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Runaway pulsar has astronomers scratching their heads

Master blaster A newly discovered fast-moving pulsar streaking across the galaxy with enormous x-ray jets, appears difficult to explain based on our understanding of the laws of physics, according to scientists.

A report in the journal Astronomy and Astrophysics, says the pulsar called IGR J11014-6103, also known as the Lighthouse nebula, is moving at more than eight million kilometres per hour and generating the longest jets in the galaxy.

Pulsars are spinning neutron stars, the left over core of a massive star after it explodes as a supernova.

But according to study co-author, Associate Professor Miroslav Filipovic of the University of Western Sydney, "we haven't seen anything like this before".

"It's moving at great speed, wobbling like a top as it spins, and creating these powerful high energy particle jets 37 light years long; ten times the distance between us and the nearest star."

The pulsar's wobbling motion causes the jets to twist into a distinct corkscrew shape.

"One of the biggest mysteries is that we only see these jets in x-rays, there's no radio signature, that's totally shocking to us," says Filipovic.

"Pulsars were first discovered because of their characteristic radio signals, so this is extremely difficult to explain through any theories we have at the moment."

Stranger and stranger

The latest images from NASA's Chandra x-ray telescope and the CSIRO's Australia Telescope Compact Array at Narrabri in northern New South Wales, have also revealed details of a cocoon of high-energy particles, which enshrouds the pulsar, and produces a comet-like tail behind it.

Called a pulsar wind nebula, the tail shoots out perpendicular to the jets back to the pulsar's birthplace, a supernova remnant 60 light years away known as SNR MSH 11-61A.

The findings are intriguing because a pulsar's direction of motion, its jets, and its pulsar wind nebula are all usually aligned with one another.

"This remnant is also very unusual, being what we call a mixed morphology supernovae remnant," says Filipovic.

"These [remnants] look different depending on whether you observe them in x-ray or radio waves. So everything about this star is strange, there are all these mysteries that don't add up."

According to Filipovic, the engine driving the pulsar's high speed movement is most likely due to an uneven stellar core collapse during the supernovae explosion which created it 10 to 20 thousand years ago.

"That's one possibility, but there are about half a dozen other ideas, such as black holes, or the influence of local magnetic fields generated by nearby stars which could have squeezed the pulsar out from the remnant in no time," says Filipovic.

"One of the problems is, it's impossible to prove any of these ideas."

More study needed

The pulsar was originally discovered by the European Space Agency's INTEGRAL satellite.

"We don't see this object very clearly with low resolution optical telescopes, so we're going for observing time with the Hubble Space Telescope and larger eight-metre class telescopes on the ground," says Filipovic.

The pulsar will also be a prime object for study with the next generation of telescopes such as the Australian Square Kilometre Array Pathfinder (ASKAP).

"But the major work on this object over the next few years will be through theoretical physics," says Filipovic.

"It's impossible to easily explain all these crazy things we've seen in this object."