In January 2011, NASA's Kepler mission announced its first rocky planet: Kepler-10b.
Just 1.4 times the size of Earth but 4.6 times its mass, Kepler-10b packs a density of 8.8 grams per cubic centimeter — denser than Earth itself, a world of iron and rock.
But don't pack your bags. This planet whips around its star once every 20 hours — a year shorter than a single Earth day — and its star-facing side is a molten lava ocean.
And the star? Kepler-10 is almost 12 billion years old — more than twice the age of our Sun. One of the oldest planet-hosting stars ever found.
Over 600 light-years away in the constellation Draco, Kepler-10b was a milestone on the road to finding another Earth.
