Take that, Tiffany's. About 20 quadrillion miles from Earth is a decidedly unusual planet. It's not its size — about the diameter of Jupiter — that makes it special; rather, it's its composition. The planet is thought to be made mostly or even entirely of diamond. The improbable world orbits a body known as a pulsar — an ex-star that exploded and collapsed in on itself so that it is now a rapidly spinning, superdense mass emitting powerful bursts of radio waves with each rotation. The diamond world was once a star too, and it too eventually burned out and blew up. The core it left behind would be mostly oxygen and carbon, and its own great mass would have crushed that carbon down to crystalline form — in other words, into diamond. We'll leave it to jewelers to calculate the karats — but 5 or 6 kajillion is a pretty good bet.