Kepler Finds 1,284 New Planets
By DENNIS OVERBYE
Planets keep falling out of the sky for the Kepler spacecraft. And as their number grows, so grows the age-old dream of ending human cosmic loneliness.
Astronomers operating NASA’s planet-finding spacecraft announced Tuesday that they had validated the planethood of 1,284 new candidates from Kepler’s voluminous catalog of potential exoplanets, the largest collection of new planets announced at one time. It brings the total of actual planets Kepler has discovered to more than 2,000.
All of them orbit stars in a patch of sky on the Cygnus-Lyra border, where Kepler, launched in 2009, spent four years staring at 150,000 stars looking for the characteristic dimming when planets crossed their faces, until its pointing system broke down and the team had to develop a new observing strategy. Since then, Kepler has identified some 4,700 possible planets, and more keep being found.
In the past, it took lengthy and arduous ground-based telescopic observations to winnow impostors like double stars and other pretenders from the planet list. But the numbers have grown too large, the cosmos too verdant, for this case-by-case analysis.
The new results rely on a statistical technique developed by Timothy Morton, an astronomer at Princeton University, to vet the potential candidates in bulk, by analyzing the shape of the dips they make in starlight and taking into account how common the various types of impostors are and assigning a reliability score to each one.
“Planet candidates can be thought of like bread crumbs,” said Dr. Morton in a NASA teleconference on Tuesday. “If you drop a few large crumbs on the floor, you can pick them up one by one. But if you spill a whole bag of tiny crumbs, you’re going to need a broom. This statistical analysis is our broom.”
So far, two dozen of the planets found and confirmed by Kepler occupy the so-called Goldilocks zones of their stars where liquid water and perhaps “Life as We Think We Know It” could exist.
Extrapolating these results to the entire galaxy, Natalie Batalha, Kepler mission scientist from the Ames Research Center, said there could be 10 billion roughly Earth-size planets in the galaxy within their stars’ habitable zones. The nearest habitable planet, she estimated, could be as close as 11 light-years. In the cosmic scheme of things, that is next door and reachable in our lifetimes with current or near-future technology. Last month, scientists announced a plan to try to send smartphone-like spacecraft to Alpha Centauri, which is 4.4 light-years away.
Kepler was conceived as a mission to determine how common Earth-size planets, possible habitable rocks, are in the universe. The Kepler team, Dr. Batalha said, is now approaching in the next year or two the closeout of that mission, one that has helped change humanity’s view of how friendly the cosmos might be to life, and has made exoplanets one of the most explosive fields in astronomy.
That quest will go on. Kepler will be passing the baton to future missions like NASA’s TESS, which will search for planets around nearby bright stars, starting in 2017.