1 00:00:02,035 --> 00:00:04,629 This is an exploding star. 2 00:00:04,704 --> 00:00:07,195 lt's called a supernova. 3 00:00:12,112 --> 00:00:15,206 A supernova is the greatest cataclysm 4 00:00:15,281 --> 00:00:18,148 in the history of the entire universe. 5 00:00:18,218 --> 00:00:22,621 Supernovas come in different sizes and types. 6 00:00:22,689 --> 00:00:24,452 All of them are so bright, 7 00:00:24,524 --> 00:00:27,982 they can be seen across the universe. 8 00:00:28,061 --> 00:00:31,428 A supernova is the most violent death of a star you can imagine. 9 00:00:33,867 --> 00:00:36,859 But this violent destruction of a star 10 00:00:36,936 --> 00:00:41,066 is also the birth of everything we see around us. 11 00:00:56,689 --> 00:01:02,218 Really big stars go out with a bang, called a supernova. 12 00:01:02,295 --> 00:01:05,662 A supernova can outshine an entire galaxy, 13 00:01:05,732 --> 00:01:09,691 releasing trillions of times the energy of our Sun. 14 00:01:19,079 --> 00:01:20,944 They're so violent, 15 00:01:21,014 --> 00:01:24,575 if one of them exploded just a few dozen light-years away, 16 00:01:24,651 --> 00:01:27,211 planet Earth would be toast. 17 00:01:36,896 --> 00:01:40,627 A nearby supernova would really ruin our day. 18 00:01:43,069 --> 00:01:44,434 First of all, 19 00:01:44,504 --> 00:01:48,804 the sudden burst of radiation would scorch the atmosphere. 20 00:01:48,875 --> 00:01:52,367 The only place to go is underground. 21 00:01:52,445 --> 00:01:53,673 Underground, 22 00:01:53,746 --> 00:01:57,113 you could then withstand the blistering burst of x-rays 23 00:01:57,183 --> 00:01:58,582 which hit the Earth. 24 00:01:58,651 --> 00:02:01,449 And then it would scorch all plant life. 25 00:02:01,521 --> 00:02:03,785 And with the collapse of the food chain, 26 00:02:03,857 --> 00:02:06,826 we're talking about a possible extinction on the Earth. 27 00:02:11,264 --> 00:02:14,131 Supernovas are killers. 28 00:02:19,305 --> 00:02:23,799 But they also create the basic elements that make up our world. 29 00:02:27,914 --> 00:02:30,007 Our planet, our star, everything around us 30 00:02:30,083 --> 00:02:33,541 formed out of the debris of a dead exploded star. 31 00:02:33,620 --> 00:02:38,216 Everything that makes up our bodies and the skyline 32 00:02:38,291 --> 00:02:40,259 came from supernovae. 33 00:02:42,695 --> 00:02:45,163 All of the iron, all of the silicon, 34 00:02:45,231 --> 00:02:48,530 all of the elements that went into these buildings. 35 00:02:48,601 --> 00:02:50,899 The things that make up my blood, my body, 36 00:02:50,970 --> 00:02:52,597 the gold in my wedding ring... 37 00:02:52,672 --> 00:02:55,641 everything you see here is a supernova. 38 00:03:04,117 --> 00:03:06,585 But our Sun won't become a supernova. 39 00:03:06,653 --> 00:03:07,950 lt's too small. 40 00:03:20,099 --> 00:03:25,196 Like all stars, it's basically a giant nuclear reactor. 41 00:03:28,041 --> 00:03:31,670 The fusion reactor inside a star burns hydrogen, 42 00:03:31,744 --> 00:03:34,440 the simplest, most common element. 43 00:03:38,184 --> 00:03:41,745 The reaction fuses hydrogen atoms together... 44 00:03:43,590 --> 00:03:46,320 ...producing helium and energy. 45 00:03:52,332 --> 00:03:54,732 And when the hydrogen runs out, 46 00:03:54,801 --> 00:03:58,737 stars keep burning by fusing helium into carbon... 47 00:04:00,073 --> 00:04:03,042 ...then carbon into o xygen. 48 00:04:05,912 --> 00:04:08,779 When small stars like our Sun make carbon, 49 00:04:08,848 --> 00:04:11,078 they begin to die. 50 00:04:11,150 --> 00:04:13,311 During the lifetime of a star, 51 00:04:13,386 --> 00:04:15,411 there's a balance between gravity pulling in 52 00:04:15,488 --> 00:04:16,819 and pressure pushing out. 53 00:04:16,889 --> 00:04:20,222 For a star that's generating energy, there's no problem. 54 00:04:20,293 --> 00:04:23,524 But once energy generation switches off, 55 00:04:23,596 --> 00:04:26,929 the pressure goes away, and gravity wins. 56 00:04:29,102 --> 00:04:33,334 Now gravity begins to crush the center of the star. 57 00:04:37,944 --> 00:04:41,778 The star's outer layers are pushed outwards. 58 00:04:43,583 --> 00:04:48,748 They expand into a huge ball of gas called a red giant. 59 00:04:51,024 --> 00:04:55,290 Our Sun, when it dies 4 1 /2 to 5 billion years from now, 60 00:04:55,361 --> 00:04:57,921 its corona will go all the way out to Mars. 61 00:05:02,435 --> 00:05:06,531 Everything on the planet Earth will vaporize. 62 00:05:13,212 --> 00:05:15,703 While the outer layers expand, 63 00:05:15,782 --> 00:05:17,272 in the center of the Sun, 64 00:05:17,350 --> 00:05:19,716 gravity will have the opposite effect. 65 00:05:24,891 --> 00:05:26,518 lt'll crush the Sun's core 66 00:05:26,592 --> 00:05:29,390 to just a millionth of its original size... 67 00:05:29,462 --> 00:05:31,225 about the size of the Earth. 68 00:05:33,366 --> 00:05:38,804 Now it's a dense ball of o xygen and carbon called a white dwarf. 69 00:05:44,677 --> 00:05:46,167 ln our solar system, 70 00:05:46,245 --> 00:05:49,874 this will be the end of the story. 71 00:05:49,949 --> 00:05:53,885 The gas from the dying star will gradually disperse, 72 00:05:53,953 --> 00:05:58,219 but the tiny white dwarf will burn for billions of years. 73 00:06:03,730 --> 00:06:06,824 But our solar system is unusual. 74 00:06:06,899 --> 00:06:09,026 lt has just one star. 75 00:06:15,108 --> 00:06:19,909 The fact is, the vast majority of stars orbit in pairs. 