Kathryn Volk

At the outskirts of the Solar System, beyond Neptune's orbit, millions of icy chunks circle the Sun — leftover building material from the era of planet formation. Astronomers call them trans-Neptunian objects, and they have a peculiarity: their surfaces are painted in various shades of red. Some are merely reddish, like rust, while others are very red, like dried blood.

When a telescope catches the light of a distant white dwarf, the spectrograph sometimes fishes out heavy elements — calcium, iron, magnesium. These metals could not have stayed in the thin atmosphere of the stellar remnant; they are the traces of recently fallen planetary debris.