1000th Planet Discovered By Kepler Just Got Verified

“Kepler gathered data for four years -- long enough that we can now clown out the Earth-size contestants in one Earth-year orbits”, said Fergal Mullally, SETI Institute Kepler researcher at Ames who managed the study of a new candidate catalogue. “We’re closer than we’ve ever been to discover Earth twins around other sun-like stars. These are the planets we’re looking for”.

"With each new finding of these small, probably rocky worlds, our confidence strengthens in the resolve of the true frequency of planets like Earth," said co-author Doug Caldwell, SETI Institute Kepler researcher at NASA's Ames Research Center at Moffett Field, California. "The day is on the skyline when we’ll know how common moderate, rocky planets like Earth are.”

NASA’s Kepler Space Telescope constantly observed more than 150,000 stars beyond our solar system, and to date has offered researchers a variety of more than 4,000 candidate planets for further study -- the 1,000th of which was just verified. Work is in progress to interpret these recent findings into approximations of how often rocky planets appear in the comfortable zones of stars like our sun, a key step toward NASA's goal of comprehending our place in the cosmos.

Using Kepler data, researchers reached this millenary breakthrough after validating that eight more candidates marked by the planet-hunting telescope are, in fact, planets. The Kepler crew also has added another 554 contestants to the roll of potential planets, six of which are near-Earth-size and orbit in the comfortable zone of stars like our sun.

Three of the newly-validated planets are situated in their distant suns’ comfortable zone, the range of distances from the host star where liquid water might occur on the surface of a circling planet. Of the three, two are expected to be made of rock, like Earth.

"Each result from the planet-hunting Kepler mission's treasure trove of data takes us another step closer to responding the question of if we are by ourselves in the Universe," said John Grunsfeld, assistant administrator of NASA’s Science Mission Directorate at the agency’s headquarters in Washington. “The Kepler team and its science communal carry on producing remarkable results with the data from this esteemed explorer."

To decide whether a planet is made of rock, water or gas, researchers must know its size and mass. When its mass can’t be directly found, researchers can conclude what the planet is made of based on its size. Two of the newly validated planets, Kepler-438b and Kepler-442b, are less than 1.5 times the diameter of Earth. Kepler-438b, 475 light-years away, is 12% larger than Earth and circles its star once every 35.2 days. Kepler-442b, 1,100 light-years away, is 33% larger than Earth and circles its star once every 112 days.

Both Kepler-438b and Kepler-442b orbit stars smaller and cooler than our sun, making the comfortable zone closer to their parent star, in the direction of the constellation “Lyra”.

With the discovery of 554 more planet candidates from Kepler observations directed May 2009 to April 2013, the Kepler team has elevated the candidate count to 4,175. Eight of these new candidates are among one to two times the size of Earth, and orbit in their sun's inhabitable zone. Of these eight, six orbit stars that are like our sun in size and temperature. All candidates need follow-up observations and study to verify they are real planets.

Researchers also are working on the next catalogue publication of Kepler’s four-year data set. The study will comprise the final month of data gathered by the mission and also will be conducted using sophisticated software that is more delicate to the tiny tell-tale signatures of small Earth-size planets than software used in the past.