1
00:00:02,333 --> 00:00:06,166
♪ ♪

2
00:00:09,866 --> 00:00:12,833
NARRATOR:
At this precise moment,

3
00:00:12,866 --> 00:00:16,366
{\an1}on a planet far, far away...

4
00:00:19,333 --> 00:00:23,666
{\an1}...an alien sunrise ushers in
a new day.

5
00:00:28,900 --> 00:00:32,800
♪ ♪

6
00:00:32,833 --> 00:00:38,566
{\an1}But will alien eyes
gaze upon it?

7
00:00:38,600 --> 00:00:41,400
{\an1}CLARA SOUSA-SILVA:
For me, the most exciting
question in the universe

8
00:00:41,433 --> 00:00:43,533
{\an1}is whether or not there are
inhabited planets

9
00:00:43,566 --> 00:00:44,533
{\an1}other than the Earth.

10
00:00:44,566 --> 00:00:46,233
♪ ♪

11
00:00:46,266 --> 00:00:49,666
ANJALI TRIPATHI:
What are the chances that
out there in the Milky Way,

12
00:00:49,700 --> 00:00:53,733
{\an1}there is other complex, advanced
life like our own?

13
00:00:53,766 --> 00:00:56,633
{\an8}♪ ♪

14
00:00:56,666 --> 00:01:00,533
{\an8}NARRATOR:
Today, our telescopes
are combing the skies,

15
00:01:00,566 --> 00:01:03,966
{\an1}discovering bizarre worlds--

16
00:01:04,000 --> 00:01:07,433
even in places
they shouldn't be.

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00:01:07,466 --> 00:01:10,900
ANJALI PIETTE:
We didn't even know that that
kind of planet existed.

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00:01:10,933 --> 00:01:12,933
{\an1}So it completely shocked
our theories of planets

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00:01:12,966 --> 00:01:13,933
{\an1}and how they form.

20
00:01:13,966 --> 00:01:16,866
♪ ♪

21
00:01:16,900 --> 00:01:21,200
NARRATOR:
Will we ever find a world
that resembles our home?

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00:01:21,233 --> 00:01:23,700
PHIL MUIRHEAD:
Earth-like planets
that orbit their stars

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00:01:23,733 --> 00:01:25,700
{\an1}at the same distance
we orbit the sun

24
00:01:25,733 --> 00:01:27,933
{\an1}are very difficult to detect.

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00:01:27,966 --> 00:01:31,166
{\an1}Looking for life is not easy,
and we're going to get

26
00:01:31,200 --> 00:01:32,866
{\an1}constant setbacks.

27
00:01:32,900 --> 00:01:34,766
♪ ♪

28
00:01:34,800 --> 00:01:40,533
NARRATOR:
Are we finally on the verge of
answering the ultimate question:

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00:01:40,566 --> 00:01:43,133
are we alone?

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00:01:43,166 --> 00:01:45,433
{\an1}I think we'll actually find the
answer while I'm still alive.

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00:01:45,466 --> 00:01:46,733
{\an1}At least I hope so.

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00:01:46,766 --> 00:01:48,266
♪ ♪

33
00:01:48,300 --> 00:01:51,600
NARRATOR:
The search is on.

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00:01:51,633 --> 00:01:53,666
"Alien Worlds."

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00:01:53,700 --> 00:01:56,000
{\an1}Right now, on "NOVA."

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00:01:56,033 --> 00:02:00,333
♪ ♪

37
00:02:18,100 --> 00:02:20,500
{\an1}♪ See me when I float
like a dove ♪

38
00:02:20,533 --> 00:02:24,566
{\an1}♪ The skies above are lined
with trees ♪

39
00:02:24,600 --> 00:02:28,266
{\an1}♪ I'm on my knees,
begging please ♪

40
00:02:28,300 --> 00:02:35,233
{\an1}♪ Come and take me away ♪

41
00:02:41,333 --> 00:02:46,766
♪ ♪

42
00:02:49,933 --> 00:02:51,466
NARRATOR:
The Milky Way,

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00:02:51,500 --> 00:02:54,533
our galaxy.

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00:02:54,566 --> 00:03:00,200
{\an1}As many as 400 billion stars.

45
00:03:00,233 --> 00:03:03,033
♪ ♪

46
00:03:03,066 --> 00:03:08,333
{\an1}Spread across 100,000
light-years.

47
00:03:14,000 --> 00:03:17,566
{\an1}Among these stars, the sun,

48
00:03:17,600 --> 00:03:22,000
{\an1}with eight planets orbiting
around it--

49
00:03:22,033 --> 00:03:26,966
{\an1}including our home.

50
00:03:27,000 --> 00:03:31,066
SARA SEAGER:
Humans have been looking up
at the stars for millennia.

51
00:03:31,100 --> 00:03:33,000
{\an1}I think we're just so curious
about it,

52
00:03:33,033 --> 00:03:34,966
{\an7}yet we don't really know
what's out there.

53
00:03:35,000 --> 00:03:40,033
♪ ♪

54
00:03:40,066 --> 00:03:45,266
NARRATOR:
Not only what, but who?

55
00:03:45,300 --> 00:03:48,200
GIBOR BASRI:
We've gotten to the point
in astrophysics where I think

56
00:03:48,233 --> 00:03:51,433
{\an7}the big question on everyone's
mind really is: are we alone?

57
00:03:51,466 --> 00:03:55,533
♪ ♪

58
00:03:55,566 --> 00:03:57,966
PIETTE:
Is all life like us

59
00:03:58,000 --> 00:04:00,000
{\an7}and will we recognize it
when we see it?

60
00:04:00,033 --> 00:04:03,100
♪ ♪

61
00:04:03,133 --> 00:04:09,266
NARRATOR:
Today, we stand on the brink
of answering these questions.

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00:04:09,300 --> 00:04:12,300
DOUGLAS LIN:
What is different today is that
we have a chance

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00:04:12,333 --> 00:04:17,500
{\an7}to actually address some of
these issues quantitatively,

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00:04:17,533 --> 00:04:19,666
{\an8}scientifically.

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00:04:19,700 --> 00:04:25,866
{\an1}Not just sheer speculation
and philosophically.

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00:04:25,900 --> 00:04:29,300
HANNAH WAKEFORD:
If and when we do find life,

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00:04:29,333 --> 00:04:30,833
{\an1}it's going to completely change

68
00:04:30,866 --> 00:04:34,533
{\an7}the way we view ourselves,
our planet, our universe.

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00:04:34,566 --> 00:04:38,966
♪ ♪

70
00:04:39,000 --> 00:04:43,866
NARRATOR:
Over the last 50 years,
humanity's robotic space probes

71
00:04:43,900 --> 00:04:48,133
{\an1}have found their way to every
planet in our solar system.

72
00:04:48,166 --> 00:04:54,966
♪ ♪

73
00:04:55,000 --> 00:04:58,133
{\an1}And even some of their moons.

74
00:05:01,100 --> 00:05:07,533
{\an8}♪ ♪

75
00:05:07,566 --> 00:05:08,800
{\an8}But so far,

76
00:05:08,833 --> 00:05:14,833
{\an1}no convincing evidence of life
has been discovered.

77
00:05:14,866 --> 00:05:19,566
♪ ♪

78
00:05:19,600 --> 00:05:24,166
{\an1}As far as we know,
Earth remains one of a kind.

79
00:05:24,200 --> 00:05:29,466
{\an8}♪ ♪

80
00:05:29,500 --> 00:05:35,933
{\an7}The only world where chemistry
gave rise to biology.

81
00:05:38,166 --> 00:05:43,000
{\an1}But even as the exploration
of the solar system continues,

82
00:05:43,033 --> 00:05:48,866
{\an1}another quest has begun to
discover other planets out there

83
00:05:48,900 --> 00:05:52,533
{\an1}orbiting distant stars:

84
00:05:52,566 --> 00:05:56,266
exoplanets.

85
00:05:56,300 --> 00:05:59,033
GRANT TREMBLAY:
It's really only in the last
few decades that we've had

86
00:05:59,066 --> 00:06:00,966
{\an7}the ability to search for
exoplanets.

87
00:06:01,000 --> 00:06:03,166
♪ ♪

88
00:06:03,200 --> 00:06:07,366
NARRATOR:
And from the start,
scientists dream of finding one

89
00:06:07,400 --> 00:06:10,766
{\an1}that might host life
like our own.

90
00:06:10,800 --> 00:06:12,700
SOUSA-SILVA:
It's completely reasonable
to expect that alien life

91
00:06:12,733 --> 00:06:15,466
{\an1}will be quite different from
the life we find on Earth.

92
00:06:15,500 --> 00:06:18,333
{\an7}But Earth is the only place
in the galaxy that we know

93
00:06:18,366 --> 00:06:19,666
{\an7}for sure hosts life.

94
00:06:19,700 --> 00:06:22,933
{\an7}So we start there--
looking for an Earth twin.

95
00:06:22,966 --> 00:06:24,500
{\an1}And then the question becomes:

96
00:06:24,533 --> 00:06:27,133
{\an1}how common are Earths
across the galaxy?

97
00:06:27,166 --> 00:06:31,000
♪ ♪

98
00:06:34,500 --> 00:06:36,566
NARRATOR:
Over the last three decades,

99
00:06:36,600 --> 00:06:39,466
{\an1}scientists have deployed
some of the most

100
00:06:39,500 --> 00:06:42,500
{\an1}powerful telescopes on Earth.

101
00:06:42,533 --> 00:06:48,066
{\an1}And used a clever technique to
detect the presence of planets

102
00:06:48,100 --> 00:06:53,500
{\an1}that are too dim to see next
to the bright stars they orbit.

103
00:06:57,300 --> 00:06:59,200
MUIRHEAD:
Many teams started to look
for planets

104
00:06:59,233 --> 00:07:00,733
{\an1}using the same technique.

105
00:07:00,766 --> 00:07:03,300
{\an7}This is the Doppler technique,
or the wobble technique.

