Telescope Launches to Scout for High-Energy Action

June 11, 2008 -- NASA launched a telescope today that will scour the skies for the most intense and violent phenomena in the universe.

The next-generation gamma ray telescope will track high energy radiation. These photons of light are so jacked with power they register not by bouncing off a mirror but by blasting into bits of matter and antimatter.

It is the job of GLAST -- the Gamma Ray Large Area Telescope -- to sort through the particles and figure out where they came from. The observatory, which weighs nearly 5 tons, launched aboard an unmanned Delta rocket at 12:05 a.m. ET today from Cape Canaveral Air Force Station in Florida.

"Throughout all of human existence, there's been a shared experience of looking up at the night sky at the stars ... but it's only very recently that we have come to understand that all that light is only secondary byproducts of high-energy physical properties," said Steve Ritz, the lead scientist for GLAST from NASA's Goddard Space Flight Center in Greenbelt, Md.

It has been eight years since NASA's Compton Gamma Ray Observatory fell from space after a productive and eye-opening mission to study the gamma ray bursts.

Putting telescopes in orbit, beyond the filter of Earth's atmosphere, has opened new windows for exploring the universe.

"What we see when we look in other parts of the electromagnetic spectrum is very different than what we see with our natural eyesight," Ritz said. "GLAST is giving us a chance to peak behind the curtain or under the hood to see how things are working."

Gamma radiation is light's most energetic form, millions to hundreds of billions of times more powerful than visible light. The energies are so high that Albert Einstein's famous E=mc2 equation, which captures the relationship between matter and energy, provides the framework for designing how the telescope works.

Gamma rays, which are pure energy, slam into a layer of tungsten in the detector and split into pairs of subatomic particles, an electron and its antimatter partner, a positron. Layers of silicon can then trace the direction of the incoming gamma rays. Another detector, called a calorimeter, absorbs and measures the particles' energy.

Many more particles besides gamma rays will bombard GLAST's detectors, so the telescope wears what engineers call a "hat" to sort out cosmic ray hits and other unwanted visitors.

The Gamma Ray Universe

It's a huge effort, one that NASA is spending close to $700 million to mount, but the scientific payoffs have the potential to rewire our understanding of the universe. For starters, there is GLAST's range.

The telescope's two instruments can detect such a broad span of gamma radiation that if it were a piano it would cover 23 octaves, Ritz said.

That's important because gamma rays are tied to a wide variety of phenomena including neutron stars, black holes and dark matter. An instrument on the predecessor Compton Telescope mapped 271 gamma ray targets, 171 of which have not been unidentified. Another device found bursts of gamma rays coming from all over the sky.

"We've seen just the tip of the iceberg," Ritz said.