[meteorite-list] Asteroids Pound Distant Pulsar

[Ron Baalke]

http://www.csiro.au/en/Portals/Media/Rocks-around-the-clock.aspx

Rocks around the clock: asteroids pound tiny star
Asteroids hit the Earth, the Moon and even, it seems, distant stars.
CSIRO press release
20 February 2014

Scientists using CSIRO's Parkes telescope and another telescope in South 
Africa have found evidence that a tiny star called PSR J0738-4042 is being 
pounded by asteroids - large lumps of rock from space.

"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.

PSR J0738-4042 lies 37,000 light-years from Earth in the constellation 
of Puppis.

The environment around this star is especially harsh, full of radiation 
and violent winds of particles.

"If a large rocky object can form here, planets could form around any 
star. That's exciting," Dr Shannon said.

The star is a special one, 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.

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.

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 Mr Paul Brook, a PhD student co-supervised by the University 
of Oxford and CSIRO who led the study of PSR J0738-4042.

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.

The new study has been published as a paper in The Astrophysical Journal 
Letters, a leading journal of astronomical research: Evidence of an asteroid 
encountering a pulsar 
http://iopscience.iop.org/2041-8205/780/2/L31/