106
00:07:03,333 --> 00:07:07,233
{\an7}DAVID CHARBONNEAU:
The way the wobble method works

107
00:07:07,266 --> 00:07:08,566
{\an7}is that you can imagine
that you've got

108
00:07:08,600 --> 00:07:10,466
{\an7}two dance partners, okay?

109
00:07:10,500 --> 00:07:14,033
{\an8}One is the star
and one is the planet,

110
00:07:14,066 --> 00:07:16,200
{\an1}but you don't see the planet

111
00:07:16,233 --> 00:07:18,000
{\an1}because it doesn't put out
much light.

112
00:07:18,033 --> 00:07:21,433
{\an1}And so if we look very carefully
at the star, we can see that

113
00:07:21,466 --> 00:07:23,733
{\an1}the star appears to be moving
away from us

114
00:07:23,766 --> 00:07:26,766
and towards us,
back and forth over time.

115
00:07:26,800 --> 00:07:30,566
{\an1}And we can deduce just from a
basic understanding of gravity

116
00:07:30,600 --> 00:07:32,666
{\an1}that there must be something
else there

117
00:07:32,700 --> 00:07:37,333
{\an1}and even measure its mass.

118
00:07:37,366 --> 00:07:40,133
NARRATOR:
But what astronomers discover

119
00:07:40,166 --> 00:07:46,066
{\an1}is something completely
unexpected.

120
00:07:46,100 --> 00:07:48,066
PIETTE:
The first-ever exoplanet
that was discovered

121
00:07:48,100 --> 00:07:49,500
{\an1}around a sun-like star

122
00:07:49,533 --> 00:07:52,800
{\an1}was 51 Pegasi b in 1995.

123
00:07:52,833 --> 00:07:57,966
♪ ♪

124
00:08:01,700 --> 00:08:07,033
NARRATOR:
51 Pegasi b is a gas giant.

125
00:08:07,066 --> 00:08:13,133
{\an1}Around half the mass of Jupiter,
but so close to its star

126
00:08:13,166 --> 00:08:17,166
{\an1}that part of its atmosphere
may have been ripped away.

127
00:08:19,700 --> 00:08:23,066
{\an1}These planets are baked
by their stars' radiation.

128
00:08:23,100 --> 00:08:26,000
{\an1}The temperatures are in
the thousands.

129
00:08:26,033 --> 00:08:28,666
♪ ♪

130
00:08:28,700 --> 00:08:31,500
CHARBONNEAU:
Many astronomers didn't believe
it because the planet

131
00:08:31,533 --> 00:08:34,500
{\an1}was in the wrong place.

132
00:08:34,533 --> 00:08:35,600
It was enormous,

133
00:08:35,633 --> 00:08:37,666
it was massive,
and yet it was parked

134
00:08:37,700 --> 00:08:40,466
{\an1}right next to its star.

135
00:08:40,500 --> 00:08:42,300
SEAGER:
And a planet has no business
being there.

136
00:08:42,333 --> 00:08:43,733
{\an1}There's not enough material

137
00:08:43,766 --> 00:08:46,900
{\an1}around a forming star to make
a planet that close to the star.

138
00:08:46,933 --> 00:08:53,766
♪ ♪

139
00:08:53,800 --> 00:08:57,500
NARRATOR:
Its skies whipped into
titanic winds...

140
00:09:01,433 --> 00:09:07,833
{\an1}...and a hot interior, pelted by
raindrops of molten iron.

141
00:09:07,866 --> 00:09:13,166
♪ ♪

142
00:09:13,200 --> 00:09:14,700
JAYNE BIRKBY:
The discovery of 51 Peg

143
00:09:14,733 --> 00:09:17,133
{\an7}meant that we had to tear up
the rulebook.

144
00:09:17,166 --> 00:09:19,966
♪ ♪

145
00:09:20,000 --> 00:09:22,566
{\an1}NIKKU MADHUSUDHAN:
We were hoping to discover
a planet,

146
00:09:22,600 --> 00:09:24,900
{\an1}something like what we see
in the solar system,

147
00:09:24,933 --> 00:09:28,266
{\an7}but instead found a planet
that had absolutely no analogue

148
00:09:28,300 --> 00:09:30,466
{\an7}in the solar system, and no one
could have predicted

149
00:09:30,500 --> 00:09:32,766
{\an7}that such planets
were even possible.

150
00:09:32,800 --> 00:09:37,433
{\an8}♪ ♪

151
00:09:37,466 --> 00:09:41,300
{\an8}NARRATOR:
And other discoveries
were stranger still.

152
00:09:41,333 --> 00:09:45,733
{\an7}Planets blasted by
fierce radiation.

153
00:09:45,766 --> 00:09:49,600
♪ ♪

154
00:09:51,666 --> 00:09:55,133
{\an1}Their surfaces battered
and stripped

155
00:09:55,166 --> 00:09:59,833
{\an1}by the high-energy
strobing light of their star.

156
00:09:59,866 --> 00:10:06,366
♪ ♪

157
00:10:06,400 --> 00:10:11,333
{\an1}Rocky worlds large enough
to hold on to some atmosphere,

158
00:10:11,366 --> 00:10:15,733
{\an7}but so cold that the entire
surface has frozen over.

159
00:10:19,566 --> 00:10:23,800
{\an8}♪ ♪

160
00:10:23,833 --> 00:10:26,500
{\an7}And great puffy planets

161
00:10:26,533 --> 00:10:31,166
{\an7}with an average density
like Styrofoam.

162
00:10:31,200 --> 00:10:36,600
♪ ♪

163
00:10:39,266 --> 00:10:44,166
{\an1}And with diamond-crushing
pressures at their centers.

164
00:10:48,733 --> 00:10:53,933
{\an1}These discoveries electrified
the world's astronomers.

165
00:10:53,966 --> 00:10:58,766
{\an1}At long last, confirmation that
there are other solar systems

166
00:10:58,800 --> 00:11:04,033
{\an1}out there, inhospitable
though they might be.

167
00:11:04,066 --> 00:11:06,466
{\an1}These worlds are truly
amazing places,

168
00:11:06,500 --> 00:11:09,966
{\an1}and we've learnt so much about
the physics and the chemistry

169
00:11:10,000 --> 00:11:13,833
{\an1}of a world like this,
but they are not places

170
00:11:13,866 --> 00:11:16,900
{\an1}to look for life.

171
00:11:16,933 --> 00:11:21,066
NARRATOR:
Because these are worlds
too bizarre, too large,

172
00:11:21,100 --> 00:11:23,733
{\an1}and often too close
to their stars

173
00:11:23,766 --> 00:11:27,533
{\an1}for living things to survive.

174
00:11:27,566 --> 00:11:30,433
MADHUSUDHAN:
Like any major scientific
revolution,

175
00:11:30,466 --> 00:11:33,700
{\an1}looking for life is going to be
filled with setbacks

176
00:11:33,733 --> 00:11:37,133
{\an1}and many false positives.

177
00:11:37,166 --> 00:11:38,500
{\an1}But we have to keep on.

178
00:11:38,533 --> 00:11:40,933
♪ ♪

179
00:11:40,966 --> 00:11:44,500
TRIPATHI:
It's a lot easier to find
something that's big

180
00:11:44,533 --> 00:11:46,466
{\an1}and far away rather than
something that's small

181
00:11:46,500 --> 00:11:47,800
and far away.

182
00:11:47,833 --> 00:11:50,766
{\an1}So the fact that we've found
more large planets

183
00:11:50,800 --> 00:11:53,566
{\an7}is not an indication of what's
actually out there.

184
00:11:53,600 --> 00:11:55,500
{\an7}It's just a matter of what's
easier to find.

185
00:11:55,533 --> 00:11:58,733
♪ ♪

186
00:11:58,766 --> 00:12:05,400
NARRATOR:
Finding planets like Earth would
take an extraordinary mission.

187
00:12:05,433 --> 00:12:07,633
SOUSA-SILVA:
We really needed a space mission
dedicated to finding

188
00:12:07,666 --> 00:12:10,033
{\an1}Earth-sized planets
in our galaxy,

189
00:12:10,066 --> 00:12:13,000
{\an1}and ideally, enough of them
to give us real insights.

190
00:12:13,033 --> 00:12:14,566
♪ ♪

191
00:12:14,600 --> 00:12:15,766
NARRATOR:
The solution?

192
00:12:15,800 --> 00:12:19,900
A telescope
almost 20 years in the making.

193
00:12:19,933 --> 00:12:22,366
WILLIAM BORUCKI:
I was working for NASA Ames.

194
00:12:22,400 --> 00:12:25,133
{\an7}I realized that if we were going
to find Earth-size planets,

195
00:12:25,166 --> 00:12:28,666
{\an7}we had to build a photometer
that was good enough to see

196
00:12:28,700 --> 00:12:30,466
{\an7}these small, Earth-size planets

197
00:12:30,500 --> 00:12:33,200
{\an1}and find out about them.

198
00:12:33,233 --> 00:12:38,166
{\an1}Some 17 years after I started,
NASA headquarters said, "Yes.

199
00:12:38,200 --> 00:12:41,066
{\an1}We will build that mission."

200
00:12:41,100 --> 00:12:44,833
BASRI:
I was very privileged to be
at the Kepler launch,

201
00:12:44,866 --> 00:12:48,466
{\an1}and we were all incredibly
nervous a few days before,

202
00:12:48,500 --> 00:12:50,266
{\an7}because the previous mission
that had launched

203
00:12:50,300 --> 00:12:53,166
{\an7}on the same rocket had failed.

204
00:12:53,200 --> 00:12:55,233
{\an8}(chuckling):
Their satellite went...

205
00:12:55,266 --> 00:12:56,833
{\an1}Went down in Antarctica.

206
00:12:56,866 --> 00:12:59,266
{\an1}And we were, like, "Uh-oh, no."

207
00:12:59,300 --> 00:13:01,233
{\an1}So we were very nervous.

