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First Light from Space Telescope Reveals Gamma-Ray Sky

GLAST orbiting observatory renamed for Enrico Fermi
gamma-ray sky



NASA/DOE/International LAT Team

The first results from a powerful gamma-ray telescope launched into orbit earlier this summer show it is on track to unlock new secrets of the most energetic explosions in the universe. That was the message from NASA researchers speaking at a teleconference this afternoon to present the findings and to announce the mission's new name.

Jon Morse, director of the space agency's astrophysics division at NASA Headquarters in Washington, D.C., announced that GLAST, or the Gamma-ray Large Area Space Telescope, would now be known as the Fermi Gamma-ray Space Telescope, after the late Nobel laureate physicist, Enrico Fermi.

Launched on June 11, GLAST was built to scan the cosmos for gamma rays, particularly those generated by the powerful explosions produced by black holes in the centers of so-called active galactic nuclei, as well as those from gamma-ray bursts (GRBs), the brightest explosions in the universe.

Researchers presented the first data from GLAST's two instruments. The Large Area Telescope (LAT) scans the whole sky once every two orbits (about three hours). During its first 95 hours of operation, the telescope generated a gamma-ray map of the sky comparable to that obtained by the Energetic Gamma-Ray Experiment Telescope, or EGRET, which gathered data for nine years in the 1990s.

Familiar landmarks such as the Vala pulsar—the brightest persistent source of gamma rays in the sky—punctuated a backdrop of more diffuse radiation from high-energy cosmic rays striking interstellar gas. The difference was that GLAST made its map in days, whereas EGRET needed years, Steve Ritz, GLAST project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., says.

Ritz compared GLAST's first view of the cosmos with opening one's eyes for the first time following Lasik surgery. That first view was a dazzling one: It included the active galaxy 3C454.3 some seven billion light-years from Earth. "When the LAT turned on, it was just blazing. It was impossible to miss. It wasn't like that before" with EGRET, says Peter Michelson of Stanford University in Palo Alto, Calif., the lead investigator for LAT.

Fermi's namesake proved equally adept at spotting GRBs—the purpose of its second instrument, the GLAST Burst Monitor, which detected 31 bursts in its first month of activity, or about one per day, according to Charles "Chip" Meegan, the experiment's lead investigator at Marshall Space Flight Center in Huntsville, Ala. Unlike the LAT, the burst monitor was ready for operation almost immediately after being turned on.

The rechristening of GLAST in honor of Fermi reflects the ongoing mystery of the gamma-ray sky. Fermi, who won the 1938 Nobel Prize in Physics*, is best known for building the first man-made nuclear reactor in 1942. A brilliant theoretical physicist as well, he was also the first to propose a mechanism by which powerful cosmic objects could accelerate electrons strongly enough to generate gamma rays.

Researchers still don't know exactly what those mechanisms are in active galactic nuclei and GRBs but they hope GLAST will allow them to test models by making precise measurements of flares as they happen. Ritz says that the pace of data gathering so far "holds a tremendous amount of promise for things to come."

* Correction (8/27/08): This article originally stated that Enrico Fermi won the Nobel Prize in 1938 for buildilng the first nuclear reactor, which in fact he did not do until 1942; he won the Nobel in part for work on nuclear reactions.

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