Rarest elements reveal planets eaten by white dwarfs (opens in new tab)

All across the Universe, we can learn what stars are made of simply by taking a spectrum of the light coming from them. While some stars are low in what astronomers call metallicity — the fraction of elements that are heavier than hydrogen and helium — and others have high metallicities, the ratios of the heavy elements inside of them are normally fairly consistent. Oxygen is the third most abundant element in the Universe; carbon is fourth, followed by neon, nitrogen, magnesium, silicon, iro...