1 00:00:00,612 --> 00:00:02,070 ANNA FREBEL: Have you ever wondered 2 00:00:02,070 --> 00:00:06,120 how all the chemical elements are made? 3 00:00:06,120 --> 00:00:09,450 Then join me as we are lifting all the stardust secrets 4 00:00:09,450 --> 00:00:12,130 to understand the cosmic origin of the chemical elements. 5 00:00:15,890 --> 00:00:18,860 We have come to the end of our little journey 6 00:00:18,860 --> 00:00:21,380 where we wanted to explore the origin of the chemical 7 00:00:21,380 --> 00:00:21,890 elements. 8 00:00:21,890 --> 00:00:24,716 [MUSIC PLAYING] 9 00:00:28,490 --> 00:00:30,163 I hope you enjoyed it, and I hope 10 00:00:30,163 --> 00:00:32,330 I could help you to understand that this is actually 11 00:00:32,330 --> 00:00:33,920 not just one origin. 12 00:00:33,920 --> 00:00:35,480 It's a whole process. 13 00:00:35,480 --> 00:00:38,570 And it's a process that's still going on. 14 00:00:38,570 --> 00:00:41,210 So let's summarize what we covered. 15 00:00:41,210 --> 00:00:44,480 Well, we talked a lot about fusion and neutron capture 16 00:00:44,480 --> 00:00:48,150 processes that create all the elements in the first place. 17 00:00:48,150 --> 00:00:50,150 We talked a little bit about where that happens, 18 00:00:50,150 --> 00:00:52,130 I mean the cores of stars, as well as 19 00:00:52,130 --> 00:00:55,160 in supernova and neutron star mergers. 20 00:00:55,160 --> 00:00:57,980 And once these elements are created, 21 00:00:57,980 --> 00:00:59,780 they can then be observed, and they 22 00:00:59,780 --> 00:01:04,220 contribute to the chemical evolution of the universe. 23 00:01:04,220 --> 00:01:08,180 If they are produced in the early universe, 24 00:01:08,180 --> 00:01:12,750 then we can see them in the older stars. 25 00:01:12,750 --> 00:01:16,910 So if produced in the early universe, then 26 00:01:16,910 --> 00:01:20,060 we have this chance of observing clean signatures. 27 00:01:20,060 --> 00:01:21,560 Today, that is not possible anymore, 28 00:01:21,560 --> 00:01:24,230 because chemical evolution has moved on too far. 29 00:01:24,230 --> 00:01:26,510 It's too messy today. 30 00:01:26,510 --> 00:01:29,450 And so, we use the most metal poor stars in order 31 00:01:29,450 --> 00:01:32,690 to detect these clean signatures, 32 00:01:32,690 --> 00:01:34,520 and to work with nuclear physicists 33 00:01:34,520 --> 00:01:37,100 to understand how these processes exactly work, 34 00:01:37,100 --> 00:01:40,590 and in what astrophysical sites that might occur. 35 00:01:40,590 --> 00:01:43,460 So here we have the oldest stars. 36 00:01:43,460 --> 00:01:47,150 And one reason why we can infer that these stars must 37 00:01:47,150 --> 00:01:49,040 be very old, because if there weren't we 38 00:01:49,040 --> 00:01:51,050 wouldn't get these very clean signatures 39 00:01:51,050 --> 00:01:54,260 that were only present at the earliest times. 40 00:01:54,260 --> 00:01:57,140 Now the very fortunate coincidence for us, 41 00:01:57,140 --> 00:02:00,140 is that these older stars actually found in the Milky Way 42 00:02:00,140 --> 00:02:03,340 today, so they are fairly local objects. 43 00:02:03,340 --> 00:02:07,610 And that is a great advantage over very distant galaxies 44 00:02:07,610 --> 00:02:11,930 that are also often used to study the early universe. 45 00:02:11,930 --> 00:02:14,215 We find them in the Milky Way, but we 46 00:02:14,215 --> 00:02:15,590 need the kind of data, of course, 47 00:02:15,590 --> 00:02:17,910 to do a chemical analysis. 48 00:02:17,910 --> 00:02:20,810 And we do that with spectroscopic observations. 