article image

Pulsar zaps incoming asteroids

Jenny Winder, News Writer
Feb 24, 2014, 8:00 UTC

Sen—Scientists have found evidence that a tiny star called PSR J0738-4042 is being pounded by asteroids which are possibly being vaporised by the star.

PSR J0738-4042 is a 'pulsar' that emits a beam of radio waves. As the star spins, its radio beam flashes over Earth again and again with the regularity of a clock. The environment around this star, which lies 37,000 light-years from Earth in the constellation of Puppis, is especially harsh, full of radiation and violent winds of particles. The pulsar's radio beam is possibly vaporising infalling asteroids.

"One of these rocks seems to have had a mass of about a billion tonnes," CSIRO astronomer and member of the research team Dr Ryan Shannon said in a statement. "If a large rocky object can form here, planets could form around any star. That's exciting," Dr Shannon said.

The researchers used the Commonwealth Scientific and Industrial Research Organisation's (CSIRO) Parkes telescope. The 64-metre Parkes radio telescope has been in operation since 1961 and is one of the telescopes comprising CSIRO’s Australia Telescope National Facility. Affectionately known as "the Dish", it famously relayed television signals from the Apollo 11 Moon landing to a worldwide audience of 600 million in 1969.

In 2008 Dr Shannon and a colleague predicted how an infalling asteroid would affect a pulsar. It would, they said, alter the slowing of the pulsar's spin rate and the shape of the radio pulse that we see on Earth.

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

Asteroids around a pulsar could be created by the exploding star that formed the pulsar itself, the scientists say. The material blasted out from the explosion could fall back towards the forming pulsar, forming a disk of debris.

The astronomers have found a dust disk 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, in a statement.

In 1992 two planet-sized objects were found around a pulsar called PSR 1257+12, but these were probably formed by a different mechanism, the astronomers say.