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♪

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        narrator: Earth.

3
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         [ dog barking ]

4
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     the cradle of humanity
    throughout our existence.

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                     ♪

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    but it won't be forever.

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   All it would take would be
       one giant meteorite

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         to wipe us off
     the face of the earth.

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                     ♪

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            narrator:
     It's not just meteors.

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     Our planet will change.

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  Our planet could freeze over
      or it could heat up.

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Narrator: And our sun will
         eventually die.

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  We are actually near the end
    of habitability of earth.

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  To survive in this universe,
 we need an insurance policy...

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                     ♪

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  ...To colonize other worlds.

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     Having multiple planets
       which are colonized

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    is really in our interest
      for our own survival.

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    Narrator: So can we find
    a new home in the galaxy?

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     Can we find earth 2.0?

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                     ♪

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--<font color="
www.Vitac.Com

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captions paid for by
discovery communications

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♪

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for centuries, we only knew
of the handful of planets

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in our own solar system.

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♪

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now astronomers are finding
thousands of new worlds

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around alien stars --
exoplanets.

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We are discovering exoplanets
by the bucketful.

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Plait: There are as many planets
  out there as there are stars,

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    and there are hundreds of
billions of stars in the galaxy.

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  Narrator: But out of billions
         of exoplanets,

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 are there any that could offer
        new opportunities

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     for humanity to thrive

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      and provide sanctuary
    in a dangerous universe?

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     Is there an earth 2.0?

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     Is earth 2.0 out there?

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  That would be truly amazing.

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                     ♪

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     narrator: August 2016.

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Astronomers announce
         that earth 2.0

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         could be closer
  than anyone ever expected...

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 ...A planet orbiting the sun's
    nearest stellar neighbor,

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 the red dwarf proxima centauri.

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So it turns out that our nearest
 star neighbor has an exoplanet.

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         It's only about
       4 light-years away,

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so that means that it's actually
   potentially possible for us

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 to get there and to explore it.

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   Narrator: Scientists named
   the planet after the star,

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proxima centauri b,
    or proxima b for short...

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  ...A world that appears to be
        a lot like earth.

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    From the way it's tugging
 on the star, proxima centauri,

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       we know that it has
   1.3 times the earth's mass.

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   It's roughly the same size
          as the earth.

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                     ♪

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   narrator: Of the exoplanets
         we know about,

59
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     most are uninhabitable
    gas giants, like jupiter.

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    Proxima b is a rare find,
an earth-sized planet,

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    but an earth-sized planet
     might not be earthlike.

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A true second earth must also be
       the right distance

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         from its star.

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       The habitable zone,
     or some people call it

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     the goldilocks region,
is a distance away from the star

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    where you're not so close
  where you're going to burn up

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          and evaporate
      all of your liquids,

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   and you're not so far away
  where you're frigid and cold.

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So it's that special region
  where it's just, just right.

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    Narrator: Does proxima b
       lie in this region?

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   Could it have liquid water?

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    Proxima centauri b orbits
 its star once every 11.2 days,

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  so compare that to the earth,
    which goes around the sun

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      once every 365 days.

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    That's because the planet
is much, much closer to the star

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  than the earth is to the sun.

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                     ♪

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     narrator: Earth orbits
 93 million miles from the sun.

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Proxima b orbits
        20 times closer,

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      under 5 million miles
         from its star.

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         You might think
    that proxima b should be,

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you know, really a fried world,
a burnt-out husk, if you will.

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Narrator: But proxima b's sun is
    very different than ours.

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   At just over 5,000 degrees
           fahrenheit,

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        it's half as hot
  and roughly 8 times smaller,

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   an m-class red dwarf star.

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    An m-dwarf that proxima b
is around is much less bright,

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         much less hot,

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        so you can orbit
    much closer to that star

90
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 and be at the same temperature
   that we are here on earth.

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                     ♪

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      narrator: Proxima b's
tight orbit around the red dwarf

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           could make
      the planet habitable,

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         but it would be
   very different from earth.

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   The star dominates the sky,

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       lighting any oceans
          and mountains

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     with an alien red glow.

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So proxima b may be
          the earth 2.0

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  that we've been looking for.

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     Narrator: But in 2017,

101
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     the dim red dwarf star
         erupts in a way

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     that's unlike anything
      we've seen before...

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     ...Blasting the planet
        with radiation...

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          A megaflare.

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   They're like solar flares,

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         but they can be
       much more powerful.

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   In fact, they can outshine
        the star itself.

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   Narrator: Our sun releases
powerful solar flares

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     when its magnetic field
        becomes tangled.

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      But the megaflare is
        10 times stronger

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         than our sun's
        strongest flares.

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       On an m dwarf star,
       that magnetic field

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   can get a lot more tangled
      than on our own sun.

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  That means that when a flare
            happens,

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         it can release
       a lot more energy.

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                     ♪

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  narrator: Scientists believe
that megaflares like this

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       are planet killers.

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                     ♪

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         radiation tears
 the atmosphere from the planet,

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and these megaflares hit proxima
   b roughly once every year.

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         Red dwarf stars
  are incredibly temperamental.

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    They are not good parents
        to their planets,

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    so if proxima b did have
   an atmosphere at one point,

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 it would've been stripped away

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         by one of these
       violent outbursts.

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Narrator: Leaving proxima b
  dangerously exposed to space.

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      An atmosphere dampens
    the temperature gradients

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    between light and shadow,

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         so in sunlight,
     it is just burning hot,

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but right next door in a shadow,
      it is freezing cold.

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            Narrator:
     Without an atmosphere,

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         proxima b would
     be a barren wasteland,

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  blasted by intense radiation
        from its star --

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    completely uninhabitable.

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Proxima b, our perhaps best shot
  at finding earth 2.0 so far,

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           is actually
   a dried out husk of a world

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  that has lost its atmosphere,

139
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      maybe lost any water
     that it also harbored,

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   simply by being that close
       to its parent star.

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                     ♪

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   narrator: Proxima b may be
     the nearest exoplanet,

143
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  but it's not the only option.

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 The future of humanity may lie
  in an incredible star system

145
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    just 40 light-years away.

146
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We've just found
    a really exciting system

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   where there's not just one
   chance to have a new earth,

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           but seven.

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                     ♪

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          [ explosion ]

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                     ♪

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            narrator:
    In an unforgiving galaxy,

153
00:10:01,468 --> 00:10:05,070
   finding earth 2.0 could be
         the difference

154
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between extinction and survival.

155
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    It's a pretty wild place
           out there.

156
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     Our planet is not going
       to be here forever,

157
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and it would be wonderful
if we could find a place like it

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     so that we could live.

159
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                     ♪

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narrator: The future of humanity
   lies on an alien exoplanet.

161
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     The question is, where?

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                     ♪

163
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              2016.

164
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   Astronomers scan the skies
          with the new

165
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     transiting planets and
 planetesimals small telescope,

166
00:10:46,513 --> 00:10:48,246
          or trappist.