208
00:13:01,266 --> 00:13:05,533
{\an8}MAN:
T minus ten, nine, eight,

209
00:13:05,566 --> 00:13:08,266
{\an7}seven, six, five,

210
00:13:08,300 --> 00:13:12,666
{\an7}four, three, two...

211
00:13:12,700 --> 00:13:15,666
{\an1}Engine start, one, zero,
and lift-off

212
00:13:15,700 --> 00:13:19,966
{\an1}of the Delta 2 rocket with
Kepler on a search for planets

213
00:13:20,000 --> 00:13:21,600
{\an1}in some way like our own.

214
00:13:21,633 --> 00:13:26,566
{\an1}(man speaking indistinctly
on radio)

215
00:13:26,600 --> 00:13:31,533
♪ ♪

216
00:13:31,566 --> 00:13:32,733
{\an1}MAN 2 (on radio):
And we have separation!

217
00:13:32,766 --> 00:13:36,733
SEAGER:
It was a spectacular
night launch.

218
00:13:36,766 --> 00:13:39,033
{\an1}Kepler was launched without
a single flaw.

219
00:13:39,066 --> 00:13:44,500
NARRATOR:
NASA's Kepler Space Telescope
takes the search

220
00:13:44,533 --> 00:13:48,733
{\an1}above Earth's atmosphere
into space.

221
00:13:50,733 --> 00:13:55,400
{\an1}Kepler travels 94 million miles
away...

222
00:14:02,733 --> 00:14:07,366
{\an7}...until it arrives on a stable
orbit around the sun,

223
00:14:07,400 --> 00:14:14,033
{\an7}where it looks out
with a fixed and clear gaze

224
00:14:14,066 --> 00:14:17,800
{\an7}to a single patch of sky
in the constellations

225
00:14:17,833 --> 00:14:21,200
{\an7}of Cygnus, Lyra, and Draco.

226
00:14:21,233 --> 00:14:25,300
{\an8}♪ ♪

227
00:14:28,966 --> 00:14:31,500
BORUCKI:
What was special finally
was, the lid opens up

228
00:14:31,533 --> 00:14:33,866
{\an1}and we see the nighttime sky.

229
00:14:33,900 --> 00:14:37,066
{\an1}What we see is, the sky is
covered with star.

230
00:14:37,100 --> 00:14:38,433
{\an1}Every detector is working.

231
00:14:38,466 --> 00:14:44,466
♪ ♪

232
00:14:44,500 --> 00:14:49,866
NARRATOR:
Exposing 42 incredibly sensitive
light sensors

233
00:14:49,900 --> 00:14:55,700
{\an7}to the light of 150,000 stars...

234
00:14:55,733 --> 00:14:58,933
{\an8}♪ ♪

235
00:14:58,966 --> 00:15:01,100
{\an7}...Kepler begins its search

236
00:15:01,133 --> 00:15:04,633
{\an1}for Earth-like worlds.

237
00:15:22,366 --> 00:15:24,700
HAKEEM OLUSEYI:
The problem with finding
exoplanets is,

238
00:15:24,733 --> 00:15:26,300
{\an1}they just don't shine at all

239
00:15:26,333 --> 00:15:30,533
{\an1}and they're around
really bright stars.

240
00:15:30,566 --> 00:15:32,733
{\an1}That makes them virtually
impossible to image.

241
00:15:32,766 --> 00:15:37,066
{\an1}So, astronomers came up
with a different method,

242
00:15:37,100 --> 00:15:41,366
{\an1}and that's called
the transit method.

243
00:15:41,400 --> 00:15:44,100
{\an7}Kepler uses the transit method
for discovering planets

244
00:15:44,133 --> 00:15:45,600
{\an7}around other stars.

245
00:15:45,633 --> 00:15:47,200
{\an7}And it's really simple.

246
00:15:47,233 --> 00:15:51,400
{\an7}A star is bright,
and if a planet is orbiting it,

247
00:15:51,433 --> 00:15:54,433
{\an1}if the planet passes in front of
the face of the star,

248
00:15:54,466 --> 00:15:56,900
{\an1}the planet blocks
some of that light

249
00:15:56,933 --> 00:15:59,000
{\an1}and the star temporarily
appears dimmer.

250
00:15:59,033 --> 00:16:01,733
{\an1}So, if we were to bring that
down to Earth,

251
00:16:01,766 --> 00:16:05,766
{\an1}imagine this lighthouse is your
star, is your source of light.

252
00:16:05,800 --> 00:16:08,633
{\an1}If a moth flies in front of
that light,

253
00:16:08,666 --> 00:16:12,100
{\an1}even though to your naked eye
the light looks the same,

254
00:16:12,133 --> 00:16:14,500
{\an1}it actually has become
a little bit dimmer

255
00:16:14,533 --> 00:16:17,000
{\an1}because the light has been
blocked by the moth.

256
00:16:17,033 --> 00:16:19,100
{\an1}That's the transit method.

257
00:16:19,133 --> 00:16:24,266
♪ ♪

258
00:16:32,366 --> 00:16:37,400
NARRATOR:
At the time the largest camera
ever launched into space...

259
00:16:39,266 --> 00:16:45,400
{\an1}...Kepler is able to look for
smaller, more Earth-like worlds:

260
00:16:45,433 --> 00:16:47,966
{\an1}those too small to be
easily found

261
00:16:48,000 --> 00:16:52,200
{\an1}using terrestrial telescopes.

262
00:16:52,233 --> 00:16:55,233
{\an1}Soon, it starts to spot planets.

263
00:16:55,266 --> 00:16:56,633
SOUSA-SILVA:
The amount of dimming

264
00:16:56,666 --> 00:16:59,600
{\an7}and the time between
each dimming event gave us clues

265
00:16:59,633 --> 00:17:02,500
{\an7}to a planet's size and its
distance from its star.

266
00:17:02,533 --> 00:17:07,033
NARRATOR:
And with every world it finds,

267
00:17:07,066 --> 00:17:12,500
{\an1}astronomers hold their breath,

268
00:17:12,533 --> 00:17:16,133
{\an1}hoping for a rocky planet
that might in some way

269
00:17:16,166 --> 00:17:21,833
{\an1}remind them of Earth:

270
00:17:21,866 --> 00:17:25,200
{\an1}worlds like Kepler-36b.

271
00:17:25,233 --> 00:17:30,333
{\an8}♪ ♪

272
00:17:40,166 --> 00:17:43,300
{\an8}♪ ♪

273
00:17:43,333 --> 00:17:46,166
{\an1}Orbiting a star similar
to our own.

274
00:17:46,200 --> 00:17:49,100
At first glance,

275
00:17:49,133 --> 00:17:54,800
{\an1}a planet that resembles ours.

276
00:17:54,833 --> 00:17:58,233
TREMBLAY:
So when we started finding these
rocky planets like Kepler-36b,

277
00:17:58,266 --> 00:18:00,033
{\an7}that were getting closer
to Earth mass,

278
00:18:00,066 --> 00:18:01,866
{\an7}it was just the greatest
feeling.

279
00:18:03,800 --> 00:18:08,733
NARRATOR:
Weighing in at around four times
the mass of our own planet,

280
00:18:08,766 --> 00:18:11,466
{\an1}we'd found one of the first
rocky worlds

281
00:18:11,500 --> 00:18:14,666
{\an1}that could have an atmosphere.

282
00:18:14,700 --> 00:18:18,833
{\an1}A so-called Super-Earth.

283
00:18:26,100 --> 00:18:27,533
OLUSEYI:
What's so cool about Kepler

284
00:18:27,566 --> 00:18:31,466
{\an1}is that it tells us so much more
than just, the planets exist.

285
00:18:31,500 --> 00:18:34,633
{\an1}We get their sizes, we get their
orbital characteristics,

286
00:18:34,666 --> 00:18:36,500
{\an1}we can get their masses.

287
00:18:36,533 --> 00:18:37,833
{\an1}And so what we're learning

288
00:18:37,866 --> 00:18:40,633
{\an1}is not just that the planets
are there,

289
00:18:40,666 --> 00:18:43,500
{\an1}but what these planets are like.

290
00:18:48,800 --> 00:18:55,000
♪ ♪

291
00:18:55,033 --> 00:18:59,433
NARRATOR:
But the more closely we examine
Kepler-36b,

292
00:18:59,466 --> 00:19:01,566
{\an1}the clearer it becomes

293
00:19:01,600 --> 00:19:06,700
{\an1}that this is not a world like
our own.

294
00:19:06,733 --> 00:19:09,766
BIRKBY:
Finding exoplanets
in the Kepler data,

295
00:19:09,800 --> 00:19:11,866
{\an1}you really have to do some
detective work.

296
00:19:11,900 --> 00:19:15,966
{\an1}You're trying to find a signal
that's less than one percent

297
00:19:16,000 --> 00:19:19,133
{\an1}of all the other things that are
going on in that data.

298
00:19:21,033 --> 00:19:25,566
NARRATOR:
The light from the star dims
every 14 days,

299
00:19:25,600 --> 00:19:29,333
{\an1}the length of a year
for the orbiting planet.

300
00:19:29,366 --> 00:19:33,533
{\an1}This rocky world orbits
incredibly close.

301
00:19:33,566 --> 00:19:37,233
{\an7}And it has company--

302
00:19:37,266 --> 00:19:41,733
{\an7}a gigantic gassy companion
planet.

303
00:19:44,100 --> 00:19:46,933
{\an1}COURTNEY DRESSING:
The discovery of the Kepler-36
system is really interesting

304
00:19:46,966 --> 00:19:50,333
{\an1}because the first planet found
was Kepler-36c.

305
00:19:50,366 --> 00:19:52,100
{\an7}That's a gas giant planet.

306
00:19:52,133 --> 00:19:56,433
♪ ♪

307
00:19:56,466 --> 00:20:00,900
NARRATOR:
The two planets have
unusually close orbits,

308
00:20:00,933 --> 00:20:02,933
{\an1}creating bizarre conditions

309
00:20:02,966 --> 00:20:08,266
{\an1}on the surface of Kepler-36b.

