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00:01As scientists and astronomers peer more closely and with ever more fidelity at nearby stars,
00:07they are discovering exoplanets, worlds outside our own solar system.
00:13Stars with planets were once thought to be a rarity.
00:16They are turning out to be the norm and not the exception.
00:20With some confidence, scientists now calculate
00:23there could be as many as 40 billion Earth-like planets in our Milky Way galaxy alone.
00:30We'll see you next time.
01:00The first exoplanets were detected in 1992, orbiting a pulsar, the remnants of a massive exploded star that was now a fast-spinning neutron star.
01:18With data collected from the Arecibo antennae in Puerto Rico, Alexander Volshan discovered three terrestrial planets orbiting the pulsar PSRB-1257-12.
01:30Other pulsars have been detected with dust clouds and disks orbiting them.
01:36This suggests that these three planets are second generation.
01:40The original planets were destroyed by the stellar explosion and the subsequent debris disk enabled these new planets to form.
01:50It was another three years before the first planet orbiting a G-class star similar to our Sun was identified.
01:57A gas giant like Jupiter orbiting 51 Pegasi every four days.
02:02Five years later, another main sequence star was found to have multiple planets.
02:09Exoplanets were not easy to detect.
02:11They are tiny, their light smothered by the light of their star, and they are so far away.
02:17There are three main methods for planetary detection.
02:24The hardest is direct visual observation via telescope, both on the ground and in orbit.
02:30Some 59 planets have been discovered this way.
02:34More indirect methods are employed, one of which is the radial velocity method.
02:46As a planet orbits, its gravitational pool causes the parent star to move back and forth.
02:52This tiny radial motion shifts the observed spectrum of the star by a correspondingly small amount because of the Doppler shift.
03:00With super sensitive spectrographs, the shifts can be measured and used to infer details of a planet's mass and orbit.
03:10The 3.6 meter telescope at La Silla, Chile, has such a spectrographic instrument called HART and is the leading exoplanet hunter.
03:21This is Tal Bortes, one of the first planets discovered utilizing this method.
03:2651 light years from Earth, this planet is massive, some four times the mass of Jupiter.
03:34So far, over 600 planets have been detected by this method.
03:41Another observational tool, and the most successful to date, is the transit method.
03:46A 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.
03:57Some 1,200 have been located this way.
04:00Until 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.
04:11However, new results unexpectedly show that many exoplanets actually orbit at a large angle to their star's spin axis.
04:19In the case shown here, WASP-8b, the orbit is completely reversed.
04:26There are other tools and techniques in the planet hunting toolbox, including microlensing, oculation and TTV or transit timing variation.
04:35Often, more than one technique is used to verify findings.
04:42In fact, revisiting a planet after some time for verification can lead to surprising results, as in HD 189733b, a hot Jupiter-type planet.
04:56On revisiting it, Hubble discovered the atmosphere was being stripped from it by a violent stellar flare.
05:06With the Hubble Space Telescope dividing its valuable time between many varied tasks and objectives, a dedicated planet hunter called KORO was launched.
05:31The mission was led by the French Space Agency CNES with contributions from ESA, Austria, Belgium, Germany, Spain and Brazil.
05:44Launched in 2006, the mission lasted seven years.
05:47It located two planets around the star KORO-7, one of which was the first found to display a density similar to Earth's.
06:00In all, it located 32 planets and 100 others are awaiting confirmation.
06:06The NASA Spitzer Infrared Space Telescope was launched to study protoplanetary and debris disks around stars and the curious brown dwarfs, often referred to as failed stars.
06:23Spitzer's infrared capability quickly led to numerous planetary discoveries and infrared mapping of other known planets, like hot Jupiter HD 149026b.
06:35Some 256 light years away in the constellation Hercules, a planet dubbed a hot Jupiter, it is a sweltering 2040 degrees Celsius, the hottest planet yet detected, and also the darkest, reflecting no sunlight back into space.
06:53It speeds around its star every 2.9 days.
06:56A world just two-thirds the size of Earth, one of the smallest on record, and only 33 light years away around the star GJ436, planet UCF-1.01 might be the nearest world to our solar system that is smaller than Earth.
07:17The planet, a rocky world, orbits so close to the star that the surface is probably molten.
07:23As with HD 189733b and the constellation Vulpecula, it appears to be tidally locked to its star, showing only one face as it orbits.
07:35Spitzer was able to distinguish the various temperatures of its clouds from 650 to 1700 degrees Celsius.
07:43Thermal imaging of these hot giants has provided more details of these distant worlds.
07:48In 2009, the game changed, with the launch of the Kepler Space Observatory.
08:00As 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.
08:11It observed around 165,000 stars, watching for any changes in their brightness.
