NASA Says Data Reveals anEarth-Like Planet, Kepler 452b

By DENNIS OVERBYE

Inching ahead on their quest for what they call Earth 2.0, astronomers from NASA’sKepler planet-hunting spacecraft announced on Thursday that they had found what might be one of the closest analogues to our own world yet.
It is a planet a little more than one and a half times as big in radius as Earth. Known as Kepler 452b, it circles a sunlike star in an orbit that takes 385 days, just slightly longer than our own year, putting it firmly in the “Goldilocks” habitable zone where the temperatures are lukewarm and suitable for liquid water on the surface — if it has a surface.
The new planet’s size puts it right on the edge between being rocky like Earth and being a fluffy gas ball like Neptune, according to studies of other such exoplanets. In an email, Jon Jenkins ofNASA’s Ames Research Center, home of the Kepler project, and lead author of a paper being published in The Astronomical Journal, said the likelihood of the planet’s being rocky was 50 percent to 62 percent, depending on uncertainties in the size of its home star. That would mean its mass is about five times that of Earth.
Such a planet would probably have a thick, cloudy atmosphere and active volcanoes, Dr. Jenkins said, and twice the gravity of Earth. Describing the planet during a news conference, Dr. Jenkins lapsed into lines from John Keats’s poem “On First Looking Into Chapman’s Homer”: “Then felt I like some watcher of the skies / When a new planet swims into his ken.