It's Raining Asteroids on a Tiny Star

A tiny star, called PSR J0738-4042, is being pounded by asteroids, according to scientists observing the star using the Parkes Telescope operated by Australia's national science agency, CSIRO, and another telescope in South Africa.

"One of these rocks seems to have had a mass of about a billion tonnes," said Ryan Shannon, CSIRO astronomer and member of the research team, in reference to the asteroids.

PSR J0738-4042 lies 37,000 light-years from Earth in the constellation of Puppis, according to the press release announcing the discovery.

The environment surrounding the observed star is full of radiation and high speed winds full of particles.

"If a large rocky object can form here, planets could form around any star. That's exciting," Shannon said. The star Shannon studied is a pulsar, which emits a beam of radio waves. As the star rotates, its radio beam regularly flashes over Earth's surface.

In 2008, Shannon and a colleague hypothesized that asteroids falling to the pulsar's surface would slow the star's spin rate and alter the shape of the radio pulse, as observed from Earth.

"That is exactly what we see in this case," Shannon said. "We think the pulsar's radio beam zaps the asteroid, vaporizing it. But the vaporized particles are electrically charged and they slightly alter the process that creates the pulsar's beam."

The asteroids around the pulsar star could have been created when the star that formed the pulsar exploded, according to the astronomers. These materials could form a disk of debris around the star, which they have observed around another pulsar called J0146+61.

"This sort of dust disk could provide the 'seeds' that grow into larger asteroids," said Paul Brook, a PhD student co-supervised by the University of Oxford and CSIRO who led the study of PSR J0738-4042.

The study is published in The Astrophysical Journal Letters.