08:18It has located over 1,100 planetary candidates.
08:21Now, these are candidates, but most of them, I'm convinced, will be confirmed in the coming months and years.
08:30That's more than all the people have found so far in history.
08:33A veritable menagerie of planet types is emerging, like Kepler-16b, orbiting two stars.
08:42Ice worlds and water worlds like Gliese 1214b.
08:46The Kepler team announced today 1,094 new planet candidates, bringing the total roster up to 2,326.
09:02Of those, 207 are Earth-size, and we now have 48 that are in the habitable zone,
09:0810 of which are smaller than two Earth radii.
09:14So these are planets that could potentially be rocky.
09:17So it's an exciting milestone because we are really honing in on truly Earth-sized, habitable planets.
09:28The combined surface and space-based system observations have led scientists to believe that planets around stars are the rule rather than the exception.
09:38And the average number of planets per star is greater than one.
09:45Kepler has discovered at least 86 stars with multiple planetary systems.
09:51Kepler-11, for example, has six confirmed planets orbiting a Sun-like star.
09:58The Kepler-11 planetary system is amazing.
10:02It's amazingly compact.
10:04It's amazingly flat.
10:05There's an amazingly large number of big planets orbiting close to their star.
10:12We didn't know such systems could even exist.
10:15There are certainly far fewer than one percent of stars have systems like Kepler-11.
10:23But whether it's one in a thousand, one in ten thousand, or one in a million, that we don't know, because we only know one of them.
10:31The growing number of confirmed planets is opening up new insights into planet formation.
10:41We're learning so much more about the orbits of planets, the masses of planets, the sizes of planets.
10:51And we're just beginning.
10:52Kepler is still returning data, and we're going to learn a fantastic amount about the diversity of planets out there around stars within our galaxy.
11:05Around each star is a circumstellar region called the habitable zone.
11:20Sometimes referred to as the Goldilocks zone, this is a region neither too cold nor too hot,
11:25where a planet could under the right conditions support liquid water at its surface and in turn could support life.
11:38The first Earth-sized planet in a habitable zone was discovered around a red dwarf.
11:43Named Kepler-186f, it is just ten percent larger than Earth.
11:50Kepler-186f is the first validated Earth-sized planet in the habitable zone of its star.
11:56It's the outermost of five planets to orbit a star that is smaller and cooler than the Sun.
12:01This planet orbits its star every 130 days, and so this places it in the habitable zone,
12:08where it's in a region where it could have liquid water on its surface.
12:11The star Kepler-186 is 500 light-years from Earth in the constellation Cygnus.
12:19This planet Kepler-186f orbits a star that's cooler and dimmer than the Sun.
12:26So while we may have found a planet that's the same size as Earth,
12:30and receives a similar amount of energy to what Earth receives,
12:34it orbits a very different star.
12:36So perhaps instead of an Earth twin, we have discovered an Earth cousin.
12:42Believed to be a rocky world, its mass and density are yet to be determined.
12:48This is one of the big milestones that we've been looking for in our attempts to find out
12:54if there are places just like home and if there's life out there.
12:59One of the big steps is to say, is there somewhere that looks, to all intents and purposes, like Earth?
13:06Well, we don't know just yet, but we know that there are places that at least look similar.
13:11To date, over 48 Earth-like planets have been located within habitable zones.
13:21Gliese 581 has four known planets.
13:33The outer D planet is thought to be an icy planet that has migrated closer to the star
13:39and would thus be covered by a large and deep ocean.
13:41Kepler-62f is likely to have a rocky composition and is only 40% larger than Earth,
13:58making it the exoplanet closest to the size of our planet known in the habitable zone of another star.
14:03Kepler-62e orbits on the inner edge of the habitable zone and is roughly 60% larger than Earth.
14:13Other recent discoveries include Kepler-438b, 442b and 440b, a super-Earth.
14:24The super-Earth exoplanet GJ1214b orbits its faint red parent star.
14:30This is the first super-Earth exoplanet to have had its atmosphere analyzed.
14:37It has a mass about six times that of the Earth
14:40and appears to be surrounded by an atmosphere of steam or thick clouds or haze.
14:44Based on observations, scientists believe that of the Sun-like stars, some 22% have an Earth-sized planet orbiting in the habitable zone.
14:58Assuming 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.
15:11If the Sun-like stars in the Milky Way, the Sun-like stars in the Milky Way, that would be 11 billion potentially habitable Earths, rising to 40 billion worlds if brown dwarfs are included.
15:25If the Sun-like stars or any other stars are still in the Milky Way, it is then very close to Earth.
15:33Are any of these worlds close to Earth?
15:36In fact, yes.
15:38Are any of these worlds close to Earth?
15:48In fact, yes.
