GLAST Performance Meets Expectations

GLAST Performance Meets Expectations
NASA’s Gamma-ray Large Area Space Telescope (GLAST), recently renamed the Fermi Gamma-ray Space Telescope in honor of Enrico Fermi, has begun its exploration of the universe. The spacecraft and its revolutionary instruments passed their orbital checkout with flying colors. In the few months since its launch, it has verified sources found by other gamma-ray detectors, found new ones and produced an image of the entire sky.




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 This all-sky view from GLAST reveals bright emission in the plane of the Milky Way (center), bright pulsars, and super-massive black holes. (Credit: NASA/DOE/International LAT Team).
This all-sky view from GLAST reveals bright
emission in the plane of the Milky Way
(center), bright pulsars, and super-massive
black holes (Credit: NASA/DOE/International LAT Team).

NASA’s newest observatory, GLAST, launched June 11th, was renamed last month the Fermi Gamma-ray Space Telescope. This name is in honor of Enrico Fermi (1901-1954), an Italian physicist and Nobel laureate, who made important contributions in the fields of particle and nuclear physics, statistical mechanics and quantum theory. “Fermi was the first to suggest how cosmic particles could be accelerated to high speeds, and this work provides the foundation for understanding the powerful phenomena his namesake will observe,” said Paul Hertz, chief scientist for science missions at NASA headquarters in Washington, D.C.

The Fermi Gamma-ray Space Telescope’s mission is to explore the universe in high energy gamma rays. It will capture photons with energies that our thousands to hundreds of billions times greater than those we see with our eyes. It is expected to discover new pulsars (highly magnetized rotating neutron stars) in the Milky Way, shed light on the processes taking place in black holes located in galaxy centers, and maybe even reveal clues to unknown laws of physics.

The telescope has two instruments: the Large Area Telescope (LAT), Fermi’s primary instrument, and the GLAST Burst Monitor (GBM), a complementary instrument. The GBM is sensitive to less energetic gamma rays than LAT (8,000 to 30 million electron volts, as opposed to LAT’s spectrum of 30 million to 300 billion electron volts). Bursts seen by both instruments will provide an unprecedented look across a broad gamma-ray spectrum.

Development of the gamma-ray tracker was led by a team of physicists at the Santa Cruz Institute for Particle Physics of UC Santa Cruz. Robert Johnson, who led the team, said the tracker, which includes nearly 900,000 active detection channels, is performing exceedingly well: “The entire instrument is performing according to the design expectations. The initial images illustrate well the enormous leap in capability of GLAST relative to previous instruments.” 

Photograph of Enrico Fermi from 1950 (Credit: The National Archives and Records Administration) 
Photograph of Enrico Fermi
from 1950 (Credit: The National
Archives and Records Administration)

The LAT has already verified sources found by other gamma-ray detectors and discovered additional ones. Last month the LAT team unveiled an all-sky image showing the glowing gas of the Milky Way, blinking pulsar,s and a flaring galaxy billions of light years away. It combines 95 hours of the instrument’s observations. In comparison, a similar image produced by NASA’s now-defunct Compton Gamma-ray Observatory, took years of observations to produce. “The released images already show extraordinary flaring behavior of distant active galaxies,” Johnson said. “Closer to home, the images illustrate gamma-ray pulsations from a neutron star, a topic of great interest to the UCSC group.”

In the new image, gas and dust in the plane of the Milky Way glow in gamma rays thanks to collisions with cosmic ray particles. The 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 and was discovered by an earlier gamma-ray satellite. Fermi is expected to discover many more pulsars that aren’t active in radio wavelength, providing key information about how these exotic objects work. A fourth bright spot in the LAT image, 3C 454.3 in Pegasus, lies some 7.1 billion light-years away. It is a type of active galaxy called a blazer that is now undergoing a flaring episode making it especially bright.

The GBM has spotted 31 gamma-ray bursts in its first month of operation. These high-energy blasts occur when massive stars die or when orbiting neutron stars spiral together and merge. “Our job is to see the whole sky and identify burst locations well enough to tell the LAT where to look,” says Charles Meegan, GBM’s principal investigator at NASA’s Marshall Space Flight Center in Huntsville, Ala.

Future LAT and GBM revelations can be followed on NASA’s website and will be featured in future TFOT articles. 

TFOT has been following the development of GLAST and covered the June 11th GLAST launch. In another related article TFOT reported on IceCube, a unique project where scientists from the University of Delaware, backed by the National Science Foundation, are building the world’s largest “telescope” under hundreds of feet of Polar ice. The new instrument will help scientists detect the elusive neutrino, and might also help scientists learn more about the origin of gamma ray bursts. 

Further information on the Fermi Gamma-ray Space Telescope and its activities can be found in NASA’s and UCSC’s press releases.

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About the author

Shalhevet Bar-Asher

Shalhevet is finishing her B.A. degree in physics and mathematics at the Hebrew University in Jerusalem. She will begin her M.A. studies in physics next year and will focus on cosmology and astrophysics, her main topics of interest.

View all articles by Shalhevet Bar-Asher