76 00:06:25,985 --> 00:06:29,887 When one of the two stars dies and becomes a white dwarf, 77 00:06:29,956 --> 00:06:31,446 if it's close enough, 78 00:06:31,524 --> 00:06:34,516 it starts stealing material from the other star. 79 00:06:45,071 --> 00:06:49,405 Think of two stars rotating around each other. 80 00:06:49,475 --> 00:06:54,412 One star's slowly sucking all the hydrogen and helium 81 00:06:54,480 --> 00:06:55,845 from its companion star. 82 00:06:55,915 --> 00:06:59,316 lt's like a vampire. 83 00:07:01,487 --> 00:07:04,354 As the white dwarf sucks more and more fuel 84 00:07:04,424 --> 00:07:06,221 out of its companion star, 85 00:07:06,292 --> 00:07:10,228 it gets heavier and denser and less stable. 86 00:07:13,065 --> 00:07:18,093 lnside, carbon and o xygen atoms are about to fuse together, 87 00:07:18,171 --> 00:07:19,968 and that's bad news. 88 00:07:25,845 --> 00:07:29,508 A white dwarf, in some sense, 89 00:07:29,582 --> 00:07:32,949 is like a bomb waiting to be lit. 90 00:07:33,019 --> 00:07:35,681 There's a huge amount of energy stored in that star... 91 00:07:35,755 --> 00:07:37,814 gravitational energy and nuclear energy. 92 00:07:40,760 --> 00:07:44,196 This white dwarf is turning into a monster... 93 00:07:44,263 --> 00:07:47,858 a type 1 A monster. 94 00:07:47,934 --> 00:07:49,458 A type 1 A supernova 95 00:07:49,535 --> 00:07:52,265 is a 20-billion-billion-billion- megaton 96 00:07:52,338 --> 00:07:55,034 thermonuclear carbon bomb. 97 00:07:55,107 --> 00:07:58,338 lt's one of the most explosive substances in the universe. 98 00:08:01,948 --> 00:08:03,381 Eventually, 99 00:08:03,449 --> 00:08:07,249 the white dwarf drains so much material from its companion, 100 00:08:07,320 --> 00:08:09,254 it goes into nuclear overload. 101 00:08:14,827 --> 00:08:17,159 The carbon and o xygen inside it 102 00:08:17,230 --> 00:08:21,223 start to turn into a common but dangerous element... 103 00:08:21,300 --> 00:08:23,825 at least to stars. 104 00:08:25,972 --> 00:08:27,701 You've probably seen in "Star Trek" 105 00:08:27,773 --> 00:08:30,105 the idea that there is some sort of secret technology 106 00:08:30,176 --> 00:08:31,200 that kills a star. 107 00:08:31,277 --> 00:08:32,801 Well, l mean, it's in your frying pan 108 00:08:32,879 --> 00:08:35,074 that you used this morning for breakfast... iron. 109 00:08:35,147 --> 00:08:38,605 The moment the white-dwarf star 110 00:08:38,684 --> 00:08:43,212 starts to fuse carbon and o xygen into iron, it's doomed. 111 00:08:45,892 --> 00:08:49,692 Suddenly, the white dwarf explodes. 112 00:09:06,312 --> 00:09:09,543 The nuclear explosion of a white dwarf include, 113 00:09:09,615 --> 00:09:12,106 among other things, huge amounts of iron. 114 00:09:12,184 --> 00:09:14,015 And, in fact, type 1 A supernovae 115 00:09:14,086 --> 00:09:16,884 are of vital importance to populating the universe 116 00:09:16,956 --> 00:09:19,823 with the kind of elements that are important to us. 117 00:09:27,166 --> 00:09:32,661 Type 1 A supernovas blast iron trillions of miles into space. 118 00:09:34,307 --> 00:09:38,243 lt's where most of the iron in the cosmos comes from. 119 00:09:43,349 --> 00:09:47,342 But what about all the elements that are heavier than iron, 120 00:09:47,420 --> 00:09:48,910 like gold and silver? 121 00:09:48,988 --> 00:09:50,649 Where do they come from? 122 00:09:50,723 --> 00:09:55,717 The answer, again, is other stars... 123 00:09:55,795 --> 00:09:57,660 single stars, 124 00:09:57,730 --> 00:09:59,391 bigger stars. 125 00:10:11,811 --> 00:10:15,440 Supernovas make everything in the universe. 126 00:10:15,514 --> 00:10:17,072 Everything we see, 127 00:10:17,149 --> 00:10:19,413 all the material in planet Earth, 128 00:10:19,485 --> 00:10:22,648 was created inside a supernova. 129 00:10:22,722 --> 00:10:27,386 Even you and l are made from dying stars. 130 00:10:27,460 --> 00:10:31,658 Without supernovae, we wouldn't be here. 131 00:10:31,731 --> 00:10:36,930 Every atom in your body was once inside a star that exploded. 132 00:10:37,003 --> 00:10:38,436 And the atoms in your left hand 133 00:10:38,504 --> 00:10:40,267 may have come from a different star 134 00:10:40,339 --> 00:10:41,738 than the atoms in your right hand. 135 00:10:41,807 --> 00:10:43,399 You are literally stardust. 136 00:10:48,514 --> 00:10:51,449 Almost all of the iron in our solar system 137 00:10:51,517 --> 00:10:53,747 came from a double-star supernova 138 00:10:53,819 --> 00:10:57,152 that exploded more than five billion years ago. 139 00:10:59,959 --> 00:11:03,554 From our planet's molten core... 140 00:11:03,629 --> 00:11:06,097 To our skyscrapers... 141 00:11:06,165 --> 00:11:09,566 To the hemoglobin in our blood... 142 00:11:11,837 --> 00:11:16,399 ...it's all made of iron from type 1 A supernovas. 143 00:11:19,311 --> 00:11:21,973 But the heavier elements in our world, 144 00:11:22,048 --> 00:11:24,107 like gold, silver, and uranium, 145 00:11:24,183 --> 00:11:26,845 come from another type of supernova... 146 00:11:31,257 --> 00:11:34,192 ...a single-star supernova. 147 00:11:37,129 --> 00:11:40,223 This is our Sun. 148 00:11:40,299 --> 00:11:44,429 A single star has to weigh much more than our Sun 149 00:11:44,503 --> 00:11:45,936 to go supernova. 150 00:11:47,339 --> 00:11:51,207 And there are some monster stars out there. 151 00:11:54,346 --> 00:11:58,077 Some are dozens of times heavier than our Sun. 152 00:11:59,452 --> 00:12:03,252 And some are hundreds of times more massive. 153 00:12:07,193 --> 00:12:11,596 The heavier the star, the faster it burns. 