310
00:20:08,300 --> 00:20:11,200
{\an8}Kepler-36b,
in many ways, is Earth-like,

311
00:20:11,233 --> 00:20:15,466
{\an7}but it also is very
un-Earth-like

312
00:20:15,500 --> 00:20:17,033
{\an1}in pretty profound ways

313
00:20:17,066 --> 00:20:19,700
{\an1}that mean it's unlikely to have
life on its surface.

314
00:20:19,733 --> 00:20:25,800
♪ ♪

315
00:20:25,833 --> 00:20:28,400
NARRATOR:
Thanks to its close-by star,

316
00:20:28,433 --> 00:20:33,600
{\an1}the planet's rotation becomes
tidally locked.

317
00:20:33,633 --> 00:20:36,400
{\an1}One face rests permanently

318
00:20:36,433 --> 00:20:39,000
{\an7}under its star's bright glare.

319
00:20:39,033 --> 00:20:44,633
{\an8}♪ ♪

320
00:20:44,666 --> 00:20:48,900
{\an1}Punishing heat likely turns
the ground molten...

321
00:20:48,933 --> 00:20:54,266
♪ ♪

322
00:20:54,300 --> 00:20:58,500
{\an1}...creating rivers of lava
that crisscross the surface.

323
00:21:00,600 --> 00:21:03,200
On top of that,

324
00:21:03,233 --> 00:21:07,100
every 97 days,
the immense gravitational pull

325
00:21:07,133 --> 00:21:10,666
{\an1}from the gas giant may trigger

326
00:21:10,700 --> 00:21:15,900
{\an1}intense volcanism
on the smaller planet

327
00:21:15,933 --> 00:21:21,000
{\an1}each time it passes between
the giant and the star...

328
00:21:21,033 --> 00:21:23,833
♪ ♪

329
00:21:23,866 --> 00:21:29,366
{\an1}...throwing lava high
in violent eruptions.

330
00:21:31,766 --> 00:21:36,900
♪ ♪

331
00:21:46,300 --> 00:21:51,433
♪ ♪

332
00:21:54,233 --> 00:21:58,933
{\an1}But Kepler-36b is a planet
of molten rock,

333
00:21:58,966 --> 00:22:02,333
fire, and ice,

334
00:22:02,366 --> 00:22:07,366
{\an1}because its far side permanently
faces away from the star...

335
00:22:09,633 --> 00:22:15,500
{\an1}...creating a frigid hemisphere
shrouded in eternal darkness...

336
00:22:18,133 --> 00:22:25,066
{\an1}...where magma freezes into a
strange, desolate landscape.

337
00:22:25,100 --> 00:22:26,466
PIETTE:
The Kepler-36 system

338
00:22:26,500 --> 00:22:30,066
{\an7}is a perfect example of how
exoplanets are completely

339
00:22:30,100 --> 00:22:32,166
{\an7}different to what we know
in the solar system.

340
00:22:32,200 --> 00:22:37,733
♪ ♪

341
00:22:37,766 --> 00:22:42,833
NARRATOR:
Kepler-36b is just one of
the first among hundreds

342
00:22:42,866 --> 00:22:45,633
{\an1}of Super-Earth-size planets

343
00:22:45,666 --> 00:22:49,066
{\an1}that the Kepler telescope
discovers.

344
00:22:49,100 --> 00:22:53,300
{\an1}The more scientists look,
the more they find.

345
00:22:53,333 --> 00:22:55,100
CHARBONNEAU:
At the time that the Kepler
mission launched,

346
00:22:55,133 --> 00:22:59,400
{\an1}the team was hoping they might
find a few exciting planets

347
00:22:59,433 --> 00:23:01,700
{\an1}and they were very prepared
to analyze those data.

348
00:23:01,733 --> 00:23:04,833
{\an1}Within the first few months, we
realized that we did not have

349
00:23:04,866 --> 00:23:08,533
{\an1}enough people to handle
the deluge of planets.

350
00:23:08,566 --> 00:23:14,766
♪ ♪

351
00:23:14,800 --> 00:23:18,900
NARRATOR:
The mission shows beyond doubt
that our galaxy is home

352
00:23:18,933 --> 00:23:23,500
{\an1}to a multitude of diverse
alien worlds.

353
00:23:23,533 --> 00:23:27,466
♪ ♪

354
00:23:27,500 --> 00:23:30,033
WAKEFORD:
Kepler was a game-changer
for exoplanets.

355
00:23:30,066 --> 00:23:33,300
{\an7}It was a game-changer for us
here on Earth,

356
00:23:33,333 --> 00:23:38,066
{\an7}understanding that there are
planets in their thousands,

357
00:23:38,100 --> 00:23:43,266
{\an1}in their millions, in their
billions in our galaxy alone.

358
00:23:43,300 --> 00:23:47,633
♪ ♪

359
00:23:47,666 --> 00:23:49,000
SOUSA-SILVA:
We suddenly had this
new problem.

360
00:23:49,033 --> 00:23:51,900
{\an1}We had gone from just having
a handful of planets

361
00:23:51,933 --> 00:23:54,100
{\an1}to hundreds of planets
to look through.

362
00:23:54,133 --> 00:23:56,400
{\an1}So, we needed to tighten
the net, focusing on planets

363
00:23:56,433 --> 00:23:58,200
{\an1}that didn't just resemble
Earth's size,

364
00:23:58,233 --> 00:23:59,666
{\an1}but its habitability.

365
00:23:59,700 --> 00:24:02,800
♪ ♪

366
00:24:02,833 --> 00:24:06,366
NARRATOR:
Now that they have discovered
that planets are plentiful,

367
00:24:06,400 --> 00:24:11,033
{\an1}astronomers must narrow
their search to home in on

368
00:24:11,066 --> 00:24:12,800
{\an1}hard-to-find planets.

369
00:24:12,833 --> 00:24:16,133
{\an1}(bird screeching)

370
00:24:16,166 --> 00:24:21,466
{\an1}Rocky worlds that hold the one
precious ingredient that makes

371
00:24:21,500 --> 00:24:23,933
{\an1}Earth a living world.

372
00:24:23,966 --> 00:24:29,600
{\an1}(monkey chattering,
insects and birds chirping)

373
00:24:29,633 --> 00:24:35,600
♪ ♪

374
00:24:38,233 --> 00:24:43,766
{\an1}Everything we know about life

375
00:24:43,800 --> 00:24:49,433
{\an1}we've discovered by looking
at ourselves and our world.

376
00:24:49,466 --> 00:24:54,166
♪ ♪

377
00:24:54,200 --> 00:24:56,633
SOUSA-SILVA:
Life on Earth is extremely
diverse.

378
00:24:56,666 --> 00:25:01,033
{\an1}Millions and millions of species
of all kinds.

379
00:25:01,066 --> 00:25:06,033
NARRATOR:
And these endless
beautiful forms

380
00:25:06,066 --> 00:25:10,833
{\an1}occupy just about every
available niche on the planet.

381
00:25:10,866 --> 00:25:14,700
♪ ♪

382
00:25:14,733 --> 00:25:17,733
DRESSING:
We've had the opportunity
to explore a variety

383
00:25:17,766 --> 00:25:18,966
{\an1}of extreme environments,

384
00:25:19,000 --> 00:25:22,766
{\an1}and in pretty much all of them,
we find life.

385
00:25:22,800 --> 00:25:25,433
NARRATOR:
Earth has taught us that,

386
00:25:25,466 --> 00:25:27,566
{\an1}given the right conditions,

387
00:25:27,600 --> 00:25:30,100
{\an1}life is remarkably adaptable--

388
00:25:30,133 --> 00:25:34,333
and resilient.

389
00:25:34,366 --> 00:25:37,300
♪ ♪

390
00:25:45,666 --> 00:25:47,133
{\an8}Life.

391
00:25:47,166 --> 00:25:50,833
{\an7}Here on Earth, it is absolutely
everywhere.

392
00:25:50,866 --> 00:25:55,000
{\an7}Once life got started,
it has held on tenaciously.

393
00:25:55,033 --> 00:25:58,633
{\an1}But, where can we find life
elsewhere in the universe?

394
00:25:58,666 --> 00:26:00,966
{\an1}If it's done so well here
on Earth,

395
00:26:01,000 --> 00:26:03,333
{\an1}certainly this can't be
the only place.

396
00:26:03,366 --> 00:26:08,566
♪ ♪

397
00:26:08,600 --> 00:26:10,500
{\an1}But if we're going to find life
on other worlds,

398
00:26:10,533 --> 00:26:13,066
{\an1}we're going to need to know
where to look,

399
00:26:13,100 --> 00:26:15,233
{\an1}because there's a lot of worlds
out there, and man,

400
00:26:15,266 --> 00:26:18,366
{\an1}is the volume of space huge!

401
00:26:18,400 --> 00:26:21,466
{\an1}So you can't just go looking
willy-nilly.

402
00:26:21,500 --> 00:26:23,300
{\an1}You need to find a marker

403
00:26:23,333 --> 00:26:26,733
{\an1}that guides you to where life
most likely can be found.

404
00:26:26,766 --> 00:26:32,766
♪ ♪

405
00:26:32,800 --> 00:26:34,333
{\an1}For life to get started
on a planet,

406
00:26:34,366 --> 00:26:36,800
{\an1}it needs a few specific things.

407
00:26:36,833 --> 00:26:39,833
{\an1}You have to have energy
to power that life

408
00:26:39,866 --> 00:26:41,600
{\an1}and you have to have
the right chemistry.

409
00:26:41,633 --> 00:26:43,833
{\an1}But even if you have
both of those,

410
00:26:43,866 --> 00:26:46,833
{\an1}there is still one more thing
that we don't know

411
00:26:46,866 --> 00:26:51,000
{\an1}is necessarily going to be found
on exoplanets.

412
00:26:51,033 --> 00:26:54,133
Water,
and it has to be liquid water.

413
00:26:54,166 --> 00:26:58,100
♪ ♪

414
00:26:58,133 --> 00:27:03,933
NARRATOR:
Every single living thing
on Earth requires liquid water

415
00:27:03,966 --> 00:27:06,900
to exist.

