All language subtitles for A597C6E938B955C5CF1F1064C084B4AE_eng

- As scientists and astronomers
peer more closely and

with ever more fidelity at nearby stars,

they're discovering
exoplanets, worlds outside our

own solar system.

Stars with planets were
once thought to be a rarity;

they're turning out to be the
norm and not the exception.

With some confidence,
scientists now calculate there

could be as many as 40
billion Earth-like planets

in our Milky Way galaxy alone.

The first exoplanets were
detected in 1992, orbiting a

pulsar, the remnants of a
massive exploded star that

was now a fast-spinning neutron star.

With data collected from the
Arecibo Antenna in Puerto Rico,

Aleksander Wolszczan discovered
three terrestrial planets

orbiting the pulsar PSR B1257 + 12.

Other pulsars have been
detected with dust clouds

and discs orbiting them.

This suggests that these three planets

are second generation.

The original planets were
destroyed by the stellar

explosion, and the subsequent
debris disc enabled

these new planets to form.

It was another three years
before the first planet

orbiting a G-class star similar
to our sun was identified.

A gas giant like Jupiter orbiting
51 Pegasi every four days.

Five years later, another
main sequence star was

found to have multiple planets.

Exoplanets were not easy to
detect; they are tiny, their

light smothered by the
light of their star,

and they are so far away.

There are three main methods
for planetary detection.

The hardest is direct visual
observation via telescope,

both on the ground and in orbit.

Some 59 planets have
been discovered this way.

More indirect methods are
employed, one of which is

the radio velocity method.

As a planet orbits, its
gravitational pull causes the parent

star to move back and forth.

This tiny radio motion
shifts the observed spectrum

of the star by a correspondingly
small amount, because

of the Doppler shift.

With super-sensitive
spectrographs, the shifts can be

measured and used to infer
details of the planet's

mass and orbit.

The 3.6 meter telescope at
La Silla, Chile, has such

a spectrographic instrument
called HARPS, and is the

leading exoplanet hunter.

This is Talbortis, one of
the first planets discovered

utilizing this method.

51 light years from Earth,
this planet is massive,

some four times the mass of Jupiter.

So far, over 600 planets have
been detected by this method.

Another observational tool
and the most successful

to date, is the transit method.

A planet that passes in
front of its parent star

relative to us produces a
slight dimming of the star's

light, which can be detected
by sensitive instruments.

Some 1200 have been located this way.

Until now, it was expected
that exoplanets would orbit

in more or less the same plane
and in the same direction

as the star's rotation.

However, new results
unexpectedly show that many

exoplanets actually orbit
at a large angle to their

star's spin axis.

In the case shown here,
WASP-8 b, the orbit is

completely reversed.

There are other tools and
techniques in the planet

hunting toolbox, including
micro-lensing, occulation

and TTV, or transit timing variation.

Often more than one technique
is used to verify findings.

In fact, revisiting a
planet after some time for

verification can lead to
surprising results, as in

HD-189733 b, a hot Jupiter-type planet.

Upon revisiting it, Hubble
discovered the atmosphere

was being stripped from it
by a violent stellar flare.

With the Hubble space
telescope dividing its valuable

time between many varied tasks
and objectives, a dedicated

planet-hunter called COROT was launched.

The mission was led by the
French space agency CNES,

with contributions from ESA,
Austria, Belgium, Germany,

Spain, and Brazil.

Launched in 2006, the
mission lasted seven years.

It located two planets around
the star COROT-7, one of which

was the first found to display
a density similar to Earth's.

In all, it located 32 planets,
and 100 others are awaiting

confirmation.

The NASA Spitzer infrared
space telescope was launched

to study proto-planetary and
debris discs around stars,

and a curious brown dwarfs, often referred

to as failed stars.

Spitzer's infrared capability
quickly led to numerous

planetary discoveries, and
infrared mapping of other

known planets, like Hot
Jupiter HD-149026 b.

Some 256 light-years away in
the constellation Hercules,

a planet, dubbed a Hot Jupiter,
it is a sweltering 2,040

degrees Celsius, the hottest
planet yet detected, and also

the darkest, reflecting no
sunlight back into space.

It speeds around its star every 2.9 days.

A world just two-thirds the
size of Earth, one of the

smallest on record, and
only 33 light-years away

around the star GJ-436, planet

UCF-1.01 might be the
nearest world to our solar

system that is smaller than Earth.

The planet, a rocky world,
orbits so close to the star

that the surface is probably molten.

As with HD-189733 b in the
constellation Vulpecula,

it appears to be tidily locked
to its star, showing only

one face as it orbits.

