File size: 27,669 Bytes
c3c3fe3 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 | align:start position:0% have you ever wondered how all the align:start position:0% have you ever wondered how all the align:start position:0% have you ever wondered how all the chemical elements are made then join me align:start position:0% chemical elements are made then join me align:start position:0% chemical elements are made then join me as we are lifting all the status secrets align:start position:0% as we are lifting all the status secrets align:start position:0% as we are lifting all the status secrets to understand the cosmic origin of the align:start position:0% to understand the cosmic origin of the align:start position:0% to understand the cosmic origin of the chemical elements let's look at the align:start position:0% chemical elements let's look at the align:start position:0% chemical elements let's look at the early chemical evolution align:start position:0% early chemical evolution align:start position:0% early chemical evolution [Music] align:start position:0% align:start position:0% some 14 billion years ago everything align:start position:0% some 14 billion years ago everything align:start position:0% some 14 billion years ago everything started with a big bang bang and it left align:start position:0% started with a big bang bang and it left align:start position:0% started with a big bang bang and it left behind a universe that was made from align:start position:0% behind a universe that was made from align:start position:0% behind a universe that was made from just hydrogen and helium gas I mentioned align:start position:0% just hydrogen and helium gas I mentioned align:start position:0% just hydrogen and helium gas I mentioned before there's a tiny tiny little trace align:start position:0% before there's a tiny tiny little trace align:start position:0% before there's a tiny tiny little trace of lithium but we're not going to worry align:start position:0% of lithium but we're not going to worry align:start position:0% of lithium but we're not going to worry about that so we had a universe but align:start position:0% about that so we had a universe but align:start position:0% about that so we had a universe but there were no stars yet so it was align:start position:0% there were no stars yet so it was align:start position:0% there were no stars yet so it was actually dark and some people call that align:start position:0% actually dark and some people call that align:start position:0% actually dark and some people call that the cosmic Dark Ages but structure began align:start position:0% the cosmic Dark Ages but structure began align:start position:0% the cosmic Dark Ages but structure began to form and gas began to clump and so align:start position:0% to form and gas began to clump and so align:start position:0% to form and gas began to clump and so eventually in a gas cloud the very first align:start position:0% eventually in a gas cloud the very first align:start position:0% eventually in a gas cloud the very first stars formed here are two of the first align:start position:0% stars formed here are two of the first align:start position:0% stars formed here are two of the first stars and they were made just from align:start position:0% stars and they were made just from align:start position:0% stars and they were made just from hydrogen and helium because the gas was align:start position:0% hydrogen and helium because the gas was align:start position:0% hydrogen and helium because the gas was just hydrogen helium but for energy align:start position:0% just hydrogen helium but for energy align:start position:0% just hydrogen helium but for energy generation purposes need stars needed to align:start position:0% generation purposes need stars needed to align:start position:0% generation purposes need stars needed to have nuclear fusion go on in their align:start position:0% have nuclear fusion go on in their align:start position:0% have nuclear fusion go on in their course to produce energy and so the align:start position:0% course to produce energy and so the align:start position:0% course to produce energy and so the first elements heavier than hydrogen align:start position:0% first elements heavier than hydrogen align:start position:0% first elements heavier than hydrogen helium were created inside of these align:start position:0% helium were created inside of these align:start position:0% helium were created inside of these stars and later when they exploded a align:start position:0% stars and later when they exploded a align:start position:0% stars and later when they exploded a supernova they were expelled into this align:start position:0% supernova they were expelled into this align:start position:0% supernova they were expelled into this gas cloud so we had the first elements align:start position:0% gas cloud so we had the first elements align:start position:0% gas cloud so we had the first elements here and of course they also gave the align:start position:0% here and of course they also gave the align:start position:0% here and of course they also gave the first light they lit up the universe for align:start position:0% first light they lit up the universe for align:start position:0% first light they lit up the universe for the first time and changed it in in a align:start position:0% the first time and changed it in in a align:start position:0% the first time and changed it in in a number of ways not just by bringing in align:start position:0% number of ways not just by bringing in align:start position:0% number of ways not just by bringing in light but also by producing the first align:start position:0% light but also by producing the first align:start position:0% light but also by producing the first heavier elements and that set in motion align:start position:0% heavier elements and that set in motion align:start position:0% heavier elements and that set in motion the chemical evolution of the elements align:start position:0% the chemical evolution of the elements align:start position:0% the chemical evolution of the elements that's an ongoing process until today align:start position:0% that's an ongoing process until today align:start position:0% that's an ongoing process until today now these stars here because they form align:start position:0% now these stars here because they form align:start position:0% now these stars here because they form from just hydrogen and helium gas were align:start position:0% from just hydrogen and helium gas were align:start position:0% from just hydrogen and helium gas were very massive rather large maybe