1 00:00:00,000 --> 00:00:01,020 [MUSIC PLAYING] 2 00:00:01,020 --> 00:00:02,478 ANNA FREBEL: Have you ever wondered 3 00:00:02,478 --> 00:00:06,120 how all the chemical elements are made? 4 00:00:06,120 --> 00:00:09,420 Then join me as we are lifting all the stardust secrets 5 00:00:09,420 --> 00:00:12,090 to understand the cosmic origin of the chemical elements. 6 00:00:16,129 --> 00:00:19,020 We want to talk about the cosmic origin of the chemical elements 7 00:00:19,020 --> 00:00:19,520 today. 8 00:00:28,280 --> 00:00:31,040 In order to understand where the elements come from, 9 00:00:31,040 --> 00:00:34,410 we need to consider two different components-- 10 00:00:34,410 --> 00:00:37,090 one is nuclear physics and one is astrophysics. 11 00:00:37,090 --> 00:00:39,260 When the nicely combine, when we want 12 00:00:39,260 --> 00:00:42,500 to understand where the chemical elements come from, 13 00:00:42,500 --> 00:00:44,695 and so let's look at that in more detail. 14 00:00:44,695 --> 00:00:46,070 We have the nuclear physics part. 15 00:00:49,790 --> 00:00:51,530 And we have astrophysics. 16 00:00:54,970 --> 00:00:57,070 And on the nuclear physics side, we 17 00:00:57,070 --> 00:01:01,150 have two things that we want to consider or learn about, 18 00:01:01,150 --> 00:01:06,320 namely how the light elements are formed, 19 00:01:06,320 --> 00:01:10,210 light elements up to iron. 20 00:01:10,210 --> 00:01:15,010 And they are formed in fusion processes in stars. 21 00:01:15,010 --> 00:01:19,650 Fusion processes. 22 00:01:19,650 --> 00:01:22,550 And so this is one. 23 00:01:22,550 --> 00:01:24,687 And then we have also lots and lots 24 00:01:24,687 --> 00:01:26,270 of elements on the periodic table that 25 00:01:26,270 --> 00:01:27,620 are heavier than iron. 26 00:01:27,620 --> 00:01:32,900 So how are the heavy elements formed? 27 00:01:32,900 --> 00:01:35,780 That would be heavier than iron. 28 00:01:35,780 --> 00:01:37,495 And so they are made in what's called 29 00:01:37,495 --> 00:01:39,410 a neutron-capture processes. 30 00:01:43,200 --> 00:01:48,460 And that's a really neat way of making big heavy nuclei. 31 00:01:48,460 --> 00:01:51,270 And so these two parts here together 32 00:01:51,270 --> 00:01:55,080 really explain how most of the elements in the periodic table 33 00:01:55,080 --> 00:01:55,580 are made. 34 00:01:55,580 --> 00:01:57,038 And there are a few extra processes 35 00:01:57,038 --> 00:01:58,450 that we will not consider. 36 00:01:58,450 --> 00:02:01,290 But this gets us almost there. 37 00:02:01,290 --> 00:02:04,650 Then we have the astrophysics, because this is basically 38 00:02:04,650 --> 00:02:06,190 a lot of theory. 39 00:02:06,190 --> 00:02:08,400 And we need to put this to the test. 40 00:02:08,400 --> 00:02:11,460 And one test that the universe offers 41 00:02:11,460 --> 00:02:14,610 us is investigating chemical evolution. 42 00:02:17,490 --> 00:02:20,100 Chemical evolution is that the successive build up 43 00:02:20,100 --> 00:02:22,830 of heavy elements in the universe with time, 44 00:02:22,830 --> 00:02:26,940 with cosmic time, over the last 13.8 billion years. 45 00:02:26,940 --> 00:02:32,070 And we can observe stars at different times 46 00:02:32,070 --> 00:02:36,300 and thus trace the signatures of these nuclear sort of processes 47 00:02:36,300 --> 00:02:42,350 here and reconstruct how the nuclear physics operated. 48 00:02:42,350 --> 00:02:44,730 That works particularly well at early times 49 00:02:44,730 --> 00:02:47,040 when the universe was a much less messy place 50 00:02:47,040 --> 00:02:48,190 than it is now. 51 00:02:48,190 --> 00:02:50,760 And so the second portion here is 52 00:02:50,760 --> 00:02:55,230 going to be the oldest stars because they 53 00:02:55,230 --> 00:02:58,470 are the tool for us to really figure out 54 00:02:58,470 --> 00:03:01,860 how the elements were made first in the universe. 55 00:03:01,860 --> 00:03:04,770 That allows us to again obtain clean signatures 56 00:03:04,770 --> 00:03:07,720 of these processes there. 57 00:03:07,720 --> 00:03:11,940 And that's a very exciting and timely avenue for us to study. 58 00:03:11,940 --> 00:03:13,590 And together with the older stars, 59 00:03:13,590 --> 00:03:16,290 comes the concept of stellar archeology. 60 00:03:20,200 --> 00:03:23,290 And that sort of encompasses how we 61 00:03:23,290 --> 00:03:28,030 use stars that are still available and shining today 62 00:03:28,030 --> 00:03:32,710 to study the early universe when everything got started. 63 00:03:32,710 --> 00:03:35,950 And in order to study chemical evolution with old stars, 64 00:03:35,950 --> 00:03:38,860 we actually need to use a scientific method called 65 00:03:38,860 --> 00:03:40,640 spectroscopy. 66 00:03:40,640 --> 00:03:46,120 So we're also going to look at spectroscopy and how 67 00:03:46,120 --> 00:03:50,860 that works, observing all the little stellar little rainbows. 68 00:03:50,860 --> 00:03:54,000 And because we do that with big telescopes, 69 00:03:54,000 --> 00:03:58,030 we're also going to look at what it's like to use big telescopes 70 00:03:58,030 --> 00:04:00,590 and observing. 71 00:04:00,590 --> 00:04:02,920 Because all of this work is based 72 00:04:02,920 --> 00:04:06,130 on astronomical observations with the largest 73 00:04:06,130 --> 00:04:09,940 telescopes, mostly in Chile. 74 00:04:09,940 --> 00:04:14,610 And I will explain all these different parts one by one. 75 00:04:14,610 --> 00:04:16,360 And then in the end, we're going to put it 76 00:04:16,360 --> 00:04:19,030 all together to understand the origin of the elements. 77 00:04:19,030 --> 00:04:21,480 [MUSIC PLAYING]