by Elizabeth Gibney
as it orbits a white dwarf star.
Distant white dwarf
hints at the fate of the Solar
A white dwarf forms when a relatively low-mass star, such as the Sun, runs out of fuel.
After first expanding into a red giant
and engulfing the inner planets (which in the Solar System will
include Earth), the star sheds its outer layers to leave a small and
very dense core. Heavy elements are pulled towards the centre of the
dead star under its strong gravity.
To explain this puzzle, astronomers speculated that the stars might be feeding off the remains of outer planets and asteroids, which could have been kicked into the inner solar system during the white dwarf's turbulent formation and broken up by its intense gravity.
Later sightings of disks of debris
around a small fraction of white dwarfs backed up that theory. The
study, published in Nature on 21 October1 (A
Disintegrating Minor Planet Transiting a White Dwarf), is
the first to see the process in action.
patched-up Kepler space telescope
in its second mission, K2, they studied the light coming from the
star and found that it dipped briefly roughly every 4.5 hours, as if
obscured by a passing body. Follow-up studies using ground-based
telescopes suggest that at least one, and probably six or more,
small rocky bodies are orbiting the star, trailed by a dusty tail,
the researchers say.
The researchers estimate that 8 million kilograms of matter are being vaporized every second by the star's intense heat.
Follow-up studies may allow astronomers to analyze the composition of each orbiting chunk and conduct an "autopsy" on whatever larger body they once came from, says Michael Jura, an astronomer at the University of California, Los Angeles.