167
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  They look for the flickering
            of a star

168
00:10:53,654 --> 00:10:59,057
    caused by the silhouette
of a planet.

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  The planet can pass in front
     of the disk of its star

170
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         once per orbit,
 causing a little mini eclipse,

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  a little dimming temporarily
    in the light of the star.

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            Narrator:
   Scientists spot the dimming

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00:11:10,737 --> 00:11:12,971
   of a nearby red dwarf star

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 just 40 light-years from earth,

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     the first alien system
   detected by the telescope,

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         the incredible
       trappist-1 system.

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                     ♪

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    the trappist-1 discovery

179
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was a really great
 bang for our buck in a sense...

180
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   [ laughs ] because we found
  seven exoplanets all at once.

181
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        Narrator: But are
   any of these seven planets

182
00:11:41,935 --> 00:11:44,135
       actually habitable?

183
00:11:44,137 --> 00:11:45,603
         With the worlds
     of the trappist system,

184
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        there's probably
      a range of climates.

185
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       The innermost ones
     are probably very hot.

186
00:11:50,477 --> 00:11:54,045
    You might even be looking
         at lava worlds.

187
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          Farther away,
 they're probably worlds of ice.

188
00:11:59,352 --> 00:12:03,121
Narrator: But the middle
    planets -- d, e, and f --

189
00:12:03,123 --> 00:12:04,789
    are all prime candidates.

190
00:12:07,561 --> 00:12:10,061
   It's exciting to think that
      three of the planets

191
00:12:10,063 --> 00:12:13,031
       orbiting trappist-1
  are in the "habitable zone,"

192
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    are at the right distance
         from that star

193
00:12:14,601 --> 00:12:16,801
      to have liquid water
        on their surface.

194
00:12:16,803 --> 00:12:21,272
                     ♪

195
00:12:21,274 --> 00:12:25,310
    and one planet stands out
         as a new earth,

196
00:12:25,312 --> 00:12:29,447
 orbiting just 2.7 million miles
        from the star --

197
00:12:29,449 --> 00:12:31,649
          trappist-1e.

198
00:12:33,787 --> 00:12:36,955
The composition of trappist-1e
   suggests that it could have

199
00:12:36,957 --> 00:12:40,492
 a pretty significant iron core,
  kind of like the earth does.

200
00:12:40,494 --> 00:12:43,695
  There's a potential there for
 a very powerful magnetic field.

201
00:12:46,399 --> 00:12:48,399
     Like earth, trappist-1e

202
00:12:48,401 --> 00:12:51,402
           could host
  a protective magnetic field,

203
00:12:51,404 --> 00:12:54,072
deflecting the harsh solar winds

204
00:12:54,074 --> 00:12:57,542
     and powerful outbursts
  that strip away atmospheres.

205
00:12:59,813 --> 00:13:01,479
        So magnetic field
        is a good thing.

206
00:13:01,481 --> 00:13:05,383
   It's a kind of a protection
from the evil forces of the star

207
00:13:05,385 --> 00:13:07,952
that you're orbiting around.

208
00:13:07,954 --> 00:13:10,255
            Narrator:
  And unlike proxima centauri,

209
00:13:10,257 --> 00:13:15,493
       the trappist-1 star
    appears unusually quiet.

210
00:13:15,495 --> 00:13:18,696
     Trappist-1 is actually
  a very old, much calmer star

211
00:13:18,698 --> 00:13:21,232
    and doesn't undergo a lot
      of these huge flares

212
00:13:21,234 --> 00:13:23,067
   like proxima centauri does.

213
00:13:23,069 --> 00:13:25,837
 And so it's a somewhat perhaps
      better system to look

214
00:13:25,839 --> 00:13:28,640
    for an earthlike planet,
          an earth 2.0.

215
00:13:28,642 --> 00:13:33,077
                     ♪

216
00:13:33,079 --> 00:13:36,047
   narrator: The data suggests
        that trappist-1e

217
00:13:36,049 --> 00:13:37,782
could have vast oceans,

218
00:13:37,784 --> 00:13:41,653
    a protective atmosphere,
   and habitable temperatures.

219
00:13:41,655 --> 00:13:51,596
                     ♪

220
00:13:51,598 --> 00:13:56,935
but living here would be nothing
      like living on earth.

221
00:13:56,937 --> 00:13:59,070
  Oluseyi: The thing to keep in
 mind about the trappist system

222
00:13:59,072 --> 00:14:01,306
    is that it's very unlike
            our own.

223
00:14:01,308 --> 00:14:05,443
 The planets are much closer in,
  so because they're closer in,

224
00:14:05,445 --> 00:14:08,446
          their orbits
     are faster and smaller.

225
00:14:08,448 --> 00:14:12,750
    Narrator: On trappist-1e,
         an entire year

226
00:14:12,752 --> 00:14:15,286
takes just 6 earth days.

227
00:14:15,288 --> 00:14:17,021
   Can you imagine you're just
        basically tearing

228
00:14:17,023 --> 00:14:19,657
your calendar days off day after
  day after day really quickly?

229
00:14:19,659 --> 00:14:22,727
  Your birthday would be today
       and then tomorrow.

230
00:14:22,729 --> 00:14:24,162
     Happy birthday, again!

231
00:14:24,164 --> 00:14:26,097
     Wedding anniversaries,
  you're constantly forgetting

232
00:14:26,099 --> 00:14:30,568
    your wedding anniversary,
      and it would be hard.

233
00:14:30,570 --> 00:14:33,571
  And on this strange and alien
             world,

234
00:14:33,573 --> 00:14:39,844
 explorers would witness sights
  unlike anything seen before.

235
00:14:39,846 --> 00:14:43,147
In a lot of ways, it really is
 sort of a science fiction sky,

236
00:14:43,149 --> 00:14:45,917
       the kind of things
 that are envisioned in movies.

237
00:14:45,919 --> 00:14:48,786
    You could look up and see
  the other planets in your sky

238
00:14:48,788 --> 00:14:51,723
    much like how we can see
          our own moon.

239
00:14:51,725 --> 00:14:54,459
  You could physically resolve
     features on the surface

240
00:14:54,461 --> 00:14:58,596
       such as continents
       with your own eyes.

241
00:14:58,598 --> 00:15:03,468
      But could this planet
     be too good to be true?

242
00:15:03,470 --> 00:15:07,705
 So we could have a potentially
        habitable planet

243
00:15:07,707 --> 00:15:09,641
that's really close to its star,

244
00:15:09,643 --> 00:15:12,410
     but other issues arise
  when you have a solar system

245
00:15:12,412 --> 00:15:14,078
     that's that compressed,

246
00:15:14,080 --> 00:15:17,715
       and one of those is
the potential for tidal locking.

247
00:15:20,887 --> 00:15:24,188
       Orbiting just a few
  million miles from the star,

248
00:15:24,190 --> 00:15:30,795
  trappist-1e is likely tidally
      locked with one side

249
00:15:30,797 --> 00:15:34,666
    facing the star forever.

