One of the
fastest moving stars ever seen is challenging theories to explain its
blistering speed.
The cosmic
cannonball, a neutron star known as RX J0822-4300, was discovered with NASA's
Chandra X-ray Observatory.
Astronomers
used five years of Chandra observations to show that the
rogue star is careening away from the Puppis A supernova remnant, leftovers
of a star that exploded about 3,700 years ago. The neutron star is racing out of
our 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—likely shot toward interstellar space by an aggressive, supermassive
black hole at our galaxy's center.
In the case
of RX J0822-4300, however, a tremendous lopsided supernova explosion rocketed 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 are at a loss of words.
"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.
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