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1
00:00:04,472 --> 00:00:08,640
Narrator:
THE FATE OF OUR GALAXY
HANGS IN THE BALANCE.
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00:00:08,642 --> 00:00:14,880
THE MILKY WAY IS DYING,
AND WE DON'T KNOW WHY.
3
00:00:14,882 --> 00:00:19,785
OUR GALAXY, LIKE ALL GALAXIES,
HAS A LIMITED LIFE-SPAN.
4
00:00:19,787 --> 00:00:23,622
AFTER THAT, IT'S LIGHTS OUT.
5
00:00:23,624 --> 00:00:26,492
Narrator: THE RACE IS ON
TO FIND A SMOKING GUN.
6
00:00:28,829 --> 00:00:32,598
IT'S SAFE TO SAY RIGHT NOW THERE
ARE MANY WAYS TO KILL A GALAXY.
7
00:00:35,803 --> 00:00:39,738
Narrator: IT'S A COSMIC
CRIME SCENE INVESTIGATION.
8
00:00:39,740 --> 00:00:42,908
IS IT MURDER MOST FOUL?
9
00:00:42,910 --> 00:00:45,010
OR IS IT
DEATH BY NATURAL CAUSES?
10
00:00:47,314 --> 00:00:49,782
Narrator:
THE SUSPECTS ARE LINED UP.
11
00:00:49,784 --> 00:00:52,251
THE INTERROGATION IS UNDERWAY.
12
00:00:56,257 --> 00:00:58,557
IT'S ANOTHER EXAMPLE OF THIS BIG
UNIVERSE OF OURS
13
00:00:58,559 --> 00:01:01,093
THROWING PUZZLES AT US
THAT NOW WE HAVE TO SOLVE.
14
00:01:04,031 --> 00:01:07,266
Narrator:
WHAT IS KILLING THE MILKY WAY?
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00:01:07,268 --> 00:01:10,269
-- Captions by VITAC --
www.vitac.com
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00:01:10,271 --> 00:01:13,272
CAPTIONS PAID FOR BY
DISCOVERY COMMUNICATIONS
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♪♪
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00:01:23,284 --> 00:01:25,517
♪♪
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EARTH.
20
00:01:27,855 --> 00:01:30,422
OUR HOME.
21
00:01:30,424 --> 00:01:34,626
JUST ONE OF 100 BILLION PLANETS
22
00:01:34,628 --> 00:01:38,897
ORBITING 400 BILLION STARS
23
00:01:38,899 --> 00:01:42,568
THAT MAKE UP AN IMMENSE
GALACTIC SPIRAL...
24
00:01:44,572 --> 00:01:47,106
...THE MILKY WAY.
25
00:01:49,877 --> 00:01:52,478
Thaller:
GALAXIES ARE WHERE STARS FORM,
26
00:01:52,480 --> 00:01:54,813
AND, OF COURSE,
PLANETS FORM AROUND STARS,
27
00:01:54,815 --> 00:01:56,648
SO THE STORY OF THE EARTH,
28
00:01:56,650 --> 00:01:58,884
OF YOURSELF,
OF THE SOLAR SYSTEM
29
00:01:58,886 --> 00:02:02,321
HAS EVERYTHING TO DO
WITH THE STORY OF THE GALAXIES.
30
00:02:05,626 --> 00:02:10,863
Narrator:
THE STORY OF THE MILKY WAY
BEGINS 13.6 BILLION YEARS AGO,
31
00:02:10,865 --> 00:02:13,465
JUST AFTER THE BIG BANG.
32
00:02:13,467 --> 00:02:17,536
IT'S A TIME WHEN THERE ARE
NO PLANETS AND NO STARS --
33
00:02:17,538 --> 00:02:22,741
JUST A VAST, LUMPY SOUP
OF SUPERHEATED HYDROGEN GAS.
34
00:02:25,479 --> 00:02:28,647
OVER MILLIONS OF YEARS,
THE TEMPERATURE DROPS,
35
00:02:28,649 --> 00:02:33,051
AND GRAVITY COMPRESSES
THE LUMPS DOWN, UNTIL EVENTUALLY
36
00:02:33,053 --> 00:02:37,856
THE HYDROGEN MOLECULES FUSE
AND IGNITE A STAR.
37
00:02:42,329 --> 00:02:47,833
IN TIME, BILLIONS OF STARS
BURST INTO LIFE.
38
00:02:47,835 --> 00:02:51,103
AND THE MILKY WAY
BEGINS TO TAKE SHAPE.
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00:02:51,105 --> 00:02:56,175
♪♪
40
00:02:56,177 --> 00:02:58,911
YOU CAN THINK OF A GALAXY
AS SORT OF LIKE A HUMAN BEING.
41
00:02:58,913 --> 00:03:01,346
WHEN YOU'RE YOUNG AND IN YOUR
ADOLESCENT STAGE,
42
00:03:01,348 --> 00:03:02,814
YOU'RE VIBRANT AND ACTIVE.
43
00:03:02,816 --> 00:03:05,584
THAT'S A YOUNG GALAXY
FORMING STARS IN A CRAZY WAY,
44
00:03:05,586 --> 00:03:07,219
AND IT'S NOT
EVEN FULLY FORMED YET.
45
00:03:07,221 --> 00:03:09,888
AT A CERTAIN POINT,
GALAXY REACHES MIDDLE AGE,
46
00:03:09,890 --> 00:03:12,491
AND A MIDDLE-AGED GALAXY REALLY
IS WHAT IT'S GOING TO BE --
47
00:03:12,493 --> 00:03:13,792
IT HAS ITS SHAPE --
48
00:03:13,794 --> 00:03:17,062
BUT IN THE LONG RUN, A GALAXY
WILL STOP FORMING STARS,
49
00:03:17,064 --> 00:03:20,699
AND EVENTUALLY, JUST LIKE WE
ALL DIE, OUR GALAXY WILL DIE.
50
00:03:24,004 --> 00:03:27,806
Narrator:
SO, AT WHAT STAGE OF LIFE
IS THE MILKY WAY?
51
00:03:27,808 --> 00:03:30,409
IS IT A HEALTHY,
ACTIVE YOUNGSTER,
52
00:03:30,411 --> 00:03:32,578
OR IS IT HEADING
FOR ITS DEATHBED?
53
00:03:35,783 --> 00:03:39,518
SCIENTISTS CAN DETERMINE
EACH GALAXY'S STAGE OF LIFE
54
00:03:39,520 --> 00:03:42,387
BY ITS COLOR.
55
00:03:42,389 --> 00:03:47,226
Sutter:
SO, WE SEE DIFFERENT COLORS
OF GALAXIES IN THE UNIVERSE.
56
00:03:47,228 --> 00:03:49,761
WE SEE GALAXIES
THAT ARE TINTED BLUE
57
00:03:49,763 --> 00:03:54,499
AND GALAXIES
THAT ARE TINTED RED.
58
00:03:54,501 --> 00:03:59,705
WHEN WE SEE A BLUE GALAXY, THAT
TENDS TO BE A YOUNGER GALAXY
59
00:03:59,707 --> 00:04:04,009
FULL OF BRIGHT,
HOT, NEWLY FORMED STARS.
60
00:04:06,480 --> 00:04:08,647
WHEN WE SEE A REDDER GALAXY,
61
00:04:08,649 --> 00:04:11,817
THAT TENDS
TO BE A DIMMER, OLDER GALAXY
62
00:04:11,819 --> 00:04:15,654
THAT ISN'T FORMING NEW STARS
IN THE PRESENT MOMENT.
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00:04:15,656 --> 00:04:18,857
ALL ITS STARS ARE AGED
AND OLDER AND REDDER,
64
00:04:18,859 --> 00:04:22,494
AND SO THE ENTIRE GALAXY
CASTS A DIFFERENT HUE.
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00:04:22,496 --> 00:04:27,866
♪♪
66
00:04:27,868 --> 00:04:32,804
Narrator:
SO, WHAT COLOR IS OUR GALAXY?
67
00:04:32,806 --> 00:04:38,777
IT'S A SIMPLE QUESTION, BUT THE
ANSWER IS HARD TO COME BY,
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EVEN THOUGH WE'VE BEEN LOOKING
AT THE MILKY WAY
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00:04:41,715 --> 00:04:44,783
FOR THOUSANDS OF YEARS.
70
00:04:44,785 --> 00:04:46,852
THE TERM "MILKY WAY" IS ANCIENT.
71
00:04:46,854 --> 00:04:49,054
IT GOES BACK TO A TIME
WHEN IN THE DARK SKY,
72
00:04:49,056 --> 00:04:51,290
PEOPLE NOTICED
THERE WAS THIS LIGHT BAND
73
00:04:51,292 --> 00:04:53,625
THAT ACTUALLY WENT
FROM HORIZON TO HORIZON,
74
00:04:53,627 --> 00:04:54,860
AND THAT BAND TURNED OUT
75
00:04:54,862 --> 00:04:57,095
TO BE MADE OF THOUSANDS
AND THOUSANDS OF STARS
76
00:04:57,097 --> 00:04:59,798
ACTUALLY TOO FAR AWAY
TO SEE INDIVIDUALLY.
77
00:04:59,800 --> 00:05:01,600
BUT IT TOOK US
A LONG TIME TO REALIZE
78
00:05:01,602 --> 00:05:06,538
WHAT THE SHAPE AND THE SCALE
OF THE MILKY WAY GALAXY IS.
79
00:05:06,540 --> 00:05:09,408
THE AMAZING THING TO THINK ABOUT
IS THAT WE ACTUALLY DON'T KNOW
80
00:05:09,410 --> 00:05:11,710
OUR HOME GALAXY
VERY WELL AT ALL.
81
00:05:11,712 --> 00:05:15,414
WE ACTUALLY LIVE IN THE MIDDLE
OF THIS DISK OF GAS AND DUST,
82
00:05:15,416 --> 00:05:19,418
AND THAT OBSCURES OUR VIEW OF
THE LARGER MILKY WAY.
83
00:05:19,420 --> 00:05:21,987
USING VISIBLE LIGHT,
WE CAN'T EVEN SEE TO THE CENTER,
84
00:05:21,989 --> 00:05:26,158
LET ALONE THE OTHER SIDE
OF THE MILKY WAY GALAXY.
85
00:05:30,164 --> 00:05:32,764
Narrator: THE SOLUTION
IS TO USE A FORM OF LIGHT
86
00:05:32,766 --> 00:05:36,735
THAT PASSES THROUGH THE GAS
AND DUST --
87
00:05:36,737 --> 00:05:38,303
INFRARED.
88
00:05:41,809 --> 00:05:45,677
THIS IS THE SLOAN
DIGITAL SKY SURVEY TELESCOPE
89
00:05:45,679 --> 00:05:50,115
AT THE APACHE POINT OBSERVATORY
IN NEW MEXICO.