250
00:15:34,668 --> 00:15:38,236
So you could imagine a situation
  where, gosh, it's constant day

251
00:15:38,238 --> 00:15:39,904
        and it might just
        produce something

252
00:15:39,906 --> 00:15:41,739
  that's like a scorched earth,

253
00:15:41,741 --> 00:15:43,808
kind of like what we see
           behind me,

254
00:15:43,810 --> 00:15:46,544
     but on the other side,
      it is constant night,

255
00:15:46,546 --> 00:15:48,246
      and so in that case,
     it might just be, like,

256
00:15:48,248 --> 00:15:51,849
       a frozen wasteland.

257
00:15:51,851 --> 00:15:56,854
   And trappist-1e's problems
     get even more extreme.

258
00:15:56,856 --> 00:16:00,325
If you have a permanent day side
   and a permanent night side,

259
00:16:00,327 --> 00:16:03,261
  the night side of the planet
     is going to get so cold

260
00:16:03,263 --> 00:16:06,764
  that everything just freezes
 out, including the atmosphere.

261
00:16:10,737 --> 00:16:13,504
   The gases of trappist-1e's
atmosphere

262
00:16:13,506 --> 00:16:15,974
   could freeze into solid ice

263
00:16:15,976 --> 00:16:19,877
       on the frigid night
       side of the planet,

264
00:16:19,879 --> 00:16:24,816
  and the gases on the day side
           burn away.

265
00:16:24,818 --> 00:16:31,055
      The atmosphere thins
   and eventually disappears,

266
00:16:31,057 --> 00:16:38,162
     and trappist-1e ends up
    completely inhospitable.

267
00:16:38,164 --> 00:16:41,899
  So even though we found maybe
 a perfect planet around a star,

268
00:16:41,901 --> 00:16:43,634
        the type of star
     and where it's orbiting

269
00:16:43,636 --> 00:16:45,470
           could have
    a really important effect

270
00:16:45,472 --> 00:16:48,106
      as to whether or not
that planet might be habitable.

271
00:16:50,944 --> 00:16:53,444
            Narrator:
 Despite its apparent potential,

272
00:16:53,446 --> 00:16:58,549
        our future is not
    in the trappist-1 system.

273
00:16:58,551 --> 00:17:03,621
      The search for truly
  earthlike planets continues.

274
00:17:03,623 --> 00:17:08,126
    In the trappist-1 system,
 we find a very earthlike world,

275
00:17:08,128 --> 00:17:11,362
    but the star its orbiting
      is not very sunlike.

276
00:17:11,364 --> 00:17:14,332
        So what we should
    be looking for, perhaps,

277
00:17:14,334 --> 00:17:17,468
      is a earthlike planet
     around a sunlike star.

278
00:17:19,572 --> 00:17:25,810
  Narrator: To find earth 2.0,
we need a sun 2.0.

279
00:17:25,812 --> 00:17:29,514
                     ♪

280
00:17:35,822 --> 00:17:40,224
          [ explosion ]

281
00:17:40,226 --> 00:17:44,962
                     ♪

282
00:17:44,964 --> 00:17:47,365
   narrator: The milky way --

283
00:17:47,367 --> 00:17:50,701
  home to hundreds of billions
           of stars...

284
00:17:53,006 --> 00:17:57,075
      ...Ranging from dim,
    explosive red dwarves...

285
00:17:59,179 --> 00:18:02,046
        ...To short-lived
         blazing giants.

286
00:18:02,048 --> 00:18:08,086
                     ♪

287
00:18:08,088 --> 00:18:13,091
   but in the middle are stars
          like our sun.

288
00:18:13,093 --> 00:18:16,260
       Strictly speaking,
  if we really want earth 2.0,

289
00:18:16,262 --> 00:18:20,498
   we need to look for planets
around stars like our sun.

290
00:18:20,500 --> 00:18:22,533
  Narrator: Stars like our sun

291
00:18:22,535 --> 00:18:25,470
    are calm and stable with
          long lives...

292
00:18:27,941 --> 00:18:31,175
    ...And the habitable zone
      lies far enough away

293
00:18:31,177 --> 00:18:35,179
       that planets avoid
         tidal locking.

294
00:18:35,181 --> 00:18:38,783
  We stand a much better chance
     of colonizing a planet

295
00:18:38,785 --> 00:18:41,853
     around a sunlike star.

296
00:18:41,855 --> 00:18:46,157
    We're hunting for planets
 in the habitable zone of stars

297
00:18:46,159 --> 00:18:50,828
        like our own sun,
 and we have found worlds there.

298
00:18:50,830 --> 00:18:55,066
                     ♪

299
00:18:55,068 --> 00:19:00,304
            narrator:
Worlds like kepler-452b,

300
00:19:00,306 --> 00:19:04,408
          an exoplanet
     1,800 light-years away,

301
00:19:04,410 --> 00:19:08,446
 orbiting the same type of star
           as our sun.

302
00:19:10,717 --> 00:19:13,017
     You really couldn't ask
   for a more earthlike orbit

303
00:19:13,019 --> 00:19:14,352
        around this star.

304
00:19:14,354 --> 00:19:18,089
   The year is about 385 days.
         We're 365 days.

305
00:19:18,091 --> 00:19:21,792
    This really is very much
         like the earth.

306
00:19:21,794 --> 00:19:25,429
   The planet orbits its star
  at roughly the same distance

307
00:19:25,431 --> 00:19:28,966
  as the earth orbits the sun,

308
00:19:28,968 --> 00:19:31,769
          and could be
      very much like home.

309
00:19:33,740 --> 00:19:38,609
Kepler-452b is in
 the habitable zone of its star,

310
00:19:38,611 --> 00:19:40,745
         so if there is
       liquid water there,

311
00:19:40,747 --> 00:19:45,483
 there could be oceans and lakes
     and rivers and streams

312
00:19:45,485 --> 00:19:48,219
 and blue skies and cloudy days.

313
00:19:51,124 --> 00:19:54,692
     Narrator: Sounds nice,
         but kepler-452b

314
00:19:54,694 --> 00:19:56,727
   is a lot larger than earth.

315
00:19:59,866 --> 00:20:04,035
         Kepler-452b is
  a great earth 2.0 candidate,

316
00:20:04,037 --> 00:20:09,207
      but it's sort of like
       earth on steroids.

317
00:20:09,209 --> 00:20:14,111
   This world is about 5 times
more massive than our own planet

318
00:20:14,113 --> 00:20:17,915
and about 60% wider.

319
00:20:17,917 --> 00:20:22,220
    Narrator: Scientists call
  large worlds like kepler-452b

320
00:20:22,222 --> 00:20:23,621
          super-earths.

321
00:20:23,623 --> 00:20:27,692
                     ♪

322
00:20:27,694 --> 00:20:29,160
             durda:
     These worlds are maybe

323
00:20:29,162 --> 00:20:31,596
         1.5 or 2 times
     the size of the earth,

324
00:20:31,598 --> 00:20:35,499
       with maybe as much
      as 10 times the mass.

