1 00:00:00,000 --> 00:00:04,300 the sun has gone through some interesting developments. 2 00:00:04,300 --> 00:00:07,614 We have one last phase and it's the pretty one. 3 00:00:07,614 --> 00:00:11,351 So the sun does get to go out with a pretty sight. 4 00:00:11,351 --> 00:00:15,229 What happens? Remember when we stopped we said that the 5 00:00:15,229 --> 00:00:19,459 thermal pulses were going to eject the envelope of the star. 6 00:00:19,459 --> 00:00:24,052 What we would be left with is the inert. Not fusing, no energy source. 7 00:00:24,052 --> 00:00:29,054 Completely degenerate Carbon Oxygen core. This is an object, we'll talk about it, 8 00:00:29,054 --> 00:00:33,296 it's called a whi, it starts out life as what we call a white dwarf. 9 00:00:33,296 --> 00:00:37,728 It's got about the radius of earth. It's got about the mass of the sun. 10 00:00:37,728 --> 00:00:41,970 It's extraordinarily dense. It's extraordinarily hot even though no 11 00:00:41,970 --> 00:00:46,846 fusion is going on because it just stopped being the core of a star that was 12 00:00:46,846 --> 00:00:51,594 fusing Helium and Hydrogen and so on. And was compressed by great masses. 13 00:00:51,594 --> 00:00:56,090 So this object has temperatures in, of many tens of thousands of Kelvin. 14 00:00:56,090 --> 00:01:00,987 It is surrounded. by the atmosphere that it ejected which 15 00:01:00,987 --> 00:01:05,381 since it was ejected has been moving steadily out into space. 16 00:01:05,381 --> 00:01:11,432 what you have therefore is an expanding bubble of gas surrounding an object with 17 00:01:11,432 --> 00:01:14,746 temperatures in the tens of thousands degrees. 18 00:01:14,746 --> 00:01:21,013 the ultraviolet light produced by this exposed core is of course going to ionize 19 00:01:21,013 --> 00:01:22,757 the gas. That's been expelled. 20 00:01:22,757 --> 00:01:27,038 The ionized gas will then glow in the same way the aurora glows and the same 21 00:01:27,038 --> 00:01:30,486 way that lighting glows. And, the resulting objects are some of 22 00:01:30,486 --> 00:01:34,767 the prettiest in the sky, so we're just going to spend a few minutes relaxing, 23 00:01:34,767 --> 00:01:37,112 and. Viewing them because they are pretty. 24 00:01:37,112 --> 00:01:41,587 They're called planetary nebulae because they look round in a small telescope. 25 00:01:41,587 --> 00:01:44,054 They look somewhat like a gas planet would. 26 00:01:44,054 --> 00:01:47,440 This is the ring nebula. We talked about it in our first, 27 00:01:47,440 --> 00:01:52,489 Video clip and promise to come back and explain what this beautiful object is so 28 00:01:52,489 --> 00:01:57,538 what this beautiful object is, is in the middle sits a white world star and these 29 00:01:57,538 --> 00:02:02,462 are the ejector that they form these planetary nebule can be a light year or a 30 00:02:02,462 --> 00:02:07,262 couple of light years across before the material melts into the interstellar 31 00:02:07,262 --> 00:02:11,999 media taking with it some of the carbon and whatever that the star produced 32 00:02:11,999 --> 00:02:17,111 dredged up and ejected in its solar wind so they seed the planetary nebula is the 33 00:02:17,111 --> 00:02:21,350 stars we have seedingly interstellar media with heavier elements 34 00:02:21,350 --> 00:02:28,447 And we see here oxygen and nitrogen lines in the colours, the red is, ionized 35 00:02:28,447 --> 00:02:32,720 hydrogen, these are the H alpha lines, and, 36 00:02:32,720 --> 00:02:38,161 What we, at some point, people thought that this was sort of a slice through a 37 00:02:38,161 --> 00:02:41,977 spherical bubble of gas. It was discovered, upon closer 38 00:02:41,977 --> 00:02:47,560 examination, that in fact, just like the T Tauri Winds, the planetary nebulae, the 39 00:02:47,560 --> 00:02:53,214 atmosphere of a star gets ejected, but not in spherically symmetric way but in a 40 00:02:53,214 --> 00:02:56,465 biploar flow. So this thing has the shape of a 41 00:02:56,465 --> 00:02:59,998 cylinder. The axis of the star's rotation happened 42 00:02:59,998 --> 00:03:03,320 to have pointed at Earth. So we're looking down. 43 00:03:03,320 --> 00:03:08,309 A tube of the cylinder other nebulee we get a different view angle, so we get 44 00:03:08,309 --> 00:03:12,758 more of a picture of the structure. This is the Helux nebula, the cat's eye 45 00:03:12,758 --> 00:03:17,387 is certainly instructed in telling you that there's more structure than just 46 00:03:17,387 --> 00:03:20,333 spherical. There's a lot of interesting questions 47 00:03:20,333 --> 00:03:23,820 here this one is very nice, its not the dumbbell, it's a. 48 00:03:23,820 --> 00:03:29,099 Another one, but it does show very nicely the bipolar nature of the ejecta coming 49 00:03:29,099 --> 00:03:32,880 out of the store. I believe this was a Christmas astronomy 50 00:03:32,880 --> 00:03:36,596 picture of the day. This is one whose intricate structure 51 00:03:36,596 --> 00:03:39,790 apparently follows from several generations of a. 52 00:03:39,790 --> 00:03:44,334 Ejection of material, in between which the axis of the star rotated perhaps 53 00:03:44,334 --> 00:03:47,789 because a binary partner was influencing it or something. 54 00:03:47,789 --> 00:03:52,637 So that we have ejections in several different direction and the combination 55 00:03:52,637 --> 00:03:57,182 makes for this beautiful shape. Conotary nebulus if nothing else, they're 56 00:03:57,182 --> 00:04:02,030 very interesting but also extraordinary pretty and they deserve some aesthetics. 57 00:04:02,030 --> 00:04:03,147 Before we move on with sun.