416
00:27:06,933 --> 00:27:10,200
{\an1}To uncover life that resembles
anything like what we have here,

417
00:27:10,233 --> 00:27:14,466
{\an1}finding liquid water will
be crucial.

418
00:27:14,500 --> 00:27:16,100
SEAGER:
There's a concept:

419
00:27:16,133 --> 00:27:17,700
{\an7}follow the water.

420
00:27:17,733 --> 00:27:19,733
{\an7}That where there's water,
there might be life.

421
00:27:19,766 --> 00:27:23,033
♪ ♪

422
00:27:36,000 --> 00:27:40,400
{\an8}NARRATOR:
The universe itself
is awash with water.

423
00:27:46,466 --> 00:27:51,533
{\an7}Great reservoirs have been
detected throughout the galaxy

424
00:27:51,566 --> 00:27:55,100
{\an7}in vast, interstellar clouds.

425
00:28:00,533 --> 00:28:03,600
{\an1}But just because water
is plentiful,

426
00:28:03,633 --> 00:28:06,933
{\an1}that doesn't mean that planets
are necessarily

427
00:28:06,966 --> 00:28:09,533
{\an1}the places where it ends up.

428
00:28:09,566 --> 00:28:15,466
♪ ♪

429
00:28:17,033 --> 00:28:18,733
{\an1}So, while we've detected water

430
00:28:18,766 --> 00:28:22,833
{\an1}on the moons of Jupiter
and Saturn...

431
00:28:28,066 --> 00:28:31,900
{\an1}...only one of the eight planets
in our solar system

432
00:28:31,933 --> 00:28:36,000
{\an1}has liquid water flowing on
its surface.

433
00:28:36,033 --> 00:28:39,733
♪ ♪

434
00:28:39,766 --> 00:28:45,433
{\an1}An ocean world where, long ago,
life began to thrive.

435
00:28:45,466 --> 00:28:50,633
♪ ♪

436
00:28:50,666 --> 00:28:52,700
TREMBLAY:
So the challenge, then,

437
00:28:52,733 --> 00:28:55,866
{\an1}was to find an Earth-mass planet
in a habitable zone.

438
00:28:55,900 --> 00:28:57,966
{\an7}Meaning it's the right distance
from its host star

439
00:28:58,000 --> 00:29:00,166
{\an7}to support liquid water on
its surface.

440
00:29:00,200 --> 00:29:03,000
{\an7}Earth-like planets that orbit
their stars

441
00:29:03,033 --> 00:29:04,766
{\an7}at the same distance we orbit
the sun,

442
00:29:04,800 --> 00:29:09,066
{\an1}who are right on the limit
of what Kepler could find.

443
00:29:09,100 --> 00:29:12,200
SOUSA-SILVA:
We need to see the planet cross
in front of its star,

444
00:29:12,233 --> 00:29:14,900
{\an7}and it takes us multiple orbits
to observe this.

445
00:29:14,933 --> 00:29:20,466
{\an1}And so it's really, really
difficult to find these planets.

446
00:29:20,500 --> 00:29:23,600
NARRATOR:
And while Kepler
can detect planets,

447
00:29:23,633 --> 00:29:28,600
{\an1}it cannot tell what
they're made of.

448
00:29:28,633 --> 00:29:34,100
{\an1}To detect water, the most
powerful space telescope yet

449
00:29:34,133 --> 00:29:36,166
{\an1}must join the quest.

450
00:29:36,200 --> 00:29:39,400
♪ ♪

451
00:29:39,433 --> 00:29:42,900
DRESSING:
Kepler and Hubble worked well
in coordination.

452
00:29:42,933 --> 00:29:45,500
{\an7}Kepler would find planets around
distant stars,

453
00:29:45,533 --> 00:29:48,000
{\an7}and then Hubble would follow
them up in more detail,

454
00:29:48,033 --> 00:29:50,100
{\an7}to teach us more about
the atmospheres

455
00:29:50,133 --> 00:29:52,333
{\an7}of the planets found by Kepler.

456
00:29:52,366 --> 00:29:55,500
♪ ♪

457
00:29:55,533 --> 00:29:57,966
SEAGER:
When a planet goes
in front of the star,

458
00:29:58,000 --> 00:30:00,733
{\an1}some of the starlight shines
through the atmosphere.

459
00:30:00,766 --> 00:30:04,300
{\an1}But just like shining a
flashlight through the fog,

460
00:30:04,333 --> 00:30:07,500
{\an1}some light doesn't make it
through and some does.

461
00:30:07,533 --> 00:30:10,133
{\an1}And by piecing together which
parts of the starlight

462
00:30:10,166 --> 00:30:12,533
{\an1}make it through the planet
atmosphere and which don't,

463
00:30:12,566 --> 00:30:14,733
{\an1}we can actually tell something
about the gases

464
00:30:14,766 --> 00:30:17,800
{\an1}in the atmosphere of the planet
that are absorbing.

465
00:30:17,833 --> 00:30:20,100
{\an1}And then we can tell something
about the makeup of the planet.

466
00:30:20,133 --> 00:30:24,600
{\an8}♪ ♪

467
00:30:28,100 --> 00:30:32,533
{\an8}NARRATOR:
In 2015, Kepler finds Hubble
a target.

468
00:30:32,566 --> 00:30:35,833
♪ ♪

469
00:30:35,866 --> 00:30:39,500
A world within
its star's habitable zone.

470
00:30:42,500 --> 00:30:47,266
♪ ♪

471
00:30:47,300 --> 00:30:50,633
{\an1}More than eight times the mass
of Earth,

472
00:30:50,666 --> 00:30:55,300
{\an1}K2-18b is enormous.

473
00:30:55,333 --> 00:30:58,933
♪ ♪

474
00:31:04,533 --> 00:31:11,033
With a powerful
gravitational pull

475
00:31:11,066 --> 00:31:16,233
{\an1}that allows it to form, and hang
on to, an atmosphere.

476
00:31:16,266 --> 00:31:20,800
♪ ♪

477
00:31:26,766 --> 00:31:30,300
♪ ♪

478
00:31:30,333 --> 00:31:35,133
{\an1}Hubble examines light from
K2-18b's star

479
00:31:35,166 --> 00:31:37,266
{\an1}as the planet passes
in front of it.

480
00:31:37,300 --> 00:31:42,833
♪ ♪

481
00:31:42,866 --> 00:31:46,700
And discovers
a long-awaited signature.

482
00:31:49,100 --> 00:31:53,400
Water vapor.

483
00:31:53,433 --> 00:31:55,933
MADHUSUDHAN:
K2-18b is exciting because,

484
00:31:55,966 --> 00:31:57,800
{\an7}with the Hubble observations,

485
00:31:57,833 --> 00:32:01,266
{\an7}we found water vapor in its
atmosphere.

486
00:32:01,300 --> 00:32:04,266
{\an7}And this is the smallest planet
to date

487
00:32:04,300 --> 00:32:06,566
{\an1}which sits in the habitable zone
of its host star

488
00:32:06,600 --> 00:32:08,766
{\an1}and in whose atmosphere
water has been detected.

489
00:32:08,800 --> 00:32:11,166
{\an1}Earth has tiny but
environmentally significant

490
00:32:11,200 --> 00:32:13,200
{\an1}amounts of water vapor in our
atmosphere,

491
00:32:13,233 --> 00:32:16,633
{\an1}ranging from four percent to
less than one percent.

492
00:32:16,666 --> 00:32:19,100
PIETTE:
So far, the data we have has
shown

493
00:32:19,133 --> 00:32:24,266
{\an1}that there's anywhere between
0.01% and about 15% water vapor

494
00:32:24,300 --> 00:32:26,700
{\an1}in the atmosphere of K2-18b.

495
00:32:26,733 --> 00:32:29,033
{\an7}And that might seem like quite
a broad constraint,

496
00:32:29,066 --> 00:32:30,600
{\an7}but we have to remember that

497
00:32:30,633 --> 00:32:33,166
{\an7}this is a planet that's
many, many light-years away.

498
00:32:33,200 --> 00:32:35,200
{\an1}So the fact that we can detect
this water at all

499
00:32:35,233 --> 00:32:36,566
{\an1}is already really exciting.

500
00:32:36,600 --> 00:32:41,400
♪ ♪

501
00:32:41,433 --> 00:32:44,866
NARRATOR:
124 light-years from Earth,

502
00:32:44,900 --> 00:32:49,833
{\an1}we may have found evidence
of water on another world.

503
00:32:49,866 --> 00:32:52,666
SEAGER:
K2-18b is a huge milestone.

504
00:32:52,700 --> 00:32:55,433
{\an1}It's what we call
a sub-Neptune-sized exoplanet.

505
00:32:55,466 --> 00:32:58,200
♪ ♪

506
00:32:58,233 --> 00:32:59,966
BORUCKI:
Now, what does that mean?

507
00:33:00,000 --> 00:33:03,366
{\an1}Well, it could be, it's a planet
sort of like Jupiter,

508
00:33:03,400 --> 00:33:06,600
{\an1}heavy, massive hydrogen
atmosphere, no life.

509
00:33:06,633 --> 00:33:08,000
{\an7}That's like Jupiter.

510
00:33:08,033 --> 00:33:11,333
{\an7}Or it could be that water
represents an ocean.

511
00:33:11,366 --> 00:33:13,800
{\an8}It doesn't have
a heavy atmosphere.

512
00:33:13,833 --> 00:33:15,933
{\an1}Instead, it has an ocean
and the water is evaporating.

513
00:33:15,966 --> 00:33:18,766
{\an1}So it's a wonderful discovery.

514
00:33:18,800 --> 00:33:23,100
♪ ♪

515
00:33:26,266 --> 00:33:31,266
NARRATOR:
Within the data lies
a tantalizing possibility.