align:start position:0% very massive rather large maybe align:start position:0% very massive rather large maybe something like a hundred solar masses so align:start position:0% something like a hundred solar masses so align:start position:0% something like a hundred solar masses so we use the unit here of solar mass this align:start position:0% we use the unit here of solar mass this align:start position:0% we use the unit here of solar mass this is the symbol for the Sun here as a unit align:start position:0% is the symbol for the Sun here as a unit align:start position:0% is the symbol for the Sun here as a unit so a hundred times more hundred times as align:start position:0% so a hundred times more hundred times as align:start position:0% so a hundred times more hundred times as heavy as the Sun and align:start position:0% align:start position:0% the reason for that is that hydrogen align:start position:0% the reason for that is that hydrogen align:start position:0% the reason for that is that hydrogen helium gas has trouble getting really align:start position:0% helium gas has trouble getting really align:start position:0% helium gas has trouble getting really cold align:start position:0% cold align:start position:0% cold making small stars the the important align:start position:0% making small stars the the important align:start position:0% making small stars the the important thing with massive stars is that they align:start position:0% thing with massive stars is that they align:start position:0% thing with massive stars is that they have really short lifetime so they have align:start position:0% have really short lifetime so they have align:start position:0% have really short lifetime so they have a short lifetime of maybe a few a few align:start position:0% a short lifetime of maybe a few a few align:start position:0% a short lifetime of maybe a few a few million years only a few million years align:start position:0% million years only a few million years align:start position:0% million years only a few million years is not much for on a cosmic time scale align:start position:0% is not much for on a cosmic time scale align:start position:0% is not much for on a cosmic time scale which means they exploded pretty quickly align:start position:0% which means they exploded pretty quickly align:start position:0% which means they exploded pretty quickly as gigantic supernova and as already align:start position:0% as gigantic supernova and as already align:start position:0% as gigantic supernova and as already indicated what happened at a later time align:start position:0% indicated what happened at a later time align:start position:0% indicated what happened at a later time these stars were gone but they left align:start position:0% these stars were gone but they left align:start position:0% these stars were gone but they left behind all the heavy elements that they align:start position:0% behind all the heavy elements that they align:start position:0% behind all the heavy elements that they are created and I should be specific align:start position:0% are created and I should be specific align:start position:0% are created and I should be specific here these have your elements where all align:start position:0% here these have your elements where all align:start position:0% here these have your elements where all the elements made in fusion processes up align:start position:0% the elements made in fusion processes up align:start position:0% the elements made in fusion processes up to iron so we have fusion elements in in align:start position:0% to iron so we have fusion elements in in align:start position:0% to iron so we have fusion elements in in the gas and with the onset of these align:start position:0% the gas and with the onset of these align:start position:0% the gas and with the onset of these little other elements being in the gas align:start position:0% little other elements being in the gas align:start position:0% little other elements being in the gas now the gas could for a clump much align:start position:0% now the gas could for a clump much align:start position:0% now the gas could for a clump much better and actually make small stars so align:start position:0% better and actually make small stars so align:start position:0% better and actually make small stars so the next generation of stars so this was align:start position:0% the next generation of stars so this was align:start position:0% the next generation of stars so this was the first generation first generation align:start position:0% the first generation first generation align:start position:0% the first generation first generation and here now we have the formation of align:start position:0% and here now we have the formation of align:start position:0% and here now we have the formation of second-generation stars here as a align:start position:0% second-generation stars here as a align:start position:0% second-generation stars here as a second-generation star here's a second align:start position:0% second-generation star here's a second align:start position:0% second-generation star here's a second generation starts off small stars align:start position:0% generation starts off small stars align:start position:0% generation starts off small stars similar to the Sun and perhaps a little align:start position:0% similar to the Sun and perhaps a little align:start position:0% similar to the Sun and perhaps a little bit less massive than the Sun actually align:start position:0% bit less massive than the Sun actually align:start position:0% bit less massive than the Sun actually but of course you're not going to make align:start position:0% but of course you're not going to make align:start position:0% but of course you're not going to make just small stars you're also gonna make align:start position:0% just small stars you're also gonna make align:start position:0% just small stars you're also gonna make big stars so we have a few big stars align:start position:0% big stars so we have a few big stars align:start position:0% big stars so we have a few big stars here again a few intermediate ones align:start position:0% here again a few intermediate ones align:start position:0% here again a few intermediate ones and the big ones the massive ones will align:start position:0% and the big ones the massive ones will align:start position:0% and the big ones the massive ones will again explode on a pretty fast timescale align:start position:0% again explode on a pretty fast timescale align:start position:0% again explode on a pretty fast timescale and make more elements but these little align:start