325
00:20:35,501 --> 00:20:38,603
      Narrator: Could this
  super-sized earthlike planet

326
00:20:38,605 --> 00:20:40,972
       be our second home?

327
00:20:40,974 --> 00:20:43,140
A planet like this seems to meet

328
00:20:43,142 --> 00:20:45,209
     a lot of our standards
        for an earth 2.0.

329
00:20:45,211 --> 00:20:47,812
It's around a star like our sun.

330
00:20:47,814 --> 00:20:50,915
  It's smack-dab in the middle
     of the habitable zone.

331
00:20:50,917 --> 00:20:53,417
      The problem is there
   are other factors at play.

332
00:20:53,419 --> 00:20:56,087
     One of those is simply
     the mass of the planet.

333
00:20:56,089 --> 00:21:02,627
                     ♪

334
00:21:02,629 --> 00:21:04,762
  narrator: Kepler-452b's size

335
00:21:04,764 --> 00:21:09,033
      has an extreme effect
         on its gravity.

336
00:21:09,035 --> 00:21:12,970
 Because of its incredible mass,
   the gravity on the surface

337
00:21:12,972 --> 00:21:16,841
         is about twice
 what we feel here on the earth.

338
00:21:18,911 --> 00:21:20,711
  Narrator: That extra gravity

339
00:21:20,713 --> 00:21:24,382
would make colonizing the planet
           difficult.

340
00:21:24,384 --> 00:21:25,850
      Just about any chore
        you could imagine

341
00:21:25,852 --> 00:21:27,852
      doing that you don't
    like doing on the earth,

342
00:21:27,854 --> 00:21:30,821
     you're going to like it
even less on a planet like that.

343
00:21:30,823 --> 00:21:33,324
   When the garbage can weighs
  twice as much as it does here

344
00:21:33,326 --> 00:21:35,860
 on the earth, that's not going
      to be very much fun.

345
00:21:35,862 --> 00:21:38,295
    Maybe lebron james and I
          will be okay,

346
00:21:38,297 --> 00:21:42,033
       but normal humans,
        I'm not so sure.

347
00:21:43,436 --> 00:21:47,004
Narrator: And we could be stuck
    on the planet's surface.

348
00:21:48,608 --> 00:21:51,242
  If you landed on the surface
  of one of these super-earths,

349
00:21:51,244 --> 00:21:53,678
       it'd be pretty easy
  to get down onto the surface,

350
00:21:53,680 --> 00:21:57,248
 but it would be very difficult
         to get back up.

351
00:21:57,250 --> 00:21:59,383
          It's already
      incredibly difficult

352
00:21:59,385 --> 00:22:00,685
   for us to leave the earth.

353
00:22:00,687 --> 00:22:03,621
   Think of our giant engines
          and rockets,

354
00:22:03,623 --> 00:22:05,656
    these incredible miracles
         of engineering

355
00:22:05,658 --> 00:22:07,858
   that we need to blast off.

356
00:22:07,860 --> 00:22:12,063
You need twice that
   to get off of kepler-452b.

357
00:22:12,065 --> 00:22:15,433
         [ thunderclap ]

358
00:22:15,435 --> 00:22:19,970
   and to make matters worse,
    kepler-452b's atmosphere

359
00:22:19,972 --> 00:22:24,075
   is thought to be radically
     different from earth's.

360
00:22:24,077 --> 00:22:25,943
         In some sense,
     how big the planet is,

361
00:22:25,945 --> 00:22:30,081
how massive it is will determine
  what its atmosphere is like.

362
00:22:30,083 --> 00:22:32,249
    If you have a lot of mass
      and a lot of gravity,

363
00:22:32,251 --> 00:22:34,285
 you can hold onto a lot of air.

364
00:22:34,287 --> 00:22:36,887
          You can have
    a much larger atmosphere,

365
00:22:36,889 --> 00:22:40,491
much thicker, much denser, and
 higher pressure at the surface.

366
00:22:42,662 --> 00:22:47,531
 Narrator: The thick atmosphere
 could trap heat from the star.

367
00:22:47,533 --> 00:22:51,035
   Surface temperatures become
        ferociously hot,

368
00:22:51,037 --> 00:22:52,570
     and crushing pressures

369
00:22:52,572 --> 00:22:57,074
        make the surface
    completely uninhabitable.

370
00:22:57,076 --> 00:22:59,844
So it's possible this planet has
     a very thick atmosphere

371
00:22:59,846 --> 00:23:02,546
      that's become more of
  a runaway greenhouse effect.

372
00:23:02,548 --> 00:23:05,116
  The planet has gotten hotter
      and hotter over time.

373
00:23:05,118 --> 00:23:07,118
    Maybe instead of finding
an earth 2.0,

374
00:23:07,120 --> 00:23:09,687
what we've found is a venus 2.0.

375
00:23:09,689 --> 00:23:14,625
                     ♪

376
00:23:14,627 --> 00:23:18,195
 narrator: Super-earths may have
       an appealing name,

377
00:23:18,197 --> 00:23:22,400
 but their intense gravity would
 make them difficult to live on,

378
00:23:22,402 --> 00:23:26,036
    and we could not survive
   in their thick atmospheres.

379
00:23:26,038 --> 00:23:31,976
                     ♪

380
00:23:31,978 --> 00:23:34,945
     so far, all the worlds
   we've found have turned out

381
00:23:34,947 --> 00:23:38,616
      to be uninhabitable,

382
00:23:38,618 --> 00:23:44,422
    but what if our new home
        is not a planet?

383
00:23:44,424 --> 00:23:48,192
      Earth 2.0 may not be
      an exoplanet at all.

384
00:23:48,194 --> 00:23:50,494
It might be an exomoon.

385
00:23:50,496 --> 00:23:55,299
                     ♪

386
00:24:01,707 --> 00:24:06,110
          [ explosion ]

387
00:24:06,112 --> 00:24:09,880
                     ♪

388
00:24:09,882 --> 00:24:12,583
      narrator: We live in
     a cosmic shooting range

389
00:24:14,654 --> 00:24:17,154
  where planets die every day,

390
00:24:19,725 --> 00:24:25,996
 but backup planets like our own
 seem almost impossible to find.

391
00:24:25,998 --> 00:24:30,167
    Have we been looking for
        the wrong thing?

392
00:24:30,169 --> 00:24:32,002
         I think there's
      a pretty good chance

393
00:24:32,004 --> 00:24:35,539
   that earth 2.0 might not be
        a planet per se,

394
00:24:35,541 --> 00:24:39,109
       but actually a moon
       of a giant planet.

395
00:24:39,111 --> 00:24:40,444
The exciting thing
        about an exomoon

396
00:24:40,446 --> 00:24:42,947
       is that they could
    potentially be habitable.

397
00:24:42,949 --> 00:24:44,148
   Thaller: So is it possible

398
00:24:44,150 --> 00:24:46,083
         that as we look
   at different solar systems,

399
00:24:46,085 --> 00:24:50,321
  the real analog for earth 2.0
 will turn out to be an exomoon?