516
00:33:32,833 --> 00:33:39,200
{\an1}If K2-18b's vast mass
is formed from water,

517
00:33:39,233 --> 00:33:43,566
{\an1}its skies could be full
of clouds,

518
00:33:43,600 --> 00:33:47,833
{\an1}where water vapor collects,

519
00:33:47,866 --> 00:33:50,666
forming droplets

520
00:33:50,700 --> 00:33:54,433
{\an1}and eventually falling.

521
00:33:54,466 --> 00:34:00,166
♪ ♪

522
00:34:00,200 --> 00:34:04,933
{\an1}A cycle, potentially feeding
vast oceans...

523
00:34:04,966 --> 00:34:07,600
♪ ♪

524
00:34:07,633 --> 00:34:13,900
{\an1}...that could stretch across
the entire planet,

525
00:34:13,933 --> 00:34:18,333
{\an1}making it a water world.

526
00:34:18,366 --> 00:34:20,566
MADHUSUDHAN:
This finding is remarkable

527
00:34:20,600 --> 00:34:23,566
{\an1}because, 20 years ago,
no one would have dreamt

528
00:34:23,600 --> 00:34:26,700
{\an1}that we would be here today,

529
00:34:26,733 --> 00:34:28,900
{\an1}talking about detecting
the atmosphere of a planet

530
00:34:28,933 --> 00:34:34,900
{\an1}and trying to understand
the conditions on its surface.

531
00:34:40,733 --> 00:34:44,666
PIETTE:
For me, K2-18b has been
a real turning point

532
00:34:44,700 --> 00:34:47,100
{\an1}because it really
opens up the field

533
00:34:47,133 --> 00:34:50,266
{\an1}to looking for life in these
slightly bigger planets.

534
00:34:50,300 --> 00:34:53,433
♪ ♪

535
00:34:53,466 --> 00:34:58,300
NARRATOR:
After the astonishing
breakthrough of K2-18b,

536
00:34:58,333 --> 00:35:02,266
{\an1}Kepler goes on to make
many more discoveries.

537
00:35:02,300 --> 00:35:04,966
TREMBLAY:
So, Kepler was
a really simple mission.

538
00:35:05,000 --> 00:35:06,933
{\an1}It's just this minivan-sized
spacecraft

539
00:35:06,966 --> 00:35:09,100
{\an1}that stared at this field
of stars.

540
00:35:09,133 --> 00:35:13,000
{\an1}But that one mission discovered
so many alien worlds.

541
00:35:13,033 --> 00:35:17,533
♪ ♪

542
00:35:17,566 --> 00:35:20,933
NARRATOR:
Worlds that astound astronomers

543
00:35:20,966 --> 00:35:26,233
{\an1}and dramatically expand our
understanding of the universe.

544
00:35:26,266 --> 00:35:28,666
DRESSING:
As we look out into the galaxy,

545
00:35:28,700 --> 00:35:30,866
we can start
to answer the question

546
00:35:30,900 --> 00:35:34,433
{\an1}of what properties do planets
and planetary systems need

547
00:35:34,466 --> 00:35:36,600
{\an1}in order to support the
evolution,

548
00:35:36,633 --> 00:35:39,000
{\an1}and continued existence,
of life.

549
00:35:39,033 --> 00:35:42,466
♪ ♪

550
00:35:42,500 --> 00:35:46,466
NARRATOR:
But nothing lasts forever.

551
00:35:46,500 --> 00:35:52,333
In October 2018,
Kepler finally runs out of fuel.

552
00:35:52,366 --> 00:35:54,900
BORUCKI:
It was sad to see
an old friend leave

553
00:35:54,933 --> 00:35:57,800
{\an1}when they sent the command
to shut everything down.

554
00:35:57,833 --> 00:35:59,400
It's asleep now.

555
00:35:59,433 --> 00:36:02,333
{\an1}It's in orbit around the sun,
and it will continue that orbit.

556
00:36:02,366 --> 00:36:04,933
♪ ♪

557
00:36:04,966 --> 00:36:06,933
SOUSA-SILVA:
To date, Kepler has given us

558
00:36:06,966 --> 00:36:09,600
{\an1}over two and a half thousand
planets.

559
00:36:09,633 --> 00:36:11,333
{\an1}And we're still analyzing
the Kepler data,

560
00:36:11,366 --> 00:36:14,600
{\an1}so there could be many more
to come.

561
00:36:14,633 --> 00:36:17,966
♪ ♪

562
00:36:18,000 --> 00:36:20,333
NARRATOR:
A galactic census,

563
00:36:20,366 --> 00:36:27,300
{\an1}showing us just how common
planets like K2-18b might be.

564
00:36:27,333 --> 00:36:32,466
♪ ♪

565
00:36:32,500 --> 00:36:35,366
BORUCKI:
We know there's about,
on average,

566
00:36:35,400 --> 00:36:37,766
{\an1}two or more planets per star.

567
00:36:37,800 --> 00:36:40,666
{\an1}Maybe ten percent of those are
small planets,

568
00:36:40,700 --> 00:36:42,466
{\an1}ten percent of those in
the habitable zone.

569
00:36:42,500 --> 00:36:47,533
{\an1}So that means there is about
20 billion planets

570
00:36:47,566 --> 00:36:48,600
{\an1}about the size of the Earth

571
00:36:48,633 --> 00:36:50,100
{\an1}in the habitable zone
of their star.

572
00:36:50,133 --> 00:36:53,000
{\an1}We don't know about it, and we
might never know about it,

573
00:36:53,033 --> 00:36:56,733
{\an1}but it is absolutely possible
that of the panoply of planets,

574
00:36:56,766 --> 00:36:58,966
of alien worlds
that Kepler has observed,

575
00:36:59,000 --> 00:37:04,133
{\an1}there's actually been some
planets that host alien life.

576
00:37:04,166 --> 00:37:06,600
BIRKBY:
Maybe they have their own
forests and lakes

577
00:37:06,633 --> 00:37:10,333
{\an1}filled with fish,
and skies filled with birds.

578
00:37:10,366 --> 00:37:13,433
{\an7}It's so incredible to think
about the endless possibilities

579
00:37:13,466 --> 00:37:15,066
{\an7}that are out there for life
to take.

580
00:37:16,333 --> 00:37:20,100
NARRATOR:
These tantalizing glimpses
of worlds

581
00:37:20,133 --> 00:37:23,766
{\an1}give us a foundation
to build upon

582
00:37:23,800 --> 00:37:26,766
for the next,
even more ambitious mission.

583
00:37:26,800 --> 00:37:29,466
MAN:
...one, zero.

584
00:37:29,500 --> 00:37:32,000
{\an1}Lift-off, the SpaceX Falcon 9

585
00:37:32,033 --> 00:37:35,166
carrying TESS,
a planet-hunting spacecraft

586
00:37:35,200 --> 00:37:38,466
{\an1}that will search for new worlds
beyond our solar system.

587
00:37:38,500 --> 00:37:43,366
♪ ♪

588
00:37:43,400 --> 00:37:44,966
DRESSING:
Kepler taught us about
statistics

589
00:37:45,000 --> 00:37:46,333
{\an1}and how common planets are.

590
00:37:46,366 --> 00:37:50,266
{\an1}But the planets found by Kepler
were often orbiting stars

591
00:37:50,300 --> 00:37:52,900
{\an1}that were too distant
and too faint for further study.

592
00:37:52,933 --> 00:37:56,700
{\an1}With TESS, we're looking at all
of the nearby stars.

593
00:37:56,733 --> 00:37:59,033
MAN (on radio):
Vehicle has passed maximum
aerodynamic pressure.

594
00:37:59,066 --> 00:38:01,566
CHARBONNEAU:
Because they are close

595
00:38:01,600 --> 00:38:03,966
{\an1}and the stars appear bright
to us,

596
00:38:04,000 --> 00:38:07,266
{\an7}we can go and learn whether they
have atmospheres,

597
00:38:07,300 --> 00:38:08,933
{\an7}what the atmospheres
are made of,

598
00:38:08,966 --> 00:38:10,633
{\an7}whether they have moons
and rings--

599
00:38:10,666 --> 00:38:13,533
{\an1}all the stuff that is far too
difficult to study

600
00:38:13,566 --> 00:38:16,033
{\an1}for the Kepler stars themselves.

601
00:38:17,866 --> 00:38:19,866
DRESSING:
There are hundreds of people
involved

602
00:38:19,900 --> 00:38:21,400
{\an1}in making the TESS mission
a success,

603
00:38:21,433 --> 00:38:23,466
{\an1}and now the world
is analyzing the data.

604
00:38:23,500 --> 00:38:25,900
SEAGER:
TESS is finding the planets

605
00:38:25,933 --> 00:38:27,733
{\an1}that will make the legacy
catalogue

606
00:38:27,766 --> 00:38:29,700
{\an1}that will be used
for generations to come.

607
00:38:29,733 --> 00:38:35,200
NARRATOR:
Among this vast array
of worlds, what kind of life

608
00:38:35,233 --> 00:38:37,600
{\an1}are we hoping to find?

609
00:38:37,633 --> 00:38:40,000
BASRI:
When we say we're looking
for life,

610
00:38:40,033 --> 00:38:42,933
{\an1}we usually don't say exactly
what we mean by that.

611
00:38:42,966 --> 00:38:45,500
{\an1}And in fact, it turns out
defining life

612
00:38:45,533 --> 00:38:49,033
{\an1}in a way that satisfies
everybody hasn't been done yet.

613
00:38:49,066 --> 00:38:51,200
♪ ♪

614
00:38:51,233 --> 00:38:54,533
TRIPATHI:
We have to distinguish between
simple life

615
00:38:54,566 --> 00:38:57,900
{\an7}and more complex,
advanced life like ourselves.

616
00:38:57,933 --> 00:38:59,933
{\an7}And there's quite a difference
there, between the two.

617
00:38:59,966 --> 00:39:07,133
♪ ♪

618
00:39:09,333 --> 00:39:12,266
NARRATOR:
We are the product of a story
that has been playing out

619
00:39:12,300 --> 00:39:17,500
{\an1}for over a quarter of the age
of the universe itself.

