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First images from NASA's Gamma-ray telescope

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August 31, 2008

The all-sky image combines 95 hours of “first light” observations from the Large Area Tele...

The all-sky image combines 95 hours of “first light” observations from the Large Area Telescope, which is 30 times more sensitive than any previous space-based gamma-ray instrument.

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Aug 31, 2008 After two months of calibration and testing, NASA’s Gamma-ray Large Area Space Telescope has started to deliver the goods, providing scientists with an all-sky image of the Milky Way. Scientists are extremely excited about the observatory, rewarding it with a snappy new name (the Fermi Gamma-ray Space Telescope) and even its own theme song (astronomers are presumably getting tired of Also Sprach Zarathustra). The international, multi-agency observatory will conduct gamma-ray astronomy observations from low-Earth orbit, with a goal of ten years of operations.

The all-sky image combines 95 hours of “first light” observations from the Large Area Telescope, which is 30 times more sensitive than any previous space-based gamma-ray instrument. The LAT image is comparable to an image produced by the Compton Gamma-ray Observatory, which took several years to produce. The LAT image reveals the Milky Way, Crab Nebula, Vela and Geminga pulsars, and the Pegasus blazar galaxy.

Gamma rays are the highest-energy form of light, and present unique challenges to scientists who wish to study them - the Earth’s atmosphere (luckily for us) absorbs the rays, and the waves can pass right through lenses and mirrors. The Fermi Gamma-ray Space Telescope uses the Large Area Telescope and the GLAST Burst Monitor to detect particles in the photon energy range of 8,000 to 300 billion electronvolts. Scientists anticipate that it will discover new pulsars in our galaxy, reveal powerful processes near supermassive black holes, enable a search for signs of new physical laws, and provide insight into active galactic nuclei, gamma ray bursts, and dark matter.

The Large Area Telescope has a field of view of over two steradians (one-fifth of the entire sky), and can measure the locations of bright sources to within one arcminute (1/30 of the diameter of the Moon). The LAT includes four main subsystems: a tracker, calorimeter, anticoincidence detector, and data acquisition system. The telescope covers the entire sky every three hours, and can automatically focus on gamma-ray bursts.

The GLAST Burst Monitor measures a larger range of energy than the LAT, and is designed to detect gamma-ray bursts over a wide range of timescales. The instrument has spotted 31 gamma-ray bursts in its first month of operation.

Kyle Sherer

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