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New Telescope Pinpoints Gamma Rays

Story by
Nancy Joseph

NASA’s newest space telescope is giving scientists their best look yet at the highest-energy gamma rays generated by violent events in space. For Toby Burnett, professor of physics, it’s a welcome payoff for 13 long years of work. 

Launched in June as the Gamma-ray Large Area Satellite Telescope, the instrument’s observations already are exceeding expectations. Using UW-designed software, the telescope homes in on gamma rays throughout the universe and pinpoints their locations.

“The instrument is working beautifully. It's like hitting the first pitch out of the park,” says Burnett. “Plus, we can scan the entire sky. No instrument before us could do that.”

The first image from the Fermi Gamma-ray Space Telescope was made by the UW team. It reveals bright emission in the plane of the Milky Way (center), bright pulsars, and super-massive black holes.

The first image from the Fermi Gamma-ray Space Telescope was made by the UW team. It reveals bright emission in the plane of the Milky Way (center), bright pulsars, and super-massive black holes.  Media credit: NASA/Department of Energy/Large Area Telescope team

In fact, the telescope can scan the entire sky several times a day, which means it is more likely than predecessors to identify and locate extreme events such as particle jet emissions from supermassive black holes or immense star explosions called supernovae. 

NASA announced this week that the mission has been renamed the Fermi Gamma-ray Space Telescope. The project is a successor to an instrument called the Energetic Gamma Ray Experiment Telescope, which in its five-year functional life identified and located 270 gamma-ray sources. The new telescope is designed to far exceed that number.

“We came close to 100 new sources in the first week after we started operating,” says Burnett. “Already we are able to make pictures that are better than the previous mission produced.”

The new telescope can measure the location of a specific gamma-ray source to two tenths of a degree. That’s four times more accurate than the previous telescope, reducing by a factor of 16 the area of the sky needed to search for optical counterparts. 

Burnett and UW physics graduate students wrote basic software to simulate and reconstruct positions of gamma-ray sources so they can be analyzed. The UW team also contributed to the ability to determine the angle of a gamma ray entering the telescope's detector—a key to pinpointing location—and created software that compares the spacecraft’s view of space with an onboard space map to make sure the telescope is aimed correctly. 

The telescope, about 9 feet high and 8 feet in diameter, cost nearly $700 million and is expected to operate for at least five years, with a goal of ten years. 

The project involves a broad collaboration, including NASA and the U.S. Department of Energy, along with seven U.S. universities and other public and private partners from the U.S., France, Germany, Italy, Japan, and Sweden.