620
00:39:17,533 --> 00:39:20,466
♪ ♪

621
00:39:20,500 --> 00:39:21,600
From microbes

622
00:39:21,633 --> 00:39:24,366
{\an1}to a global technological
civilization.

623
00:39:26,733 --> 00:39:30,866
{\an1}With our telescopes,
we stand on the cusp

624
00:39:30,900 --> 00:39:33,900
{\an1}of finding signs of at least

625
00:39:33,933 --> 00:39:36,466
{\an1}simple life-forms on other
planets.

626
00:39:39,133 --> 00:39:41,433
{\an1}But we have also been
calling out,

627
00:39:41,466 --> 00:39:45,033
{\an1}sending out transmissions into
the galaxy,

628
00:39:45,066 --> 00:39:47,133
{\an1}in the hope of connecting

629
00:39:47,166 --> 00:39:49,933
with another
intelligent species.

630
00:39:51,900 --> 00:39:55,666
TRIPATHI:
For millennia,
we've looked out at the skies.

631
00:39:55,700 --> 00:39:57,733
{\an1}And it's only in the last
century,

632
00:39:57,766 --> 00:40:00,066
{\an1}really, the blink of an eye
for humanity,

633
00:40:00,100 --> 00:40:02,200
{\an1}that we've actually been able
to send messages

634
00:40:02,233 --> 00:40:04,266
{\an1}and probes beyond the Earth.

635
00:40:04,300 --> 00:40:08,033
{\an1}And as of yet, we're
still waiting for a response.

636
00:40:08,066 --> 00:40:09,533
(static hissing)

637
00:40:09,566 --> 00:40:12,033
{\an1}What we're hearing is
just silence.

638
00:40:15,100 --> 00:40:18,366
{\an8}NARRATOR:
But with millions of potentially
habitable worlds

639
00:40:18,400 --> 00:40:22,833
{\an7}in the Milky Way,
why is no one calling to us?

640
00:40:22,866 --> 00:40:25,566
{\an8}♪ ♪

641
00:40:25,600 --> 00:40:31,000
{\an7}In 2020, scientists make an
unsettling find:

642
00:40:31,033 --> 00:40:35,000
{\an1}a planet, almost the size of
Earth,

643
00:40:35,033 --> 00:40:39,966
floating freely
through the galaxy, all alone.

644
00:40:40,000 --> 00:40:41,800
BIRKBY:
Did it form there by itself

645
00:40:41,833 --> 00:40:44,866
{\an1}or has it been thrown out
of another planetary system?

646
00:40:44,900 --> 00:40:50,200
NARRATOR:
A planet that shows us that
the galaxy is more chaotic,

647
00:40:50,233 --> 00:40:54,833
{\an1}and perhaps more hostile,
than we thought.

648
00:40:54,866 --> 00:40:56,733
DRESSING:
As we look out through
the galaxy,

649
00:40:56,766 --> 00:40:58,566
{\an7}there are many cases

650
00:40:58,600 --> 00:41:01,666
{\an7}where planets would experience
much more violent histories,

651
00:41:01,700 --> 00:41:03,900
{\an7}and life might not be able
to survive

652
00:41:03,933 --> 00:41:08,100
{\an1}more than a billion years.

653
00:41:08,133 --> 00:41:11,933
NARRATOR:
The rogue planet may be
a refugee,

654
00:41:11,966 --> 00:41:16,500
{\an1}telling us about systems
far more chaotic than our own.

655
00:41:18,833 --> 00:41:22,333
{\an1}Because not all stars
exist alone.

656
00:41:24,233 --> 00:41:27,700
{\an1}Some have company,

657
00:41:27,733 --> 00:41:31,900
{\an1}orbiting one another in
a careful dance.

658
00:41:35,433 --> 00:41:37,200
MUIRHEAD:
So when we look up at the
night sky

659
00:41:37,233 --> 00:41:39,333
{\an1}and we see single points
of light,

660
00:41:39,366 --> 00:41:41,833
{\an1}which we assume are stars,

661
00:41:41,866 --> 00:41:45,800
{\an7}often what's actually there are
two stars orbiting each other.

662
00:41:45,833 --> 00:41:49,933
{\an7}But they are so close together
that they appear as one.

663
00:41:49,966 --> 00:41:55,066
TRIPATHI:
We're finding that these binary
and multiple-star systems

664
00:41:55,100 --> 00:41:59,200
{\an1}are actually amongst the most
common types in the universe.

665
00:41:59,233 --> 00:42:03,033
{\an1}Sometimes planets orbit both of
these stars together,

666
00:42:03,066 --> 00:42:05,866
{\an1}and other times, the planet
will orbit one of the two stars,

667
00:42:05,900 --> 00:42:07,166
{\an1}but not the other star.

668
00:42:07,200 --> 00:42:10,666
{\an8}♪ ♪

669
00:42:20,100 --> 00:42:22,000
NARRATOR:
Dawn.

670
00:42:26,400 --> 00:42:31,466
{\an1}Ushered in by not one star,

671
00:42:31,500 --> 00:42:33,000
but two.

672
00:42:35,333 --> 00:42:38,833
{\an1}Perhaps the rogue world
began its life

673
00:42:38,866 --> 00:42:42,666
{\an1}in a binary system, like this.

674
00:42:42,700 --> 00:42:45,166
SEAGER:
On a planet that's orbiting
two stars,

675
00:42:45,200 --> 00:42:47,266
{\an1}there would always be
two shadows

676
00:42:47,300 --> 00:42:49,533
{\an1}and you would see two sunsets.

677
00:42:49,566 --> 00:42:52,166
{\an7}I like to say that science
fiction got some things right.

678
00:42:52,200 --> 00:42:56,133
{\an7}What does that feel like,
the heat of two suns?

679
00:42:56,166 --> 00:42:59,500
{\an7}Is that a nice heat,
or is that too much?

680
00:42:59,533 --> 00:43:01,366
{\an1}There's so many questions

681
00:43:01,400 --> 00:43:04,500
{\an1}around binary star systems.

682
00:43:04,533 --> 00:43:10,866
♪ ♪

683
00:43:10,900 --> 00:43:15,400
NARRATOR:
For a time, the planet may
enjoy a stable period

684
00:43:15,433 --> 00:43:19,000
{\an1}in the habitable zone of one
of these stars.

685
00:43:22,933 --> 00:43:27,866
{\an1}But the peace does not last.

686
00:43:27,900 --> 00:43:30,800
OLUSEYI:
The moment there's more than
two bodies involved

687
00:43:30,833 --> 00:43:35,966
{\an1}in a gravitational dance, things
get complicated really fast.

688
00:43:36,000 --> 00:43:39,066
{\an7}Because each body
gravitationally affects

689
00:43:39,100 --> 00:43:41,233
{\an7}every other body.

690
00:43:41,266 --> 00:43:44,266
{\an1}On Earth, the most obvious
manifestation of gravity

691
00:43:44,300 --> 00:43:47,466
{\an1}from a body that's not Earth
is the tides.

692
00:43:47,500 --> 00:43:49,466
{\an1}The moon affects our tides.

693
00:43:49,500 --> 00:43:51,700
{\an1}What can happen in these
binary systems

694
00:43:51,733 --> 00:43:54,866
{\an1}is that this strong gravity
between these two stars

695
00:43:54,900 --> 00:43:58,533
{\an1}can shift orbits drastically.

696
00:44:00,866 --> 00:44:05,400
NARRATOR:
This huge, combined
gravitational force...

697
00:44:07,966 --> 00:44:12,700
{\an1}...interferes with
the planet's orbit,

698
00:44:12,733 --> 00:44:14,966
creating chaos.

699
00:44:15,000 --> 00:44:19,633
♪ ♪

700
00:44:25,600 --> 00:44:27,266
OLUSEYI:
There's a very thin line

701
00:44:27,300 --> 00:44:31,300
{\an1}between stability
and instability.

702
00:44:31,333 --> 00:44:32,933
{\an1}And when instability kicks in,

703
00:44:32,966 --> 00:44:35,966
{\an1}it goes from a stable system
to a chaotic system.

704
00:44:36,000 --> 00:44:39,600
{\an1}And at that point,
anything can happen.

705
00:44:39,633 --> 00:44:42,633
♪ ♪

706
00:44:42,666 --> 00:44:49,466
NARRATOR:
As each star and every planet
in the system pulls the rest,

707
00:44:49,500 --> 00:44:53,433
{\an1}the orbits of each world
constantly shift.

708
00:44:53,466 --> 00:44:56,666
{\an8}♪ ♪

709
00:44:56,700 --> 00:44:59,733
{\an7}Further adding to the turmoil.

710
00:44:59,766 --> 00:45:04,933
{\an8}♪ ♪

711
00:45:07,900 --> 00:45:11,900
{\an1}Until a close encounter with
another world

712
00:45:11,933 --> 00:45:17,400
{\an1}gives the planet a huge
gravitational kick.

713
00:45:17,433 --> 00:45:20,200
♪ ♪

714
00:45:30,133 --> 00:45:32,233
{\an1}Flinging it outwards.

715
00:45:32,266 --> 00:45:37,200
♪ ♪

716
00:45:37,233 --> 00:45:41,633
{\an1}And releasing it from the grip
of its parent stars.

717
00:45:41,666 --> 00:45:45,666
♪ ♪

718
00:45:50,033 --> 00:45:55,666
♪ ♪

719
00:45:57,933 --> 00:46:00,033
{\an1}Setting it loose.

720
00:46:00,066 --> 00:46:03,400
A rogue planet,
wandering the galaxy.

721
00:46:03,433 --> 00:46:07,133
MARITZA SOTO:
The planet will slowly start
to cool down

722
00:46:07,166 --> 00:46:11,866
{\an7}until it is just a rock with
no source of heat,

723
00:46:11,900 --> 00:46:15,666
{\an7}traveling alone through
the universe.

724
00:46:15,700 --> 00:46:20,766
♪ ♪

725
00:46:30,133 --> 00:46:34,233
NARRATOR:
Far from the warm embrace of
its parent stars.

