White dwarf gnaws at giant planet
The star system WD J0914+1914 has given the astronomer Boris Gänsicke and his colleagues a lot of puzzles, but now it's clear: the white dwarf surrounds itself with a disk of gas, which it steals from a nearby planet. As the international team from the University of Warwick in England reports in the journal Nature, this is the best explanation for the star corpse's unusual spectrum. The researchers have thus discovered the first giant planet orbiting a white dwarf.
Actually, WD J0914+1914 was identified as a binary star system in which two white dwarfs move around the common center of mass. But something struck Gänsicke and his colleagues as strange, because the light spectrum of the system did not match the hypothesis correctly. So the researchers took a closer look: Using the Very Large Telescope of the European Southern Observatory ESO in Chile and the spectrograph X-Shooter, they analyzed the composition of the light and found that WD J0914+1914 has more in common with a star surrounded by a debris disk than with it a binary star system. Such formations around white dwarfs are not uncommon: Since these burned-out star cores are very dense, their tidal forces can be so strong that they tear apart minor planets and grind the debris into a dust disk orbiting them…
