Bad news for bling-lovers: diamond worlds are much rarer than imagined. Material left over from a star's birth can coalesce into planets. Stars with more oxygen than carbon give rise to rocky planets that are mostly oxygen-bearing silicates, like Earth. Stars with more carbon should make carbon planets, where internal pressure creates a thick layer of diamond. Previous work estimated that a third of all rocky planets might be carbon worlds. But a more detailed look at stellar spectra, by Poul Nissen of Aarhus University in Denmark, says diamond planets are much rarer (arxiv.org/ abs/1303.1726). Instead, there is possibly only one carbon planet for every 1000 silicate worlds.
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