154 00:12:11,664 --> 00:12:16,101 And when these massive stars begin to age and die, 155 00:12:16,168 --> 00:12:20,070 the nuclear reactions inside them speed up. 156 00:12:22,575 --> 00:12:26,978 Giant stars burn through their nuclear fuel very, very fast... 157 00:12:27,046 --> 00:12:29,241 sort of the, you know, the "live fast, die young." 158 00:12:29,315 --> 00:12:31,977 The more mass a star has, the hotter it burns inside, 159 00:12:32,051 --> 00:12:33,985 the faster it burns through its fuel. 160 00:12:36,722 --> 00:12:39,748 Unlike double-star supernovas, 161 00:12:39,825 --> 00:12:41,759 really massive single stars 162 00:12:41,827 --> 00:12:45,092 create lots of elements before they explode. 163 00:12:51,137 --> 00:12:54,004 Once they turn hydrogen into helium, 164 00:12:54,073 --> 00:12:57,440 helium into carbon, and carbon into o xygen, 165 00:12:57,510 --> 00:13:00,843 they don't collapse into white-dwarf stars. 166 00:13:08,621 --> 00:13:11,954 lnstead, giant stars keep on burning, 167 00:13:12,024 --> 00:13:15,983 building up layer after layer of new elements 168 00:13:16,061 --> 00:13:17,756 deep in their core. 169 00:13:22,268 --> 00:13:24,168 Big stars don't stop 170 00:13:24,236 --> 00:13:27,171 after they've burned helium to carbon and o xygen. 171 00:13:27,239 --> 00:13:30,140 They go ahead and burn carbon to still heavier elements 172 00:13:30,209 --> 00:13:32,905 and then neon and o xygen to silicon... 173 00:13:32,978 --> 00:13:35,242 Until you get this nested Russian-doll 174 00:13:35,314 --> 00:13:37,441 spherical layer cake kind of thing. 175 00:13:39,251 --> 00:13:44,211 These elements are the building blocks of the universe. 176 00:13:44,290 --> 00:13:48,454 But they're trapped inside the giant star. 177 00:13:48,527 --> 00:13:52,896 Somehow, they've got to get out. 178 00:13:52,965 --> 00:13:55,058 Studying exploding stars 179 00:13:55,134 --> 00:13:57,432 has taught us how the heavy elements of the universe 180 00:13:57,503 --> 00:13:58,765 came to be. 181 00:13:58,838 --> 00:14:02,740 They were formed by nuclear reactions inside stars. 182 00:14:02,808 --> 00:14:06,403 But if some of those stars were not to explode, 183 00:14:06,478 --> 00:14:10,107 then those elements would be locked up forever. 184 00:14:12,751 --> 00:14:15,515 The trigger that'll release the elements 185 00:14:15,588 --> 00:14:18,819 in the single giant star is the same element 186 00:14:18,891 --> 00:14:22,657 that causes the type 1 A supernova to blow up... 187 00:14:22,728 --> 00:14:24,320 iron. 188 00:14:26,232 --> 00:14:30,726 lron eats up all the energy of the star's nuclear fusion. 189 00:14:36,308 --> 00:14:39,573 Without the energy from nuclear fusion pushing out, 190 00:14:39,645 --> 00:14:43,240 gravity begins to crush down. 191 00:14:43,315 --> 00:14:46,375 The big star is doomed. 192 00:14:49,355 --> 00:14:52,415 The last moments of a star are really phenomenal. 193 00:14:52,491 --> 00:14:55,051 The star might last for 1 0 million years 194 00:14:55,127 --> 00:14:57,391 on the way to becoming a supernova, 195 00:14:57,463 --> 00:15:00,523 but the last little bit takes place very rapidly. 196 00:15:00,599 --> 00:15:04,365 Once you have an iron core and once it gets out of balance, 197 00:15:04,436 --> 00:15:06,666 it collapses in a thousandth of a second, 198 00:15:06,739 --> 00:15:09,071 a millisecond, from the size of the Earth 199 00:15:09,141 --> 00:15:11,371 down to the size of manhattan. 200 00:15:11,443 --> 00:15:14,469 lt's traveling about 1 /3 of the speed of light 201 00:15:14,546 --> 00:15:16,377 as it crunches down. 202 00:15:19,551 --> 00:15:21,985 As the star becomes unstable, 203 00:15:22,054 --> 00:15:26,582 the massive power of gravity causes the core to collapse. 204 00:15:26,659 --> 00:15:29,787 This happens with such incredible power, 205 00:15:29,862 --> 00:15:33,389 even the atoms inside start to crush together. 206 00:15:41,840 --> 00:15:44,365 As it gets smaller and denser, 207 00:15:44,443 --> 00:15:48,038 the core builds up more and more energy. 208 00:15:48,113 --> 00:15:52,516 lt's something with about 1 1 /2 times the mass of the Sun 209 00:15:52,584 --> 00:15:54,381 that is collapsed to something 210 00:15:54,453 --> 00:15:56,683 that's only about 1 5 miles across. 211 00:15:59,591 --> 00:16:01,923 lt's got incredible density. 212 00:16:01,994 --> 00:16:06,328 lt's a thousand trillion times the density of water. 213 00:16:06,398 --> 00:16:09,390 Now the star explodes. 214 00:16:25,484 --> 00:16:28,419 The blast rips through the star's outer layers 215 00:16:28,487 --> 00:16:29,715 and in the process, 216 00:16:29,788 --> 00:16:32,416 makes all the elements heavier than iron. 217 00:16:41,500 --> 00:16:44,560 lron becomes cobalt. 218 00:16:44,636 --> 00:16:47,628 Cobalt becomes nickel. 219 00:16:47,706 --> 00:16:51,699 And on and on to gold, platinum, and uranium. 220 00:16:58,217 --> 00:16:59,878 The explosion is so brief, 221 00:16:59,952 --> 00:17:03,388 it only makes small amounts of these heavier elements, 222 00:17:03,455 --> 00:17:05,286 which is why they're so rare. 223 00:17:09,328 --> 00:17:12,855 The supernova blasts these new elements 224 00:17:12,931 --> 00:17:15,422 billions of miles into space. 225 00:17:15,501 --> 00:17:17,264 The only method we know, 226 00:17:17,336 --> 00:17:20,703 the only mechanism that we have found anywhere in the universe 227 00:17:20,773 --> 00:17:22,138 for creating new elements 228 00:17:22,207 --> 00:17:25,404 is in the death throes of a star called a supernova. 229 00:17:25,477 --> 00:17:28,605 lt seems incredible 230 00:17:28,680 --> 00:17:33,583 that anything could survive a supernova explosion. 