On May 10, 2016, NASA confirmed the presence of more than 1,200 new planets in our galaxy, discovered by the Kepler mission. This makes the largest collection of planets ever discovered at one time.
“This announcement more than doubles the number of confirmed planets from Kepler,” said Ellen Stofan, chief scientist at NASA Headquarters in Washington. “This gives us hope that somewhere out there, around a star much like ours, we can eventually discover another Earth.”
Analysis performed on the Kepler space telescope’s July 2015 planet candidate catalog identified 4,302 potential planets, of which 1,284 have greater than 99% probability of being a planet. This is the minimum percentage required in order to receive the status of a planet. Kepler searches in particular for planets in the “habitable zone,” or the planets in close enough proximity to a star for water to pool on the surface.
“Before the Kepler space telescope launched, we did not know whether exoplanets were rare or common in the galaxy. Thanks to Kepler and the research community, we now know there could be more planets than stars,” said Paul Hertz, Astrophysics Division director at NASA Headquarters. “This knowledge informs the future missions that are needed to take us ever-closer to finding out whether we are alone in the universe.”
Kepler captures planets by detecting the slight decreases in brightness that occur when planets pass in front of their stars, comparable to the May 9 Mercury transit of the sun. Since space missions first discovered planets outside our solar system two decades ago, scientists have committed to the tedious process of verifying new planets one at a time.
“Planet candidates can be thought of like bread crumbs,” said Morton. “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.”
Among the newly confirmed planets, almost 550 could resemble rocky planets like Earth, according to their size. In addition, nine of these orbit in their sun’s habitable zone, meaning they have the perfect temperature for water to pool on the surface of the planet. With the addition of these nine, that makes a total of 21 exoplanets that have the same size and orbit as the Earth to the sun.
“They say not to count our chickens before they’re hatched, but that’s exactly what these results allow us to do based on probabilities that each egg (candidate) will hatch into a chick (bona fide planet),” said Natalie Batalha, co-author of the paper and the Kepler mission scientist at NASA’s Ames Research Center in Moffett Field, California. “This work will help Kepler reach its full potential by yielding a deeper understanding of the number of stars that harbor potentially habitable, Earth-size planets — a number that’s needed to design future missions to search for habitable environments and living worlds.”
Out of the nearly 5,000 possible planets found out there, more than 3,200 have been confirmed, and Kepler discovered 2,325 of these. Launched in March 2009, Kepler is the first NASA space mission to discover Earth-sized, habitable planets. Kepler found the new planets in a small portion of the night sky, between the constellations of Lyra and Cygnus.
For four years, Kepler monitored 150,000 stars in this single patch of sky, measuring the slight decreases in brightness when the planets transit their stars. In 2018, NASA’s Transiting Exoplanet Survey Satellite will use the same method to monitor 200,000 bright stars close by, focusing on Earth-sized and Super Earth-sized planets.
“Everything is looking good for the spacecraft,” said Charlie Sobeck, Kepler’s mission manager, who speculates that the spacecraft has “something over two more years of fuel” left to keep searching for new planets.