90
00:05:50,117 --> 00:05:53,418
IT'S MAPPING THE GALAXY
USING INFRARED
91
00:05:53,420 --> 00:05:57,189
AND GIVING SCIENTISTS
UNPRECEDENTED INSIGHTS.
92
00:05:59,793 --> 00:06:02,994
THE FIRST SENSITIVE INFRARED
OBSERVATIONS REALLY WEREN'T DONE
93
00:06:02,996 --> 00:06:04,963
TILL THE LAST 15 YEARS,
94
00:06:04,965 --> 00:06:07,265
AND EACH OF THESE NEW WINDOWS
ON THE UNIVERSE
95
00:06:07,267 --> 00:06:09,067
TEACH US DIFFERENT THINGS.
96
00:06:09,069 --> 00:06:14,139
♪♪
97
00:06:14,141 --> 00:06:15,707
Narrator:
IN THE LAST 15 YEARS,
98
00:06:15,709 --> 00:06:21,046
SLOAN HAS SURVEYED
MORE THAN 250 MILLION STARS,
99
00:06:21,048 --> 00:06:26,318
ANALYZING THEIR LIGHT TO WORK
OUT THE COLOR OF THE MILKY WAY.
100
00:06:26,320 --> 00:06:30,522
AND WHAT SCIENTISTS
SAW SHOCKED THEM.
101
00:06:30,524 --> 00:06:32,758
UNTIL VERY RECENTLY,
WE THOUGHT THE MILKY WAY
102
00:06:32,760 --> 00:06:34,760
WAS A YOUNG, HEALTHY GALAXY,
103
00:06:34,762 --> 00:06:36,228
BUT NOW THERE'S EVIDENCE
104
00:06:36,230 --> 00:06:39,664
THAT WE MAY BE ENTERING
THE PATHWAY TO DEATH.
105
00:06:41,969 --> 00:06:46,505
Narrator:
THE SLOAN TELESCOPE REVEALS THAT
STAR PRODUCTION IN OUR GALAXY
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00:06:46,507 --> 00:06:49,508
IS FALLING THROUGH THE FLOOR.
107
00:06:49,510 --> 00:06:52,477
THE MILKY WAY IS DYING.
108
00:06:52,479 --> 00:06:56,148
AND WHEN IT STOPS
FORMING NEW STARS,
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00:06:56,150 --> 00:06:57,716
ITS TIME WILL BE UP.
110
00:07:00,187 --> 00:07:02,754
PARADOXICALLY,
OUR GALAXY STILL HAS
111
00:07:02,756 --> 00:07:08,693
STAR-FORMING GAS IN THE TANK,
SO IT SHOULD BE HEALTHY,
112
00:07:08,695 --> 00:07:11,196
BUT SOMETHING IS KILLING IT OFF.
113
00:07:15,335 --> 00:07:18,036
SO, THE MILKY WAY GALAXY
IS THIS WONDERFUL DISK
114
00:07:18,038 --> 00:07:21,907
FILLED WITH RICH HYDROGEN GAS,
LOTS OF DENSE DUST CLOUDS.
115
00:07:21,909 --> 00:07:24,509
IT HAS EVERYTHING YOU NEED THERE
FOR STAR FORMATION,
116
00:07:24,511 --> 00:07:27,846
BUT IT SEEMS TO BE SLOWING DOWN
AND EVEN TURNING OFF,
117
00:07:27,848 --> 00:07:31,516
AND RIGHT NOW, WE DON'T REALLY
UNDERSTAND WHAT THE CULPRIT IS.
118
00:07:36,156 --> 00:07:38,056
Narrator:
WITH A GALAXY KILLER AT LARGE,
119
00:07:38,058 --> 00:07:42,260
SCIENTISTS EMBARK UPON THE
BIGGEST MURDER INVESTIGATION
120
00:07:42,262 --> 00:07:44,429
IN THE HISTORY
OF THE UNIVERSE.
121
00:07:46,400 --> 00:07:48,500
EVERYTHING IN SCIENCE,
WHEN YOU'RE EXPLORING A PROBLEM,
122
00:07:48,502 --> 00:07:50,802
IS A BIT LIKE A CRIME SCENE.
123
00:07:50,804 --> 00:07:53,038
YOU'VE GOT THE EVIDENCE
LAID OUT IN FRONT OF YOU...
124
00:07:57,177 --> 00:08:00,345
...AND WE HAVE TO
FIGURE OUT WHO DONE IT.
125
00:08:01,548 --> 00:08:10,388
♪
126
00:08:10,390 --> 00:08:14,392
Narrator:
OUR HOME IN THE UNIVERSE
IS DYING --
127
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NOT THE EARTH,
BUT OUR GALAXY, THE MILKY WAY.
128
00:08:20,767 --> 00:08:24,302
IT'S BEEN PRODUCING STARS
FOR BILLIONS OF YEARS,
129
00:08:24,304 --> 00:08:26,771
BUT SOON, IT WILL STOP.
130
00:08:28,842 --> 00:08:31,510
OUR OWN SUN FORMED
ABOUT 4 1/2 BILLION YEARS AGO
131
00:08:31,512 --> 00:08:32,911
IN THE MILKY WAY GALAXY,
132
00:08:32,913 --> 00:08:36,181
AND WE ARE NOT
THE OLDEST STAR BY FAR.
133
00:08:36,183 --> 00:08:38,383
AND YET, TRAGICALLY,
WE ACTUALLY SEEM TO BE
134
00:08:38,385 --> 00:08:42,120
ONE OF THE LAST GENERATIONS
OF NEW STARS IN THE MILKY WAY.
135
00:08:42,122 --> 00:08:45,557
CURRENT PROJECTIONS SUGGEST
THAT IN ABOUT 4 BILLION YEARS,
136
00:08:45,559 --> 00:08:47,559
STAR FORMATION MAY HAVE
CEASED ALL TOGETHER,
137
00:08:47,561 --> 00:08:49,427
WHICH IS ALMOST JUST
A BLINK OF AN EYE
138
00:08:49,429 --> 00:08:51,329
IN THE LIFE CYCLE
OF THE UNIVERSE.
139
00:08:55,702 --> 00:08:59,671
Narrator:
TO FIND OUT WHY, SCIENTISTS
LAUNCH AN INVESTIGATION.
140
00:08:59,673 --> 00:09:01,973
THE MOST CRUCIAL QUESTION?
141
00:09:01,975 --> 00:09:04,843
HOW IS THE MAY DYING?
142
00:09:06,680 --> 00:09:09,915
TO KILL A GALAXY, YOU HAVE
TO GET RID OF THE COLD GAS,
143
00:09:09,917 --> 00:09:12,117
BECAUSE THAT'S
WHAT STARS FORM FROM.
144
00:09:12,119 --> 00:09:13,585
THERE ARE MANY WAYS
YOU CAN DO THIS.
145
00:09:13,587 --> 00:09:15,687
YOU CAN BLAST IT OUT
FROM THE INSIDE.
146
00:09:15,689 --> 00:09:17,889
YOU CAN DRAW IT OUT
FROM THE OUTSIDE.
147
00:09:17,891 --> 00:09:20,292
YOU CAN HEAT IT UP
SO IT'S NO LONGER COLD.
148
00:09:20,294 --> 00:09:21,793
YOU CAN USE IT ALL UP,
149
00:09:21,795 --> 00:09:23,929
AND THERE'S EVEN MORE WAYS
YOU CAN STOP IT.
150
00:09:23,931 --> 00:09:25,497
WHAT WE HAVE TO DO
IS FIGURE OUT
151
00:09:25,499 --> 00:09:28,099
WHICH WAY IS HAPPENING
IN OUR GALAXY.
152
00:09:30,671 --> 00:09:36,207
Narrator:
PERHAPS THE CULPRIT IS INSIDE
THE MILKY WAY ITSELF.
153
00:09:36,209 --> 00:09:39,611
A CLUE COMES FROM
ANOTHER GALAXY ENTIRELY.
154
00:09:41,648 --> 00:09:48,453
THIS IS W2246-0526.
155
00:09:48,455 --> 00:09:52,457
SCIENTISTS CALL IT A HOT,
DUST-OBSCURED GALAXY,
156
00:09:52,459 --> 00:09:54,826
OR "HOT DOG" FOR SHORT.
157
00:09:57,598 --> 00:10:00,699
THIS GALAXY IS
12 1/2 BILLION LIGHT-YEARS AWAY.
158
00:10:00,701 --> 00:10:03,568
IT'S THE MOST LUMINOUS GALAXY
WE KNOW OF IN THE UNIVERSE.
159
00:10:03,570 --> 00:10:06,705
IT HAS THE LIGHT
OF 300 TRILLION STARS.
160
00:10:10,978 --> 00:10:14,679
Narrator:
THE SOURCE OF THE INTENSE LIGHT
IS NOT ITS STARS,
161
00:10:14,681 --> 00:10:19,684
BUT A MYSTERIOUS OBJECT
AT THE GALAXY'S CENTER.
162
00:10:19,686 --> 00:10:23,188
IT'S A MILLION TIMES SMALLER
THAN THE GALAXY ITSELF.
163
00:10:25,926 --> 00:10:29,761
THERE'S ONLY ONE THING
THAT SMALL AND THAT POWERFUL...
164
00:10:32,466 --> 00:10:34,699
...A SUPERMASSIVE BLACK HOLE.
165
00:10:38,538 --> 00:10:41,640
SO, SUPERMASSIVE BLACK HOLES,
AS THE NAME SUGGESTS,
166
00:10:41,642 --> 00:10:43,174
ARE INDEED SUPERMASSIVE.
167
00:10:43,176 --> 00:10:47,579
THESE ARE BILLIONS OF TIMES
MORE MASSIVE THAN OUR SUN.
168
00:10:47,581 --> 00:10:49,648
THESE ARE GIGANTIC OBJECTS.
169
00:10:52,552 --> 00:10:56,721
Narrator:
THE GRAVITY IN THE SUPERMASSIVE
BLACK HOLE IS OFF THE CHARTS.
170
00:11:00,260 --> 00:11:02,327
IT SUCKS IN
INCREDIBLE AMOUNTS
171
00:11:02,329 --> 00:11:05,664
OF THE HOT DOG'S
VITAL STAR-FORMING GAS.
172
00:11:09,703 --> 00:11:12,237
AND AS THE GAS SWIRLS
TO FORM A DISK,
173
00:11:12,239 --> 00:11:16,174
THE INTENSE FRICTION SUPERHEATS
IT TO MILLIONS OF DEGREES
174
00:11:16,176 --> 00:11:20,945
AND, IN SOME GALAXIES,
TRIGGERS HUGE JETS.