726
00:46:36,800 --> 00:46:41,600
♪ ♪

727
00:46:43,366 --> 00:46:48,100
{\an1}Any liquid water the rogue world
might have once had

728
00:46:48,133 --> 00:46:50,966
freezes solid.

729
00:46:53,333 --> 00:46:55,533
MUIRHEAD:
You would have the night sky
all the time

730
00:46:55,566 --> 00:46:57,666
{\an1}if you were on one of these
planets,

731
00:46:57,700 --> 00:47:00,300
{\an7}with no hope of a sun ever
rising.

732
00:47:00,333 --> 00:47:05,033
♪ ♪

733
00:47:05,066 --> 00:47:10,000
NARRATOR:
Any atmosphere that once
protected it

734
00:47:10,033 --> 00:47:12,533
freezes.

735
00:47:12,566 --> 00:47:19,133
♪ ♪

736
00:47:19,166 --> 00:47:20,600
{\an1}Leaving the surface

737
00:47:20,633 --> 00:47:25,500
{\an1}exposed to cosmic radiation,

738
00:47:25,533 --> 00:47:30,300
{\an1}conditions which no living thing
could endure.

739
00:47:30,333 --> 00:47:32,133
MUIRHEAD:
It effectively becomes

740
00:47:32,166 --> 00:47:36,266
{\an1}something of a dead planet.

741
00:47:36,300 --> 00:47:40,700
{\an1}Almost a fossil of itself
flying through space.

742
00:47:40,733 --> 00:47:46,666
♪ ♪

743
00:47:46,700 --> 00:47:51,633
NARRATOR:
Alone and adrift.

744
00:47:57,733 --> 00:48:03,433
{\an1}Only to be detected by us
millions of years later.

745
00:48:05,300 --> 00:48:06,800
{\an1}The way we find rogue worlds

746
00:48:06,833 --> 00:48:10,166
{\an1}is through a process called
gravitational microlensing.

747
00:48:10,200 --> 00:48:11,600
{\an7}We look at a distant star,

748
00:48:11,633 --> 00:48:13,766
{\an7}a star that has nothing to do
with the planets

749
00:48:13,800 --> 00:48:15,766
{\an7}that we're hoping to discover,

750
00:48:15,800 --> 00:48:18,800
{\an7}and between the telescope
that we're using

751
00:48:18,833 --> 00:48:21,833
{\an1}and that distant star,
a rogue planet

752
00:48:21,866 --> 00:48:23,400
wanders through.

753
00:48:23,433 --> 00:48:26,466
WAKEFORD:
The gravity of the planet
is really small,

754
00:48:26,500 --> 00:48:29,966
{\an1}but it's enough to bend that
distant star's light

755
00:48:30,000 --> 00:48:33,500
{\an1}so that we can see that it
exists and measure its mass.

756
00:48:35,633 --> 00:48:40,433
NARRATOR:
One of billions of planets
on which the spark of life

757
00:48:40,466 --> 00:48:45,733
may have begun,
only to be extinguished.

758
00:48:45,766 --> 00:48:49,033
{\an1}Worlds where any civilizations

759
00:48:49,066 --> 00:48:53,600
{\an1}could not have survived.

760
00:48:53,633 --> 00:48:56,233
{\an7}Our planet is a wonderful place
to exist.

761
00:48:56,266 --> 00:48:58,300
{\an7}We have been sheltered
through history.

762
00:48:58,333 --> 00:49:00,500
{\an7}We've experienced some
large impacts,

763
00:49:00,533 --> 00:49:02,933
{\an7}but we've had a relatively
benign existence.

764
00:49:02,966 --> 00:49:04,233
{\an7}It could be that the reason

765
00:49:04,266 --> 00:49:06,766
{\an7}we haven't found any alien
civilizations yet

766
00:49:06,800 --> 00:49:09,500
{\an7}is because we live in a
particularly hospitable corner

767
00:49:09,533 --> 00:49:11,666
{\an1}of our galaxy, with just the
right conditions

768
00:49:11,700 --> 00:49:13,033
{\an1}for life to arise.

769
00:49:13,066 --> 00:49:17,000
{\an1}Or maybe we just haven't
looked hard enough.

770
00:49:17,033 --> 00:49:22,766
NARRATOR:
Our quest for another living
planet has only just begun,

771
00:49:22,800 --> 00:49:28,166
{\an1}and the only way to know if we
are alone is to keep looking.

772
00:49:28,200 --> 00:49:30,066
SOTO:
I still feel very amazed

773
00:49:30,100 --> 00:49:32,966
{\an1}that we have so much knowledge
about these objects

774
00:49:33,000 --> 00:49:35,266
{\an1}that are just so far away
from us.

775
00:49:35,300 --> 00:49:38,500
♪ ♪

776
00:49:38,533 --> 00:49:42,166
NARRATOR:
We have found our first
rocky worlds.

777
00:49:42,200 --> 00:49:43,833
♪ ♪

778
00:49:43,866 --> 00:49:47,766
{\an1}Some in the habitable zone
around their stars.

779
00:49:47,800 --> 00:49:52,033
♪ ♪

780
00:49:52,066 --> 00:49:56,100
{\an1}And even worlds with water.

781
00:49:56,133 --> 00:49:58,933
PIETTE:
Kepler has found thousands
of new planets.

782
00:49:58,966 --> 00:50:01,000
{\an7}But for every question that
it's answered,

783
00:50:01,033 --> 00:50:02,966
{\an7}it's raised at least five
new ones.

784
00:50:03,000 --> 00:50:07,066
NARRATOR:
Candidate worlds
for future missions

785
00:50:07,100 --> 00:50:11,466
{\an1}to search for the evidence
of life itself.

786
00:50:11,500 --> 00:50:14,500
MADHUSUDHAN:
I am actually very optimistic,

787
00:50:14,533 --> 00:50:19,966
{\an7}personally, that we might find
life within the next ten years.

788
00:50:20,000 --> 00:50:24,733
♪ ♪

789
00:50:24,766 --> 00:50:31,066
NARRATOR:
But we have also found hordes
of bizarre, tortured worlds

790
00:50:31,100 --> 00:50:34,833
{\an1}around violent stars.

791
00:50:37,466 --> 00:50:43,166
♪ ♪

792
00:50:43,200 --> 00:50:46,733
{\an1}And rogue planets,

793
00:50:46,766 --> 00:50:52,100
{\an1}where life as we understand it
seems impossible.

794
00:50:52,133 --> 00:50:56,100
TRIPATHI:
What we see is a menagerie rife
with diversity

795
00:50:56,133 --> 00:50:59,366
{\an1}and worlds that we could never
have imagined.

796
00:50:59,400 --> 00:51:01,966
{\an7}It's like looking at those
snowflakes under the microscope

797
00:51:02,000 --> 00:51:03,466
{\an7}and seeing the wondrous
structure

798
00:51:03,500 --> 00:51:06,066
{\an7}that we never knew about before,
but is beautiful

799
00:51:06,100 --> 00:51:08,600
{\an1}and amazing to be a part of.

800
00:51:08,633 --> 00:51:11,933
♪ ♪

801
00:51:11,966 --> 00:51:16,766
NARRATOR:
Perhaps it is these worlds that
will help us understand

802
00:51:16,800 --> 00:51:23,666
{\an1}why, for now, one planet
continues to remain apart.

803
00:51:23,700 --> 00:51:29,000
♪ ♪

804
00:51:30,400 --> 00:51:31,666
TRIPATHI:
You might ask,

805
00:51:31,700 --> 00:51:35,200
{\an1}why do we keep searching for
these alien worlds?

806
00:51:35,233 --> 00:51:37,766
{\an1}And I think the answer is
profoundly human:

807
00:51:37,800 --> 00:51:40,866
{\an1}we want to know what else
is out there.

808
00:51:40,900 --> 00:51:42,866
♪ ♪

809
00:51:42,900 --> 00:51:45,433
CHARBONNEAU:
I think that it's not at all
a guarantee

810
00:51:45,466 --> 00:51:48,033
{\an1}that there's life elsewhere
in the galaxy.

811
00:51:48,066 --> 00:51:49,333
{\an1}And what we need to do is

812
00:51:49,366 --> 00:51:51,733
{\an1}to go out and make measurements
and to see,

813
00:51:51,766 --> 00:51:53,100
{\an1}which universe do we live in?

814
00:51:53,133 --> 00:51:54,466
{\an1}Do we live in the "Star Trek"
universe,

815
00:51:54,500 --> 00:51:57,200
{\an1}where every star has lots
of planets

816
00:51:57,233 --> 00:51:59,833
{\an1}with life and civilizations?

817
00:51:59,866 --> 00:52:04,066
{\an1}Or are we in fact, to the best
of our ability to measure,

818
00:52:04,100 --> 00:52:05,633
truly alone?

819
00:52:05,666 --> 00:52:10,133
♪ ♪

820
00:52:28,133 --> 00:52:32,366
{\an8}♪ ♪

821
00:52:32,400 --> 00:52:34,366
{\an8}ALOK PATEL:
Discover the science
behind the news

822
00:52:34,400 --> 00:52:36,500
{\an7}with the "NOVA Now" podcast.

823
00:52:36,533 --> 00:52:39,933
{\an7}Listen at pbs.org/novanowpodcast

824
00:52:39,966 --> 00:52:43,500
{\an7}or wherever you find your
favorite podcasts.

825
00:52:43,533 --> 00:52:47,266
{\an8}ANNOUNCER:
To order the five-part "NOVA:
Universe Revealed" on DVD,

826
00:52:47,300 --> 00:52:51,466
{\an8}visit ShopPBS
or call 1-800-PLAY-PBS.

827
00:52:51,500 --> 00:52:56,200
{\an7}Also available with PBS Passport
and on Amazon Prime Video.

828
00:52:56,233 --> 00:53:02,400
{\an8}♪ ♪

829
00:53:07,300 --> 00:53:11,600
{\an8}♪ ♪