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In this issue:
Fermi Telescope Probes "Dragons" of the Gamma-ray Sky
Happy Anniversary, Fermi Telescope
Noontime Concert Tomorrow: Tokai String Quartet

SLAC Today

Wednesday - March 3, 2010

Fermi Telescope Probes "Dragons" of the Gamma-ray Sky

Fermi data invalidate a once-popular explanation for the extragalactic gamma-ray background. Jets from active galaxies play only a minor role in producing the emission. (NASA/DOE/Fermi LAT Collaboration.)

One of the pleasures of perusing ancient maps is locating regions so poorly explored that mapmakers warned of dragons and sea monsters. Now, astronomers using the Fermi Gamma-ray Space Telescope find themselves in the same situation as cartographers of old. A new study of the ever-present fog of gamma rays from sources outside our galaxy shows that less than a third of the emission arises from what astronomers once considered the most likely suspects—black-hole-powered jets from active galaxies.

"Active galaxies can explain less than 30 percent of the extragalactic gamma-ray background Fermi sees," said Marco Ajello, an astrophysicist at the Kavli Institute for Particle Astrophysics and Cosmology, jointly located at SLAC National Accelerator Laboratory and Stanford University. "That leaves a lot of room for scientific discovery as we puzzle out what else may be responsible."

Ajello presented his findings Tuesday at a meeting of the American Astronomical Society's High-Energy Astrophysics Division in Waikoloa, Hawaii.

The sky glows in gamma rays even far away from bright sources, such as pulsars and gas clouds within our own Milky Way galaxy or the most luminous active galaxies. According to the conventional explanation, this background glow represents the accumulated emission of a vast number of active galaxies that are simply too faint and too distant to be resolved as discrete gamma-ray sources.

"Thanks to Fermi, we now know for certain that this is not the case," Ajello said. A paper on the findings has been submitted to The Astrophysical Journal.. 

Read more from NASA...

Happy Anniversary, Fermi Telescope

On February 28, 2000, NASA announced the award to Stanford University for development of a space-based gamma ray telescope named GLAST. The telescope was to be a collaboration of NASA, the Department of Energy, and five non-US nations. The management of the project was to be centered at SLAC.

GLAST is now the Fermi Gamma-ray Space Telescope.

(Photo - the Tokai String Quartet)
The Tokai String Quartet. (Image courtesy the Tokai String Quartet.)

Noontime Concert Tomorrow:
Tokai String Quartet

The Tokai String Quartet will come to SLAC tomorrow, March 4, for a concert from 12:00 to 1:00 in the Kavli Auditorium. They are one of Canada's leading string quartets. In September 2007, the quartet became prizewinners at the Banff International String Quartet Competition, the first Canadian group to do so since 1992. This is a talented, up and coming ensemble that is working with the St. Lawrence String Quartet as part of their Emerging Quartets program this quarter.

They will perform the string the quartets by Haydn Op 50/6 "The Frog," and Brahms Quartet No. 1 c-minor.

Later in the year, another of the Emerging Quartets will come to SLAC. The Cecilia String Quartet will present a noon concert on Thursday, April 15.

Please join us!

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