231 00:17:36,221 --> 00:17:41,090 But we now know that some of the biggest bangs in the universe 232 00:17:41,160 --> 00:17:42,957 leave a corpse behind. 233 00:17:45,297 --> 00:17:48,232 And these are some of the strangest 234 00:17:48,300 --> 00:17:51,565 and most deadly objects ever discovered. 235 00:17:57,810 --> 00:18:01,507 When a giant star goes supernova and explodes, 236 00:18:01,580 --> 00:18:04,174 it's not always the end. 237 00:18:04,249 --> 00:18:07,412 Sometimes there's a corpse. 238 00:18:14,793 --> 00:18:18,820 What kind of corpse depends on the size of the star. 239 00:18:24,136 --> 00:18:28,402 Supernovas from stars more than eight times bigger than our Sun 240 00:18:28,474 --> 00:18:30,704 leave behind a neutron star. 241 00:18:30,776 --> 00:18:35,076 And it's one of the strangest objects in the universe. 242 00:18:38,584 --> 00:18:40,279 These things you can almost think of 243 00:18:40,352 --> 00:18:43,185 as sort of the zombies of the stellar world. 244 00:18:43,255 --> 00:18:45,655 They're very dangerous, they're very weird, 245 00:18:45,724 --> 00:18:47,658 and stars make them all the time. 246 00:18:47,726 --> 00:18:48,954 They're all around us. 247 00:18:53,065 --> 00:18:55,898 As a giant star goes supernova, 248 00:18:55,968 --> 00:18:58,994 the core is crushed from the size of a planet 249 00:18:59,071 --> 00:19:00,561 to the size of a city. 250 00:19:04,009 --> 00:19:06,910 The pressure in the core is so intense, 251 00:19:06,979 --> 00:19:10,278 even the atoms inside it are crushed together. 252 00:19:13,819 --> 00:19:16,151 When the atoms are packed that tightly 253 00:19:16,221 --> 00:19:18,451 and there's no space left between them, 254 00:19:18,524 --> 00:19:23,154 the massive energy buildup means something's got to give. 255 00:19:32,304 --> 00:19:36,263 The core blasts off the outer layers of the star. 256 00:19:42,414 --> 00:19:48,011 And what remains is a superdense neutron star. 257 00:19:48,086 --> 00:19:51,544 A neutron star has the mass of a star 258 00:19:51,623 --> 00:19:53,989 crunched into a very small volume, 259 00:19:54,059 --> 00:19:58,052 and that means the density is incredibly high. 260 00:19:58,130 --> 00:20:00,530 Well, imagine taking the empire state building here behind me, 261 00:20:00,599 --> 00:20:04,035 crushing it into the size of a grain of sand. 262 00:20:04,102 --> 00:20:08,937 That's the density of the entire neutron star. 263 00:20:09,007 --> 00:20:11,339 So if you had something that dense, if you dropped it, 264 00:20:11,410 --> 00:20:13,241 it would fall straight through the Earth, 265 00:20:13,312 --> 00:20:15,007 just like a hot knife through butter. 266 00:20:18,217 --> 00:20:24,122 A teaspoon of neutron star would weigh 1 00 million tons. 267 00:20:29,428 --> 00:20:32,488 lmagine something as heavy as a star 268 00:20:32,564 --> 00:20:35,556 but only the size of New York City. 269 00:20:35,634 --> 00:20:39,229 And it's spinning. 270 00:20:39,304 --> 00:20:42,034 Some of them may be born rotating 1,000 times a second. 271 00:20:42,107 --> 00:20:43,369 l mean, think about it... 272 00:20:43,442 --> 00:20:45,569 something 1 1 /2 times the mass of the Sun 273 00:20:45,644 --> 00:20:47,703 going around 1,000 times a second. 274 00:20:49,915 --> 00:20:53,146 Some neutron stars spin so fast, 275 00:20:53,218 --> 00:20:56,187 they generate huge pulses of energy... 276 00:20:57,556 --> 00:20:59,581 ...beams of radiation 277 00:20:59,658 --> 00:21:04,254 blasting out of the star's north and south poles. 278 00:21:04,329 --> 00:21:08,823 This neutron star is called a pulsar. 279 00:21:08,900 --> 00:21:12,336 There's one of these things in the center of the Crab Nebula... 280 00:21:12,404 --> 00:21:14,895 a place where there was a supernova explosion 281 00:21:14,973 --> 00:21:16,270 about 1,000 years ago. 282 00:21:16,341 --> 00:21:20,334 And it's one of the fastest spinning of these objects. 283 00:21:21,813 --> 00:21:26,011 This is the actual sound a pulsar makes, 284 00:21:26,084 --> 00:21:28,177 recorded by radio telescope. 285 00:21:31,156 --> 00:21:36,116 lt will flash 30 times a second for millions of years. 286 00:21:45,804 --> 00:21:48,329 But pulsars aren't the strangest thing 287 00:21:48,407 --> 00:21:50,238 a supernova can leave behind. 288 00:21:53,879 --> 00:21:58,009 When stars 30 times bigger than our Sun explode, 289 00:21:58,083 --> 00:22:03,385 they produce a type of neutron star called a magnetar. 290 00:22:10,228 --> 00:22:13,163 Magnetars are even weirder than pulsars 291 00:22:13,231 --> 00:22:16,132 and generate powerful magnetic fields. 292 00:22:18,403 --> 00:22:20,997 Now, in the most extreme case, 293 00:22:21,073 --> 00:22:23,598 the magnetic field can be 1 0 to the 1 5, 294 00:22:23,675 --> 00:22:26,235 you know, a... a hundred trillion times 295 00:22:26,311 --> 00:22:28,245 the magnetic field of the Earth. 296 00:22:31,550 --> 00:22:33,211 That's so strong, 297 00:22:33,285 --> 00:22:36,220 it would suck the iron right out of your blood 298 00:22:36,288 --> 00:22:38,051 from thousands of miles away. 299 00:22:39,691 --> 00:22:41,784 But even pulsars and magnetars 300 00:22:41,860 --> 00:22:43,851 aren't the most dangerous objects 301 00:22:43,929 --> 00:22:46,454 a supernova can leave behind. 302 00:22:48,767 --> 00:22:52,430 When the core of a supermassive star collapses, 303 00:22:52,504 --> 00:22:54,631 it doesn't just crush atoms, 304 00:22:54,706 --> 00:22:58,301 it crushes space and time itself. 