A haul of planets from Nasa's Kepler telescope includes a world sharing many characteristics with Earth.
Kepler-452b orbits at a very similar distance from its star, though its radius is 60% larger.
Mission scientists said they believed it was the most Earth-like planet yet.
Such worlds are of interest to astronomers because they might be small and cool enough to host liquid water on their surface - and might therefore be hospitable to life.
Nasa's science chief John Grunsfeld called the new world "Earth 2.0" and the "closest so far" to our home.