175
00:11:20,947 --> 00:11:23,348
WHEN A LOT OF MATERIAL FALLS
ONTO THAT BLACK HOLE,
176
00:11:23,350 --> 00:11:25,750
IT CREATES INCREDIBLY
ENERGETIC JETS
177
00:11:25,752 --> 00:11:28,653
THAT CAN BE TENS OF THOUSANDS
OF LIGHT-YEARS ACROSS.
178
00:11:28,655 --> 00:11:30,722
ALL OF A SUDDEN,
YOU HAVE THIS BLOWTORCH
179
00:11:30,724 --> 00:11:33,391
IN THE MIDDLE OF THE GALAXY.
180
00:11:33,393 --> 00:11:35,627
Bullock: BLACK HOLE JETS
ARE BAD FOR GALAXIES
181
00:11:35,629 --> 00:11:37,762
BECAUSE THEY CAN SHUT DOWN
STAR FORMATION.
182
00:11:37,764 --> 00:11:40,365
THEY CAN HEAT GAS UP,
BLOW GAS OUT OF GALAXIES,
183
00:11:40,367 --> 00:11:41,933
AND THEY COULD REALLY KILL THEM.
184
00:11:44,271 --> 00:11:47,839
Narrator:
A SUPERMASSIVE BLACK HOLE
IS COOKING THE HOT DOG.
185
00:11:51,278 --> 00:11:53,044
WHAT'S GOING ON IN OUR GALAXY?
186
00:11:53,046 --> 00:12:02,487
♪♪
187
00:12:02,489 --> 00:12:06,658
IN 2016, SCIENTISTS AT HARVARD
DISCOVERED DAMNING EVIDENCE
188
00:12:06,660 --> 00:12:10,095
THAT MAY LINK THE MILKY WAY'S
SUPERMASSIVE BLACK HOLE
189
00:12:10,097 --> 00:12:11,863
TO THE GALAXY'S DEMISE.
190
00:12:14,868 --> 00:12:16,334
JUST LIKE THE HOT DOG,
191
00:12:16,336 --> 00:12:20,438
THE MILKY WAY IS SURROUNDED BY
A VAST CLOUD OF BLOWN-OUT GAS,
192
00:12:22,576 --> 00:12:27,846
AND THE SCIENTISTS TRACED
THE GAS BACK TO ITS SOURCE --
193
00:12:27,848 --> 00:12:32,784
SAGITTARIUS A-STAR,
OUR SUPERMASSIVE BLACK HOLE.
194
00:12:35,789 --> 00:12:37,889
WELL, IT TURNS OUT
OUR SUPERMASSIVE BLACK HOLE
195
00:12:37,891 --> 00:12:41,459
HAD A BIT OF A HICCUP ABOUT
6 MILLION YEARS AGO.
196
00:12:41,461 --> 00:12:44,295
THERE'S EVIDENCE THAT
SOME MATTER MUST HAVE FALLEN
197
00:12:44,297 --> 00:12:46,798
INTO THAT BLACK HOLE,
AND IF IT FELL IN TOO QUICKLY,
198
00:12:46,800 --> 00:12:49,868
IT WOULD HAVE GOTTEN SUPERHEATED
BY ITS OWN FRICTION,
199
00:12:49,870 --> 00:12:54,672
AND THIS WOULD HAVE ACTED,
IN A SENSE, LIKE AN EXPLOSION.
200
00:12:54,674 --> 00:12:57,008
Oluseyi:
AND THAT EVENT WAS HUGE.
201
00:12:57,010 --> 00:13:00,445
OUR GALAXY EXPELLED
AN INCREDIBLE AMOUNT OF GAS --
202
00:13:00,447 --> 00:13:03,882
130 BILLION TIMES
THE MASS OF THE SUN.
203
00:13:03,884 --> 00:13:05,750
LARGE AMOUNT OF GAS.
204
00:13:08,688 --> 00:13:10,688
Stern: THIS EVENT MUST HAVE BEEN
VERY CATASTROPHIC
205
00:13:10,690 --> 00:13:13,424
FOR THE INNER PARTS
OF THE GALAXY.
206
00:13:13,426 --> 00:13:16,161
LUCKILY, EARTH IS IN
THE OUTER PARTS OF THE GALAXY,
207
00:13:16,163 --> 00:13:18,563
WHERE WE WERE ABLE
TO SURVIVE THIS EVENT.
208
00:13:22,402 --> 00:13:25,370
Narrator:
IS THIS THE SMOKING GUN?
209
00:13:25,372 --> 00:13:30,508
IS OUR OWN SUPERMASSIVE BLACK
HOLE KILLING THE MILKY WAY?
210
00:13:30,510 --> 00:13:32,777
THE EVIDENCE SEEMS TO MOUNT UP.
211
00:13:35,348 --> 00:13:39,317
BUT SAGITTARIUS A-STAR
HAS AN ALIBI.
212
00:13:39,319 --> 00:13:42,520
IT EXPLODED TOO LATE.
213
00:13:42,522 --> 00:13:45,390
SAGITTARIUS A-STAR
GOT VERY ACTIVE,
214
00:13:45,392 --> 00:13:47,826
VERY EXPLOSIVE
ABOUT 6 MILLION YEARS AGO,
215
00:13:47,828 --> 00:13:50,295
BUT THAT'S SO RECENT, IT
SHOULDN'T HAVE REALLY AFFECTED
216
00:13:50,297 --> 00:13:51,729
THE STAR FORMATION RATES.
217
00:13:51,731 --> 00:13:53,097
SOMETHING ELSE IS GOING ON.
218
00:13:53,099 --> 00:13:55,967
THERE MUST BE ANOTHER CULPRIT
BESIDES THE BLACK HOLE.
219
00:13:58,171 --> 00:14:02,207
Narrator:
STUDIES SUGGEST OUR SUPERMASSIVE
BLACK HOLE MUST HAVE BEEN ACTIVE
220
00:14:02,209 --> 00:14:04,676
HUNDREDS OF MILLIONS
OF YEARS AGO
221
00:14:04,678 --> 00:14:09,147
TO STOP ALL STAR FORMATION
IN OUR GALAXY.
222
00:14:09,149 --> 00:14:13,017
SAGITTARIUS A-STAR
WASN'T ACTIVE AT THAT TIME,
223
00:14:13,019 --> 00:14:15,920
SO IT'S NO LONGER A SUSPECT.
224
00:14:17,991 --> 00:14:21,359
THE HUNT IS ON FOR
A DIFFERENT GALAXY KILLER,
225
00:14:21,361 --> 00:14:25,630
AND SCIENTISTS ARE WIDENING
THE INVESTIGATION.
226
00:14:25,632 --> 00:14:28,199
MAYBE THE KILLER
ISN'T INSIDE OUR GALAXY.
227
00:14:28,201 --> 00:14:31,402
IT COULD BE THAT WE SUFFERED
A HIT-AND-RUN.
228
00:14:31,404 --> 00:14:38,676
♪♪
229
00:14:39,913 --> 00:14:49,654
IT COULD BE THAT WE SUFFERED
A HIT-AND-RUN.
230
00:14:49,656 --> 00:14:53,091
♪♪
231
00:14:53,093 --> 00:14:55,693
Narrator:
OUR UNIVERSE IS A CRIME SCENE.
232
00:14:57,998 --> 00:15:03,134
STAR PRODUCTION IN THE MILKY WAY
IS BREAKING DOWN.
233
00:15:03,136 --> 00:15:05,236
OUR GALAXY IS DYING,
234
00:15:05,238 --> 00:15:08,873
AND ASTRONOMERS ARE EXAMINING
THE BODY FOR CLUES.
235
00:15:11,111 --> 00:15:16,681
THE MILKY WAY'S DISK IS MADE UP
OF THREE SECTIONS --
236
00:15:16,683 --> 00:15:21,386
A NUCLEUS, HOME TO THE GALAXY'S
SUPERMASSIVE BLACK HOLE...
237
00:15:24,291 --> 00:15:29,594
...A DENSE, CENTRAL BULGE
10,000 LIGHT-YEARS ACROSS,
238
00:15:29,596 --> 00:15:31,262
AND THE SPIRAL ARMS --
239
00:15:31,264 --> 00:15:35,099
FULL OF GAS, DUST,
AND BILLIONS OF STARS.
240
00:15:37,170 --> 00:15:41,873
THE SPIRAL ARMS SHOULD BE FLAT,
BUT THEY'RE RIPPLING.
241
00:15:41,875 --> 00:15:45,143
IS THIS A CLUE
FOR THE COSMIC DETECTIVES?
242
00:15:46,947 --> 00:15:48,980
Bullock:
TODAY, WE LOOK AT THE EDGE
OF THE MILKY WAY,
243
00:15:48,982 --> 00:15:51,049
AND WE SEE MYSTERIOUS
RIPPLES IN ITS GAS,
244
00:15:51,051 --> 00:15:53,251
AND WE WONDER,
WHAT'S THE ORIGIN?
245
00:15:53,253 --> 00:15:55,353
SOMETHING MUST HAVE
CAUSED IT TO HAPPEN.
246
00:15:55,355 --> 00:15:57,822
SOMETHING LIKE THAT
JUST DOESN'T HAPPEN ON ITS OWN.
247
00:15:57,824 --> 00:15:59,724
THE REAL QUESTION IS, WHY?
248
00:16:04,331 --> 00:16:08,900
Narrator:
WHATEVER CAUSED THE RIPPLES
DIDN'T HANG AROUND.
249
00:16:08,902 --> 00:16:11,936
IS THIS EVIDENCE OF
A GALACTIC HIT-AND-RUN?
250
00:16:15,008 --> 00:16:17,175
JANUARY 2016.
251
00:16:20,146 --> 00:16:24,182
ASTRONOMERS STUDYING DATA
FROM THE VISTA TELESCOPE
252
00:16:24,184 --> 00:16:26,184
DISCOVER SOMETHING INCREDIBLE...
253
00:16:30,290 --> 00:16:32,824
...THREE NEARBY STARS.
254
00:16:32,826 --> 00:16:35,560
ON THEIR OWN, NOTHING SPECIAL,
255
00:16:35,562 --> 00:16:39,163
EXCEPT THEY'VE RECENTLY
LEFT OUR GALAXY,
256
00:16:39,165 --> 00:16:43,735
AND THEY'RE TRAVELING
AT 350,000 MILES AN HOUR.
257
00:16:47,507 --> 00:16:49,941
SO, WE'VE DISCOVERED THESE STARS
THAT ARE CAREENING
258
00:16:49,943 --> 00:16:52,710
OUT OF THE GALAXY
AT SUPER-HIGH VELOCITIES.
259
00:16:52,712 --> 00:16:54,979
COULD THESE THREE STARS
SOMEHOW BE RESPONSIBLE
260
00:16:54,981 --> 00:16:56,881
FOR WARPING
THE MILKY WAY'S DISK?
