Inching ahead on their quest for what they call Earth 2.0, astronomers from NASA’s Kepler 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 star that lights this planet’s sky is about 1.5 billion years older than our sun and 20 percent more luminous, which has implications for the prospects of life.