Andrew Yee[_1_]
January 4th 07, 03:15 PM
News Services
North Carolina State University
Media Contacts:
Dr. John Blondin, 919/515-7096
Tracey Peake, News Services, 919/515-6142
FOR IMMEDIATE RELEASE: Jan. 3, 2007
NC State Scientist Discovers New Explanation for Pulsar's Spin
A researcher at North Carolina State University has developed a
three-dimensional computer model that shows how pulsars obtain their spin,
which could lead to a greater understanding of the processes that occur when
stars die.
Dr. John Blondin, professor of physics in NC State's College of Physical and
Mathematical Sciences, along with colleague Anthony Mezzacappa at the Oak
Ridge National Laboratory, used the CRAY X1E supercomputer to develop a
three-dimensional model of a pulsar's creation, and in the process
discovered that conventional wisdom concerning the formation of these
celestial objects wasn't correct.
Their findings are published in the Jan. 4 edition of the journal Nature.
Pulsars are rapidly rotating neutron stars formed in supernova explosions,
which occur when a massive star reaches the end of its life and explodes.
The remaining matter is compressed into a dense, rapidly spinning mass -- a
neutron star, or pulsar -- so-called because scientists first discovered
them due to their regularly timed radio emissions.
"Picture something about the mass of the sun being pushed down to the size
of a small American city, like Raleigh," Blondin says. "That's what happens
when a neutron star is formed.
"We've known about pulsars since the 1960s," Blondin continues. "We can
determine how fast they're spinning by how rapidly they pulse. It's like a
searchlight on a lighthouse -- each time the pulsar spins, and emits a radio
pulse directed toward earth, we pick up on it. The period between the pulses
tells us how fast it's spinning."
Pulsars spin very rapidly -- 20 or more times per second. Scientists have
assumed that the spin was caused by the conservation of angular momentum
from a star that was spinning before it exploded.
"Think about figure skaters," Blondin says. "They start a spin with their
arms and legs farther out from the body, and increase their rotation speed
when they pull their limbs in more tightly. That's what the conservation of
angular momentum is -- the idea that if you take a large object with a
slight rotation and compress it down, the rotation speed will increase."
However, scientists had no idea if the stars that were producing the pulsars
were even spinning to begin with. Blondin and his colleague decided to
create a computer model of a supernova explosion using the new Cray X1E
supercomputer at the National Center for Computational Sciences, the only
computer with enough processing power to accomplish the task. The resultant
model demonstrated that a pulsar's spin doesn't have anything to do with
whether or not the star that created it was spinning; instead, the spin is
created by the explosion itself.
"We modeled the shockwave, which starts deep inside the core of the star and
then moves outward," Blondin says. "We discovered that as the shockwave
gains both the momentum and the energy needed to blow outward and create the
explosion, it starts spiraling all on its own, which starts the neutron star
at the center of the star spinning in the opposite direction. None of the
previous two-dimensional modeling of supernova explosions had picked up on
this phenomena."
Blondin hopes that this new information about the creation of pulsars will
lead to a greater understanding of supernova explosions. "Supernova
explosions produce many of the heavy elements found on the periodic chart,
like gold," he says. "Understanding these explosions can help us to better
understand our own planet and solar system."
IMAGE CAPTION:
[http://news.ncsu.edu/releases/2007/jan/001_Pulsarformation.htm (72KB)]
Volume rendering of 3-D simulation of a pulsar's formation.
North Carolina State University
Media Contacts:
Dr. John Blondin, 919/515-7096
Tracey Peake, News Services, 919/515-6142
FOR IMMEDIATE RELEASE: Jan. 3, 2007
NC State Scientist Discovers New Explanation for Pulsar's Spin
A researcher at North Carolina State University has developed a
three-dimensional computer model that shows how pulsars obtain their spin,
which could lead to a greater understanding of the processes that occur when
stars die.
Dr. John Blondin, professor of physics in NC State's College of Physical and
Mathematical Sciences, along with colleague Anthony Mezzacappa at the Oak
Ridge National Laboratory, used the CRAY X1E supercomputer to develop a
three-dimensional model of a pulsar's creation, and in the process
discovered that conventional wisdom concerning the formation of these
celestial objects wasn't correct.
Their findings are published in the Jan. 4 edition of the journal Nature.
Pulsars are rapidly rotating neutron stars formed in supernova explosions,
which occur when a massive star reaches the end of its life and explodes.
The remaining matter is compressed into a dense, rapidly spinning mass -- a
neutron star, or pulsar -- so-called because scientists first discovered
them due to their regularly timed radio emissions.
"Picture something about the mass of the sun being pushed down to the size
of a small American city, like Raleigh," Blondin says. "That's what happens
when a neutron star is formed.
"We've known about pulsars since the 1960s," Blondin continues. "We can
determine how fast they're spinning by how rapidly they pulse. It's like a
searchlight on a lighthouse -- each time the pulsar spins, and emits a radio
pulse directed toward earth, we pick up on it. The period between the pulses
tells us how fast it's spinning."
Pulsars spin very rapidly -- 20 or more times per second. Scientists have
assumed that the spin was caused by the conservation of angular momentum
from a star that was spinning before it exploded.
"Think about figure skaters," Blondin says. "They start a spin with their
arms and legs farther out from the body, and increase their rotation speed
when they pull their limbs in more tightly. That's what the conservation of
angular momentum is -- the idea that if you take a large object with a
slight rotation and compress it down, the rotation speed will increase."
However, scientists had no idea if the stars that were producing the pulsars
were even spinning to begin with. Blondin and his colleague decided to
create a computer model of a supernova explosion using the new Cray X1E
supercomputer at the National Center for Computational Sciences, the only
computer with enough processing power to accomplish the task. The resultant
model demonstrated that a pulsar's spin doesn't have anything to do with
whether or not the star that created it was spinning; instead, the spin is
created by the explosion itself.
"We modeled the shockwave, which starts deep inside the core of the star and
then moves outward," Blondin says. "We discovered that as the shockwave
gains both the momentum and the energy needed to blow outward and create the
explosion, it starts spiraling all on its own, which starts the neutron star
at the center of the star spinning in the opposite direction. None of the
previous two-dimensional modeling of supernova explosions had picked up on
this phenomena."
Blondin hopes that this new information about the creation of pulsars will
lead to a greater understanding of supernova explosions. "Supernova
explosions produce many of the heavy elements found on the periodic chart,
like gold," he says. "Understanding these explosions can help us to better
understand our own planet and solar system."
IMAGE CAPTION:
[http://news.ncsu.edu/releases/2007/jan/001_Pulsarformation.htm (72KB)]
Volume rendering of 3-D simulation of a pulsar's formation.