261
00:16:56,883 --> 00:16:58,349
WELL, ABSOLUTELY NOT.
262
00:16:58,351 --> 00:17:01,586
THE MILKY WAY IS SO MUCH MORE
MASSIVE THAN JUST THREE STARS.
263
00:17:01,588 --> 00:17:04,989
THREE STARS ALONE
CAN'T WARP A GALAXY,
264
00:17:04,991 --> 00:17:08,359
BUT THOSE THREE STARS CAN BE
INDICATIVE OF MORE STARS.
265
00:17:08,361 --> 00:17:10,862
THEY CAN BE INDICATIVE
OF THE PRESENCE OF, SAY,
266
00:17:10,864 --> 00:17:14,065
A DWARF GALAXY,
AND THAT CAN WARP THE GALAXY.
267
00:17:16,036 --> 00:17:19,470
Narrator:
DWARF GALAXIES ARE ABUNDANT.
268
00:17:19,472 --> 00:17:22,774
BUT A TINY FRACTION
OF THE SIZE OF A MAJOR GALAXY,
269
00:17:22,776 --> 00:17:24,342
LIKE THE MILKY WAY.
270
00:17:26,413 --> 00:17:29,781
SO THEY'RE DIFFICULT TO DETECT.
271
00:17:29,783 --> 00:17:33,985
BUT THESE THREE BRIGHT STARS
SHOW THERE'S A DWARF GALAXY
272
00:17:33,987 --> 00:17:38,289
HIDING BEYOND THE EDGE
OF THE MILKY WAY.
273
00:17:38,291 --> 00:17:41,426
AND SCIENTISTS CAN STUDY
THE TRIO OF STARS
274
00:17:41,428 --> 00:17:43,161
TO REWIND THE CLOCK
275
00:17:43,163 --> 00:17:47,365
AND TRACK BACK THE PAST
MOVEMENTS OF THE DWARF GALAXY.
276
00:17:50,236 --> 00:17:53,037
SIMULATIONS SUGGEST
THAT MILLIONS OF YEARS AGO,
277
00:17:53,039 --> 00:17:54,305
THIS DWARF GALAXY
278
00:17:54,307 --> 00:17:56,374
PUNCHED THROUGH THE PLANE
OF THE MILKY WAY.
279
00:18:01,314 --> 00:18:06,084
Narrator:
AS THE FAST-MOVING DWARF GALAXY
HURTLES TOWARDS THE MILKY WAY,
280
00:18:06,086 --> 00:18:11,823
MILLIONS OF STARS SEEM SET
ON A COLLISION COURSE.
281
00:18:11,825 --> 00:18:14,158
CATASTROPHE LOOKS INEVITABLE.
282
00:18:16,062 --> 00:18:19,063
BUT APPEARANCES
CAN BE DECEPTIVE.
283
00:18:20,934 --> 00:18:23,401
WHEN GALAXIES COLLIDE, THE FIRST
THING YOU MIGHT IMAGINE
284
00:18:23,403 --> 00:18:26,037
IS THAT THE STARS COLLIDE, BUT
ACTUALLY, THAT DOESN'T HAPPEN.
285
00:18:26,039 --> 00:18:27,839
GALAXIES
ARE MOSTLY EMPTY SPACE.
286
00:18:27,841 --> 00:18:30,041
IF YOU TOOK THE SUN,
WHICH IS REALLY BIG --
287
00:18:30,043 --> 00:18:31,776
IT'S A MILLION MILES ACROSS --
288
00:18:31,778 --> 00:18:35,746
AND SHRUNK IT DOWN TO THE SIZE
OF A PIECE OF POLLEN,
289
00:18:35,748 --> 00:18:39,117
THE GALAXY ITSELF WOULD BE TWICE
THE SIZE OF THE PACIFIC OCEAN,
290
00:18:39,119 --> 00:18:42,587
AND THE NEAREST STAR TO THE SUN
WOULD BE A MILE AWAY.
291
00:18:42,589 --> 00:18:45,756
THOSE TINY PIECES OF POLLEN ARE
NEVER GOING TO HIT EACH OTHER.
292
00:18:49,696 --> 00:18:53,831
Narrator: THE DISTANCES INVOLVED
ARE STAGGERING.
293
00:18:53,833 --> 00:18:55,500
AND AT THE MOMENT OF IMPACT,
294
00:18:55,502 --> 00:18:58,069
MOST OF THE STARS
FROM THE TWO GALAXIES
295
00:18:58,071 --> 00:19:00,705
MISS EACH OTHER ENTIRELY.
296
00:19:00,707 --> 00:19:04,742
BUT THAT DOESN'T MEAN
THE MILKY WAY IS SAFE.
297
00:19:06,913 --> 00:19:09,680
Sutter: EVEN THOUGH THE STARS
JUST PASS EACH OTHER,
298
00:19:09,682 --> 00:19:13,518
THEY DO GRAVITATIONALLY
INTERACT AS THEY COME CLOSE,
299
00:19:13,520 --> 00:19:16,888
AND THIS GRAVITATIONAL
INTERACTION SETS THEM
300
00:19:16,890 --> 00:19:18,489
ON A COURSE THAT IS DIFFERENT
301
00:19:18,491 --> 00:19:20,925
THAN IF THEY WERE
TO LIVE BY THEMSELVES.
302
00:19:23,763 --> 00:19:25,863
Bullock: IN MUCH THE SAME WAY
THAT TAKING A STONE
303
00:19:25,865 --> 00:19:27,532
AND DROPPING IT
INTO A STILL POND
304
00:19:27,534 --> 00:19:29,667
CREATES RIPPLES IN THE WATER,
305
00:19:29,669 --> 00:19:32,336
A GALAXY LIKE THIS SLAMMING
INTO THE MILKY WAY
306
00:19:32,338 --> 00:19:34,739
CAN CREATE RIPPLE EFFECTS
THROUGHOUT THE DISK.
307
00:19:38,044 --> 00:19:39,710
Narrator:
THE RIPPLES IN THE MILKY WAY
308
00:19:39,712 --> 00:19:43,114
STRETCH ACROSS TENS
OF THOUSANDS OF LIGHT-YEARS.
309
00:19:45,285 --> 00:19:50,621
STILL, THIS HIT-AND-RUN ISN'T
ENOUGH TO KILL THE MILKY WAY.
310
00:19:50,623 --> 00:19:54,292
IT ONLY CAUSES A FLESH WOUND.
311
00:19:54,294 --> 00:19:59,797
BUT WHAT IF THIS DWARF GALAXY
ISN'T ACTING ALONE?
312
00:19:59,799 --> 00:20:01,766
WHAT IF IT HAS ACCOMPLICES?
313
00:20:04,304 --> 00:20:07,038
THERE ARE A LOT OF
DWARF GALAXIES OUT THERE,
314
00:20:07,040 --> 00:20:10,308
AND IT TURNS OUT COLLISIONS
BETWEEN THESE DWARF GALAXIES
315
00:20:10,310 --> 00:20:13,177
AND BIG GALAXIES, LIKE
THE MILKY WAY, ARE COMMON.
316
00:20:13,179 --> 00:20:14,445
THEY HAPPEN ALL THE TIME.
317
00:20:14,447 --> 00:20:16,480
RIGHT NOW, THERE ARE
SEVERAL DWARF GALAXIES
318
00:20:16,482 --> 00:20:18,516
THAT THE MILKY WAY
IS SWALLOWING UP.
319
00:20:18,518 --> 00:20:20,718
IN FACT, A REALLY FUN THING IS
THAT WE'RE ACTUALLY CLOSER
320
00:20:20,720 --> 00:20:22,887
TO THE CORE OF ONE
OF THESE GALAXIES --
321
00:20:22,889 --> 00:20:24,822
THE CANIS MAJORIS
DWARF GALAXY --
322
00:20:24,824 --> 00:20:26,657
THAN WE ARE TO THE CORE
OF THE MILKY WAY.
323
00:20:26,659 --> 00:20:29,594
SO SOME OF THE STARS THAT YOU
SEE AROUND YOU IN THE NIGHT SKY
324
00:20:29,596 --> 00:20:32,330
ARE ACTUALLY STARS
FROM A DIFFERENT GALAXY.
325
00:20:32,332 --> 00:20:35,433
SO, WHAT HAPPENS WHEN ALL THESE
DWARF GALAXIES COME TOGETHER
326
00:20:35,435 --> 00:20:38,302
AND START PULLING AND TUGGING
ON A LARGER GALAXY?
327
00:20:38,304 --> 00:20:44,108
♪♪
328
00:20:44,110 --> 00:20:47,945
Narrator:
COSMOLOGISTS BELIEVE THERE COULD
BE HUNDREDS OF DWARF GALAXIES
329
00:20:47,947 --> 00:20:50,481
SURROUNDING THE MILKY WAY.
330
00:20:53,319 --> 00:20:56,821
A COLLISION WITH JUST ONE OF
THESE DWARF GALAXIES
331
00:20:56,823 --> 00:21:00,558
MAY HAVE RIPPLED THE
MILKY WAY'S SPIRAL ARMS,
332
00:21:02,562 --> 00:21:05,763
BUT A GANG OF DWARF GALAXIES
333
00:21:05,765 --> 00:21:11,269
COULD HAVE A FAR BIGGER
AND FAR MORE DEADLY EFFECT.
334
00:21:11,271 --> 00:21:13,571
DWARF GALAXIES AND THE WAY
THEY INTERACT WITH BIG GALAXIES,
335
00:21:13,573 --> 00:21:14,805
LIKE THE MILKY WAY,
336
00:21:14,807 --> 00:21:17,775
CAN INFLECT TREMENDOUS
CHANGE IN OUR UNIVERSE.
337
00:21:17,777 --> 00:21:20,411
WHEN THEY SLAM INTO A GALAXY,
THEY CAN CHANGE ITS STRUCTURE.
338
00:21:20,413 --> 00:21:23,247
THE MILKY WAY WOULD NOT LOOK
ANYTHING LIKE IT LOOKS TODAY
339
00:21:23,249 --> 00:21:26,284
WITHOUT THOSE DWARF GALAXIES.
340
00:21:26,286 --> 00:21:29,020
Narrator:
REPEATED DWARF-GALAXY COLLISIONS
341
00:21:29,022 --> 00:21:32,723
COULD HAVE RADICALLY ALTERED THE
SHAPE OF THE MILKY WAY ITSELF.
342
00:21:35,328 --> 00:21:39,096
THEIR GRAVITATIONAL DISRUPTIONS
COULD HAVE CREATED A DISTINCTIVE
343
00:21:39,098 --> 00:21:43,167
AND POSSIBLY FATAL FEATURE
IN THE MIDDLE OF OUR GALAXY --
344
00:21:43,169 --> 00:21:44,669
THE GALACTIC BAR.
