Original subtitles

- 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.

(upbeat music)

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.

(upbeat music)

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.

(upbeat music)

- 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.

(ambient music)

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.

(ambient music)

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.

(upbeat music)

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.

(ambient music)

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?

(ambient music)