Scientists Find an ‘Earth Twin,’

It is a bit bigger and somewhat colder, but a planet circling a star 500 light-years away is otherwise the closest match of our home world yet discovered, astronomers announced on Thursday.

The planet, known as Kepler 186f, named after NASA’s Kepler planet-finding misison, which found it, has a diameter of 8,700 miles, 10 percent wider than Earth, and its orbit lies within the “Goldilocks zone” of its star, Kepler 186 — not too hot, not too cold, where temperatures could allow for liquid water to flow at the surface, making it potentially hospitable for life.

“It’s Earth size,” said Elisa V. Quintana of the SETI Institute and NASA’s Ames Research Center in Mountain View, Calif. “It’s in the habitable zone. So we now know these planets do exist.”

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