sábado, 26 de mayo de 2012

Mystery Pulsar with Unknown Wave Form Discovered


The Large Area Telescope (LAT), built by SLAC for the Fermi Gamma-ray Space Telescope, collects information on high-energy gamma rays from numerous sources in the sky. Among these are small, elusive objects called pulsars, which spin up to hundreds of times per second. Their name derives from the beams their magnetic fields produce as a result of this spin, which look like the pulsing beam of a lighthouse when, by chance, they happen to sweep across our field of view.

One especially interesting object discovered with this technique seems to have a previously unknown waveform – a gamma-ray peak before and after each radio peak – an effect the team could not explain using standard models of pulsar geometry. This suggests that the radio part of the beam may originate at two distinct points above the object’s surface. This variation increases the mystery and allure of these fascinating astrophysical phenomena.
Pulsars are very interesting to scientists because they are special types of neutron stars. Small (about 10 miles in diameter) and dense (one teaspoon weighs about a billion tons), they exhibit immense gravitational and magnetic forces not found on Earth.
The LAT has seen the gamma-ray signatures of more than 100 pulsars and is revolutionizing the study of these flashy objects in gamma rays, which are the most energetic form of light.
A team led by postdoctoral researcher Matthew Kerr of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), and Columbia University radio astronomer Fernando Camilo is reporting the use of new techniques for hunting pulsars. They and their colleagues have found a way to look for likely pulsar candidates by combining observations from the LAT and  the Parkes radio telescope in Australia. This approach combines the broad reach of an all-sky telescope (the LAT) with the deep sensitivity of a radio telescope, which can view only a tiny part of the sky at a time.
The image at the top of the page gave astronomers their first view of the energetic and complex nebula surrounding the young pulsar PSR B1509-58. The blue and purple colors indicate X-rays emitted by high-energy particles of matter and anti-matter which stream away from the pulsar. The pulsar itself is the bright white source at the center of the nebula.
A thin jet, almost 20 light years in length, extends to the lower left, and traces a beam of particles being shot out from the pulsar's south pole at more than 130 million miles per hour. Just above the pulsar can be seen a small arc of X-ray emission, which marks a shock wave produced by particles flowing away from the pulsar's equator.
The green cloud near the top of the image is due to multimillion degree Celsius gas. This gas, possibly a remnant of the supernova explosion associated with the creation of the pulsar, may have been heated by collisions with high-energy particles produced by the pulsar.
More information: Astrophysical Journal (ApJ, 2012, 748, 2)Journal reference: Astrophysical Journa
Image credit: NASA/MIT/B. Gaensler et al.
Source: The Daily Galaxy via SLAC National Accelerator Laboratory

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