Speed Demon Star Seen Zooming Out of Milky Way

Nov. 30, 2007 -- Astronomers have spotted and clocked a star ripping through the Milky Way at more than 3,000,000 miles per hour. That sort of excessive speed -- one of the fastest ever measured -- is certain to kick the star out of the Milky Way.

The star itself is a neutron star dubbed RX J0822-4300. It's the dead, very dense remnant of what was once a large star. It has been observed over the last five years by the Chandra X-ray Observatory as the star has shot away from the 3,700-year-old remnant of a supernova, or exploding star, known as Puppis A.

In fact, the supernova is precisely what sped up the neutron star.

The pair was once a set of companion stars, then one blew up, apparently in a very lopsided manner, and shot RX J0822-4300 out just like a cannonball out of a cannon.

"The analogy is not bad," said astronomer Frank Winkler of Middlebury College in Vermont. Winkler is the coauthor of a paper on the cannonball of a neutron star in the Nov. 20 issue of The Astrophysical Journal.

By putting together three Chandra observations over five years that show the changing position of the neutron star, along with measurements of the star's distance, it was a straightforward matter to calculate its speed.

Previous measurements in X-rays had hinted at a lopsided supernova explosion, Winkler told Discovery News. They had detected shards of the exploding star's core, which are still-intact lumps of pure oxygen created by nuclear fusion, shooting off in one direction in Puppis A. So it wasn't entirely surprising to find the neutron star being kicked.

It's the speed that is a surprise.