Days after it switched on, the main instrument on the Gamma-ray Large Area Space Telescope began observing an extraordinarily bright gamma-ray blazar known as 3C 454.3, according to a new report. Scientists have known about this object for a while -- it's been monitored by the AGILE gamma-ray satellite and the Whole Earth Blazar Telescope -- so this is not a new discovery. But it's exciting because the instrument, called the Large Area Telescope, is still undergoing the arduous tweaking and testing known as commissioning. And while the researchers aren't giving out exact details -- they can't, really, until the instrument is properly calibrated -- they say the blazar is much brighter and more intense than reported by earlier observers.
The news was posted yesterday on The Astronomer's Telegram on behalf of the GLAST Large Area Telescope Collaboration by Gino Tosti of the INFN-Perugia lab in Italy; James Chiang, Eduardo do Couto e Silva and Jana Thayar John Gregg Thayer of Stanford Linear Accelerator Center; B. Lott of CENBG/Bordeaux; and J. Eric Grove of the US Naval Research Laboratory.
"What's exciting is that we're already seeing interesting things in the sky and reporting to the overall community, which suggests that the instrument is working very well,'' do Couto e Silva told me this afternoon. "The point is to essentially say listen, there is something interesting happening in the sky. If you have another instrument, another telescope, and you want to observe it, go for it, because it will be worthwhile.''
Launched June 11, GLAST is a cooperative effort between NASA and the US Department of Energy, with key international contributions. SLAC managed the construction of the Large Area Telescope and played a key role in assembling the instrument, whose data flows into a control center at the lab for distribution to scientists around the world.
It's a follow-on to an earlier mission called CGRO-EGRET, which also looked at gamma rays -- the highest-energy form of light -- generated by the most violent processes in the universe. GLAST has two advantages over EGRET. It returns to the same patch of sky every three hours, rather than briefly pointing at one object at a time; "We'll be able to make movies, where before we could only make photographs," do Couto e Silva says. And it monitors the most extremely energetic gamma rays, which earlier missions could not. (For an overview, see this piece in the February 2006 symmetry.) So GLAST should fill a gap in our understanding of the universe -- as if we had been seeing the world in every color but red and now can add the missing hue.
Blazars are powerful jets of radiation spewing out of active galactic nuclei, or AGNs -- the centers of galaxies containing supermassive black holes, millions to billions of times more massive than our sun. The Large Area Telescope started observing blazar 3C 454.3 on June 28, five days after the instrument was switched on. The researchers said they won't be able to monitor the blazar regularly until commissioning is completed in early August, but they urged others to start following the blazar in other wavelengths of light.