400
00:24:50,323 --> 00:24:56,727
                     ♪

401
00:24:56,729 --> 00:24:59,697
         narrator: 2017.

402
00:24:59,699 --> 00:25:02,766
      The kepler telescope
     scanned a sunlike star

403
00:25:02,768 --> 00:25:05,236
     8,000 light-years away,

404
00:25:05,238 --> 00:25:07,972
   and professor david kipping
          and his team

405
00:25:07,974 --> 00:25:12,543
watched the transiting exoplanet

406
00:25:12,545 --> 00:25:17,348
kepler-1625b.

407
00:25:17,350 --> 00:25:22,219
     Kepler-1625 was one of
  the many thousands of planets

408
00:25:22,221 --> 00:25:24,221
      discovered by kepler,

409
00:25:24,223 --> 00:25:26,891
   but what made it different
      from our perspective

410
00:25:26,893 --> 00:25:29,493
        as a moon hunter
    was that this is a planet

411
00:25:29,495 --> 00:25:32,897
    which was jupiter-sized,
     far away from its star,

412
00:25:32,899 --> 00:25:35,065
         and apparently
    on a near-circular orbit,

413
00:25:35,067 --> 00:25:39,003
   so everything that we want
      for finding exomoons.

414
00:25:39,005 --> 00:25:43,874
                     ♪

415
00:25:43,876 --> 00:25:47,144
            narrator:
   The exoplanet kepler-1625b

416
00:25:47,146 --> 00:25:50,681
is an uninhabitable gas giant,
          like jupiter.

417
00:25:52,785 --> 00:25:56,020
But it is in the habitable zone,

418
00:25:56,022 --> 00:25:59,890
    and that means its moons
         would be, too.

419
00:26:02,028 --> 00:26:06,230
  Unfortunately, these exomoons
   are incredibly hard to see.

420
00:26:09,702 --> 00:26:13,337
       The way that kepler
   finds exoplanets out there

421
00:26:13,339 --> 00:26:16,240
       really does relate
   to the size of the planet,

422
00:26:16,242 --> 00:26:17,841
    and for moons, it's much,
       much more difficult

423
00:26:17,843 --> 00:26:20,978
      because it's smaller
    so it's harder to detect.

424
00:26:20,980 --> 00:26:22,980
    Kipping: The largest moon
in the solar system

425
00:26:22,982 --> 00:26:24,748
   is ganymede around jupiter.

426
00:26:24,750 --> 00:26:27,351
         It's about 40%
     the size of the earth,

427
00:26:27,353 --> 00:26:31,255
    and we really very rarely
   detect planets that small.

428
00:26:31,257 --> 00:26:33,624
         So, of course,
      looking for exomoons

429
00:26:33,626 --> 00:26:36,560
      is going to be very,
        very challenging.

430
00:26:36,562 --> 00:26:41,098
                     ♪

431
00:26:41,100 --> 00:26:43,601
            narrator:
   In 2018, the team recruited

432
00:26:43,603 --> 00:26:47,004
          the powerful
     hubble space telescope

433
00:26:47,006 --> 00:26:50,941
    and used the data to hunt
     for the tiny silhouette

434
00:26:50,943 --> 00:26:54,011
of any moons.

435
00:26:54,013 --> 00:26:56,146
     If you have an exomoon
       orbiting a planet,

436
00:26:56,148 --> 00:26:58,148
     sometimes it's going to
         lead the planet

437
00:26:58,150 --> 00:26:59,717
   when it transits the star,

438
00:26:59,719 --> 00:27:01,485
    and sometimes it's going
         to trail behind

439
00:27:01,487 --> 00:27:03,020
    as it transits the star,

440
00:27:03,022 --> 00:27:05,856
    and you see a little bump
    in the transit dip itself

441
00:27:05,858 --> 00:27:07,558
      at different places.

442
00:27:09,395 --> 00:27:12,963
 Narrator: And the team detected
          the signal --

443
00:27:12,965 --> 00:27:18,469
    not one, but two objects
       orbiting together,

444
00:27:18,471 --> 00:27:23,440
    confirmation of the first
exomoon ever discovered.

445
00:27:23,442 --> 00:27:33,050
                     ♪

446
00:27:33,052 --> 00:27:35,619
  it was an amazing discovery.

447
00:27:35,621 --> 00:27:37,921
 I've been looking for exomoons
        my entire career.

448
00:27:37,923 --> 00:27:40,491
   For 10 years, we have been
      in this quest to try

449
00:27:40,493 --> 00:27:42,893
     and find these things.

450
00:27:42,895 --> 00:27:44,228
     Caspi: This discovery,

451
00:27:44,230 --> 00:27:47,898
        this announcement
   was absolutely remarkable.

452
00:27:47,900 --> 00:27:49,933
      Not only does it mean
       that we might find

453
00:27:49,935 --> 00:27:52,002
     earth twins everywhere
        in the milky way,

454
00:27:52,004 --> 00:27:53,871
         but it gives us
    something to strive for,

455
00:27:53,873 --> 00:27:55,472
for human exploration.

456
00:27:55,474 --> 00:28:00,444
                     ♪

457
00:28:00,446 --> 00:28:03,247
            narrator:
     On this alien exomoon,

458
00:28:03,249 --> 00:28:06,550
   the skies would be nothing
          like earth's.

459
00:28:06,552 --> 00:28:07,851
  Visually, I think it would be

460
00:28:07,853 --> 00:28:09,553
  an absolutely stunning place
             to be.

461
00:28:09,555 --> 00:28:12,089
     You look up in the sky,
 and you see this ringed planet

462
00:28:12,091 --> 00:28:14,324
    looming huge in the sky.

463
00:28:17,797 --> 00:28:21,265
  Narrator: A world that could
         be like earth,

464
00:28:21,267 --> 00:28:24,201
  only orbiting another planet.

465
00:28:24,203 --> 00:28:29,940
                     ♪

466
00:28:29,942 --> 00:28:34,311
 but don't pack your space suit
just yet.

467
00:28:34,313 --> 00:28:35,879
     Even though the planet
          and the moon

468
00:28:35,881 --> 00:28:37,614
         are potentially
       the right distance

469
00:28:37,616 --> 00:28:39,383
       away from the star
      that we might imagine

470
00:28:39,385 --> 00:28:41,785
    there being liquid water
         on the surface,

471
00:28:41,787 --> 00:28:45,122
  both the moon and the planet
   are likely gaseous objects

472
00:28:45,124 --> 00:28:47,624
      with no solid surface
          to speak of.

473
00:28:50,096 --> 00:28:53,030
   Narrator: Although the moon
    probably isn't habitable,

474
00:28:53,032 --> 00:28:55,466
     it is an important step
       for finding worlds

475
00:28:55,468 --> 00:28:59,236
like our own in the galaxy.

476
00:28:59,238 --> 00:29:02,106
       If we find exomoons
       around exoplanets,

477
00:29:02,108 --> 00:29:04,508
        that potentially
        hugely increases

478
00:29:04,510 --> 00:29:07,644
 the number of habitable worlds
       that are out there.