345
00:21:48,074 --> 00:21:50,341
THE CENTER OF THE MILKY WAY
IS ELONGATED.
346
00:21:50,343 --> 00:21:52,243
INSTEAD OF IT BEING
SHAPED LIKE A SPHERE,
347
00:21:52,245 --> 00:21:55,413
IT'S MORE SHAPED LIKE A BAR,
AND THE BAR IS MADE BY STARS
348
00:21:55,415 --> 00:21:59,550
ACTUALLY ORBITING IN THIS
SORT OF ELONGATED WAY.
349
00:21:59,552 --> 00:22:02,420
Oluseyi: AND THIS BAR CAN BE BAD
FOR THE HEALTH OF THE GALAXY
350
00:22:02,422 --> 00:22:04,989
BECAUSE WHAT THEY DO
IS HELP TO FUNNEL GAS
351
00:22:04,991 --> 00:22:06,824
INTO THE CORE OF THE GALAXY.
352
00:22:06,826 --> 00:22:11,228
THE LOSS OF THIS GAS COULD BE A
WAY OF STOPPING STAR FORMATION.
353
00:22:14,701 --> 00:22:17,902
Narrator: THE BAR-SHAPED BULGE
AT THE CENTER OF THE MILKY WAY
354
00:22:17,904 --> 00:22:20,871
SWEEPS OUR GALAXY'S
STAR-BUILDING GAS
355
00:22:20,873 --> 00:22:23,107
INTO THE GALACTIC NUCLEUS.
356
00:22:23,109 --> 00:22:24,709
HERE, IT GETS GOBBLED UP
357
00:22:24,711 --> 00:22:27,545
BY OUR GALAXY'S
SUPERMASSIVE BLACK HOLE.
358
00:22:31,617 --> 00:22:35,786
WITHOUT THE STAR-BUILDING
MATERIAL, NO NEW STARS CAN FORM,
359
00:22:35,788 --> 00:22:39,223
AND THE GALAXY DIES.
360
00:22:39,225 --> 00:22:41,258
SO, IS IT CASE CLOSED?
361
00:22:41,260 --> 00:22:43,828
ARE DWARF GALAXIES
KILLING THE MILKY WAY?
362
00:22:43,830 --> 00:22:47,865
IS THE MURDER WEAPON
A GALACTIC BAR?
363
00:22:47,867 --> 00:22:50,735
SO, IT'S POSSIBLE THAT
THE FORMATION OF THESE BARS
364
00:22:50,737 --> 00:22:54,438
HELPS TURN OFF STAR FORMATION
IN THE VERY CORE OF THE GALAXY,
365
00:22:54,440 --> 00:22:57,341
BUT THAT'S JUST THE CENTRAL
REGIONS OF THE GALAXY.
366
00:22:57,343 --> 00:22:59,210
THAT DOESN'T EXPLAIN
WHAT'S GOING FARTHER OUT
367
00:22:59,212 --> 00:23:01,045
IN THE SPIRAL ARMS.
368
00:23:01,047 --> 00:23:04,548
SO, IF STAR FORMATION REALLY IS
SHUTTING DOWN IN THE MILKY WAY,
369
00:23:04,550 --> 00:23:06,851
IT'S NOT REALLY
THE FAULT OF THE BAR.
370
00:23:09,021 --> 00:23:13,391
Narrator:
DWARF GALAXIES CAUSE THE
MILKY WAY GRIEVOUS BODILY HARM
371
00:23:13,393 --> 00:23:16,460
BY CREATING THE GALACTIC BAR.
372
00:23:16,462 --> 00:23:21,899
BUT THEY'RE OFF THE HOOK
FOR ATTEMPTED GALACTIC MURDER.
373
00:23:21,901 --> 00:23:24,635
THE INVESTIGATION CONTINUES,
374
00:23:24,637 --> 00:23:29,840
AND IT COULD BE ABOUT
TO TAKE A DRAMATIC TWIST.
375
00:23:29,842 --> 00:23:32,109
IT MIGHT NOT BE THAT
THE GALAXY'S BEING MURDERED.
376
00:23:32,111 --> 00:23:34,412
IT COULD JUST BE
EATING ITSELF TO DEATH.
377
00:23:34,414 --> 00:23:44,121
♪♪
378
00:23:45,491 --> 00:23:54,532
♪
IT COULD JUST BE
EATING ITSELF TO DEATH.
379
00:23:54,534 --> 00:23:58,536
Narrator: THE MILKY WAY
IS BEING KILLED OFF.
380
00:23:58,538 --> 00:24:01,305
AND THE PERPETRATOR
REMAINS AT LARGE.
381
00:24:03,476 --> 00:24:05,443
SCIENTISTS
INVESTIGATING THE CRIME
382
00:24:05,445 --> 00:24:07,178
ARE RUNNING OUT OF SUSPECTS.
383
00:24:09,215 --> 00:24:11,348
BUT THE HUNT
FOR CLUES CONTINUES,
384
00:24:13,319 --> 00:24:18,556
SO ASTRONOMERS ARE EXAMINING
THE DYING BODY OF THE MILKY WAY.
385
00:24:18,558 --> 00:24:21,725
OUR GALAXY IS
A HAZY DISK OF STARS
386
00:24:21,727 --> 00:24:25,296
SURROUNDED BY A HALO
OF SUPERHEATED GAS.
387
00:24:27,166 --> 00:24:31,135
IT'S OVER 100,000
LIGHT-YEARS ACROSS.
388
00:24:31,137 --> 00:24:33,304
BUT IT HASN'T ALWAYS
BEEN SO BIG.
389
00:24:35,575 --> 00:24:37,775
WHEN YOU THINK ABOUT THINGS
SO VAST,
390
00:24:37,777 --> 00:24:39,810
SO GIGANTIC AND ANCIENT
AS GALAXIES,
391
00:24:39,812 --> 00:24:41,278
YOU'RE KIND OF TEMPTED TO THINK
392
00:24:41,280 --> 00:24:42,847
THAT THEY'RE
VERY STABLE OBJECTS,
393
00:24:42,849 --> 00:24:44,815
THAT THEY DON'T CHANGE
MUCH OVER TIME,
394
00:24:44,817 --> 00:24:46,617
BUT WE NOW KNOW
THAT OUR OWN GALAXY
395
00:24:46,619 --> 00:24:48,552
IS THE PRODUCT OF MANY
SMALLER GALAXIES
396
00:24:48,554 --> 00:24:50,354
THAT CAME TOGETHER OVER TIME,
397
00:24:50,356 --> 00:24:53,057
AND THERE ARE OTHER GALAXIES
STILL COLLIDING WITH US.
398
00:24:56,028 --> 00:24:58,295
Plait: WE SEE GALAXIES
EATING EACH OTHER ALL THE TIME.
399
00:24:58,297 --> 00:25:00,998
THEY COLLIDE,
AND IF ONE GALAXY IS VERY BIG
400
00:25:01,000 --> 00:25:02,867
AND ONE GALAXY IS VERY SMALL,
401
00:25:02,869 --> 00:25:06,136
THE LITTLE GALAXY FALLS INTO
THE BIG ONE, GETS TORN APART,
402
00:25:06,138 --> 00:25:10,241
AND BECOMES A PART
OF THAT BIGGER GALAXY.
403
00:25:10,243 --> 00:25:12,576
Narrator:
THE MILKY WAY MIGHT BE DYING,
404
00:25:12,578 --> 00:25:16,046
BUT IT'S STILL A MONSTER
FORAGING THROUGH THE UNIVERSE,
405
00:25:16,048 --> 00:25:18,415
SWALLOWING SMALLER
GALAXIES WHOLE.
406
00:25:21,988 --> 00:25:24,054
IT CONSUMES THEIR STARS.
407
00:25:24,056 --> 00:25:28,125
BUT IT ALSO HAS A TASTE
FOR THEIR STAR-BUILDING GAS.
408
00:25:29,996 --> 00:25:33,330
AND IT DOESN'T HAVE
TO COLLIDE WITH OTHER GALAXIES
409
00:25:33,332 --> 00:25:36,667
TO FEED OFF OF THEM.
410
00:25:36,669 --> 00:25:39,470
NOW, THE LIFEBLOOD OF A GALAXY
IS HYDROGEN GAS.
411
00:25:39,472 --> 00:25:41,739
THAT'S WHAT ACTUALLY
CREATES NEW STARS.
412
00:25:41,741 --> 00:25:44,708
SO AS A DWARF GALAXY
PASSES BY THE MILKY WAY,
413
00:25:44,710 --> 00:25:47,912
THE TREMENDOUSLY MASSIVE
HALO OF THE MILKY WAY,
414
00:25:47,914 --> 00:25:51,282
ALL OF THAT GAS, CAN DRAW OFF
MATERIAL FROM THE DWARF GALAXY,
415
00:25:51,284 --> 00:25:53,350
ADDING IT TO THE MILKY WAY.
416
00:25:53,352 --> 00:25:55,586
SO IN THIS WAY,
THE MILKY WAY DRAINS AWAY
417
00:25:55,588 --> 00:25:58,622
THE LIFEBLOOD
OF OTHER GALAXIES.
418
00:25:58,624 --> 00:26:01,191
IN SOME SENSE, YOU COULD SAY
IT'S A VAMPIRE
419
00:26:01,193 --> 00:26:03,994
BECAUSE A VAMPIRE SUCKS THE LIFE
OUT OF OTHER THINGS
420
00:26:03,996 --> 00:26:05,429
SO IT CAN REMAIN YOUNG.
421
00:26:09,368 --> 00:26:16,674
Narrator:
IN ITS 13 BILLION-YEAR LIFE,
OUR VAMPIRE GALAXY HAS FEASTED.
422
00:26:16,676 --> 00:26:19,944
CONSUMING THE LIFEBLOOD
OF ITS GALACTIC VICTIMS,
423
00:26:19,946 --> 00:26:22,780
THE MILKY WAY HAS GROWN FAT.
424
00:26:25,217 --> 00:26:28,352
BUT COULD THIS MONSTROUS
FEEDING FRENZY BE A FACTOR
425
00:26:28,354 --> 00:26:30,187
IN THE MILKY WAY'S DEMISE?
426
00:26:33,092 --> 00:26:34,992
ONCE AGAIN, CRUCIAL EVIDENCE
427
00:26:34,994 --> 00:26:39,597
COMES FROM THE
SLOAN DIGITAL SKY SURVEY.
428
00:26:39,599 --> 00:26:42,666
THEIR TELESCOPE MAPS
THE STARS IN OUR GALAXY,
429
00:26:42,668 --> 00:26:46,470
BUT IT ALSO MAPS
THE GALAXIES IN OUR UNIVERSE.