305 00:23:00,479 --> 00:23:06,042 And that is when a supernova creates a black hole. 306 00:23:15,694 --> 00:23:20,256 When stars over 1 00 times heavier than our Sun explode, 307 00:23:20,332 --> 00:23:23,460 they make a supernova explosion so big... 308 00:23:25,036 --> 00:23:27,971 ...scientists call them hypernovas. 309 00:23:33,078 --> 00:23:37,913 And it was a hypernova that almost started World War lll. 310 00:23:45,857 --> 00:23:48,348 ln 1 963, 311 00:23:48,427 --> 00:23:50,122 the U.S. and Soviet Union 312 00:23:50,195 --> 00:23:52,891 agreed to ban testing nuclear weapons. 313 00:23:58,637 --> 00:24:01,265 To keep tabs on the Russians, 314 00:24:01,339 --> 00:24:03,739 the U.S. launched spy satellites. 315 00:24:06,745 --> 00:24:11,648 When they heard this sound coming from deep space, 316 00:24:11,716 --> 00:24:14,241 they suspected the worst. 317 00:24:18,857 --> 00:24:21,849 United States government launched the Vela satellite, 318 00:24:21,927 --> 00:24:24,555 looking for nuclear detonations. 319 00:24:30,735 --> 00:24:33,101 And then, looking in outer space, 320 00:24:33,171 --> 00:24:35,765 they saw these monster explosions take place. 321 00:24:35,841 --> 00:24:38,776 And the military thought, "Oh, my God, the Russians! 322 00:24:38,844 --> 00:24:42,007 The Russians are testing secret atomic weapons in space." 323 00:24:43,548 --> 00:24:47,006 But these weren't secret atomic-bomb tests, 324 00:24:47,085 --> 00:24:50,577 and the Russians had nothing to do with them. 325 00:24:50,655 --> 00:24:53,590 They began to look at where this radiation came from. 326 00:24:53,658 --> 00:24:56,559 lt came from all over the galaxy, beyond the galaxy. 327 00:24:56,628 --> 00:25:00,029 Now, there's no way the Russians could shoot explosions 328 00:25:00,098 --> 00:25:02,191 in outer space beyond the galaxy. 329 00:25:02,267 --> 00:25:04,497 And then people began to realize 330 00:25:04,569 --> 00:25:07,970 that we were staring something new in the face. 331 00:25:08,039 --> 00:25:11,805 They were super-powerful explosions 332 00:25:11,877 --> 00:25:15,904 of high-energy radiation called gamma-ray bursts. 333 00:25:15,981 --> 00:25:19,576 The question was, where did they come from? 334 00:25:21,620 --> 00:25:25,056 The answer was exploding hypernovas. 335 00:25:36,735 --> 00:25:39,397 During a regular supernova explosion, 336 00:25:39,471 --> 00:25:44,067 gravity crushes a star's core into a neutron star. 337 00:25:44,142 --> 00:25:47,043 But during a hypernova explosion, 338 00:25:47,112 --> 00:25:49,603 the giant star is so much bigger 339 00:25:49,681 --> 00:25:54,550 that gravity crushes the core into something much stranger... 340 00:25:57,889 --> 00:25:59,516 ...a black hole. 341 00:26:01,793 --> 00:26:03,351 And the black hole 342 00:26:03,428 --> 00:26:07,831 immediately begins to devour the dying star around it. 343 00:26:07,899 --> 00:26:09,958 The rest of the star can't all go 344 00:26:10,035 --> 00:26:12,003 in that little bitty hole in the middle. 345 00:26:12,070 --> 00:26:15,198 lt starts to swirl around, and it forms an accretion disk, 346 00:26:15,273 --> 00:26:17,002 which is feeding the black hole 347 00:26:17,075 --> 00:26:19,543 at about a million earth masses a second. 348 00:26:19,611 --> 00:26:20,839 And so, as you might imagine, 349 00:26:20,912 --> 00:26:22,743 something dramatic is gonna happen here. 350 00:26:25,216 --> 00:26:28,049 A million earth masses a second 351 00:26:28,119 --> 00:26:31,714 is too much for the black hole to consume all at once. 352 00:26:36,361 --> 00:26:41,389 So it spits a lot of it back out at nearly the speed of light. 353 00:26:46,471 --> 00:26:49,372 This creates two beams of pure energy 354 00:26:49,441 --> 00:26:52,501 blasting their way out of the black hole. 355 00:26:55,246 --> 00:26:58,238 Takes it about eight seconds to bore through the star, 356 00:26:58,316 --> 00:27:01,752 keeping a very tight focus, and erupt from the surface. 357 00:27:01,820 --> 00:27:04,983 Now, if we're standing in the opening of this jet, 358 00:27:05,056 --> 00:27:06,751 we'll see gamma-ray bursts. 359 00:27:10,228 --> 00:27:13,493 The gamma rays produced from the black hole 360 00:27:13,565 --> 00:27:17,023 tear through the outer layers of the star and into space. 361 00:27:17,102 --> 00:27:19,468 Gamma-ray bursts are the most violent event 362 00:27:19,537 --> 00:27:21,198 that we know of in the universe. 363 00:27:21,272 --> 00:27:24,366 A giant star blows itself to pieces and forms a black hole. 364 00:27:24,442 --> 00:27:25,909 lt's incredibly spectacular. 365 00:27:25,977 --> 00:27:28,445 These gamma-ray bursts are so energetic, 366 00:27:28,513 --> 00:27:30,674 they light up the entire universe. 367 00:27:30,749 --> 00:27:32,512 Any point in the universe 368 00:27:32,584 --> 00:27:36,145 will eventually pick up this astounding radiation 369 00:27:36,221 --> 00:27:37,882 coming from a gamma-ray burst. 370 00:27:37,956 --> 00:27:41,517 That's how energetic they are. 371 00:27:41,593 --> 00:27:46,257 They are the brightest things in the known universe. 372 00:27:46,331 --> 00:27:48,390 To put things in perspective, 373 00:27:48,466 --> 00:27:49,933 a typical supernova explosion 374 00:27:50,001 --> 00:27:51,866 is about what the Sun will put out 375 00:27:51,936 --> 00:27:54,029 in its entire 1 0-billion-year lifetime. 376 00:27:54,105 --> 00:27:57,040 A gamma-ray burst viewed jet on 377 00:27:57,108 --> 00:28:02,603 is a hundred million times more luminous than a supernova. 378 00:28:02,681 --> 00:28:04,876 They're the champions for brightness, for sure. 379 00:28:10,388 --> 00:28:13,687 They're not only bright, they're lethal. 