Gamma rays emitting pulsar to shed new light on stellar evolution

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Washington, Oct 17 : Astronomers have discovered a new class of pulsars that emit gamma rays, which would open a new window on the evolution of stars.

One such object was discovered by the Large Area Telescope (LAT) onboard NASA's Fermi Gamma-ray Space Telescope, a collaboration with the U.S. Department of Energy (DOE) and international partners.

About three times a second, the 10,000-year-old pulsar sweeps a beam of gamma-rays toward Earth, and is the first one known to "blink" only in gamma rays.

"This is the first example of a new class of pulsars that will give us fundamental insights into how stars work," said Stanford University's Peter Michelson, principal investigator for the LAT.

A pulsar is a rapidly spinning neutron star, the crushed core left behind when a massive sun explodes.

The LAT data is processed by the DOE's Stanford Linear Accelerator Center and analyzed by the International LAT Collaboration.

The gamma-ray-only pulsar lies within a supernova remnant known as CTA 1, which is located about 4,600 light-years away in the constellation Cepheus.

Its lighthouse-like beam sweeps Earth's way every 316.86 milliseconds and emits 1,000 times the energy of our sun.

The LAT scans the entire sky every 3 hours and detects photons with energies ranging from 20 million to over 300 billion times the energy of visible light.

The instrument sees about one gamma ray each minute from CTA 1.

That's enough for scientists to piece together the neutron star's pulsing behavior, its rotation period, and the rate at which it's slowing down.

A pulsar's beams arise because neutron stars possess intense magnetic fields and rotate rapidly.

Charged particles stream outward from the star's magnetic poles at nearly the speed of light to create the gamma-ray beams the telescope sees.

Because the beams are powered by the neutron star's rotation, they gradually slow the pulsar's spin. In the case of CTA 1, the rotation period is increasing by about one second every 87,000 years.

This measurement is also vital to understanding the dynamics of the pulsar's behavior and can be used to estimate the pulsar's age.

From the slowing period, researchers have determined that the pulsar is actually powering all the activity in the nebula where it resides.

"This observation shows the power of the LAT," said Michelson. "It is so sensitive that we can now discover new types of objects just by observing their gamma-ray emissions," he added.

ANI

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