Kepler-186f is seen in a NASA artist's concept released April 17, 2014. The planet is the first validated Earth-size planet to orbit a distant star in the habitable zone which is a range of distance from a star where liquid water might pool on the planet's surface. The discovery is the closest scientists have come so far to finding a true Earth twin. The star, known as Kepler-186 and located about 500 light years away in the...
A newly discovered planet-like object, dubbed "Sedna" is seen in this artist's concept released by NASA March 26, 2014. Astronomers have found a small icy body far beyond Pluto and the Kuiper Belt, a discovery that calls into question exactly what was going on during the early days of the solar system. REUTERS/NASA/JPL-Caltech/Handout via Reuters
Dwarf planet Ceres is seen in the main asteroid belt between the orbits of Mars and Jupiter. Ceres, one of the most intriguing objects in the solar system, is gushing water vapor from its frigid surface into space, in a finding that raises questions about whether it might be hospitable to life. REUTERS/NASA/ESA
An artist's impression shows a sunset seen from the super-Earth Gliese 667 Cc. Astronomers have estimated there are tens of billions of such rocky worlds orbiting faint red dwarf stars in the Milky Way alone. REUTERS/ESO/L. Calcada
A view of a Saturn-sized planet orbiting 79 Ceti. REUTERS/Stringer
An artist's depiction of Kepler-62e. The super Earth-size planet is in the habitable zone of a star smaller and cooler than the sun, located about 1,200 light-years from Earth in the constellation Lyra. REUTERS/NASA Ames/JPL-Caltech
An icy planet-forming disk around a young star called TW Hydrae, located about 175 light-years away in the Hydra, or Sea Serpent, constellation. REUTERS/NASA/JPL-Caltech
Kepler-22b, the most Earth-like planet ever discovered, is circling a star 600 light years away. It is the smallest and the best positioned to have liquid water on its surface - among the ingredients necessary for life on Earth. REUTERS/NASA/Ames/JPL-Caltech
A newly discovered planet, designated by the unglamorous identifier of OGLE-2005-BLG-390Lb, orbits a red star five times less massive than the Sun and located at a distance of about 20,000 light years. REUTERS/ESO
An artist's impression shows the planet orbiting the star Alpha Centauri B, a member of the triple star system that is the closest to Earth. Our own Sun is visible to the upper right. REUTERS/ESO
The Jupiter-size extrasolar planet, HD 189733b, being eclipsed by its parent star. The planet is a 'hot Jupiter', so close to its parent star that it completes an orbit in only 2.2 days. REUTERS/ESA/NASA/M. Kornmesser (ESA/Hubble)/STScI.
An artist's conception of the tiny new planet Kepler-37b, which is slightly larger than Earth's moon and orbits its host star every 13 days. It likely has a surface temperature of in excess of 400C (700F). Astronomers don't think the tiny planet has an atmosphere or could support life as we know it, but the moon-size world is almost certainly rocky in composition. REUTERS/NASA/Ames/JPL-Caltech
An artist's impression of the planet 55 Cancri e orbiting its sun in the constellation of Cancer. The rocky planet, made largely out of diamond, moves so fast that a year there lasts a mere 18 hours. REUTERS/NASA/JPL-Caltech
Kepler-11, a sun-like star around which six planets orbit. At times, two or more planets pass in front of the star at once, as shown in a simultaneous transit of three planets. REUTERS/Tim Pyle/NASA
A hot, rocky, geologically active planet glowing in the deep red light of its nearby parent star, the M dwarf Gliese 876. The heat and the reddish light are among the few things about the planet that are certain, depending on the thickness and composition of its atmosphere - if any - it could range from being a barren, cratered ball of rock like Mercury or the Moon, to being a featureless, cloud-shrouded cue-ball like Venus....
The first visible-light snapshot of a planet circling another star. Estimated to be no more than three times Jupiter's mass, the planet, called Fomalhaut b, orbits the bright southern star Fomalhaut, located 25 light-years away in the constellation Piscis Australis, or the "Southern Fish." REUTERS/NASA, ESA, P. Kalas, J. Graham, E. Chiang, E. Kite (University of California, Berkeley), M. Clampin (NASA Goddard Space Flight...
A baffling planet, known as HAT-P-1, that is much larger than theory predicts. The planet has a radius about 1.38 times Jupiter's but contains only half Jupiter's mass. REUTERS/David A. Aguilar
A rich starry sky fills the view from an ancient gas-giant planet in the core of the globular star cluster M4. The 13-billion-year-old planet orbits a helium white-dwarf star and the millisecond pulsar B1620-26, seen at lower left. The globular cluster is deficient in heavier elements for making planets, so the existence of such a world implies that planet formation may have been quite efficient in the early universe....
The circumbinary planet Kepler-16b - the first planet known to definitively orbit two stars. The cold planet, with its gaseous surface, is not thought to be habitable. The largest of the two stars, a K dwarf, is about 69 percent the mass of our sun, and the smallest, a red dwarf, is about 20 percent the sun's mass. These star pairs are called eclipsing binaries. REUTERS/NASA/JPL-Caltech/T. Pyle/Handout
Planet 2003UB313, the most distant object ever detected orbiting the sun, at the lonely outer fringes of our solar system. Our sun can be seen in the distance. The planet is at least as big as Pluto and about three times farther away from the Sun than Pluto. REUTERS/NASA/JPL-Caltech
A Jupiter-sized planet passing in front of its parent star. Such events are called transits. When the planet transits the star, the star's apparent brightness drops by a few percent for a short period. REUTERS/NASA/ESA/G. Bacon
An exoplanet 6 times the size of Earth circulating around its low-mass host star at a distance equal to 1/20th of the Earth-Sun distance. The host star is a companion to two other low-mass stars, which are seen here in the distance (L). REUTERS/ESO/L. Calcada
The planet Kepler-16b with its two stars. The cold planet, with its gaseous surface, is not thought to be habitable. The largest of the two stars, a K dwarf, is about 69 percent the mass of our sun, and the smallest, a red dwarf, is about 20 percent the sun's mass. REUTERS/NASA/JPL-Caltech/R. Hurt
A unique type of exoplanet discovered with the Hubble Space Telescope. The planet is so close it to its star that it completes an orbit in 10.5 hours. The planet is only 750,000 miles from the star, or 1/130th the distance between Earth and the Sun. REUTERS/NASA/ESA/A. Schaller
A fledgling solar system containing deep within it enough water vapor to fill all the oceans on Earth five times, located in our Milky Way galaxy about 1,000 light years from Earth in the constellation Perseus. REUTERS/NASA/JPL-Caltech
The first photograph of a planet beyond our solar system, released by the University of Jena and the European Space Observatory April 5, 2005. The planet, orbiting a star similiar to our young Sun known as GQ Lupi, is thought to be one to two times as massive as Jupiter. REUTERS/Uni Jena/ESO