A sapphire- or ruby-like planet?

55 Cancri e, HD219134 b, and WASP-47 e are three rocky planets – and they have something else in common: they might belong to a new class of super-Earths, according to arguments laid out by scientists from the University of Zurich and the University of Cambridge in a new paper. The astronomers looked at how planets are formed in protoplanetary disks. If they are formed, like the Earth, at a reasonable distance from their central star, then heavy elements, such as iron, magnesium, and silicon,...