A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » News
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Astronomers Discover Fastest-Spinning Pulsar (Forwarded)



 
 
Thread Tools Display Modes
  #1  
Old January 14th 06, 04:40 AM posted to sci.space.news
external usenet poster
 
Posts: n/a
Default Astronomers Discover Fastest-Spinning Pulsar (Forwarded)

National Radio Astronomy Observatory
P.O. Box O
Socorro, NM 87801
http://www.nrao.edu

Contact:
Dave Finley, Public Information Officer, Socorro, NM
(505) 835-7302

Embargoed for Release: 2:00 p.m., EST, Thursday, January 12, 2006

Astronomers Discover Fastest-Spinning Pulsar

Astronomers using the National Science Foundation's Robert C. Byrd Green
Bank Telescope have discovered the fastest-spinning neutron star ever
found, a 20-mile-diameter superdense pulsar whirling faster than the
blades of a kitchen blender. Their work yields important new information
about the nature of one of the most exotic forms of matter known in the
Universe.

"We believe that the matter in neutron stars is denser than an atomic
nucleus, but it is unclear by how much. Our observations of such a rapidly
rotating star set a hard upper limit on its size, and hence on how dense
the star can be.," said Jason Hessels, a graduate student at McGill
University in Montreal. Hessels and his colleagues presented their
findings to the American Astronomical Society's meeting in Washington, DC.

Pulsars are spinning neutron stars that sling "lighthouse beams" of radio
waves or light around as they spin. A neutron star is what is left after a
massive star explodes at the end of its "normal" life. With no nuclear
fuel left to produce energy to offset the stellar remnant's weight, its
material is compressed to extreme densities. The pressure squeezes
together most of its protons and electrons to form neutrons; hence, the
name "neutron star."

"Neutron stars are incredible laboratories for learning about the physics
of the fundamental particles of nature, and this pulsar has given us an
important new limit," explained Scott Ransom, an astronomer at the
National Radio Astronomy Observatory and one of Hessels' collaborators on
this work.

The scientists discovered the pulsar, named PSR J1748-2446ad, in a
globular cluster of stars called Terzan 5, located some 28,000 light-years
from Earth in the constellation Sagittarius. The newly-discovered pulsar
is spinning 716 times per second, or at 716 Hertz (Hz), readily beating
the previous record of 642 Hz from a pulsar discovered in 1982. For
reference, the fastest speeds of common kitchen blenders are 250-500 Hz.

The scientists say the object's fast rotation speed means that it cannot
be any larger than about 20 miles across. According to Hessels, "If it
were any larger, material from the surface would be flung into orbit
around the star." The scientists' calculation assumed that the neutron
star contains less than two times the mass of the Sun, an assumption that
is consistent with the masses of all known neutron stars.

The spinning pulsar has a companion star that orbits it once every 26
hours. The companion passes in front of the pulsar, eclipsing the pulsar
about 40 percent of the time. The long eclipse period, probably due to
bloating of the companion, makes it difficult for the astronomers to learn
details of the orbital configuration that would allow them to precisely
measure the masses of the pulsar and its companion.

"If we could pin down these masses more precisely, we could then get a
better limit on the size of the pulsar. That, in turn, would then give us
a better figure for the true density inside the neutron star," explained
Ingrid Stairs, an assistant professor at the University of British
Columbia and another collaborator on the work.

Competing theoretical models for the types and distributions of elementary
particles inside neutron stars make widely different predictions about the
pressure and density of such an object.

"We want observational data that shows which models fit the reality of
nature," Hessels said.

If the scientists can't use PSR J1748-2446ad to do that, they are hopeful
some of its near neighbors will yield the data they seek. Using the GBT,
the astronomers so far have found 30 new fast "millisecond pulsars" in the
cluster Terzan 5, making 33 pulsars known in the cluster in total. This is
the largest number of such pulsars ever found in a single globular
cluster.

Dense globular clusters of stars are excellent places to find
fast-rotating millisecond pulsars. Giant stars explode as supernovae and
leave rotating pulsars which gradually slow down. However, if a pulsar has
a companion star from which it can draw material, that incoming material
imparts its spin, or angular momentum, to the pulsar. As a result, the
pulsar spins faster. "In a dense cluster, interactions between the stars
will create more binary pairs that can yield more fast-rotating pulsars,"
Ransom said.

The great sensitivity of the giant, 100-meter diameter GBT, along with a
special signal processor, called the Pulsar Spigot, made possible the
discovery of so many millisecond pulsars in Terzan 5. "We think there are
many more pulsars to be found in Terzan 5 and other clusters, and given
that the fast ones are often hidden by eclipses, some of them may be
spinning even faster than this new one," Ransom said.

"We're excited about using this outstanding new telescope to answer some
important questions about fundamental physics," he said.

In addition to Hessels, Ransom and Stairs, the research team includes
Paulo Freire of Arecibo Observatory in Puerto Rico, Victoria Kaspi, of
McGill University, and Fernando Camilo, of Columbia University. Their
report is being published in Science Express, the online version of the
journal Science.

The National Radio Astronomy Observatory is a facility of the National
Science Foundation, operated under cooperative agreement by Associated
Universities, Inc. The pulsar research also was supported by the Canada
Foundation for Innovation, the Natural Sciences and Engineering Research
Council of Canada, the Quebec Foundation for Research on Nature and
Technology, the Canadian Institute for Advanced Research, the Canada
Research Chairs Program, and the National Science Foundation.

Graphics: How Are Millisecond Pulsars Formed?
http://www.nrao.edu/pr/2006/mspulsar...graphics.shtml


 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Discovery of the Youngest Ever Binary Pulsar (Forwarded) Andrew Yee Astronomy Misc 2 January 14th 06 07:01 PM
Astronomers Discover Fastest-Spinning Pulsar (Forwarded) Andrew Yee Astronomy Misc 0 January 14th 06 05:11 AM
Discovery of the Youngest Ever Binary Pulsar (Forwarded) Andrew Yee News 0 January 13th 06 06:59 AM
Fastest Pulsar Speeding Out of Galaxy, Astronomers Discover (Forwarded) Andrew Yee Astronomy Misc 0 September 1st 05 02:09 AM
First-Known Double Pulsar Opens Up New Astrophysics (Forwarded) Andrew Yee Astronomy Misc 6 January 20th 04 12:49 AM


All times are GMT +1. The time now is 03:02 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.