 00:03:05,590 excited by the secondary star's intense UV light. 47 00:03:05,610 --> 00:03:09,610 This light dims near periastron, when the secondary passes through the thickest part of 48 00:03:09,630 --> 00:03:13,640 the primary's wind. The gas relaxes, settling into a lower-energy state. 49 00:03:13,660 --> 00:03:17,680 As a result, the crab appears in a different 50 00:03:17,700 --> 00:03:21,720 spectral line until the stars move apart and the UV light is restored. 51 00:03:21,740 --> 00:03:25,750 Eta Carinae is one of the closest and most 52 00:03:25,770 --> 00:03:29,790 massive colliding-wind binaries, and serves as a natural laboratory for 53 00:03:29,810 --> 00:03:33,860 studying these rare and important objects. While its past 54 00:03:33,880 --> 00:03:37,870 eruptions remain unexplained, astronomers think they have a handle on its current 55 00:03:37,890 --> 00:03:41,910 state--a claim to be tested at the next periastron in February 56 00:03:41,930 --> 00:03:45,960 2020. [Music] 57 00:03:45,980 --> 00:03:49,990 [Beeping] 58 00:03:50,010 --> 00:04:00,120 [Beeping]