LOS ANGELES — NASA scientists have discovered a faraway planet that’s smaller than Mercury — far tinier than they expected they could find when they launched the Kepler space telescope nearly four years ago.
The hot, rocky world orbits a sun-like star that’s about 210 light-years from Earth. Astronomers are excited about it because it’s smaller than any planet in our solar system, said astrophysicist Thomas Barclay of NASA’s Ames Research Center in Mountain View, Calif.
“This is the smallest exoplanet that’s ever been found,” said Barclay, lead author of a report on the discovery in the journal Nature. “We’re breaking new ground here.”
From its perch in space, the Kepler telescope trains its lenses on more than 150,000 stars in the Milky Way and searches for the telltale fluctuations in a star’s light caused by a planet’s passing orbit. A primary goal of the mission is to look for Earth-like worlds that orbit within their stars’ “habitable zones” — planets that might be able to maintain liquid water on their surfaces and, perhaps, sustain life.