Oct 1 2007
A new NASA space telescope will give scientists a peek at some of the most energetic objects and events in the universe. The new Gamma-ray Large Area Space Telescope to be launched next spring doesn't see visible light like our eyes, but gamma rays, the most energetic photons in the electromagnetic spectrum.
They are produced by black holes, supernovae, neutron stars and other phenomena.
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 ¡X 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.
GLAST follows previous gamma ray observatories, including NASA's Swift spacecraft, which was launched in 2004 and the Compton Gamma Ray Observatory was placed into orbit by the space shuttle Atlantis in 1991 and deorbited in 2000. The European Space Agency's Integral observatory, which can observe objects in gamma rays, X-rays and visible light, was launched from Kazakhstan in 2002.
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.
GLAST will also allow scientist to study how black holes, collapsed stars with extremely strong gravitational pull that suck matter in and create jets of gas and gamma rays. Cosmologists also hope to learn about the birth and early evolution of the Universe.