Astronomers zero in on source of mysterious gamma rays from space

December 21st, 2007 - 3:12 pm ICT by admin  

Washington, Dec 21 (ANI): Suzaku X-ray observatory, a joint collaboration between NASA and Japanese Exploration Agency, is shedding light on the source of mysterious gamma rays, that are some of the most energetic objects in our galaxy.

These cosmic powerhouses pour out vast amounts of energy, and they accelerate particles to almost the speed of light. But very little is known about their source because they were discovered only recently by an array of four European-built telescopes named the High Energy Stereoscopic System (H.E.S.S.)

“Understanding these objects is one of the most intriguing problems in astrophysics,” said Takayasu Anada of the Institute for Space and Astronautical Science in Kanagawa, Japan.

H.E.S.S. indirectly detects very-high-energy gamma rays from outer space, which are the highest-energy form of light ever detected from beyond Earth.

As the gamma rays interact with air molecules, they produce subatomic particles that radiate a blue-colored light known as Cherenkov radiation. H.E.S.S. detects this blue light, whose intensity and direction reveals the energy and position of the gamma-ray source.

The H.E.S.S. observations were groundbreaking, but the array’s images aren’t sharp enough to reveal the exact location where particles are being accelerated or how the particles are being accelerated. To solve this problem, several teams aimed Suzaku in the direction of some of these H.E.S.S. sources.

When Anada and his colleagues pointed Suzaku at a source known as HESS J1837-069
(the numerals express the object’s sky coordinates), the X-ray spectrum closely resembled X-ray spectra of pulsar wind nebulae - gaseous clouds that are sculpted by winds blown off by collapsed stars known as pulsars.

Pulsar wind nebulae emit hard X-rays, and their X-ray output remains relatively constant over long timescales.

“The origin of the gamma-ray emission from HESS J1837-069 remains unclear, but we suspect that this source is a pulsar wind nebula from the Suzaku observation,” said Anada.

NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton X-ray Observatory have revealed that other H.E.S.S. sources are also pulsar wind nebulae. These combined gamma-ray and X-ray observations are revealing that pulsar wind nebulae are more common and more energetic than astronomers had expected.

Another group, led by Hironori Matsumoto of the University of Kyoto in Japan, targeted Suzaku on HESS J1614-518.

This source belongs to a class of objects known as “dark particle accelerators” because their ultrahigh energies suggest they are accelerating particles to near-light speed, turning them into cosmic rays.

“Using the high sensitivity of the Suzaku satellite, we can find strong candidates for the origin of cosmic rays,” said Matsumoto. (ANI)

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