position:0% and make more elements but these little align:start position:0% and make more elements but these little guys and that's the interesting part for align:start position:0% guys and that's the interesting part for align:start position:0% guys and that's the interesting part for us here now so the low mass second align:start position:0% us here now so the low mass second align:start position:0% us here now so the low mass second generations to us they have very long align:start position:0% generations to us they have very long align:start position:0% generations to us they have very long lifetimes long lifetimes of something align:start position:0% lifetimes long lifetimes of something align:start position:0% lifetimes long lifetimes of something like 15 to 20 billion years because they align:start position:0% like 15 to 20 billion years because they align:start position:0% like 15 to 20 billion years because they have I can just write that here solo me align:start position:0% have I can just write that here solo me align:start position:0% have I can just write that here solo me as they had maybe masters or at least align:start position:0% as they had maybe masters or at least align:start position:0% as they had maybe masters or at least some of them had masses between 0.6 to align:start position:0% some of them had masses between 0.6 to align:start position:0% some of them had masses between 0.6 to 0.8 solar masses so less massive than align:start position:0% 0.8 solar masses so less massive than align:start position:0% 0.8 solar masses so less massive than our Sun and as a good rule of thumb I align:start position:0% our Sun and as a good rule of thumb I align:start position:0% our Sun and as a good rule of thumb I can write this here the Sun has by align:start position:0% can write this here the Sun has by align:start position:0% can write this here the Sun has by definition a one solar mass and that has align:start position:0% definition a one solar mass and that has align:start position:0% definition a one solar mass and that has a lifetime or the Sun has a lifetime of align:start position:0% a lifetime or the Sun has a lifetime of align:start position:0% a lifetime or the Sun has a lifetime of 10 billion years and so everything that align:start position:0% 10 billion years and so everything that align:start position:0% 10 billion years and so everything that has less mass will have a longer align:start position:0% has less mass will have a longer align:start position:0% has less mass will have a longer lifetime and everything that is more align:start position:0% lifetime and everything that is more align:start position:0% lifetime and everything that is more massive than one so let me ask will have align:start position:0% massive than one so let me ask will have align:start position:0% massive than one so let me ask will have a much shorter lifetime yeah now what align:start position:0% a much shorter lifetime yeah now what align:start position:0% a much shorter lifetime yeah now what does this imply having a long lifetime align:start position:0% does this imply having a long lifetime align:start position:0% does this imply having a long lifetime it means that these stars are still align:start position:0% it means that these stars are still align:start position:0% it means that these stars are still around they are around today we can align:start position:0% around they are around today we can align:start position:0% around they are around today we can observe them today we can see them today align:start position:0% observe them today we can see them today align:start position:0% observe them today we can see them today and that means that we can use them to align:start position:0% and that means that we can use them to align:start position:0% and that means that we can use them to study the composition of this early gas align:start position:0% study the composition of this early gas align:start position:0% study the composition of this early gas here because that's when they're formed align:start position:0% here because that's when they're formed align:start position:0% here because that's when they're formed they have incorporated in in all their align:start position:0% they have incorporated in in all their align:start position:0% they have incorporated in in all their layers throughout the composition of align:start position:0% layers throughout the composition of align:start position:0% layers throughout the composition of this gas cloud it has what that was align:start position:0% this gas cloud it has what that was align:start position:0% this gas cloud it has what that was enriched by these very first stars so we align:start position:0% enriched by these very first stars so we align:start position:0% enriched by these very first stars so we have means to study the first stars and align:start position:0% have means to study the first stars and align:start position:0% have means to study the first stars and what came out of their supernova align:start position:0% what came out of their supernova align:start position:0% what came out of their supernova explosions and what happened at this align:start position:0% explosions and what happened at this align:start position:0% explosions and what happened at this very early phase of star formation align:start position:0% very early phase of star formation align:start position:0% very early phase of star formation galaxy formation and formation of all align:start position:0% galaxy formation and formation of all align:start position:0% galaxy formation and formation of all the chemical elements align:start position:0% the chemical elements align:start position:0% the chemical elements if you then wind the clock forward many align:start position:0% if you then wind the clock forward many align:start position:0% if you then wind the clock forward many things happened after well of course align:start position:0% things happened after well of course align:start position:0% things happened after well of course more stories formed many many more cells align:start position:0% more stories formed many many more cells align:start position:0% more stories formed many many more cells more supernovae and with every align:start position:0% more supernovae and with every align:start position:0% more supernovae and with every generation of supernovae more of all the align:start position:0% generation of supernovae more of all the align:start position:0% generation of supernovae more of all the elements was provided more of all the align:start position:0% elements was provided more of all the align:start