The discoveries bring the total number of known planets outside our solar system—so-called exoplanets—to roughly 1,700.
Launched in 2009, NASA’s $591 million Kepler Space Telescope has now discovered most of the planets orbiting nearby stars.
“We’ve hit the motherlode; we’ve got a veritable exoplanet bonanza,” says Kepler co-leader Jack Lissauer of NASA’s Ames Research Center in Moffett Field, California.
The newly announced exoplanets reinforce the view that most solar systems around sunlike stars have smaller-size planets.
Most of those planets range in width from Earth-size (on the smaller side) to Neptune-size (on the larger). That’s quite a change from the Jupiter-size planets that were often spotted orbiting nearby stars during the early planet searches that started in 1995.
“Nature likes to make small planets,” says the Massachusetts Institute of Technology’s Sara Seager, who was not part of the discovery team but commented on the findings at a Wednesday NASA briefing.
Four of the newly discovered planets orbit around their stars in “habitable zones”—regions where temperatures are just right for oceans, which bring with them the possibility of life. …