The first rocky planet
What happened: Kepler finds the first unquestionably rocky planet beyond our Solar System When it happened: January 2011
Our Solar System plays host to four rocky planets, and many more rocky moons and other bodies. Until Kepler, however, we had yet to find a rocky exoplanet. Larger planets on shorter orbits, like hot Jupiters, were much easier to find as they caused a bigger dip in a star’s light and orbited more quickly, so the transits were more noticeable.
In January 2011 that all changed with the announcement of Kepler-10b, the first confirmed rocky exoplanet. About 560 light years from Earth, the planet was nearly four-times the mass of our planet and 1.4-times the size. By confirming the properties of its host star, Kepler-10, scientists were also able to work out the properties of this planet, confirming without doubt that it must be terrestrial. Unfortunately, as the planet orbits its star 20-times closer than Mercury does our
Sun, it is almost certain to be a scorching-hot uninhabitable word.