Scientists using NASA's Kepler space telescope have uncovered strong evidence of a tiny, rocky 'planet' being torn apart as it spirals around a white dwarf star. This discovery validates a long-held theory that white dwarfs are capable of cannibalising remnant planets that have survived within its solar system, researchers said.
"We are for the first time witnessing a miniature planet ripped apart by intense gravity, being vaporised by starlight and raining rocky material onto its star," said Andrew Vanderburg, graduate student at the Harvard-Smithsonian Centre for Astrophysics.
As stars like our Sun age, they puff up into red giants and then gradually lose about half their mass, shrinking down to 1100th of their original size to roughly the size of Earth. This dead, dense star remnant is called a white dwarf. The devastated planete simal, or cosmic object formed from dust, rock, and other materials, is estimated to be the size of a large asteroid, and is the first planetary object to be confirmed transiting a white dwarf. It orbits its white dwarf, WD 1145+017, once every 4.5 hours. This orbital period places it extremely close to the white dwarf and its searing heat and shearing gravity. During its first observing campaign last year, K2 trained its gaze on a patch of sky in the constellation Virgo, measuring the minuscule change in brightness of the distant white dwarf.
When an object transits, or passes in front of a star from the vantage point of the space telescope, a dip in starlight is recorded. The periodic dimming of starlight indicates the presence of an object in orbit about the star. A research team led by Vanderburg found an unusual, but vaguely familiar pattern in the data. While there was a prominent dip in brightness occurring every 4.5 hours, blocking up to 40% of the white dwarf's light, the transit signal of the tiny planet did not exhibit the typical symmetric U-shaped pattern.
It showed an asymmetric elongated slope pattern that would indicate the presence of a comet-like tail. Together these features indicated a ring of dusty debris circling the white dwarf, and what could be the signature of a small planet being vaporised.
