(Agencies)
Updated: 2007-11-29 19:31

A super-fast moving star whose image has been captured by NASA's Chandra X-ray Observatory, is challenging theories about why it's moving so fast.

Astronomers used five years of Chandra observations to show the rogue star, dubbed RX J0822-4300. It is careening away from what's left of a star that exploded about 3,700 years ago. The neutron star, a piece of the Puppis A supernova remnant, is departing the Milky Way Galaxy at about 3 million mph (4.8 million kph).

"Just after it was born, this neutron star got a one-way ticket out of the galaxy," said co-author Robert Petre, an astronomer at NASA's Goddard Space Flight Center in Greenbelt, Md. "Astronomers have seen other stars being flung out of the Milky Way, but few as fast as this."

Other hypervelocity stars known to be exiting the Milky Way move at speeds about one-third as great - probably hurled toward interstellar space by an aggressive, supermassive black hole at our galaxy's center.

In the case of RX J0822-4300, a tremendous lopsided supernova explosion launched the neutron star to its blinding speed. It has traveled 20 light-years thus far, and will take millions of years to escape the clutches of the Milky Way.

Despite using advanced computer models to simulate how such a stellar rocket could form, astronomers have no concrete explanation.

"The problem with discovering this cosmic cannonball is we aren't sure how to make the cannon powerful enough." said Frank Winkler, an astronomer at Middlebury College in Vermont. "The high speed might be explained by an unusually energetic explosion, but the models are complicated and hard to apply to real explosions."

Winkler and Petre's research is detailed in a recent issue of the Astrophysical Journal.