position:0% elements was provided more of all the elements because as we will see later in align:start position:0% elements because as we will see later in align:start position:0% elements because as we will see later in some of these very early processes align:start position:0% some of these very early processes align:start position:0% some of these very early processes nuclear physics processes all the align:start position:0% nuclear physics processes all the align:start position:0% nuclear physics processes all the elements from the periodic table could align:start position:0% elements from the periodic table could align:start position:0% elements from the periodic table could have been were created already at the align:start position:0% have been were created already at the align:start position:0% have been were created already at the earliest times then with time more and align:start position:0% earliest times then with time more and align:start position:0% earliest times then with time more and more of all of them were created it's align:start position:0% more of all of them were created it's align:start position:0% more of all of them were created it's not like that the universe because it align:start position:0% not like that the universe because it align:start position:0% not like that the universe because it was just hydrogen and helium in the align:start position:0% was just hydrogen and helium in the align:start position:0% was just hydrogen and helium in the beginning then it took time to build up align:start position:0% beginning then it took time to build up align:start position:0% beginning then it took time to build up all the elements and march through the align:start position:0% all the elements and march through the align:start position:0% all the elements and march through the periodic table with time that is not the align:start position:0% periodic table with time that is not the align:start position:0% periodic table with time that is not the case align:start position:0% case align:start position:0% case everything was produced from early on align:start position:0% everything was produced from early on align:start position:0% everything was produced from early on and then just more and more and so well align:start position:0% and then just more and more and so well align:start position:0% and then just more and more and so well we have more stories and more chemical align:start position:0% we have more stories and more chemical align:start position:0% we have more stories and more chemical and enrichment but also the formation of align:start position:0% and enrichment but also the formation of align:start position:0% and enrichment but also the formation of the first bigger structures larger align:start position:0% the first bigger structures larger align:start position:0% the first bigger structures larger structures including the the Milky Way align:start position:0% structures including the the Milky Way align:start position:0% structures including the the Milky Way just going to breathe yet in like this align:start position:0% just going to breathe yet in like this align:start position:0% just going to breathe yet in like this because this all happened in in small align:start position:0% because this all happened in in small align:start position:0% because this all happened in in small gravitationally bound systems and they align:start position:0% gravitationally bound systems and they align:start position:0% gravitationally bound systems and they were then gobbled up later by slightly align:start position:0% were then gobbled up later by slightly align:start position:0% were then gobbled up later by slightly bigger neighbors and then those who may align:start position:0% bigger neighbors and then those who may align:start position:0% bigger neighbors and then those who may be gobbled up by the proton Milky Way align:start position:0% be gobbled up by the proton Milky Way align:start position:0% be gobbled up by the proton Milky Way and eventually the Milky Way formed and align:start position:0% and eventually the Milky Way formed and align:start position:0% and eventually the Milky Way formed and formed from from the remnants of all align:start position:0% formed from from the remnants of all align:start position:0% formed from from the remnants of all these little metal systems and so all of align:start position:0% these little metal systems and so all of align:start position:0% these little metal systems and so all of this here happened as time went on and align:start position:0% this here happened as time went on and align:start position:0% this here happened as time went on and until today today we have a universe align:start position:0% until today today we have a universe align:start position:0% until today today we have a universe that's full of structure and and full of align:start position:0% that's full of structure and and full of align:start position:0% that's full of structure and and full of all the elements well a whole two align:start position:0% all the elements well a whole two align:start position:0% all the elements well a whole two percent but I think we can consider this align:start position:0% percent but I think we can consider this align:start position:0% percent but I think we can consider this for at least you know if you're an align:start position:0% for at least you know if you're an align:start position:0% for at least you know if you're an astronomer and this and chemical align:start position:0% astronomer and this and chemical align:start position:0% astronomer and this and chemical evolution is is an ongoing align:start position:0% evolution is is an ongoing align:start position:0% evolution is is an ongoing so in the following we're going to look align:start position:0% so in the following we're going to look align:start position:0% so in the following we're going to look in more detail at chemical enrichment align:start position:0% in more detail at chemical enrichment align:start position:0% in more detail at chemical enrichment and chemical evolution and also stellar align:start position:0% and chemical evolution and also stellar align:start position:0% and chemical evolution and also stellar archaeology which is the way how we use align:start position:0% archaeology which is the way how we use align:start position:0% archaeology which is the way how we use old stars to trace these different early align:start position:0% old stars to trace these different early align:start position:0% old stars to trace these different early stages of chemical evolution align:start position:0% align:start position:0% you |