380 00:28:17,095 --> 00:28:20,394 lf a gamma-ray burst were to hit the Earth, 381 00:28:20,465 --> 00:28:24,299 it would destroy most of the atmosphere in seconds. 382 00:28:28,039 --> 00:28:30,803 A gamma-ray burster is like a rifle shot. 383 00:28:33,678 --> 00:28:36,977 And if you're in the line of sight... 384 00:28:37,048 --> 00:28:38,379 Watch out. 385 00:28:38,450 --> 00:28:40,350 Once the radiation hits you, 386 00:28:40,418 --> 00:28:44,650 it'll bathe the entire surface of the Earth with nitric o xides, 387 00:28:44,723 --> 00:28:47,317 which will wipe out the ozone layer. 388 00:28:48,860 --> 00:28:52,591 Blistering radiation would hit plant life, hit algae. 389 00:28:52,664 --> 00:28:55,326 The whole food chain would collapse. 390 00:28:55,400 --> 00:28:57,527 lf the burst was close enough, 391 00:28:57,602 --> 00:29:00,093 it would cause mass extinctions. 392 00:29:00,171 --> 00:29:03,004 Gamma-ray bursts turn out to be a lot more common 393 00:29:03,074 --> 00:29:04,098 than we thought they would be. 394 00:29:04,175 --> 00:29:05,437 So it's possible that some of these 395 00:29:05,510 --> 00:29:06,943 have even hit the Earth in the past. 396 00:29:07,011 --> 00:29:11,641 That's a pretty scary scenario. lt may already have happened. 397 00:29:11,716 --> 00:29:15,618 The question is, if it happened before, 398 00:29:15,687 --> 00:29:18,121 could it happen again? 399 00:29:22,327 --> 00:29:25,660 A gamma-ray burster is basically a supernova on steroids. 400 00:29:25,730 --> 00:29:28,130 You need a giant star to die violently. 401 00:29:28,199 --> 00:29:31,134 Now, the nearest star to us that might do that is Eta Carinae, 402 00:29:31,202 --> 00:29:33,261 and it's a spectacular nebula. 403 00:29:33,338 --> 00:29:36,034 There's all kinds of material flying off this star. 404 00:29:36,107 --> 00:29:37,506 lt's very unstable. 405 00:29:37,575 --> 00:29:40,976 lt may already have exploded in a gamma-ray burst. 406 00:29:41,045 --> 00:29:44,913 But Eta Carinae may not be the only threat. 407 00:29:44,983 --> 00:29:49,079 There are other dying stars out there. 408 00:29:49,154 --> 00:29:52,453 Believe it or not, one of them is pointed in our direction. 409 00:29:52,524 --> 00:29:59,054 We are staring down the gun barrel of WR1 04... 410 00:29:59,130 --> 00:30:03,760 two dying stars that will one day undergo the gamma-ray burst. 411 00:30:03,835 --> 00:30:08,966 Not a question of if, a question of when. 412 00:30:09,040 --> 00:30:12,669 That WR1 04 may have our name on it. 413 00:30:12,744 --> 00:30:13,836 But the good news is 414 00:30:13,912 --> 00:30:16,073 we probably wouldn't know about it in advance. 415 00:30:16,147 --> 00:30:19,048 The shock would hit us before we had a chance to do anything. 416 00:30:19,117 --> 00:30:21,347 So there's no sense worrying about it anyway. 417 00:30:26,958 --> 00:30:28,448 The truth is, 418 00:30:28,526 --> 00:30:31,620 we'll never know if a star is about to go hypernova 419 00:30:31,696 --> 00:30:32,958 and explode. 420 00:30:36,634 --> 00:30:40,661 Anyway, by the time we see it, it'll already be too late. 421 00:30:44,475 --> 00:30:50,107 ln fact, we're already exposed to rays from dying stars 422 00:30:50,181 --> 00:30:52,877 every second of every day. 423 00:31:00,191 --> 00:31:02,819 When giant stars explode... 424 00:31:04,729 --> 00:31:07,823 ...they make the biggest bangs in the universe. 425 00:31:13,338 --> 00:31:16,239 But what gives them so much punch? 426 00:31:19,377 --> 00:31:22,869 Until recently, no one knew. 427 00:31:22,947 --> 00:31:24,437 Scientists, 428 00:31:24,515 --> 00:31:27,541 when they tried to simulate a supernova explosion 429 00:31:27,619 --> 00:31:30,952 in a computer, had a problem. 430 00:31:31,022 --> 00:31:34,822 They simply could not get enough energy out of the dying star 431 00:31:34,893 --> 00:31:36,326 to create a supernova. 432 00:31:36,394 --> 00:31:38,624 This was a calamity in astronomy. 433 00:31:47,005 --> 00:31:51,305 Computer models couldn't make the simulated stars blow up. 434 00:31:56,581 --> 00:32:00,381 To blow up a star, you need a lot of energy. 435 00:32:02,353 --> 00:32:06,653 The trouble was, astronomers couldn't find it. 436 00:32:06,724 --> 00:32:09,750 The visible radiation that you see 437 00:32:09,827 --> 00:32:13,888 is a tiny fraction of the total energy emitted. 438 00:32:13,965 --> 00:32:17,833 Even the energy of motion of the expanding gases 439 00:32:17,902 --> 00:32:20,302 is only 1 % of the total energy. 440 00:32:20,371 --> 00:32:24,239 Where was the missing 99% of the energy 441 00:32:24,309 --> 00:32:25,867 from the explosion? 442 00:32:25,944 --> 00:32:27,309 The only way scientists 443 00:32:27,378 --> 00:32:30,472 could get their simulations to match the real thing 444 00:32:30,548 --> 00:32:35,281 was to add in a mysterious particle called the neutrino. 445 00:32:35,353 --> 00:32:39,414 Without it, their numbers didn't add up. 446 00:32:39,490 --> 00:32:43,017 That was the easy bit. 447 00:32:43,094 --> 00:32:44,584 Their next step 448 00:32:44,662 --> 00:32:49,326 was to prove supernovas really do produce neutrinos. 449 00:32:53,271 --> 00:32:56,832 ln 1 987, they got lucky. 450 00:33:00,745 --> 00:33:03,111 1 68,000 years ago, 451 00:33:03,181 --> 00:33:06,344 a supernova exploded in a nearby galaxy 452 00:33:06,417 --> 00:33:09,215 called the Large Magellanic Cloud. 453 00:33:11,756 --> 00:33:14,884 When scientists saw the light from the blast, 454 00:33:14,959 --> 00:33:18,520 they called it supernova 1 987. 