430
00:26:48,941 --> 00:26:54,445
LOOKING AT DISTANT GALAXIES
IS LIKE LOOKING BACK IN TIME.
431
00:26:54,447 --> 00:26:56,847
BECAUSE THE FARTHER AWAY
THEY ARE,
432
00:26:56,849 --> 00:26:59,617
THE LONGER THEIR LIGHT
TAKES TO REACH US.
433
00:27:02,488 --> 00:27:07,424
WE SEE THE MOST DISTANT
GALAXIES NOT AS THEY ARE NOW,
434
00:27:07,426 --> 00:27:12,096
BUT AS THEY WERE --
BILLIONS OF YEARS AGO.
435
00:27:12,098 --> 00:27:13,530
SO, WHEN YOU LOOK
AT THESE GALAXIES,
436
00:27:13,532 --> 00:27:15,799
YOU'RE SEEING THEM AS THEY WERE
WHEN THEY WERE VERY YOUNG,
437
00:27:15,801 --> 00:27:18,802
AND YOU'RE SEEING THESE GALAXIES
AS THEY ARE MORE RECENTLY,
438
00:27:18,804 --> 00:27:21,171
SO YOU CAN ACTUALLY LOOK
AT THE EVOLUTION --
439
00:27:21,173 --> 00:27:25,075
HOW GALAXIES CHANGE OVER TIME
AS THE UNIVERSE AGES.
440
00:27:27,213 --> 00:27:28,779
Narrator:
WHILE STUDYING THE DATA,
441
00:27:28,781 --> 00:27:31,782
SCIENTISTS MAKE
A DRAMATIC DISCOVERY.
442
00:27:31,784 --> 00:27:36,353
THEY FIND SPIRAL GALAXIES,
JUST LIKE THE MILKY WAY,
443
00:27:36,355 --> 00:27:40,090
DYING ALL OVER THE UNIVERSE.
444
00:27:40,092 --> 00:27:42,926
AND WHAT CONNECTS THEM
IS THEIR MASS.
445
00:27:44,964 --> 00:27:46,530
THERE SEEMS TO BE
AN UPPER WEIGHT LIMIT
446
00:27:46,532 --> 00:27:49,366
FOR THE SIZES OF
SPIRAL GALAXIES.
447
00:27:49,368 --> 00:27:51,835
UP TO ABOUT A TRILLION TIMES
THE MASS OF THE SUN,
448
00:27:51,837 --> 00:27:54,738
WE SEE SPIRAL GALAXIES
THAT CONTINUE TO FORM STARS,
449
00:27:54,740 --> 00:27:56,707
BUT ONCE THEY PASS
THIS THRESHOLD,
450
00:27:56,709 --> 00:27:59,109
GALAXIES TEND TO DIE
AND RUN OUT OF STARS.
451
00:28:01,280 --> 00:28:03,380
Narrator: WHILE DEVOURING
THE STAR-BUILDING GAS
452
00:28:03,382 --> 00:28:05,582
OF SMALLER GALAXIES,
453
00:28:05,584 --> 00:28:08,686
THE MILKY WAY
MAY HAVE GROWN OBESE,
454
00:28:08,688 --> 00:28:12,690
AND NOW IT COULD BE CHOKING
TO DEATH ON ITS OWN DINNER.
455
00:28:12,692 --> 00:28:14,958
BUT HOW?
456
00:28:14,960 --> 00:28:17,661
ONCE A SPIRAL GALAXY
IS SUFFICIENTLY BIG,
457
00:28:17,663 --> 00:28:20,264
IT'S GOING TO HAVE AN
INCREDIBLE GRAVITATIONAL FORCE,
458
00:28:20,266 --> 00:28:22,666
SO ANY GAS THAT IT PULLS
TO ITSELF
459
00:28:22,668 --> 00:28:26,236
IS GOING TO COME IN
AT AN INCREDIBLY HIGH SPEED.
460
00:28:26,238 --> 00:28:28,439
THAT GAS IS GOING TO BE
SUPERHEATED.
461
00:28:32,344 --> 00:28:34,978
Narrator: THE SUPERHEATED GAS
MOVES SO QUICKLY
462
00:28:34,980 --> 00:28:39,083
THAT IT'S PREVENTED
FROM FALLING INTO THE MILKY WAY.
463
00:28:39,085 --> 00:28:44,254
THE GAS IS TOO ENERGETIC FOR OUR
GALAXY'S GRAVITY TO PULL IT IN.
464
00:28:44,256 --> 00:28:48,459
INSTEAD, IT STAYS IN THE HALO
AROUND THE MILKY WAY,
465
00:28:48,461 --> 00:28:53,197
AND OUR GALAXY'S FOOD
SUPPLY IS CHOKED OFF.
466
00:28:53,199 --> 00:28:57,634
EVENTUALLY, OUR GALAXY
WILL STARVE.
467
00:28:57,636 --> 00:28:59,536
THIS WILL ONLY HAPPEN
IF THE MILKY WAY
468
00:28:59,538 --> 00:29:02,973
IS OVER THE STAR-BUILDING
WEIGHT LIMIT.
469
00:29:02,975 --> 00:29:07,511
BUT HOW EXACTLY
DO YOU WEIGH A GALAXY?
470
00:29:07,513 --> 00:29:09,980
ONE BASIC WAY
WE CAN WEIGH A GALAXY
471
00:29:09,982 --> 00:29:12,683
IS MEASURE HOW FAST
THE STARS ARE MOVING WITHIN IT.
472
00:29:12,685 --> 00:29:15,619
SO THE FASTER THE STARS ORBIT
AROUND THE CENTER OF THE GALAXY,
473
00:29:15,621 --> 00:29:18,489
THE MORE MASSIVE THE GALAXY IS.
474
00:29:18,491 --> 00:29:22,793
Narrator:
THIS METHOD OF WEIGHING
THE MILKY WAY RELIES ON GRAVITY.
475
00:29:22,795 --> 00:29:26,063
FAST-MOVING STARS NEED
MORE GRAVITY TO HOLD THEM
476
00:29:26,065 --> 00:29:27,397
IN THEIR ORBITS,
477
00:29:27,399 --> 00:29:32,269
AND MORE GRAVITY MEANS
MORE GALACTIC MASS.
478
00:29:32,271 --> 00:29:36,373
WHEN SCIENTISTS USE THIS
INFORMATION TO RUN THE MATH,
479
00:29:36,375 --> 00:29:39,910
THE HORRIBLE TRUTH IS REVEALED.
480
00:29:39,912 --> 00:29:42,613
Thaller: WE'VE PASSED
KIND OF A CRITICAL LEVEL.
481
00:29:42,615 --> 00:29:46,183
THE MILKY WAY IS FAR TOO MASSIVE
FOR ITS OWN HEALTH,
482
00:29:46,185 --> 00:29:49,019
AND WE'VE ENTERED
THE BEGINNING OF THE END.
483
00:29:49,021 --> 00:29:52,222
Plait:
WE'RE RUNNING OUT OF GAS,
AND I MEAN THIS LITERALLY.
484
00:29:52,224 --> 00:29:54,091
GAS CLOUDS FORM STARS,
485
00:29:54,093 --> 00:29:57,528
AND AS THEY FORM STARS,
THEY'RE USED UP,
486
00:29:57,530 --> 00:29:59,763
AND SO OUR GAS TANK
IS GETTING CLOSER AND CLOSER
487
00:29:59,765 --> 00:30:02,266
TO EMPTY EVERY DAY.
488
00:30:06,038 --> 00:30:09,072
Narrator:
THE INVESTIGATION INTO
THE KILLING OF THE MILKY WAY
489
00:30:09,074 --> 00:30:10,440
IS CLOSED.
490
00:30:12,645 --> 00:30:14,011
THE VERDICT?
491
00:30:14,013 --> 00:30:17,815
THE GREEDY MILKY WAY
IS KILLING ITSELF.
492
00:30:20,452 --> 00:30:24,454
OVER MILLIONS OF YEARS,
STAR FORMATION GRINDS TO A HALT,
493
00:30:24,456 --> 00:30:26,356
AND THE GALAXY DIES.
494
00:30:28,994 --> 00:30:34,131
BUT COULD
THE GALAXY BE RESURRECTED?
495
00:30:34,133 --> 00:30:35,999
WE SEEM TO BE TELLING
A VERY SAD STORY.
496
00:30:36,001 --> 00:30:38,202
WE'RE TALKING ABOUT THE DEMISE
OF THE MILKY WAY GALAXY --
497
00:30:38,204 --> 00:30:39,970
THE END OF STAR FORMATION --
498
00:30:39,972 --> 00:30:41,805
BUT MAYBE IT'S JUST
A LITTLE BIT TOO SOON
499
00:30:41,807 --> 00:30:43,574
TO WRITE THE DEATH
ANNOUNCEMENT YET.
500
00:30:43,576 --> 00:30:46,076
HOPE COULD BE
JUST OVER THE HORIZON.
501
00:30:48,914 --> 00:30:52,149
IN SPACE AND ASTROPHYSICS,
REALLY ANYTHING IS POSSIBLE.
502
00:30:52,151 --> 00:30:58,355
♪♪
503
00:30:59,758 --> 00:31:08,165
♪
IN SPACE AND ASTROPHYSICS,
REALLY ANYTHING IS POSSIBLE.
504
00:31:08,167 --> 00:31:12,936
Narrator:
THE SHOCKING CASE OF OUR
DYING GALAXY HAS BEEN SOLVED.
505
00:31:12,938 --> 00:31:15,272
THERE WAS NO KILLER.
506
00:31:15,274 --> 00:31:18,942
TURNS OUT, THE MILKY WAY
IS EATING ITSELF TO DEATH.
507
00:31:23,182 --> 00:31:26,650
BUT IS THIS REALLY THE END?
508
00:31:26,652 --> 00:31:29,620
COULD SALVATION
BE HEADING OUR WAY?
509
00:31:31,523 --> 00:31:33,390
EVEN IF STAR FORMATION IS
TURNING OFF
510
00:31:33,392 --> 00:31:34,758
IN THE MILKY WAY NOW,
511
00:31:34,760 --> 00:31:36,560
WE KNOW THAT IT'S ON
A COLLISION COURSE
512
00:31:36,562 --> 00:31:38,528
WITH THE ANDROMEDA GALAXY.
513
00:31:38,530 --> 00:31:39,696
THEY'RE MOVING TOWARD EACH OTHER
514
00:31:39,698 --> 00:31:44,001
AT HUNDREDS OF THOUSANDS
OF MILES PER HOUR.