479
00:29:07,646 --> 00:29:09,346
   We just need more accurate
          measurements,

480
00:29:09,348 --> 00:29:10,714
    and then all of a sudden,

481
00:29:10,716 --> 00:29:12,983
   the universe is going to be
        full of exomoons.

482
00:29:12,985 --> 00:29:18,455
                     ♪

483
00:29:18,457 --> 00:29:20,290
   narrator: But these worlds
         need to be more

484
00:29:20,292 --> 00:29:24,294
  than just earth look-alikes.

485
00:29:24,296 --> 00:29:25,696
   Everyone gets very excited

486
00:29:25,698 --> 00:29:28,365
when we find earthlike planets
       around other stars,

487
00:29:28,367 --> 00:29:31,335
     but "earthlike" kind of
    just means how big it is

488
00:29:31,337 --> 00:29:33,537
   and whether it can support
          liquid water

489
00:29:33,539 --> 00:29:35,672
     where it is in relation
          to its star.

490
00:29:35,674 --> 00:29:39,676
      All of that is great,
    but it's just not enough.

491
00:29:42,982 --> 00:29:46,183
Narrator: A planet's composition
     could be make-or-break

492
00:29:46,185 --> 00:29:47,951
       for our new home...

493
00:29:50,089 --> 00:29:53,423
    ...The difference between
        the perfect world

494
00:29:53,425 --> 00:29:55,359
    and a ticking time bomb.

495
00:29:55,361 --> 00:30:00,998
                     ♪

496
00:30:07,339 --> 00:30:11,775
[ explosion ]

497
00:30:11,777 --> 00:30:15,612
                     ♪

498
00:30:15,614 --> 00:30:19,950
narrator: The hunt for earth 2.0
          is still on.

499
00:30:19,952 --> 00:30:23,687
     We've examined intense,
      red dwarf systems...

500
00:30:24,957 --> 00:30:27,858
    ...Massive super-earths,

501
00:30:27,860 --> 00:30:31,495
       and alien exomoons

502
00:30:31,497 --> 00:30:36,266
           but so far,
   there's no place like home.

503
00:30:36,268 --> 00:30:38,702
  There are all these criteria
     we have to tick off --

504
00:30:38,704 --> 00:30:40,938
         a sunlike star,

505
00:30:40,940 --> 00:30:43,941
    an orbit that puts it at
  about the right temperature,

506
00:30:43,943 --> 00:30:46,944
   a solid surface, something
that could retain an atmosphere.

507
00:30:48,981 --> 00:30:52,516
Narrator: But a planet that
appears earthlike on the outside

508
00:30:52,518 --> 00:30:55,586
      may not be earthlike
         on the inside.

509
00:30:55,588 --> 00:30:59,523
                     ♪

510
00:30:59,525 --> 00:31:01,625
  one of the things that makes
       our world so unique

511
00:31:01,627 --> 00:31:02,893
     is its plate tectonics,

512
00:31:02,895 --> 00:31:04,928
   and that actually regulates
          our climate.

513
00:31:08,000 --> 00:31:11,368
  Narrator: The earth's climate
 depends on cycles of materials,

514
00:31:11,370 --> 00:31:14,905
 like carbon dioxide and water.

515
00:31:14,907 --> 00:31:18,508
     Molecules move between
   the earth's molten interior

516
00:31:18,510 --> 00:31:21,912
     and the surface through
active plate tectonics

517
00:31:21,914 --> 00:31:23,680
     and volcanic eruptions.

518
00:31:25,851 --> 00:31:28,619
  These cycles help to regulate
         the temperature

519
00:31:28,621 --> 00:31:31,054
         and composition
   of the earth's atmosphere.

520
00:31:34,560 --> 00:31:37,361
   If we were to find another
   earthlike planet out there,

521
00:31:37,363 --> 00:31:40,197
  and it had geologic activity,
    that means that at least

522
00:31:40,199 --> 00:31:43,634
   it has the means to sustain
        the carbon cycle

523
00:31:43,636 --> 00:31:45,435
        and all of these
       natural phenomenon

524
00:31:45,437 --> 00:31:50,007
     that makes this planet
   habitable and sustainable.

525
00:31:50,009 --> 00:31:54,144
                     ♪

526
00:31:54,146 --> 00:31:57,581
narrator: How can we know what's
   happening inside a planet?

527
00:31:59,919 --> 00:32:05,389
     A clue can be found in
 vast ranges across our world --

528
00:32:05,391 --> 00:32:07,090
           mountains.

529
00:32:07,092 --> 00:32:13,497
                     ♪

530
00:32:13,499 --> 00:32:17,100
  kipping: These topographical
    features are an indicator

531
00:32:17,102 --> 00:32:20,170
    that the planet is alive
  and there is still processes

532
00:32:20,172 --> 00:32:22,072
      happening underneath
          its surface.

533
00:32:22,074 --> 00:32:25,075
     [ cracking, thudding ]

534
00:32:25,077 --> 00:32:26,877
                     ♪

535
00:32:26,879 --> 00:32:28,445
            narrator:
   Mountain ranges are created

536
00:32:28,447 --> 00:32:31,715
         when a planet's
tectonic plates collide,

537
00:32:33,719 --> 00:32:37,120
   and even though exoplanets
      are light-years away,

538
00:32:37,122 --> 00:32:40,657
   astronomers could work out
     whether their surfaces

539
00:32:40,659 --> 00:32:43,660
           are smooth
      or covered in peaks.

540
00:32:47,166 --> 00:32:49,466
 Kipping: Those mountain ranges
         are poking out,

541
00:32:49,468 --> 00:32:52,869
 and depending on which rotation
        the planet is in,

542
00:32:52,871 --> 00:32:55,272
     the planet will appear
      very slightly bigger

543
00:32:55,274 --> 00:32:58,141
    or very slightly smaller
   depending on the silhouette

544
00:32:58,143 --> 00:32:59,643
      which is being cast.

545
00:32:59,645 --> 00:33:03,981
                     ♪

546
00:33:03,983 --> 00:33:07,317
narrator: These tiny changes
   in light could be the sign

547
00:33:07,319 --> 00:33:10,454
        that an exoplanet
     is healthy and active.

548
00:33:13,425 --> 00:33:15,492
 But we can only use this method

549
00:33:15,494 --> 00:33:19,162
          when a planet
    is in front of its star.

550
00:33:19,164 --> 00:33:22,899
       What if astronomers
   could use starlight itself

551
00:33:22,901 --> 00:33:27,504
          to determine
    the geology of a planet?

552
00:33:27,506 --> 00:33:30,974
   We think that planets form
at roughly the same sort of time

553
00:33:30,976 --> 00:33:32,442
        that stars form,

554
00:33:32,444 --> 00:33:36,113
and they all form from this same
    giant cloud of material.

