What Kepler found is quite incredible. When the Kepler observatory completed its primary mission objectives in 2012, it had detected nearly five thousand exoplanets. Perhaps its strangest discovery is a so-called Styrofoam planet, a world with just one-tenth the density of Jupiter. And its most stunning discovery is the first confirmation of a rocky planet outside our solar system. In 2015, Kepler scientists announced the discovery of the Earth’s “closest twin.”
