NASA’s nearly doubled the number of known exoplanets in one fell swoop, with the announcement of 11 new planetary systems hosting 26 planets.
The discovery also triples the number of stars known to have more than one planet that transits its star.
The planets orbit closer to their host stars than Venus does to our own sun, and range in size from one and a half times the radius of Earth to larger than Jupiter. Fifteen are between Earth and Neptune in size. It’s not yet known which, if any, are rocky planets like Earth.
“Prior to the Kepler mission, we knew of perhaps 500 exoplanets across the whole sky,” says Doug Hudgins, Kepler program scientist at NASA Headquarters in Washington.
“Now, in just two years staring at a patch of sky not much bigger than your fist, Kepler has discovered more than 60 planets and more than 2,300 planet candidates. This tells us that our galaxy is positively loaded with planets of all sizes and orbits.”
The finiding supports recent calculations that, in the Milky Way at least, most stars support at least one planet.
Indeed, each of the newly confirmed systems has between two and five closely spaced transiting planets.
Five of the systems – Kepler-25, Kepler-27, Kepler-30, Kepler-31 and Kepler-33 – contain a pair of planets where the inner planet orbits the star twice during each orbit of the outer planet. Four of the systems – Kepler-23, Kepler-24, Kepler-28 and Kepler-32 – contain a pairing where the outer planet circles the star twice for every three times the inner planet orbits its star.
“These configurations help to amplify the gravitational interactions between the planets, similar to how my sons kick their legs on a swing at the right time to go higher,” says Jason Steffen, the Brinson postdoctoral fellow at Fermilab Center for Particle Astrophysics.
Kepler-33, a star that is older and more massive than our sun, had the most planets – five, ranging in size from 1.5 to five times that of Earth. All are located closer to their star than any planet is to our sun.