555
00:33:38,684 --> 00:33:41,318
And so if you measure
   the composition of a star,

556
00:33:41,320 --> 00:33:44,154
    then it seems reasonable
 to take those values and assume

557
00:33:44,156 --> 00:33:47,090
    they're somewhat similar
    for the planets as well.

558
00:33:47,092 --> 00:33:49,960
                     ♪

559
00:33:49,962 --> 00:33:52,996
    narrator: Astronomers can
 work out what chemical elements

560
00:33:52,998 --> 00:33:56,700
    are present in the star,
     by splitting its light

561
00:33:56,702 --> 00:34:02,072
   into different wavelengths,
and any planets around that star

562
00:34:02,074 --> 00:34:05,842
       will have a similar
      chemical composition.

563
00:34:05,844 --> 00:34:08,812
     Composition is actually
a really important part

564
00:34:08,814 --> 00:34:11,548
 of whether or not it's actually
     going to be habitable.

565
00:34:11,550 --> 00:34:14,918
         The composition
     really is its geology.

566
00:34:17,656 --> 00:34:20,123
            Narrator:
  Rocky exoplanets are all made

567
00:34:20,125 --> 00:34:23,260
          from the same
      basic ingredients --

568
00:34:23,262 --> 00:34:28,331
 chemical elements like oxygen,
     silicon, and aluminum.

569
00:34:28,333 --> 00:34:30,600
      Change the balance of
          ingredients,

570
00:34:30,602 --> 00:34:34,771
           and you get
     very different planets.

571
00:34:34,773 --> 00:34:36,173
      If we have some idea

572
00:34:36,175 --> 00:34:38,708
      of the composition of
a rocky planet,

573
00:34:38,710 --> 00:34:41,344
       we can actually use
      that to give us clues

574
00:34:41,346 --> 00:34:45,682
    as to whether a world has
or doesn't have plate tectonics.

575
00:34:45,684 --> 00:34:49,352
                     ♪

576
00:34:49,354 --> 00:34:50,987
            narrator:
     New research indicates

577
00:34:50,989 --> 00:34:53,990
  that exoplanets with too much
       silicon and sodium

578
00:34:53,992 --> 00:34:58,395
  form different types of rock
      than those on earth,

579
00:34:58,397 --> 00:35:02,866
     creating rigid planets
   where plate tectonics stall

580
00:35:02,868 --> 00:35:08,105
  and carbon dioxide builds up
 with devastating consequences.

581
00:35:10,375 --> 00:35:12,309
Without active geology,
         we end up with

582
00:35:12,311 --> 00:35:14,945
  maybe a venetian atmosphere.

583
00:35:14,947 --> 00:35:17,414
    Thaller: That means there
  a runaway greenhouse effect.

584
00:35:17,416 --> 00:35:19,149
 It's gotten hotter and hotter.

585
00:35:19,151 --> 00:35:21,051
         Gases are baked
        out of the rocks.

586
00:35:21,053 --> 00:35:23,186
   There's no way to actually
       rein them back out,

587
00:35:23,188 --> 00:35:24,955
    not a good place for life
             at all.

588
00:35:24,957 --> 00:35:29,359
                     ♪

589
00:35:29,361 --> 00:35:33,463
 narrator: At worse, the planet
   becomes a pressure cooker,

590
00:35:33,465 --> 00:35:36,333
       waiting to explode.

591
00:35:36,335 --> 00:35:38,168
  If we change the composition
of a planet,

592
00:35:38,170 --> 00:35:39,803
 it affects its tectonic system.

593
00:35:39,805 --> 00:35:42,572
      That entirely changes
    how a planet loses heat,

594
00:35:42,574 --> 00:35:44,407
     and the heat builds up
  and builds up and builds up,

595
00:35:44,409 --> 00:35:46,943
     and then maybe there's
     a catastrophic overturn

596
00:35:46,945 --> 00:35:48,211
          of the crust.

597
00:35:48,213 --> 00:35:53,383
                     ♪

598
00:35:53,385 --> 00:35:58,555
                     ♪

599
00:35:58,557 --> 00:36:01,591
  narrator: The solid crust of
      the planet collapses.

600
00:36:04,663 --> 00:36:07,864
    Oceans of lava bubble up,

601
00:36:07,866 --> 00:36:13,170
   and a greenhouse atmosphere
      boils the surface --

602
00:36:13,172 --> 00:36:17,107
          a violent end
to a potential new home.

603
00:36:20,112 --> 00:36:21,778
            Kipping:
    Clearly, you need to know

604
00:36:21,780 --> 00:36:23,046
      about the composition
        of those planets

605
00:36:23,048 --> 00:36:24,915
      before you can start
        making statements

606
00:36:24,917 --> 00:36:27,884
       about how habitable
     those worlds truly are.

607
00:36:30,789 --> 00:36:33,757
 Narrator: But there's something
    else that a planet needs

608
00:36:33,759 --> 00:36:37,293
        to be earthlike,
       an invisible shield

609
00:36:37,295 --> 00:36:42,098
        that protects it
   from the dangers of space,

610
00:36:42,100 --> 00:36:45,602
        providing warmth
    and life-giving water --

611
00:36:45,604 --> 00:36:47,137
an atmosphere.

612
00:36:47,139 --> 00:36:51,241
                     ♪

613
00:36:57,549 --> 00:37:02,052
          [ explosion ]

614
00:37:02,054 --> 00:37:05,222
                     ♪

615
00:37:05,224 --> 00:37:10,493
narrator: The hunt for earth 2.0
has turned up plenty of planets,

616
00:37:10,495 --> 00:37:13,230
     but for a planet to be
           like earth,

617
00:37:13,232 --> 00:37:17,167
 it has to check a lot of boxes.

618
00:37:17,169 --> 00:37:20,170
    If you're really looking
         for earth 2.0,

619
00:37:20,172 --> 00:37:21,871
        then you're gonna
      have to find a planet

620
00:37:21,873 --> 00:37:24,641
      that's the same mass
       and size as earth,

621
00:37:24,643 --> 00:37:26,776
     orbiting a sunlike star

622
00:37:26,778 --> 00:37:30,914
   at about the same distance
with a similar atmosphere

623
00:37:30,916 --> 00:37:35,085
   and a lot of surface water
     that's in liquid form.

624
00:37:35,087 --> 00:37:36,319
           Good luck.

625
00:37:40,359 --> 00:37:42,292
    Narrator: And on the list
        of requirements,

626
00:37:42,294 --> 00:37:47,564
    an exoplanet's atmosphere
          is critical.

627
00:37:47,566 --> 00:37:50,467
     It protects the planet
  from huge temperature swings.

628
00:37:50,469 --> 00:37:53,236
     It protects the planet
  from small asteroid impacts.

629
00:37:53,238 --> 00:37:55,572
     It protects the planet
    from dangerous radiation

630
00:37:55,574 --> 00:37:57,274
  from space and from the star.

631
00:37:57,276 --> 00:38:00,010
 It is almost literally a shield
around the planet,

632
00:38:00,012 --> 00:38:03,747
 protecting us from outer space.

633
00:38:03,749 --> 00:38:07,917
      But to also has to be
  the right kind of atmosphere.

