Advancing Basic Science for Humanity
08/26/2008 - GLAST Observatory Renamed for Fermi, Reveals Entire Gamma-Ray Sky
(Originally published by the Stanford Linear Acclerator Center)
August 26, 2008
The U.S. Department of Energy (DOE) and NASA announced today that the Gamma-Ray Large Area Space Telescope (GLAST) has revealed its first all-sky map in gamma rays. The onboard Large Area Telescope's (LAT) all-sky image—which shows the glowing gas of the Milky Way, blinking pulsars and a flaring galaxy billions of light-years away—was created using only 95 hours of "first light" observations, compared with past missions which took years to produce a similar image. Scientists expect the telescope will discover many new pulsars in our own galaxy, reveal powerful processes near super-massive black holes at the cores of thousands of active galaxies and enable a search for signs of new physical laws.
The NASA mission was made possible by collaboration with many U.S. and international partners. As part of its support for particle physics research, DOE contributed funding to the LAT—the primary instrument on GLAST—and DOE's Stanford Linear Accelerator Center (SLAC) managed the LAT construction. SLAC also played a key role in assembling the instrument and now plays the central role in LAT science operations, data processing and making scientific data available to collaborators for analysis.
"The DOE-NASA collaboration on this new observatory has been very successful and shows what can be accomplished when we work together," said Dennis Kovar, DOE Associate Director of Science for High Energy Physics. "We look forward to the scientific discoveries it will enable in both particle physics and astrophysics."
NASA also announced today that GLAST has been renamed the Fermi Gamma-ray Space Telescope. The new name honors Prof. Enrico Fermi (1901-1954), a pioneer in high-energy physics. "Enrico Fermi was the first person to suggest how cosmic particles could be accelerated to high speeds," said Paul Hertz, chief scientist for the Science Mission Directorate at NASA Headquarters in Washington, D.C. "His theory provides the foundation for understanding the powerful phenomena his namesake telescope will discover."
For two months following the mission's June 11, 2008 launch, scientists tested and calibrated its two instruments, the LAT and the GLAST Burst Monitor (GBM). "What impressed me the most is that everything went by the book," said Peter Michelson, LAT principal investigator at Stanford University, Calif. "We're elated." The LAT has already verified sources found by other gamma-ray detectors—and discovered more.
The all-sky image shows gas and dust in the plane of the Milky Way glowing in gamma rays due to collisions with accelerated nuclei called cosmic rays. The famous Crab Nebula and Vela pulsars also shine brightly at these wavelengths. These fast-spinning neutron stars, which form when massive stars die, were originally discovered by their radio emissions. The image's third pulsar, named Geminga and located in Gemini, is not a radio source. It was discovered by an earlier gamma-ray satellite. The Fermi Gamma-ray Space Telescope is expected to discover many more radio-quiet pulsars, providing key information about how these exotic objects work.
A fourth bright spot in the LAT image lies some 7.1 billion light-years away, far beyond our galaxy. This is 3C 454.3 in Pegasus, a type of active galaxy called a blazar. It's now undergoing a flaring episode that makes it especially bright.
The LAT scans the entire sky every three hours when operating in survey mode, which will occupy most of the telescope's observing time during the first year of operations. These fast snapshots will let scientists monitor rapidly changing sources.
The LAT instrument detects photons with energies ranging from 20 million electronvolts to over 300 billion electronvolts. The high end of this range, which corresponds to energies more than 5 million times greater than dental X-rays, is little explored.
The spacecraft's secondary instrument, the GBM, spotted 31 gamma-ray bursts in its first month of operation. These high-energy blasts occur when massive stars die and when orbiting neutron stars spiral together and merge.
The GBM is sensitive to lower energy range gamma rays (8000 to 30 million electronvolts) than LAT. Bursts seen by both instruments will provide an unprecedented look across a broad gamma-ray spectrum, enabling scientists to peer into the processes powering these events.
NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.