455 00:33:21,466 --> 00:33:23,661 Supernova 1 987 A is really important 456 00:33:23,735 --> 00:33:26,898 in the study of supernovae because it's the first one 457 00:33:26,971 --> 00:33:29,405 since the invention of the telescope. 458 00:33:29,474 --> 00:33:32,034 lt's the one that we've been able to study 459 00:33:32,110 --> 00:33:34,840 right from the time of explosion through now, 460 00:33:34,912 --> 00:33:37,745 using all the instruments that we've developed. 461 00:33:37,815 --> 00:33:39,942 One of those instruments 462 00:33:40,018 --> 00:33:44,421 was a giant neutrino detector buried deep underground. 463 00:33:44,489 --> 00:33:47,549 And bingo... we saw a burst of radiation 464 00:33:47,625 --> 00:33:49,616 go through our neutrino detectors, 465 00:33:49,694 --> 00:33:53,221 and we said, "Aha! That's the proof!" 466 00:33:53,297 --> 00:33:56,630 The discovery of neutrinos from supernova 1 987 A 467 00:33:56,701 --> 00:33:57,963 was a tremendous thing 468 00:33:58,036 --> 00:34:00,664 because for many years people had been saying, 469 00:34:00,738 --> 00:34:02,968 "That's where 99% of the energy goes," 470 00:34:03,041 --> 00:34:04,565 but no one had ever seen it. 471 00:34:04,642 --> 00:34:06,576 This is now the smoking gun 472 00:34:06,644 --> 00:34:09,408 that we can now prove that neutrinos 473 00:34:09,480 --> 00:34:11,710 carry the energy of a supernova, 474 00:34:11,783 --> 00:34:14,115 and we detected it right on the Earth 475 00:34:14,185 --> 00:34:17,484 as we saw a supernova in outer space. 476 00:34:19,424 --> 00:34:24,828 Neutrinos are trillions of times smaller than atoms. 477 00:34:28,066 --> 00:34:32,162 They're created by all sorts of nuclear reactions... 478 00:34:33,604 --> 00:34:38,439 ...from nuclear power plants and bombs to exploding stars. 479 00:34:40,111 --> 00:34:45,344 lf you had "neutrino-vision," you'd see them everywhere. 480 00:34:50,254 --> 00:34:53,621 Neutrinos are ghostlike particles. 481 00:34:55,326 --> 00:34:58,523 Literally, trillions of them are going through my body 482 00:34:58,596 --> 00:34:59,893 even as we speak. 483 00:34:59,964 --> 00:35:02,899 ln fact, neutrinos come from the bottom of the floor, 484 00:35:02,967 --> 00:35:04,434 right through the Earth, 485 00:35:04,502 --> 00:35:06,868 and even hit me right through my legs. 486 00:35:06,938 --> 00:35:10,499 Pretty strange. 487 00:35:10,575 --> 00:35:16,070 lmagine so many tiny particles zooming through our bodies. 488 00:35:16,147 --> 00:35:20,208 But where do they get all their energy? 489 00:35:22,954 --> 00:35:27,721 When a core crushes down just before a supernova explosion, 490 00:35:27,792 --> 00:35:30,784 the atoms inside it are broken up. 491 00:35:34,465 --> 00:35:36,296 The core gets so hot, 492 00:35:36,367 --> 00:35:40,701 it turns this atomic debris into blazing neutrinos. 493 00:35:45,143 --> 00:35:49,546 We think that supernovae produce a stupendous sum of neutrinos 494 00:35:49,614 --> 00:35:52,777 when the core collapses to a neutron star. 495 00:35:52,850 --> 00:35:54,112 For about 1 0 seconds, 496 00:35:54,185 --> 00:35:56,813 that core shines with a neutrino luminosity 497 00:35:56,888 --> 00:36:00,016 that is greater than all of the energy being produced 498 00:36:00,091 --> 00:36:02,582 in the rest of the universe at that time. 499 00:36:02,660 --> 00:36:07,324 ln other words, it's really bright. 500 00:36:07,398 --> 00:36:11,357 But gravity can't hold these neutrinos in the core. 501 00:36:13,538 --> 00:36:17,304 They burst free in a blinding flash of light 502 00:36:17,375 --> 00:36:19,900 that rips the dying star apart. 503 00:36:25,516 --> 00:36:26,983 The discovery of neutrinos 504 00:36:27,051 --> 00:36:30,145 transformed the science of supernovas. 505 00:36:31,856 --> 00:36:34,848 But supernovas were about to reveal 506 00:36:34,926 --> 00:36:37,895 the most mysterious force of all... 507 00:36:37,962 --> 00:36:41,864 one that's changing the destiny of the universe. 508 00:36:50,141 --> 00:36:52,541 Supernova explosions are so bright, 509 00:36:52,610 --> 00:36:55,738 we can see them across the entire universe. 510 00:36:58,015 --> 00:37:00,040 This has helped astronomers 511 00:37:00,117 --> 00:37:03,883 unlock one of the deepest mysteries of the cosmos. 512 00:37:08,125 --> 00:37:10,286 The universe came to life 513 00:37:10,361 --> 00:37:13,694 in the Big Bang 1 4 billion years ago. 514 00:37:17,802 --> 00:37:23,035 lt expanded from a tiny ball of energy smaller than an atom 515 00:37:23,107 --> 00:37:28,272 to a universe billions and billions of light-years across. 516 00:37:28,346 --> 00:37:31,338 And it's still expanding. 517 00:37:32,917 --> 00:37:34,942 l've often wondered how far future people 518 00:37:35,019 --> 00:37:36,919 will even know the Big Bang happened, 519 00:37:36,988 --> 00:37:38,853 because we know the Big Bang happened 520 00:37:38,923 --> 00:37:41,255 from watching all the galaxies fly away from us. 521 00:37:43,494 --> 00:37:47,487 Someday, the galaxies will be so far away from each other, 522 00:37:47,565 --> 00:37:51,296 it will be impossible to see anything else in the sky. 523 00:37:51,369 --> 00:37:53,394 Scientists used to think 524 00:37:53,471 --> 00:37:56,201 the expanding universe was slowing down, 525 00:37:56,274 --> 00:37:59,038 but there was no way to prove it... 526 00:38:02,113 --> 00:38:07,517 ...until they found double-star supernovas, type 1 AS. 527 00:38:09,987 --> 00:38:13,923 They always explode when the white-dwarf star 528 00:38:13,991 --> 00:38:17,984 reaches exactly 1 .4 times the mass of our Sun. 529 00:38:23,367 --> 00:38:25,358 And their explosions 530 00:38:25,436 --> 00:38:30,066 always release exactly the same amount of light. 