Spitzer was able to distinguish
the various temperatures

of its clouds from 650
to 1700 degrees Celsius.

Thermal imaging of these
hot giants has provided

more details of these distant worlds.

In 2009, the game changed
with the launch of the

Kepler Space observatory.

As part of NASA's discovery
program, the Kepler Space

Telescope was launched to
survey and monitor a fixed field

of stars of the nearby Milky
Way, trailing behind Earth.

It observed around 165,000
stars, watching for any

changes in their brightness.

It has located over 1100
planetary candidates.

- Now these are candidates,
but most of them I'm

convinced will be confirmed in
the coming months and years.

That's more than all the people have found

so far in history.

- A veritable menagerie of
planet types is emerging,

like Kepler-16 b, orbiting two stars.

Ice worlds and water
worlds like Gliese 1214 b.

- The Kepler team
announced today 1,094 new

planet candidates,
bringing the total roster

up to 2,326.

Of those, 207 are Earth-size,
and we now have 48 that

are in the habitable zone, 10 of which

are smaller than two Earth radii,

so these are planets that
could potentially be rocky,

so it's an exciting
milestone, because we are

really honing in on, on truly
Earth-sized habitable planets.

- The combined surface and
space-based system observations

have led scientists to believe
that planets around stars

are the rule, rather than the
exception, and the average

number of planets by a
star is greater than one.

Kepler has discovered at
least 86 stars with multiple

planetary systems.

Kepler-11, for example,
has six confirmed planets

orbiting a sun-like star.

- The Kepler-11 planetary
system is amazing.

It's amazingly compact, it's
amazingly flat, there's an

amazingly large number of
big planets orbiting close

to their star.

We didn't know such
systems could even exist.

There's certainly far
fewer than 1% of stars

have systems like Kepler-11.

But whether it's one in a
thousand, one in ten thousand,

or one in a million, that
we don't know, cause we only

know one of them.

- The growing number of
confirmed planets is opening

up new insights into planet formation.

- We're learning so much more
about the orbits of planets,

the masses of planets,
the sizes of planets, and

we're just beginning.

Kepler's still returning
data, and we're going to learn

a fantastic amount about
the diversity of planets

out there around stars within our galaxy.

- Around each star is a
circumstellar region called

the habitable zone.

Sometimes referred to as
the Goldilocks zone, this is

a region neither too cold
nor too hot, where a planet

cooled under the right
conditions, supports liquid water

in its surface, and in
turn could support life.

The first Earth-sized planet
in a habitable zone was

discovered around a red dwarf.

Named Kepler-186f, it just
10% larger than Earth.

- Kepler-186f is the first
validated Earth-sized planet

in the habitable zone of its star.

It's the outermost of five
planets to orbit a star

that is smaller and cooler than the sun.

This planet orbits its star
every 130 days, and so this

places it in the habitable zone.

It's in a region where it
could have liquid water

in its surface.

- The star Kepler-186 is
500 light-years from Earth

in the constellation Cygnus.

- This planet Kepler-186f
orbits a star that's cooler

and dimmer than the sun,
so while we may have found

a planet that's the same
size as Earth, and receives

a similar amount of energy
to what Earth receives,

it orbits a very different star.

So, perhaps instead of an
Earth twin, we've discovered

an Earth cousin.

- Believed to be a rocky
world, its mass and density

are yet to be determined.

- This is one of the big
milestones that we've been

looking for in our attempts
to find out if there are

places just like home, and
if there's life out there.

One of the big steps is
to say, is there somewhere

that looks, to all intents
and purposes, like Earth?

Well, we don't know just
yet, but we know that there

are places that at least look similar.

- To date, over 48 Earth-like
planets have been located

within habitable zones.

Gliese 581 has four known planets.

The outer d planet is thought
to be an icy planet that has

migrated closer to the star
and would thus be covered

by a large and deep ocean.

Kepler-62f is likely to
have a rocky composition,

and is only 40% larger
than Earth, making it the

exoplanet closest to the
size of our planet, known

in the habitable zone of another star.

Kepler-62e orbits on the
inner edge of the habitable

zone, and is roughly
60% larger than Earth.

Other recent discoveries
include Kepler-438b, 442b,

and 440b, a super Earth.

The super Earth exoplanet
GJ-1214b orbits its faint

red parent star.

This is the first super Earth
exoplanet to have had its

atmosphere analyzed.

It has a mass about six times
that of the Earth, and appears

to be surrounded by an
atmosphere of steam, or thick

clouds or haze.

Based on observations,
scientists believe that of the

sun-like stars, some 22%
have an Earth-sized planet

orbiting in the habitable zone.

