LOS ANGELES – NASA scientists announced Thursday that the Kepler mission had confirmed finding three planets, slightly larger than our own Earth, orbiting in their stars’ so-called habitable zones – that “Goldilocks” region where temperatures are not too hot and not too cold.
Researchers don’t know for sure, but the planets’ sizes and proximity to their stars mean that they could be rocky and could have liquid water, two attributes thought necessary for a planet to harbor life. What is certain, the scientists said during a press conference Thursday, is that the discoveries mark yet another step forward in the space agency’s quest to find an Earth-sized planet in a star’s habitable zone.
“We’re not quite there, but we’re pushing toward it,” said Thomas Barclay, a Kepler scientist at the Bay Area Environmental Research Institute in Sonoma.
“These are our best candidates for planets that might be habitable,” said William Borucki, Kepler science principal investigator at NASA’s Ames Research Center in Moffett Field, Calif., and a longtime advocate for the mission.
Since its launch in 2009, the Kepler spacecraft has kept its telescope trained on a patch of of the Milky Way containing more than 150,000 stars, recording the tiny dips in light that result when a planet’s orbit carries it between its star and the craft. Scientists on the ground (occasionally with the help of volunteer citizen scientists) then analyze the light curves in various ways to confirm that the dips do – or don’t – correspond to distant planets.
The newly confirmed super-Earths orbit two different stars.
One planet of interest, Kepler-69c, is about 70 percent larger than Earth and orbits a star that is similar to our sun and is 2,000 light-years away, Barclay said Thursday. It lies on the inner edge of its star’s habitable zone, and could be “more of a super-Venus than a super-Earth,” he added – in other words, very hot. Its discovery was published Thursday in the Astrophysical Journal.
The other two planets, known as Kepler-62e and Kepler-62f, are also somewhat larger than Earth (60 percent and 40 percent larger, respectively) and are somewhat closer by, at 1,200 light-years away. Kepler-62e orbits the star Kepler-62 in 122 days and could be rocky or a “water world” unlike anything in our solar system, Borucki said.