| |
 |
|
|
Science Forum Index » Astro Forum » Weird Stellar Pair Puzzles Scientists (Forwarded)...
Page 1 of 1
|
| Author |
Message |
| Andrew Yee... |
 Posted: Thu May 15, 2008 8:34 pm |
|
|
|
Guest
|
National Radio Astronomy Observatory
P.O. Box O
Socorro, NM 87801
http://www.nrao.edu
Contact:
Dave Finley, Public Information Officer
(575) 835-7302
EMBARGOED For Release: 2:00 p.m. EDT, Thursday, May 15, 2008
Weird Stellar Pair Puzzles Scientists
Astronomers have discovered a speedy spinning pulsar in an elongated orbit
around an apparent Sun-like star, a combination never seen before, and one
that has them puzzled about how the strange system developed.
"Our ideas about how the fastest-spinning pulsars are produced do not
predict either the kind of orbit or the type of companion star this one
has," said David Champion of the Australia Telescope National Facility.
"We have to come up with some new scenarios to explain this weird pair,"
he added.
Astronomers first detected the pulsar, called J1903+0327, as part of a
long-term survey using the National Science Foundation's Arecibo radio
telescope in Puerto Rico. They made the discovery in 2006 doing data
analysis at McGill University, where Champion worked at the time. They
followed up the discovery with detailed studies using the Arecibo
telescope, the NSF's Robert C. Byrd Green Bank Telescope (GBT) in West
Virginia, the Westerbork radio telescope in the Netherlands, and the
Gemini North optical telescope in Hawaii.
The pulsar, a city-sized superdense stellar corpse left over after a
massive star exploded as a supernova, is spinning on its axis 465 times
every second. Nearly 21,000 light-years from Earth, it is in a
highly-elongated orbit that takes it around its companion star once every
95 days. An infrared image made with the Gemini North telescope in Hawaii
shows a Sun-like star at the pulsar's position. If this is an orbital
companion to the pulsar, it is unlike any companions of other rapidly
rotating pulsars. The pulsar, a neutron star, also is unusually massive
for its type.
"This combination of properties is unprecedented. Not only does it require
us to figure out how this system was produced, but the large mass may help
us understand how matter behaves at extremely high densities," said Scott
Ransom of the National Radio Astronomy Observatory.
Pulsars are neutron stars whose strong magnetic fields channel
lighthouse-like beams of light and radio waves that whirl around as the
star spins. Typical pulsars spin a few times a second, but some, like PSR
J1903+0327, are much faster, rotating hundreds of times a second. They are
called millisecond pulsars.
Astronomers think most millisecond pulsars are sped up by material falling
onto them from a companion star. This requires the pulsar to be in a tight
orbit around its companion that becomes more and more circular with time.
The orbits of some millisecond pulsars are the most perfect circles in the
Universe, so the elongated orbit of the new pulsar is a mystery.
"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," Champion said.
"Now we have to figure out how this strange system was produced."
The scientists are considering three possibilities. The first, that the
pulsar simply was born spinning quickly, seems unlikely to them. Another
possibility, they say, is that the pulsar was formed in a tight group of
stars known as a globular cluster, where it had a companion that spun it
up. Later, a close encounter with another star in the cluster stripped it
of its companion and flung it out of the cluster. For several reasons,
including the fact that they don't see a nearby cluster from which it
could have come, they don't like that explanation either.
A third scenario says the pulsar may be part of a triple, not a double,
star system. In this case, the pulsar's 95-day orbit is around a neutron
star or white dwarf, not the Sun-like star seen in the infrared image. The
Sun-like star would then be in a more-distant orbit around the pulsar and
its close companion.
"We've found about 50 pulsars in binary systems. We may now have found our
first pulsar in a stellar triple system," Ransom said.
The international research team is busy trying to get their answers. They
will study the star in the infrared image further to confirm the
indications that it is similar to our Sun and that it actually is a
companion to the pulsar. Additional radio observations will study the
pulsar's orbit and seek to measure its motion in space.
"This is a fascinating object that has a lot to teach us about physics.
It's going to be exciting to peel away the mystery of how this thing came
to be," Champion said.
Meanwhile the survey with Arecibo goes on. Other, more conventional
millisecond pulsars have been found, but it is almost certain that there
will be more surprises, said Jim Cordes of Cornell University, chair of
the consortium that is doing the survey. The large volume of data for the
survey is archived at the Cornell Center for Advanced Computing, and is
then processed using computer clusters at several consortium-member sites
around the world.
The National Astronomy and Ionosphere Center is operated by Cornell
University under a cooperative agreement with the National Science
Foundation.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation, operated under cooperative agreement by Associated
Universities, Inc.
[NOTE: An image supporting this release is available at
http://www.nrao.edu/pr/2008/strangepulsar/graphics.shtml ] |
|
|
| Back to top |
|
| |
|
Page 1 of 1
All times are GMT - 5 Hours
The time now is Wed Jul 09, 2008 1:39 am
|
|