49 00:02:20,810 --> 00:02:26,420 And we use the world's largest telescopes for that, 50 00:02:26,420 --> 00:02:30,080 because only they can give us the kind of data quality 51 00:02:30,080 --> 00:02:33,672 that we need in order to measure these tiny little absorption 52 00:02:33,672 --> 00:02:35,630 lines that tell us about the composition of all 53 00:02:35,630 --> 00:02:38,700 the different elements across the periodic table. 54 00:02:38,700 --> 00:02:40,820 And then finally, if we put this all together, 55 00:02:40,820 --> 00:02:44,330 we can determine the chemical composition of our old stars, 56 00:02:44,330 --> 00:02:46,970 and actually we can do so not just of old stars, 57 00:02:46,970 --> 00:02:49,640 but of stars at a variety of ages, 58 00:02:49,640 --> 00:02:52,010 a variety of metal contents. 59 00:02:52,010 --> 00:02:54,710 And that helps us to piece together 60 00:02:54,710 --> 00:02:59,510 how the amount of each metal actually changed with time. 61 00:02:59,510 --> 00:03:03,440 And that's a very exciting prospect. 62 00:03:03,440 --> 00:03:06,980 So that's chemical evolution. 63 00:03:06,980 --> 00:03:11,900 And as I mentioned before, this is an ongoing process. 64 00:03:11,900 --> 00:03:15,080 Much of all the elements are still being produced. 65 00:03:15,080 --> 00:03:15,580 right now. 66 00:03:15,580 --> 00:03:17,690 There's probably a supernova going off right now 67 00:03:17,690 --> 00:03:19,440 as we speak somewhere in the universe 68 00:03:19,440 --> 00:03:21,320 where more elements have been created. 69 00:03:21,320 --> 00:03:24,830 And so, the chemical makeup of the universe is changed again. 70 00:03:24,830 --> 00:03:28,260 So it's continuously changing process. 71 00:03:28,260 --> 00:03:30,830 And that brings us to the end. 72 00:03:30,830 --> 00:03:36,770 So this is really all the star stuff that we are made of. 73 00:03:36,770 --> 00:03:39,410 And while the origin is not entirely 74 00:03:39,410 --> 00:03:42,230 stars, but also stellar remnants, as I mentioned, 75 00:03:42,230 --> 00:03:44,450 supernova and neutron star mergers 76 00:03:44,450 --> 00:03:46,160 should be included in that. 77 00:03:46,160 --> 00:03:50,400 But, yeah, that is really our cosmic origin. 78 00:03:50,400 --> 00:03:54,350 And as humans, it lays in the cosmos, in the cosmic objects, 79 00:03:54,350 --> 00:03:55,710 in a variety of them. 80 00:03:55,710 --> 00:03:58,250 And it takes a whole bunch of processes 81 00:03:58,250 --> 00:04:03,080 in order to unravel that all those stardust secrets. 82 00:04:03,080 --> 00:04:05,260 And one last thing I wanted to mention, 83 00:04:05,260 --> 00:04:08,990 doing this kind of work with all the different elements 84 00:04:08,990 --> 00:04:12,920 has shown pretty clearly that carbon is not only 85 00:04:12,920 --> 00:04:15,200 the most important elements for us humans, 86 00:04:15,200 --> 00:04:17,870 because all lifeforms are carbon based. 87 00:04:17,870 --> 00:04:20,420 It actually turns out, it's also the most important element 88 00:04:20,420 --> 00:04:23,240 in the universe, because at that early time 89 00:04:23,240 --> 00:04:27,320 it needed the carbon to help for the gas 90 00:04:27,320 --> 00:04:31,110 to come together to form small stars in small structures. 91 00:04:31,110 --> 00:04:35,660 And so, I think carbon really plays the most fundamental role 92 00:04:35,660 --> 00:04:38,330 in the universe that we can think of, 93 00:04:38,330 --> 00:04:40,190 because it helps star formation and galaxy 94 00:04:40,190 --> 00:04:42,290 formation, and ultimately planet formation, 95 00:04:42,290 --> 00:04:43,550 and formation of life. 96 00:04:43,550 --> 00:04:46,600 [MUSIC PLAYING]