Assuming 200 billion stars
in the Milky Way, that would

be 11 billion potentially
habitable Earths, rising to

40 billion worlds if
brown dwarfs are included.

Are any of these world close to Earth?

In fact, yes.

The closest star to our own is
the well-known Alpha Centauri

group, with the bright stars
Alpha and Beta Centauri,

plus the faint red star
Proxima Centauri, the closest

star to Earth.

Alpha Centauri b is known to
be orbited by an Earth-mass

planet, making it the closest
exoplanet to our solar system,

a mere 4.37 light-years away,
almost within our reach.

Now in its fourth observing
campaign, the Kepler

spacecraft continues targeting
16,000 stars for exoplanets.

It's estimated that the
on-board fuel supply should

last until at least December 2017.

So far, Kepler has found an
astounding 1,013 confirmed

exoplanets around 440 star systems.

The terrestrial telescopes
continue to do the heavy lifting

when it comes to verifying
possible planet candidates.

The HARPS spectographic
instrument at La Silla, Chile

is being joined by the Next
Generation of Transit Survey,

or NGTS.

It will search for transiting
exoplanets, with a focus on

discovering Neptune-sized
and smaller planets.

NGTS is designed to
operate in a robotic mode.

It will continuously monitor
the brightness of hundreds

of thousands of comparatively bright stars

in the southern skies.

ESO's very large telescope
at Cerro Paranal in Chile,

composed of four individual
telescopes, will be improved

with the new next generation
of adaptive optic system,

called SPHERE.

Other improved technologies
include the Gemini planet

imager at the nearby Cerro
Pachon, now in operation,

and the Subaru Coronagraphic
Extreme techonology

currently being installed and tested.

New bigger and more
powerful telescopes are in

the pipeline as well.

The Thirty Meter Telescope,
planned for Manua Kea,

Hawaii will have 492 small
hexagon mirrors, arranged

together to form the primary
mirror 30 meters across.

The GMT, or Giant Magellan
Telescope, will be built

at the Las Campanas Observatory in Chile.

It will consist of seven
8.4 meter mirrors arranged

together to make up the primary mirror.

Work on the mirrors is well underway.

The European Extremely Large
Telescope in the Atacama

Desert is due for completion in 2024.

It will have a 39-meter
diameter mirror, made up of

798 hexagonal mirrors, and
will be the largest ever built.

It will enable scientists
to study the atmosphere of

exoplanets more closely.

Space-based telescopes
are advancing as well.

The next generation infrared
telescope, James Webb,

is nearing completion as it
goes through vigorous testing.

A scheduled launch in October
2018 will put the 6.5-meter

telescope in orbit as a
replacement for the Hubble

and Spitzer telescopes.

Likened to the California
Gold Rush, there are planets

out there to be found, and the race is on.

TESS, the Transiting
Exoplanet Survey Satellite, is

scheduled to launch in 2017.

TESS will scan the entire
sky searching for exoplanets

using four state of the art cameras.

It will be able to determine
the chemical compositions

of exoplanet atmospheres.

Also planned for a 2017 launch is CHEOPS.

Its function is to characterize
transiting exoplanets

orbiting bright host stars.

The satellite is a small
package, roughly 1.5 meters

squared, with a life
expectancy of five years.

The European Space Agency
has commenced a new

program called Cosmic Vision.

Set to fun from 2015 to 2025,
with Plato, an exoplanet

hunter, expected to be launched in 2024.

Other projects underway include
Begaz, under development

in France, EXCEDE, the
Exoplanetary Circumstellar

Environment and Disc Explorer
by NASA, and FINESSE,

the Fast Infrared Exoplanet
Spectroscopy Survey Explorer,

due to launch 2019.

The Wide-Field Infrared
Survey Telescope, WFIRST, is

another NASA observatory
designed to perform

wide-field imaging for the
planet hunting community.

It will be fitted with a
coronagraph instrument for

direct imaging of
exoplanets and debris discs.

Another NASA New Worlds mission
is the Starshade project,

scheduled for a 2019 launch.

It will physically block the
stars' light with a parasol,

to allow direct observation of exoplanets.

NASA is already thinking
about a future James Webb

replacement.

Called the Advanced Technology
Large Aperture Space

Telescope, or ATLAST, it
will be 2,000 times more

light-sensitive than Hubble.

If all goes according to
plan, ATLAST could be launched

between 2025 and 2035.

With these new tools and
technologies, it is only a matter

of time before we're able
to detect Earth-like worlds

capable of supporting life.

Perhaps one day, even a
planet emitting radio or other

signals indicative of a
sufficiently advanced intelligent

civilization, finally
answering that great question,

are we alone?