634
00:38:07,919 --> 00:38:11,921
                     ♪

635
00:38:11,923 --> 00:38:15,258
  get it wrong, and the planet
       can have crushing,

636
00:38:15,260 --> 00:38:17,694
       boiling conditions
         on the surface.

637
00:38:20,198 --> 00:38:22,032
  Look at our own solar system.

638
00:38:22,034 --> 00:38:23,867
    The sun's habitable zone
            includes

639
00:38:23,869 --> 00:38:26,903
    three different planets,
     venus, earth and mars,

640
00:38:26,905 --> 00:38:29,406
 but mars has a thin atmosphere
        and is too cold.

641
00:38:29,408 --> 00:38:32,242
       Venus has too thick
of an atmosphere and is too hot.

642
00:38:32,244 --> 00:38:35,445
      We're the only planet
 that happens to be just right.

643
00:38:35,447 --> 00:38:40,950
                     ♪

644
00:38:40,952 --> 00:38:43,753
  narrator: So far, astronomers
    have mostly had to guess

645
00:38:43,755 --> 00:38:48,091
       if these exoplanets
        have atmospheres,

646
00:38:48,093 --> 00:38:52,762
      but now we're looking
       for them directly,

647
00:38:52,764 --> 00:38:54,998
          searching for
      earthlike atmospheres

648
00:38:55,000 --> 00:38:57,400
    around earthlike planets.

649
00:38:59,638 --> 00:39:02,372
            Straughn:
 This is incredibly hard to do,

650
00:39:02,374 --> 00:39:05,675
     so in order to look at
the details of these atmospheres

651
00:39:05,677 --> 00:39:07,777
in the glare of the star

652
00:39:07,779 --> 00:39:11,915
            requires
  incredibly precise technology

653
00:39:11,917 --> 00:39:13,750
    and precise measurements.

654
00:39:16,154 --> 00:39:19,122
  Narrator: Astronomers detect
     atmospheres by watching

655
00:39:19,124 --> 00:39:22,025
     a planet pass in front
          of the star.

656
00:39:24,363 --> 00:39:28,264
A small fraction of light shines
  around the edge of the planet

657
00:39:28,266 --> 00:39:31,301
   and through the atmosphere

658
00:39:31,303 --> 00:39:35,271
   where molecules like water,
  hydrogen, and carbon dioxide

659
00:39:35,273 --> 00:39:41,211
  absorb particular wavelengths
     of light from the star.

660
00:39:41,213 --> 00:39:43,780
     If we can see the light
of the star

661
00:39:43,782 --> 00:39:46,216
         shining through
       around the planet,

662
00:39:46,218 --> 00:39:48,718
       we can maybe deduce
     some information about

663
00:39:48,720 --> 00:39:50,320
   does it have an atmosphere?

664
00:39:50,322 --> 00:39:51,821
     What are the properties
       of that atmosphere?

665
00:39:51,823 --> 00:39:54,991
         How hot is it?
     What's it made out of?

666
00:39:54,993 --> 00:39:56,926
    That's how we'll be able
          to determine

667
00:39:56,928 --> 00:39:59,796
   if things in the atmosphere
         might indicate

668
00:39:59,798 --> 00:40:02,399
        that the surface
     is hospitable to life.

669
00:40:04,803 --> 00:40:07,937
  Narrator: So far, we haven't
seen any exoplanets

670
00:40:07,939 --> 00:40:11,174
        with atmospheres
     that we could live in,

671
00:40:11,176 --> 00:40:13,443
   but that's about to change.

672
00:40:13,445 --> 00:40:19,749
                     ♪

673
00:40:19,751 --> 00:40:21,718
   scientists around the world

674
00:40:21,720 --> 00:40:24,754
     are working on the next
    generation of telescopes

675
00:40:24,756 --> 00:40:29,159
        to revolutionize
      exoplanet astronomy.

676
00:40:29,161 --> 00:40:31,094
      We've got some ideas,
       and some telescopes

677
00:40:31,096 --> 00:40:34,097
that are gonna be built probably
  in the next couple of decades

678
00:40:34,099 --> 00:40:37,367
       will be big enough,
  will be sophisticated enough

679
00:40:37,369 --> 00:40:39,736
        to be able to see
this sort of thing.

680
00:40:41,406 --> 00:40:46,409
            Narrator:
  Missions like the james webb
       space telescope --

681
00:40:46,411 --> 00:40:49,579
    seven times more powerful
          than hubble,

682
00:40:49,581 --> 00:40:53,583
    it should allow us to see
   the atmospheres of planets

683
00:40:53,585 --> 00:40:55,685
        across the galaxy

684
00:40:55,687 --> 00:41:01,858
       and be a tool that
  finally finds a second earth.

685
00:41:01,860 --> 00:41:04,427
 The key things we'd be looking
    for in these atmospheres

686
00:41:04,429 --> 00:41:07,764
    are in the infrared part
of the electromagnetic spectrum,

687
00:41:07,766 --> 00:41:11,468
       which is where webb
      is designed to work.

688
00:41:11,470 --> 00:41:13,136
The james webb
       space telescope is,

689
00:41:13,138 --> 00:41:17,540
 I believe, going to be the next
     really critical mission

690
00:41:17,542 --> 00:41:22,946
  to help us in our search for
 potentially earthlike planets.

691
00:41:22,948 --> 00:41:26,716
                     ♪

692
00:41:26,718 --> 00:41:31,721
 narrator: We're still searching
  for that perfect earth twin,

693
00:41:31,723 --> 00:41:35,058
         and every day,

694
00:41:35,060 --> 00:41:38,461
  we get closed to finding it.

695
00:41:38,463 --> 00:41:42,899
          30 years ago,
     we had zero exoplanets.

696
00:41:42,901 --> 00:41:45,668
  Today, we know of thousands.

697
00:41:45,670 --> 00:41:48,538
    With the next generation
         of instruments,

698
00:41:48,540 --> 00:41:51,541
we're going to uncover
       tens of thousands,

699
00:41:51,543 --> 00:41:56,679
     hundreds of thousands,
  even millions of exoplanets.

700
00:41:56,681 --> 00:42:00,984
 Narrator: All with the ultimate
      aim of leaving earth,

701
00:42:00,986 --> 00:42:06,155
         a civilization
    spread across the stars.

702
00:42:06,157 --> 00:42:08,191
   Oluseyi: One of the things
   I love about being a human

703
00:42:08,193 --> 00:42:10,493
    is the fact that I'm born
      with this curiosity.

704
00:42:10,495 --> 00:42:14,230
    This curiosity drives us
   to explore, explore earth,

705
00:42:14,232 --> 00:42:18,167
    explore our solar system
   and beyond into the galaxy.

706
00:42:18,169 --> 00:42:21,371
Plait: We'll be learning about
 these planets for a long time.

707
00:42:21,373 --> 00:42:23,873
      We have just started
          this journey.

708
00:42:23,875 --> 00:42:28,478
                     ♪