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Weird star baffles astronomers
16/05/2008 07:21 - (SA)
Washington - Astronomers are baffled
after finding an exotic type of star called a pulsar apparently
locked in an elongated orbit around a star much like the sun -
an arrangement defying what had been known about such objects.
The rapidly spinning pulsar - an extraordinarily dense
object created when a massive star exploded as a supernova -
is called J1903+0327 and is located about 21 000 light years
from Earth, the astronomers said.
"The big question is - how in the heck did this thing
form, because it doesn't follow our standard models of how
these things form," astronomer Scott Ransom of the National
Radio Astronomy Observatory in Charlottesville, Virginia, said
in a telephone interview on Thursday.
This object is known as a millisecond pulsar because of its
speedy whirl - it spins on its axis 465 times per second.
Until now, all of the ones found orbiting with another star
have been doing so with a white dwarf, another type of dying
star.
In each case, they shared a perfectly circular orbit. But
this one has a very elongated orbit around a star similar in
size and composition to our sun.
"What we have found is a millisecond pulsar that is in the
wrong kind of orbit around what appears to be the wrong kind of
star," astronomer David Champion of the Australia Telescope
National Facility said in a statement. "Now we have to figure
out how this strange system was produced."
It was detected using a radio telescope in Puerto Rico.
Pulsars are a rare type of neutron star whose strong
magnetic fields channel lighthouse-like beams of light and
radio waves that whirl around as the star spins.
Typical pulsars spin once a second to about 10 or 20 times
a second. But millisecond pulsars spin far more rapidly.
The understanding had been that these started out as
typical, slower-spinning pulsars, then built up speed after
material expelled from another star reached the pulsar's
surface, giving it momentum.
"If you were to ask any astronomer if we would have found a
system like this, they would have said no. So this is a very
big surprise," Ransom said.
The scientists, writing in the journal Science, speculate a
third star - perhaps a neutron star or white dwarf - might be
orbiting with the other two. Scientists know of about 100
pulsars in two-star, or binary, systems, and this might be the
first in a triple-star system, Ransom said.
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