Post by Chicago Astronomer - Astro Joe on Mar 31, 2005 0:01:29 GMT -6
Mystery objects stump astronomers
Posted March 24, 2005
Special to World Science
Astronomers are puzzled by two vast objects in our galaxy that spew powerful radiation, yet appear pitch black.
The objects are not black holes, which generally are smaller and which, despite their name, do seem to emit visible light, though that light actually comes from around them and not inside them.
The two bizarre objects were detected in a survey of sources within our galaxy of very high-energy gamma rays. Gamma rays are a type of light that is the most powerful known, yet is invisible to our eyes.
The objects appear to be light-years wide, the astronomers said. This would make them bigger than our Solar System—as measured not just out to the furthest known planet, but all the way out to the distant Oort Cloud of comets that surrounds our system, 1,000 times further. A light year is the distance light travels in a year.
The newfound objects are also distinct from another, well known type of gamma-ray source called gamma-ray bursts—momentary flashes of gamma rays, detected about once a day, which astronomers think may signal the birth of black holes as dead stars abruptly shrink out of existence.
Astronomers have dubbed the mystery objects dark accelerators.
“They are, for the moment, a complete mystery,” said Paula Chadwick of the University of Durham, U.K., one of the researchers. Durham is a member of an international team of astrophysics who found the objects and reported the findings in the March 25 issue of the research journal Science.
Astrophysicists use the term “accelerator” to refer to objects or violent processes, such as stellar explosions, that swing electrically charged particles up to high speeds. These events also emit gamma rays, which are easier to detect than charged particles because they travel outward in straight lines, unlike the particles, which are deflected by magnetic fields.
In addition to emitting gamma rays, most accelerators also radiate light of various other energy ranges. But the new dark accelerators appear to emit the very highest energy gamma rays only.
The group of researchers, known as the High Energy Stereoscopic System team, obtained the results using a special set of four gamma-ray detecting telescopes in Namibia, in South-West Africa, similarly called the High Energy Stereoscopic System.
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I wonder what it is...
