BEIJING, Sept. 20 (Xinhuanet) -- NASA has plans to launch a telescope next spring that doesn't perceive visible light, instead it sees gamma rays, the most energetic photons in the electromagnetic spectrum that are produced by black holes, supernovae, neutron stars and other phenomena.

The new Gamma-ray Large Area Space Telescope (GLAST) will be the first gamma ray observatory to survey the entire sky. Scientists are hoping it will provide clues about dark matter, the early universe and allow them to test fundamental principles of physics.

"These are the things we can think of, it's hard to say what you're going to find," said Steve Ritz, a GLAST project scientist at NASA's Goddard Space Flight Center, which is leading the project.

Gamma rays don't survive the trip through Earth's atmosphere which is why NASA is launching GLAST into orbit from Cape Canaveral. The GLAST observatory consists of two instruments, the Large Area Telescope and the GLAST Burst Monitor.

Gamma ray photons have so much energy they create matter after striking a tungsten plate in the telescope ─ producing an electron and its exact opposite, a positron. The tracks of the two particles tell which direction the gamma ray photon came from, said GLAST team member Dave Thompson.

Despite the number of observatories studying gamma rays, a lot remains to be discovered. For example, the source of more than half of the gamma rays detected by the EGRET observatory is unknown, Thompson said.

"That's why we certainly need to know more about the gamma ray sky," Thompson said. "We've only scratched the surface of the how and why."

Dark energy and dark matter are particularly intriguing because they are two of the biggest mysteries of modern science. Scientists believe some gamma ray bursts may be created by dark matter collisions.

Dark matter, thought to be atomic particles left over from the Big Bang, doesn't give off light or heat, but does have mass and affects the gravity of galaxies it inhabits. While it can't be seen, scientists believe it accounts for much of the mass of the universe.

(Agencies)