1 00:00:00,000 --> 00:00:04,299 But not so fast. Before a star settles into middle age on 2 00:00:04,299 --> 00:00:09,957 the main sequence, it has to shake off some of its, youthful energy, in 3 00:00:09,957 --> 00:00:14,710 particular, more technically what's going on is that the end of. 4 00:00:14,710 --> 00:00:22,540 Collapse is accompanied by these polar outflows that we saw in the case of L1527 5 00:00:22,540 --> 00:00:28,218 and even more directly columnated High velocity jets of material being 6 00:00:28,218 --> 00:00:32,373 ejected from the poles of the star. So along the axis of its rotation. 7 00:00:32,373 --> 00:00:36,830 It turns out that these fulfill a very important part in the mechanism of 8 00:00:36,830 --> 00:00:41,347 collapse of stellar formation itself, because they carry off excess angular 9 00:00:41,347 --> 00:00:45,985 momentum, allowing material to accrete under the star from the protoplanetary 10 00:00:45,985 --> 00:00:48,634 disc. The exact mechanism that governs their 11 00:00:48,634 --> 00:00:53,453 creation is still being nailed down but we can observe them, we can observe them 12 00:00:53,453 --> 00:00:57,970 because this ejected material plows at high speed into the surrounding gas. 13 00:00:57,970 --> 00:01:02,560 Compressing it and heating it and then as a result, the material glows. 14 00:01:02,560 --> 00:01:07,412 These were first discovered and termed, these objects, these regions of hot 15 00:01:07,412 --> 00:01:10,298 glowing gas were termed Herbig-Haro objects. 16 00:01:10,298 --> 00:01:14,363 I don't know how to pronounce either of those names correctly. 17 00:01:14,363 --> 00:01:19,478 But it was later discovered that they were associated with the formation of a 18 00:01:19,478 --> 00:01:21,839 star. So what were considered as two 19 00:01:21,839 --> 00:01:24,790 Herbig-Haro objects turned out in the middle. 20 00:01:24,790 --> 00:01:30,466 To conceal nassin star these can be 50,000, 100,000 astronomical units away 21 00:01:30,466 --> 00:01:36,198 took awhile to make sense of this and It we've been watching these objects for 22 00:01:36,198 --> 00:01:39,350 long enough now that we can actually produce a. 23 00:01:39,350 --> 00:01:43,185 Sequential year, frame a year of movies of their evolution. 24 00:01:43,185 --> 00:01:48,277 Here's the first Herbig-Haro object over eight years and you can see the jet 25 00:01:48,277 --> 00:01:50,855 expanding. Here's another film of another 26 00:01:50,855 --> 00:01:56,198 Herbig-Haro object and what you see here is that there's a structure to this jet 27 00:01:56,198 --> 00:01:59,908 that's being ejected. It's not a smooth jet, there are these 28 00:01:59,908 --> 00:02:04,309 clumps, they're about the size of the solar system to give you a scale. 29 00:02:04,309 --> 00:02:09,150 And these clumps are supposed to be expected to be regions where 30 00:02:09,150 --> 00:02:13,943 The ejector from one. rapid pulse are plowing into ejections 31 00:02:13,943 --> 00:02:19,611 from a previous pulse which tells you that there is a structure to this eject 32 00:02:19,611 --> 00:02:23,690 this process of ejection it's not completely smooth and 33 00:02:23,690 --> 00:02:29,375 What this causes in the vicinity of the star of course, is these huge stellar 34 00:02:29,375 --> 00:02:34,618 winds that we talked about, stars in this phase are low mass stars. 35 00:02:34,618 --> 00:02:40,082 At this phase of their existence are called, T Tauri stars, they exhibit 36 00:02:40,082 --> 00:02:46,063 irregular and rapid variability possibly associated, to, changes in the opacity of 37 00:02:46,063 --> 00:02:51,033 the, Dust and a clouds that still surround them they exhibit huge rates of 38 00:02:51,033 --> 00:02:55,996 mass loss as much as 100 millionth of a solar mass per year and this face can 39 00:02:55,996 --> 00:03:00,832 last for 10,000,000 years this is 1,000,000 times the rate at which the sun 40 00:03:00,832 --> 00:03:05,413 is losing mass to the solar wind currently so the sun in its 10,000,000 41 00:03:05,413 --> 00:03:10,567 year tetori stage lost a lot more mass then it will use throughout its entire 42 00:03:10,567 --> 00:03:15,340 10,000,000,000 year main sequence career and this winds are directed in. 43 00:03:15,340 --> 00:03:20,360 for out from the poles but when I say directed out from the poles you need to 44 00:03:20,360 --> 00:03:25,752 get a scale notice that the scale of this internal cylinder is about astronom a 100 45 00:03:25,752 --> 00:03:32,490 astronomical units so that there is this outward flow in all directions. 46 00:03:32,490 --> 00:03:38,205 Out into the disk, except, at the very surface of the disk, the models as I said 47 00:03:38,205 --> 00:03:43,658 are not quite clear on how to model this. there use to be the prevailing opinion 48 00:03:43,658 --> 00:03:48,914 was at some point, that these waves are generated, the outflow is generated by 49 00:03:48,914 --> 00:03:54,302 the shock wave when the collapse stops, and there's in falling matter colliding 50 00:03:54,302 --> 00:03:57,390 with it. Of course as one would expect with the 51 00:03:57,390 --> 00:04:01,071 bipolar nature it turns out that the stellar magnetic 52 00:04:01,071 --> 00:04:05,335 fields play an important role. These are very violent and dramatic 53 00:04:05,335 --> 00:04:08,112 events. You can see that here in this movie. 54 00:04:08,112 --> 00:04:13,732 That bubble is, approximately 100 billion kilometers across, and it's dramatically 55 00:04:13,732 --> 00:04:17,284 growing. these other stellar types are the higher 56 00:04:17,284 --> 00:04:22,064 mass analogues of T Tauri stars. All star formation is accompanied by this 57 00:04:22,064 --> 00:04:25,359 violent outflow. This is what cleaned out the solar 58 00:04:25,359 --> 00:04:28,330 system. And now, having shaken that off, the sun 59 00:04:28,330 --> 00:04:30,785 is indeed ready to settle in with the.