515
00:31:44,003 --> 00:31:45,502
A COLLISION SOUNDS
LIKE SOMETHING
516
00:31:45,504 --> 00:31:47,037
THAT'S ALWAYS DESTRUCTIVE,
517
00:31:47,039 --> 00:31:49,039
BUT THAT'S NOT
NECESSARILY THE CASE.
518
00:31:51,977 --> 00:31:53,176
Narrator:
THE MILKY WAY'S COLLISION
519
00:31:53,178 --> 00:31:57,114
WITH OUR GIANT
GALACTIC NEIGHBOR ANDROMEDA
520
00:31:57,116 --> 00:32:00,284
WON'T HAPPEN
FOR ANOTHER 4 BILLION YEARS.
521
00:32:02,621 --> 00:32:06,256
BY THEN, STAR FORMATION
IN BOTH OF THESE GALAXIES
522
00:32:06,258 --> 00:32:07,958
WILL HAVE STOPPED COMPLETELY.
523
00:32:10,729 --> 00:32:14,731
BUT A GIANT MEET-UP
COULD CHANGE ALL THAT.
524
00:32:18,003 --> 00:32:19,469
Sutter:
AS AN ISOLATED GALAXY,
525
00:32:19,471 --> 00:32:22,873
THE MILKY WAY IS ALREADY
IN ITS WIND-DOWN PHASE.
526
00:32:22,875 --> 00:32:26,543
IT'S NOT PRODUCING AS MANY
NEW STARS AS IT USED TO.
527
00:32:26,545 --> 00:32:30,714
BUT THERE IS ONE WAY TO GENERATE
A NEW ROUND OF STAR FORMATION,
528
00:32:30,716 --> 00:32:34,418
AND THAT'S THROUGH
A GALACTIC MERGER EVENT.
529
00:32:34,420 --> 00:32:36,386
Plait: WHEN ANDROMEDA
GETS CLOSE ENOUGH,
530
00:32:36,388 --> 00:32:38,488
THE MUTUAL GRAVITY
BETWEEN THE TWO GALAXIES
531
00:32:38,490 --> 00:32:42,793
WILL START TO STRETCH THEM OUT,
PULLING THEM OUT LIKE TAFFY.
532
00:32:42,795 --> 00:32:45,729
STARS WILL BE PULLED OUT INTO
THESE LONG, LOOPING STREAMERS,
533
00:32:45,731 --> 00:32:46,863
AND THEN THE GALAXIES
534
00:32:46,865 --> 00:32:50,033
WILL PHYSICALLY PASS
THROUGH EACH OTHER.
535
00:32:50,035 --> 00:32:53,804
EVENTUALLY, THE TWO GALAXIES
WILL DRAW BACK TOGETHER AGAIN
536
00:32:53,806 --> 00:32:56,440
AND MERGE INTO
ONE GIGANTIC GALAXY,
537
00:32:56,442 --> 00:32:58,375
AND AT THAT POINT,
ALL OF THESE GAS CLOUDS
538
00:32:58,377 --> 00:33:01,545
WILL FLASH INTO STAR FORMATION.
539
00:33:06,251 --> 00:33:10,787
Narrator: AS THE GALAXIES MERGE,
THEY'LL BE REBORN.
540
00:33:10,789 --> 00:33:13,757
TWO DYING SPIRAL-SHAPED GALAXIES
541
00:33:13,759 --> 00:33:18,028
BECOME A SINGLE LIVING
ELLIPTICAL GALAXY
542
00:33:18,030 --> 00:33:22,032
CALLED MILKOMEDA.
543
00:33:22,034 --> 00:33:24,634
IMAGINE YOU'RE LIVING IN
THE FAR FUTURE OF THE GALAXY
544
00:33:24,636 --> 00:33:26,236
AND YOU SEE THE NIGHT SKY
545
00:33:26,238 --> 00:33:28,805
WHILE THE MILKY WAY
AND ANDROMEDA ARE COLLIDING.
546
00:33:28,807 --> 00:33:31,108
IT WILL LOOK LIKE
A VERY DIFFERENT PLACE.
547
00:33:31,110 --> 00:33:33,343
RATHER THAN ONE BAND
ACROSS THE NIGHT SKY,
548
00:33:33,345 --> 00:33:36,079
YOU MIGHT HAVE TWO
AS THE TWO DISKS COME TOGETHER.
549
00:33:36,081 --> 00:33:37,748
IT WILL BE A MIRACULOUS SIGHT,
550
00:33:37,750 --> 00:33:40,584
BUT A VERY, VERY DIFFERENT
PLACE THAN WE HAVE TODAY.
551
00:33:43,889 --> 00:33:49,059
Narrator:
OUR SKY WILL LIGHT UP FOR THE
FIRST TIME IN BILLIONS OF YEARS.
552
00:33:49,061 --> 00:33:52,496
STAR FORMATION WILL FLARE
ACROSS THE GALAXY.
553
00:33:54,833 --> 00:33:57,734
BUT IS IT TOO SOON
TO CELEBRATE?
554
00:34:01,473 --> 00:34:03,840
THIS NEW ROUND OF STAR FORMATION
555
00:34:03,842 --> 00:34:07,677
DURING THE MERGER
OF OUR TWO GALAXIES --
556
00:34:07,679 --> 00:34:10,047
WHILE IT'S VERY COOL
FOR A LITTLE BIT,
557
00:34:10,049 --> 00:34:14,785
ONCE IT'S OVER, THAT KIND OF
SENDS THE NEW GALAXY
558
00:34:14,787 --> 00:34:16,186
INTO A DEATH SPIRAL.
559
00:34:16,188 --> 00:34:18,955
WHEN NEW STARS ARE BORN
IN THIS NEW GALAXY,
560
00:34:18,957 --> 00:34:23,260
MANY OF THEM ARE GOING TO
BE HOT, LARGE, BLUE STARS.
561
00:34:23,262 --> 00:34:26,463
EVENTUALLY, THOSE YOUNG, HOT
STARS ARE GOING TO START TO DIE,
562
00:34:26,465 --> 00:34:28,565
AND WHEN THEY DO,
THEY'RE GOING TO EXPLODE
563
00:34:28,567 --> 00:34:30,567
VIOLENTLY AS SUPERNOVAE.
564
00:34:30,569 --> 00:34:36,039
♪♪
565
00:34:36,041 --> 00:34:38,041
AND THOSE SUPERNOVAE
ARE GOING TO START
566
00:34:38,043 --> 00:34:40,577
BLASTING GAS OUT OF THE GALAXY.
567
00:34:44,249 --> 00:34:45,782
Bullock:
ALL OF THE GAS IS GONE.
568
00:34:45,784 --> 00:34:48,085
THERE'S NO MORE STUFF
TO FORM STARS.
569
00:34:48,087 --> 00:34:49,853
AND THAT'S WHAT KILLS A GALAXY.
570
00:34:53,625 --> 00:34:55,926
Narrator: IT'LL TAKE
HUNDREDS OF MILLIONS OF YEARS
571
00:34:55,928 --> 00:35:00,530
FOR MILKOMEDA
TO RUN OUT OF STAR-BUILDING GAS.
572
00:35:00,532 --> 00:35:04,835
AND THEN OUR NEW ELLIPTICAL
GALAXY WILL STARVE.
573
00:35:06,638 --> 00:35:09,239
BUT THE FINAL BLOW
IS STILL TO COME.
574
00:35:11,677 --> 00:35:13,910
ANOTHER ISSUE TO CONSIDER
IS WHAT HAPPENS
575
00:35:13,912 --> 00:35:15,946
TO THE TWO SUPERMASSIVE
BLACK HOLES
576
00:35:15,948 --> 00:35:18,648
AT THE CORES OF
THE TWO GALAXIES.
577
00:35:18,650 --> 00:35:21,184
WELL, INITIALLY, THEY'RE GOING
TO ORBIT EACH OTHER,
578
00:35:21,186 --> 00:35:25,755
STIRRING UP A LOT OF TURBULENCE,
AND THEY'RE GOING TO COMBINE.
579
00:35:25,757 --> 00:35:28,692
AND BECAUSE THERE'S
A LOT OF NEW, HOT, FRESH GAS,
580
00:35:28,694 --> 00:35:31,862
OUR NEW GALAXY IS
GOING TO BE A QUASAR.
581
00:35:31,864 --> 00:35:34,397
AND THAT QUASAR IS GOING
TO TURN UP THE HEAT,
582
00:35:34,399 --> 00:35:36,032
IT'S GOING TO TURN UP
THE TURBULENCE,
583
00:35:36,034 --> 00:35:39,269
AND THIS MEANS STAR FORMATION
IS GOING TO BE SHUT OFF.
584
00:35:41,540 --> 00:35:45,142
Narrator:
THE COMBINED POWER OF THE
SUPERMASSIVE BLACK HOLES
585
00:35:45,144 --> 00:35:49,146
HELP CREATE A QUASAR
THAT TEARS THROUGH THE GALAXY.
586
00:35:52,251 --> 00:35:55,452
IT RELEASES FEROCIOUS
BEAMS OF RADIATION
587
00:35:55,454 --> 00:35:59,022
THAT BLAST THROUGH MILKOMEDA'S
STAR-FORMING GAS.
588
00:36:02,361 --> 00:36:04,261
IT'S ONLY JUST BEEN REBORN,
589
00:36:04,263 --> 00:36:08,832
BUT OUR NEWLY ENLARGED GALAXY
IS ONCE AGAIN DYING.
590
00:36:11,537 --> 00:36:16,706
VAST GALAXIES, LIKE MILKOMEDA,
SEEM DOOMED FROM THE START.
591
00:36:16,708 --> 00:36:20,810
THEIR SIZE CREATES TOO MANY
PROBLEMS FOR STAR FORMATION.
592
00:36:23,315 --> 00:36:26,583
OR...SO WE THOUGHT.
593
00:36:26,585 --> 00:36:28,919
THE MORE GALAXIES WE SEE,
THE MORE WE REALIZE
594
00:36:28,921 --> 00:36:30,987
THERE'S A LOT OUT THERE
WE HAVEN'T DISCOVERED,
595
00:36:30,989 --> 00:36:32,756
AND THERE'S A NEW CLASS
OF GALAXIES
596
00:36:32,758 --> 00:36:35,158
ONLY RECENTLY IDENTIFIED.
597
00:36:35,160 --> 00:36:39,763
THESE GALAXIES ARE MORE THAN 10
TIMES THE MASS OF THE MILKY WAY.
598
00:36:39,765 --> 00:36:43,867
AND, INTRIGUINGLY,
THEY'RE STILL FORMING STARS.
599
00:36:43,869 --> 00:36:45,602
APPARENTLY
WE'VE MISSED SOMETHING.
600
00:36:45,604 --> 00:36:50,106
♪♪
601
00:36:51,510 --> 00:37:01,284
♪
APPARENTLY
WE'VE MISSED SOMETHING.