531 00:38:31,642 --> 00:38:36,545 They are the perfect markers to measure distance in space. 532 00:38:38,149 --> 00:38:39,776 Type 1 A supernovae, 533 00:38:39,850 --> 00:38:42,944 when we know how bright they are and how bright they look, 534 00:38:43,020 --> 00:38:44,385 we can tell the distance, 535 00:38:44,455 --> 00:38:46,389 'cause the farther away they are, 536 00:38:46,457 --> 00:38:48,982 the less bright they'll look in the telescope. 537 00:38:51,095 --> 00:38:54,189 And that has allowed us to accurately measure distances 538 00:38:54,265 --> 00:38:55,789 not just to nearby galaxies 539 00:38:55,866 --> 00:38:58,767 but to galaxies at the other end of the visible universe... 540 00:38:58,836 --> 00:39:01,168 billions of light-years. 541 00:39:01,238 --> 00:39:04,002 And that has allowed us to make incredible discoveries. 542 00:39:06,377 --> 00:39:09,073 Astronomers thought they had found a way 543 00:39:09,146 --> 00:39:13,344 to prove the expansion rate of the universe was slowing down. 544 00:39:13,417 --> 00:39:16,284 What they got was a big surprise. 545 00:39:17,855 --> 00:39:19,288 ln 1 998, 546 00:39:19,357 --> 00:39:23,293 astronomers made a remarkable and unexpected discovery. 547 00:39:23,361 --> 00:39:25,158 lt was recognized that the universe, 548 00:39:25,229 --> 00:39:26,526 which should be slowing down, 549 00:39:26,597 --> 00:39:28,588 'cause gravity, after all, is attractive, 550 00:39:28,666 --> 00:39:31,032 and the mass of objects should cause the expansion 551 00:39:31,102 --> 00:39:32,433 of the universe to slow down. 552 00:39:32,503 --> 00:39:35,870 But the expansion is speeding up. 553 00:39:35,940 --> 00:39:37,737 lt's accelerating. 554 00:39:40,444 --> 00:39:43,880 The constant light from type 1 A supernovas 555 00:39:43,948 --> 00:39:46,712 completely changed the way astronomers 556 00:39:46,784 --> 00:39:48,217 understand the universe. 557 00:39:48,285 --> 00:39:51,152 Every science textbook on the Earth 558 00:39:51,222 --> 00:39:54,783 says that the universe is expanding and slowing down. 559 00:39:54,859 --> 00:39:56,326 Wrong. 560 00:39:56,394 --> 00:39:59,557 We now have to rewrite all the science textbooks 561 00:39:59,630 --> 00:40:00,961 on the planet Earth. 562 00:40:06,303 --> 00:40:08,396 But astronomers still didn't know 563 00:40:08,472 --> 00:40:12,169 why the universe is expanding faster and faster. 564 00:40:13,477 --> 00:40:18,176 They began to think it's some kind of unknown energy. 565 00:40:20,418 --> 00:40:22,249 They called it "dark energy," 566 00:40:22,319 --> 00:40:24,344 but it's difficult to prove 567 00:40:24,422 --> 00:40:29,018 because it can't be seen or touched or detected. 568 00:40:29,093 --> 00:40:32,824 We really don't have a very good clue 569 00:40:32,897 --> 00:40:36,799 as to the physical nature and origin of dark energy. 570 00:40:38,702 --> 00:40:40,465 lt's perhaps the number-one 571 00:40:40,538 --> 00:40:42,870 observationally motivated problem 572 00:40:42,940 --> 00:40:46,899 in all of physics right now... the nature of the dark energy. 573 00:40:55,152 --> 00:40:57,950 From dark energy to black holes, 574 00:40:58,022 --> 00:40:59,546 supernovas have revealed 575 00:40:59,623 --> 00:41:02,990 some of the most profound mysteries of the universe. 576 00:41:07,531 --> 00:41:09,192 These exploding stars 577 00:41:09,266 --> 00:41:12,030 give us the building blocks of the universe 578 00:41:12,102 --> 00:41:15,071 and show us how it's all made. 579 00:41:17,107 --> 00:41:18,904 lt's hard to imagine, 580 00:41:18,976 --> 00:41:21,410 but the atoms in our bodies today 581 00:41:21,479 --> 00:41:25,916 were made by a supernova billions of years ago. 582 00:41:30,020 --> 00:41:32,147 The Bible say, "From dust to dust." 583 00:41:32,223 --> 00:41:35,989 Astronomers say, "From stardust to stardust." 584 00:41:36,060 --> 00:41:41,589 So supernovae are the key link in this cycle of life. 585 00:41:41,665 --> 00:41:44,259 People think of space as being something 586 00:41:44,335 --> 00:41:45,962 very distant and very remote. 587 00:41:46,036 --> 00:41:49,130 lt's light-years away, hugely distant from us. 588 00:41:49,206 --> 00:41:50,833 That's completely wrong. 589 00:41:50,908 --> 00:41:52,637 Supernovae are right here. 590 00:41:52,710 --> 00:41:54,234 We are their children. 591 00:41:54,311 --> 00:41:57,109 They made us, literally put us together. 592 00:41:57,181 --> 00:41:58,375 We are star stuff. 593 00:41:58,449 --> 00:42:01,885 Without the supernovas, we could not exist. 594 00:42:01,952 --> 00:42:05,115 So when we walk around at night and we look up at the night sky 595 00:42:05,189 --> 00:42:08,784 and we see the stars and we feel somehow a part of them... 596 00:42:10,394 --> 00:42:12,362 ...the truth is, we are. 597 00:42:12,429 --> 00:42:14,420 They are our parents. 598 00:42:22,540 --> 00:42:28,308 Some scientists believe the age of supernovas could be ending. 599 00:42:28,379 --> 00:42:31,871 Smaller, slower-burning stars, like our Sun, 600 00:42:31,949 --> 00:42:33,746 will become more common 601 00:42:33,817 --> 00:42:36,581 and giant stars become more rare. 602 00:42:42,192 --> 00:42:45,355 Supernovas have given us galaxies, 603 00:42:45,429 --> 00:42:49,263 solar systems, stars, and planets. 604 00:42:49,333 --> 00:42:53,167 They made us and everything we see. 605 00:42:55,406 --> 00:42:58,307 They are where destruction and creation meet. 606 00:42:58,375 --> 00:43:00,240 The destiny of the universe 607 00:43:00,311 --> 00:43:04,611 lies in the ashes of dying stars.