The first known Earth-sized planets orbiting another star have been found. NASA’s Kepler mission has detected two worlds – one slightly smaller than Earth and one almost exactly the same size – revolving around a Sun-like star some 950 light years away. But both these small planets are too close to their star – therefore too hot – for liquid water; too harsh an environment for life as we know it. The system – called Kepler 20 – has 5 planets in all, and is quite different from our Solar System. Here, 4 small rocky worlds – Mercury, Venus, Earth & Mars – orbit close in to the Sun… And large gassy planets Jupiter, Venus Uranus and Neptune orbit farther out. Kepler-20s planets alternate: Big/Small/Big/Small/Big. And all 5 orbit closer to their star than the diameter of the orbit of Mercury, So no twin of Erath – this time – but the Kepler mission is persistently staring at a star rich part of the sky near the constellation Cygnus, is discovering literally thousands of planets, and the linger it looks, the more planets it detects. For SPACE.com, I’m Dave Brody