The M87 jet as seen in the optical by the Hubble Space Telescope (left) and in
x-rays by the Chandra X-Ray Observatory.
A Mystery of Gamma Rays
Scattered across the universe, certain galaxies emit enormously powerful jets of relativistic particles intertwined with bursts of gamma rays. Although thousands of these jets have been observed, the precise mechanism by which gamma rays are created has mystified astronomers for more than 15 years. Recently, a team of SLAC scientists made a surprising discovery about the source of the most powerful of these gamma rays that raises as many questions as it answers.
One of the main questions researchers seek to answer about these unique radio galaxies—also known as "blazars" or "quasars" depending on the jet's orientation—is where, exactly, the gamma rays are created. Researchers believe that a black hole at the center of each quasar emits the jet of particles including electrons, positrons and protons. For years they postulated that the gamma rays were created within this jet stream. But later studies led some to believe that the gamma rays were instead produced by a yet unknown physical phenomenon very near the edge of the black hole itself. Now, SLAC researchers Teddy Cheung and Lukasz Stawarz, in collaboration with Daniel Harris at the Harvard-Smithsonian Center for Astrophysics, believe they have finally nailed down the location of gamma ray production.
"It's much farther down the jet than most scientists thought," said Cheung. "It's a very surprising result."
Click on image for larger version.
SLAC welcomed 13 new employees last week at orientation. From left to right, they are: Andrew May, Madhu Swaminathan,
Linda (Curry) Kizziah,
Lauren Elizabeth Alsberg,
Kimberely Swanson, and
Fiscal Year-End Procurement Deadlines
Please consider the following dates and dollar amounts if you are planning to submit a purchase requisition that needs to be delivered and accepted before the end of Fiscal
Year 07 (September 28, 2007). Requisitions must be entered into PeopleSoft on or before these dates:
Requisition value between $25, 000 and $99,999:
Friday, September 7th.
Requisition value of less than $25,000:
Friday, September 14th.
Any requisition entered into PeopleSoft after these dates will be processed with a delivery date of October 1st or later.
Requisition value of $100,000 or greater: Due to Purchasing
Department processing time (30 to 45 days) and Department of
Energy/Stanford Site Office review and approval requirements (2 to 5 days), these requisitions will be processed with a delivery date of October 1st or later.
For more information, please contact Purchasing Officer Bob Todaro at x2425 or
Jonathan Visits ATLAS
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Jonathan Dorfan with the SLAC
A Toroidal LHC ApparatuS (ATLAS) group at CERN
Respectful Workplace Policy Posters
Spring Up Around Lab
Click on poster for larger version.
Have you noticed the colorful R-E-S-P-E-C-T posters around the SLAC campus? Inspired by Aretha Franklin’s song RESPECT, the posters are a reminder that one of the reasons SLAC is a great place to work is its Respectful Workplace Policy.
A respectful workplace is one in which "Everyone is important; employees treat each other with respect; everyone—especially people in authority—serves as a role model; everyone can share concerns without fear of retaliation; and management listens."
To encourage a respectful workplace, employees and users can:
Catch people doing something
Don't yell unless the building is
Fix the problem, not the blame.
Walk around a problem to see it
from someone else's point of
Take responsibility for their own
mistakes and move on.
Keep a sense of humor.
Adopt the "24 hour gap" rule—
wait 24 hours before sending
an angry email; then don't send
If you would like posters for your area, please contact Charlotte Carlson in Human Resources at x2265.
Community Bulletin Board