domingo, 18 de noviembre de 2012

Mystery Sources of Gamma Rays Baffle Astronomers


The Fermi Space Telescope has detected close to 2,000 gamma ray sources in space, and nearly 600 are complete mysteries. Researchers are speculating on the nature of the mystery sources, including the possibility that they are made of dark matter. In 2011 NASA's Fermi team released the second catalog of gamma ray sources from its satellite's Large Area Telescope and have no idea where nearly one-third of gamma rays originated.

"Fermi sees gamma rays coming from directions in the sky where there are no obvious objects likely to produce gamma rays," said David Thompson, Fermi deputy project scientist, of Goddard Space Flight Center in Maryland.

Gamma rays are a "super-energetic form of light produced by sources such as black holes and massive exploding stars," according to NASA. The Fermi Researchers say two-thirds of the gamma rays come from objects such as pulsars or blazars. The remaining third are a complete mystery right now.

"Some of the mystery sources could be clouds of dark matter, something that's never been seen before," Thompson said.

NASA explains that about “85% of the gravitational mass of the universe is dark matter,” and “the stuff we see makes up the rest.”

Dark matter is something that pulls on things with the force of its gravity but can't be detected in any other way. It doesn't shine – doesn't emit or scatter light – hence the adjective ‘dark,’ ” NASA writes. "Some researchers believe that when two dark matter antiparticles bump into each other, they will annihilate, producing gamma rays. Concentrated clouds of dark matter could form agamma ray source at specific wavelengths detectable by Fermi."

"We've been using Fermi to search for dark matter for a long time," said Peter Michelson ofStanford University, the principal investigator for the Large Area Telescope. "If we see a bump in the gamma-ray spectrum – a narrow spectral line at high energies corresponding to the energy of the annihilating particles – we could be the first to 'apprehend' dark matter,” Michelson added.

Researcher point out that there are other possibilities for the mystery sources, including colliding galaxy clusters or some type of new phenomenon, such as something involving galactic black holes.

"Of course we're hoping for something really exotic like dark matter, but we have to look first at all the other options," Thompson said. "Fermi is an ongoing mission. We'll continue to search for answers to these puzzles and perhaps turn up even more surprises."
Image at the top of page is a Chandra image of a neutron star --collapsed stars whose surfaces are hot enough to emit radiation in ultraviolet and X-rays. Young neutron stars with active (populated with particles) magnetospheres manifest themselves as pulsars - objects that emit short but intense bursts of radio waves, X-rays, or visible electromagnetic radiation at regular intervals. 

Due to the extreme conditions in the neutron star interiors, these objects can be used as natural laboratories for studying the poorly understood properties of the superdense, strongly magnetized, superconducting matter. Such conditions can never be reproduced in Earth laboratories and therefore studying neutron stars provides the only way to learn about the nuclear reactions and interactions of the elementary particles under these extreme conditions. 

Image Credit: Oleg Kargatsev, Chandra X-ray Observatory, CXC/NASA
Source: The Daily Galaxy via NASA and Fermi

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