LOS ANGELES — At least one in every four stars like the sun have planets about the size of Earth circling them in very close orbits, researchers said Thursday.
That means our galaxy alone, with its 200 billion sun-like stars, has at least 46 billion Earth-size planets orbiting close to the stars, and perhaps billions more farther out in the so-called habitable zone, said astronomer Andrew Howard of the University of California, a co-author of the paper. The discovery was reported in the journal Science.
The researchers’ technique let them detect planets ranging from three to 1,000 times Earth’s mass and orbiting as much as one-quarter of an astronomical unit from the host star. An astronomical unit, Earth’s distance from the sun, is 93 million miles.
Planets that close to their stars are too hot to be habitable. But “it is not a huge stretch to speculate that nature probably makes a lot of these planets farther out,” Howard said.
