Some Planets May Be Made of Crystallized Carbon and Oxygen

Most planets are rocky, gassy, or even icy, but some may be stranger still. Planets like PSR J1719-1438 b orbit dead stars called pulsars, where only the densest materials survive. Astronomers believe this planet is mostly carbon and oxygen, so dense that much of it is probably crystalline, like a diamond—the stripped-down remnant of a once-massive star. It’s less than 60,000 km across yet has slightly more mass than Jupiter. If space miners ever need raw materials, these worlds could be the ultimate treasure troves.