Gamma rays from “star factories” in galaxies other than Milky Way detectedNovember 3rd, 2009 - 3:24 pm ICT by ANI
Washington, November 3 (ANI): NASA’s Fermi telescope has detected gamma rays from “star factories” in other galaxies.
Two so-called “starburst” galaxies, plus a satellite of our own Milky Way galaxy, represent a new category of gamma-ray-emitting objects detected both by Fermi and ground-based observatories.
“Starburst galaxies have not been accessible in gamma rays before,” said Fermi team member Seth Digel, a physicist at SLAC National Accelerator Laboratory in Menlo Park, California.
“Most of the galaxies Fermi sees are exotic and distant blazars, which produce jets powered by matter falling into enormous black holes. But these new galaxies are much closer to us and much more like our own,” he added.
Gamma rays are the most energetic form of light.
Fermi has detected more than a thousand point sources and hundreds of gamma-ray bursts, but the satellite also detects a broad glow that roughly follows the plane of our galaxy.
This diffuse gamma-ray emission results when fast-moving particles called cosmic rays strike galactic gas or even starlight.
“For the first time, we’re seeing diffuse emission from star-forming regions in galaxies other than our own,” said Jurgen Knodlseder, a Fermi collaborator at the Center for the Study of Space Radiation in Toulouse, France.
Knodlseder revealed an image captured by Fermi’s Large Area Telescope (LAT) of a star-forming region known as 30 Doradus within the Large Magellanic Cloud (LMC).
Located 170,000 light-years away in the southern constellation Dorado, the LMC is the largest of several small satellite galaxies that orbit our own.
More stars form in the 30 Doradus “star factory” than in any similar location in the Milky Way.
“The region is an intense source of gamma rays, and the diffuse emission we see with Fermi follows the glowing gas we see in visible light,” Knodlseder explained.
The region lights up in gamma rays for the same reason the Milky Way does - because cosmic rays strike gas clouds and starlight.
But Fermi shows that the LMC’s brightest diffuse emission remains close to 30 Doradus and doesn’t extend across the galaxy.
This implies that the stellar factory itself is the source of the cosmic rays producing the glow.
“Star-forming regions produce lots of massive, short-lived stars, which explode when they die,” Digel said. “The connection makes sense,” he added. (ANI)
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