Four distant white dwarfs, the remnants of dead stars, have been spotted consuming what could be the crust of pulverised planets.
Mark Hollands at the University of Warwick, UK, and his colleagues have discovered that the material is similar to Earth鈥檚 crust, which could help reveal whether the formation of our own planet is a common process throughout the galaxy.
The spectrum of light emitted by white dwarfs is, unsurprisingly, very white 鈥� 鈥漧ike a blank sheet of paper鈥�, says Jay Farihi at University College London. So, when an astronomical body hits a white dwarf, its material leaves a signature in the spectrum of light that comes from the star, allowing astronomers to determine what the other body was made of.
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The chemical elements seen polluting the spectra of white dwarfs often match what we would聽expect to see from asteroids, the cores and mantles of planets, or聽the material you would see if聽you聽crunched up the whole of Earth, says Amaury Triaud at the University of Birmingham in the UK.
But Hollands鈥檚 team has spotted four white dwarfs whose spectra contain pollution with a chemical profile that has the same ratio of lithium, sodium, potassium and calcium as Earth鈥檚 crust alone does.
鈥滻t might be that it鈥檚 a planet that got destroyed, where bits of crust flew at some point into the white dwarf,鈥� says Triaud. He says this could be an opportunity to learn whether the formation of Earth-like continental crust and plate tectonics are common throughout the galaxy.
Fahiri says there are large uncertainties in the data from Hollands鈥檚 team, and doubts whether the spectrum pollution can聽be confidently interpreted as聽being from planetary crust rather聽than coming from asteroids or other planetary material.
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