15:50The closest star to our own is the well-known Alpha Centauri group, with the bright stars
15:55Alpha and Beta Centauri, plus the faint red star Proxima Centauri, the closest star to
16:00Earth.
16:01Yeah.
16:30Alpha Centauri b is known to be orbited by an Earth-mass planet, making it the closest
16:36exoplanet to our solar system a mere 4.37 light-years away, almost within our reach.
17:00Now, in its fourth observing campaign, the Kepler spacecraft continues targeting 16,000
17:11stars for exoplanets.
17:13It's estimated that the onboard fuel supply should last until at least December 2017.
17:20So far, Kepler has found an astounding 1,013 confirmed exoplanets, around 440 star systems.
17:35The terrestrial telescopes continue to do the heavy lifting when it comes to verifying possible
17:40planet candidates.
17:41The HARPS spectrographic instrument of La Silla Chile is being joined by the Next Generation
17:47Transit Survey, or NGTS.
17:51It will search for transiting exoplanets, with a focus on discovering Neptune-sized and
17:55smaller planets.
17:57NGTS is designed to operate in a robotic mode.
18:01It will continuously monitor the brightness of hundreds of thousands of comparatively bright
18:06stars in the southern skies.
18:10EISO's very large telescope at Cerro Paranal in Chile, composed of four individual telescopes,
18:17will be improved with the new next generation of adaptive optic system called SPHERE.
18:23Other improved technologies include the Gemini Planet Imager at nearby Cerro Pachon, now in operation,
18:29and the Subaru Coronographic Extreme Technology, currently being installed and tested.
18:35New, bigger and more powerful telescopes are in the pipeline as well.
18:45The 30-metre telescope planned for Manuakia, Hawaii, will have 492 small hexagon mirrors arranged
18:53together to form the primary mirror 30 metres across.
19:06The GMT, or Giant Magellan Telescope, will be built at the Las Campañas Observatory in Chile.
19:14It will consist of seven 8.4-metre mirrors arranged together to make up the primary mirror.
19:22Work on the mirrors is well underway.
19:34The European Extremely Large Telescope in the Atacama Desert is due for completion in 2024.
19:41It will have a 39-metre diameter mirror made up of 798 hexagonal mirrors and will be the largest ever built.
19:49It will enable scientists to study the atmosphere of exoplanets more closely.
20:01Space-based telescopes are advancing as well.
20:05The next-generation infrared telescope, James Webb, is nearing completion as it goes through rigorous testing.
20:17A scheduled launch in October 2018 will put the 6.5-metre telescope in orbit as a replacement for the Hubble and Spitzer telescopes.
20:29Likened to the California Gold Rush, there are planets out there to be found, and the race is on.
20:44TESS, the Transiting Exoplanet Survey Satellite, is scheduled to launch in 2017.
20:50TESS will scan the entire sky searching for exoplanets using four state-of-the-art cameras.
20:57It will be able to determine the chemical compositions of exoplanet atmospheres.
21:05Also planned for a 2017 launch is CHEOPS.
21:08Its function is to characterize transiting exoplanets orbiting bright host stars.
21:14The satellite is a small package, roughly 1.5 metres square, with a life expectancy of five years.
21:24The European Space Agency has commenced a new programme called Cosmic Vision, set to run from 2015 to 2025, with PLATO, an exoplanet hunter, expected to be launched in 2024.
21:37Other projects underway include PEGAS, under development in France, EXSEED, the Exoplanetary Circumstellar Environments and Disc Explorer from NASA, and FINESSE, the Fast Infrared Exoplanet Spectroscopy Survey Explorer, due to launch 2019.
21:55The Wide-Field Infrared Survey Telescope, WFIRST, is another NASA observatory, designed to perform wide-field imaging for the planet-hunting community.
22:08It will be fitted with a coronagraph instrument for direct imaging of exoplanets and debris disks.
22:15Another NASA New Worlds mission is the Star Shade Project, scheduled for a 2019 launch.
22:32It will physically block the star's light with a parasol to allow direct observation of exoplanets.
22:39NASA is already thinking about a future James Webb replacement.
22:49Called the Advanced Technology Large Aperture Space Telescope, or ATLAST, it will be 2,000 times more light-sensitive than Hubble.
22:58If all goes according to plan, ATLAST could be launched between 2025 and 2035.
23:09With these new tools and technologies, it is only a matter of time before we are able to detect Earth-like worlds capable of supporting life.
23:22Perhaps one day, even a planet emitting radio or other signals indicative of a sufficiently advanced intelligent civilization.
23:35Finally answering that great question, are we alone?
23:40To theWA?
23:41That's its best way,
23:42Please view theçe neutrons and the whole comparison of operations.
23:44The
23:53I don't know.