The K2 mission using the repurposed Kepler Space Telescope has uncovered strong evidence of a tiny, rocky object being torn apart as it spirals around a white dwarf star. (That’s an artist’s concept of it above.) This discovery supports the theory that a white dwarf is capable of cannibalizing any planets that have survived within its solar system. As stars like our Sun age, they first swell into red giants and then gradually lose about half their mass, shrinking down to 1/100th of their original size (roughly the size of Earth). This dense star remnant is called a white dwarf.
During a series of observations last year, K2 was used to measure the minuscule change in brightness of distant white dwarf known as. WD 1145+017. When an object passes in front of a star from our vantage point, a dip in the starlight can be detected. A periodic dimming indicates the presence of an object in orbit around the star. The object found around WD 1145+017 was the first found orbiting a white dwarf. It’s orbital period is only 4.5 hours, placing extremely close to the white dwarf and its searing heat and shearing gravitational force.
While there was a prominent dip in brightness every 4.5 hours, the transit signal of the tiny planet did not exhibit a normal symmetric U-shaped pattern. The data (shown as the black dots) displayed an asymmetric elongated slope pattern that indicated the presence of a comet-like tail. Together these features indicated a ring of dusty debris circling the white dwarf. That could be the signature of the small planet being vaporized.
In addition to the strangely shaped transits, other data shows signs of heavier elements polluting the atmosphere of WD 1145+017. Because of their intense gravity, white dwarfs are expected to have chemically pure surfaces and be covered only with the light elements helium and hydrogen. For years, researchers have found evidence that some white dwarf atmospheres are polluted with traces of heavier elements such as calcium, silicon, magnesium, and iron, and scientists have long suspected that the source of such pollution could come from a planet being torn apart. It looks as if they found one.
Image Credits: CfA / A. Vandenberg