602
00:37:01,286 --> 00:37:04,221
♪♪
603
00:37:04,223 --> 00:37:09,459
Narrator:
4 BILLION YEARS FROM NOW,
THE MILKY WAY IS NO MORE.
604
00:37:09,461 --> 00:37:12,596
AFTER COLLIDING WITH ANDROMEDA,
IT'S REBORN
605
00:37:12,598 --> 00:37:16,499
AS A GIANT ELLIPTICAL GALAXY
CALLED MILKOMEDA.
606
00:37:18,437 --> 00:37:22,872
SCIENTISTS THOUGHT GALAXIES
THIS BIG WERE DOOMED.
607
00:37:22,874 --> 00:37:25,942
BUT IS HOPE ON THE HORIZON?
608
00:37:28,413 --> 00:37:31,982
THE SLOAN DIGITAL SKY SURVEY
HAS SPENT A DECADE
609
00:37:31,984 --> 00:37:36,553
STUDYING
OVER A MILLION GALAXIES.
610
00:37:36,555 --> 00:37:40,957
IT'S DISCOVERED A RARE
BUT ENORMOUS KIND OF GALAXY --
611
00:37:40,959 --> 00:37:42,726
A SUPER SPIRAL.
612
00:37:45,631 --> 00:37:48,565
THESE SUPER-SPIRAL GALAXIES
ARE SPIRAL GALAXIES
613
00:37:48,567 --> 00:37:50,133
THAT ARE INCREDIBLY SUPER,
614
00:37:50,135 --> 00:37:53,903
AND BY "SUPER," I MEAN
THEY HAVE FOUR TIMES THE SIZE,
615
00:37:53,905 --> 00:37:55,605
10 TIMES THE MASS,
616
00:37:55,607 --> 00:37:57,274
AND THEY'RE WEIRD
BECAUSE THEY EXCEED
617
00:37:57,276 --> 00:38:00,277
THE SUPPOSED WEIGHT LIMIT
FOR SPIRAL GALAXIES.
618
00:38:00,279 --> 00:38:03,280
SO THEY SHOULDN'T HAVE
NEW STARS, BUT THEY DO.
619
00:38:03,282 --> 00:38:05,615
THEY'RE VERY HEALTHY GALAXIES.
620
00:38:05,617 --> 00:38:11,221
♪♪
621
00:38:11,223 --> 00:38:15,125
Narrator: SCIENTISTS HAVE FOUND
JUST 53 SUPER SPIRALS.
622
00:38:18,230 --> 00:38:22,332
SUPER-SPIRAL GALAXIES SHOW
THAT IN RARE SITUATIONS,
623
00:38:22,334 --> 00:38:26,903
MASSIVE GALAXIES CONTINUE
TO PRODUCE NEW STARS.
624
00:38:30,776 --> 00:38:34,311
SO, IS THIS A LIFELINE
FOR MILKOMEDA?
625
00:38:37,149 --> 00:38:39,182
Thaller: WHEN WE THINK ABOUT
TWO GALAXIES COLLIDING,
626
00:38:39,184 --> 00:38:40,817
A LOT OF OUR COMPUTER MODELS
SUGGEST
627
00:38:40,819 --> 00:38:42,419
THAT THEY REALLY
MESS EACH OTHER UP.
628
00:38:42,421 --> 00:38:44,120
THINGS GET VERY CHAOTIC.
629
00:38:44,122 --> 00:38:47,957
BUT OVER TIME, COULD THEY SETTLE
BACK DOWN INTO A SPIRAL SHAPE?
630
00:38:47,959 --> 00:38:50,827
AND, IN FACT, THAT MAY BE
WHAT HAPPENS WITH SUPER SPIRALS.
631
00:38:50,829 --> 00:38:53,396
ONE OF THE CLUES IS THAT MANY
SUPER-SPIRAL GALAXIES
632
00:38:53,398 --> 00:38:54,931
HAVE DOUBLE CORES.
633
00:38:54,933 --> 00:38:57,400
INSTEAD OF THERE JUST BEING
ONE SUPERMASSIVE BLACK HOLE,
634
00:38:57,402 --> 00:39:01,237
THERE ARE ACTUALLY
TWO ORBITING EACH OTHER.
635
00:39:01,239 --> 00:39:03,840
THE FACT THAT WE SEE SPIRAL
GALAXIES WITH TWO CORES
636
00:39:03,842 --> 00:39:05,875
MAKES IT POSSIBLE
THAT YOU COULD HAVE A COLLISION
637
00:39:05,877 --> 00:39:08,411
AND STILL SURVIVE
AS A SPIRAL GALAXY.
638
00:39:08,413 --> 00:39:11,381
SO MAYBE THERE'S HOPE THAT EVEN
THE MILKY WAY WILL BE A SPIRAL
639
00:39:11,383 --> 00:39:13,416
ONCE IT COLLIDES
WITH ANDROMEDA.
640
00:39:17,622 --> 00:39:21,424
Narrator: PICTURE THE SCENE --
6 BILLION YEARS IN THE FUTURE.
641
00:39:23,628 --> 00:39:26,229
MILKOMEDA DRIFTS
THROUGH THE UNIVERSE...
642
00:39:28,200 --> 00:39:32,235
...NOT AS AN ELLIPTICAL GALAXY,
BUT AS A SUPER SPIRAL.
643
00:39:34,806 --> 00:39:39,476
THIS SHAPE MEANS THE GALAXY
IS FAR MORE STABLE.
644
00:39:39,478 --> 00:39:41,511
THE DAMAGING HEAT
AND TURBULENCE
645
00:39:41,513 --> 00:39:45,014
GENERATED BY MILKOMEDA'S
SUPERMASSIVE BLACK HOLES
646
00:39:45,016 --> 00:39:51,054
CAN'T DISRUPT STAR-BUILDING GAS
WAY OUT IN THE SPIRAL ARMS.
647
00:39:51,056 --> 00:39:56,893
FAR FROM DYING OFF,
OUR GALAXY LIVES ON --
648
00:39:56,895 --> 00:40:00,597
LARGER THAN EVER BEFORE.
649
00:40:00,599 --> 00:40:03,867
BUT THAT ISN'T
THE END OF THE STORY.
650
00:40:03,869 --> 00:40:06,970
TENS OF BILLIONS
OF YEARS FROM NOW,
651
00:40:06,972 --> 00:40:10,940
COULD THE GALAXY
CONTINUE TO GROW?
652
00:40:10,942 --> 00:40:13,176
OUR LOCAL GROUP OF GALAXIES --
653
00:40:13,178 --> 00:40:15,712
MILKY WAY, ANDROMEDA,
TRIANGULUM --
654
00:40:15,714 --> 00:40:19,449
AND THEN A COLLECTION
OF DWARF SATELLITE GALAXIES --
655
00:40:19,451 --> 00:40:22,519
IS GRAVITATIONALLY
BOUND TOGETHER,
656
00:40:22,521 --> 00:40:25,121
AND EVENTUALLY,
WE'RE ALL GLUED TOGETHER
657
00:40:25,123 --> 00:40:27,323
INTO A SINGLE MASSIVE OBJECT.
658
00:40:29,060 --> 00:40:30,527
Bullock: WHAT DOES THIS MEAN?
659
00:40:30,529 --> 00:40:32,962
THIS MEANS WE MIGHT BE PART OF
ONE OF THE LARGEST STRUCTURES
660
00:40:32,964 --> 00:40:35,165
IN THE UNIVERSE.
661
00:40:35,167 --> 00:40:37,434
Narrator: DURING
ITS BILLION YEARS OF LIFE,
662
00:40:37,436 --> 00:40:42,038
THE MILKY WAY CHANGES
BEYOND RECOGNITION.
663
00:40:42,040 --> 00:40:45,375
IT SUFFERS COUNTLESS COLLISIONS,
664
00:40:45,377 --> 00:40:49,546
FEASTS ON MANY SMALLER GALAXIES,
665
00:40:49,548 --> 00:40:52,615
AND GIVES BIRTH
TO INNUMERABLE STARS.
666
00:40:54,820 --> 00:40:56,886
Thaller: WE TALK ABOUT
THE LIFE CYCLE OF GALAXIES --
667
00:40:56,888 --> 00:41:00,089
HOW THEY'RE BORN, HOW THEY LIVE
HEALTHY LIVES MAKING NEW STARS,
668
00:41:00,091 --> 00:41:02,192
AND EVENTUALLY
HOW THEY DIE AWAY.
669
00:41:02,194 --> 00:41:04,360
IT'S REALLY NOT
AS DEPRESSING AS THAT.
670
00:41:04,362 --> 00:41:06,463
EVERYTHING IN
THE UNIVERSE CHANGES.
671
00:41:08,533 --> 00:41:13,837
Narrator:
GALAXIES LIKE OURS ARE IN
A CONSTANT STATE OF FLUX.
672
00:41:13,839 --> 00:41:16,639
SO WHEN IT COMES TO
THE MILKY WAY,
673
00:41:16,641 --> 00:41:19,275
DEATH REALLY ISN'T THE END.
674
00:41:21,179 --> 00:41:22,745
Oluseyi:
WHAT WE SEE IN OUR UNIVERSE
675
00:41:22,747 --> 00:41:26,516
IS THAT THERE'S ALWAYS
A PROCESS OF BIRTH AND REBIRTH,
676
00:41:26,518 --> 00:41:28,084
SO THE FUTURE
OF THE MILKY WAY
677
00:41:28,086 --> 00:41:30,386
IS THAT IT'S GOING TO
KEEP ON DOING WHAT IT DOES.
678
00:41:33,024 --> 00:41:34,724
Bullock:
GALAXIES ARE EVER-CHANGING.
679
00:41:34,726 --> 00:41:36,159
10 BILLION YEARS AGO,
THE MILKY WAY
680
00:41:36,161 --> 00:41:37,994
WAS NOTHING LIKE
WHAT IT IS TODAY,
681
00:41:37,996 --> 00:41:39,996
AND CERTAINLY,
10 BILLION YEARS IN THE FUTURE,
682
00:41:39,998 --> 00:41:41,831
IT'LL BE A VERY
DIFFERENT PLACE.
683
00:41:44,402 --> 00:41:46,769
Plait:
LOOK, I LIVE IN THIS GALAXY.
684
00:41:46,771 --> 00:41:49,372
I HOPE THAT IT CAN FIND A WAY
TO REJUVENATE ITSELF
685
00:41:49,374 --> 00:41:51,508
THROUGH COLLISIONS
OR SOME OTHER PROCESS
686
00:41:51,510 --> 00:41:53,243
BECAUSE THAT GIVES ME SOME HOPE
687
00:41:53,245 --> 00:41:56,112
THAT IT'LL GO ON
FOR A LONG, LONG TIME.
62699
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