Hubble is the most famous space telescope, but it's not the only one. In fact, it's not even the only great one. NASA built and launched four large telescopes that it classified as "Great Observatories." They were designed to study the universe at many different wavelengths of energy.
Hubble was one of the four. Another was launched 20 years ago today: the Compton Gamma-Ray Observatory.
Compton was designed to study the most powerful form of energy: gamma rays. They're produced by some of the hottest and most violent objects and events in the universe.
Leading the way are the objects known as gamma-ray bursts. Compton helped astronomers determine that these brief outbursts come from far beyond our galaxy. It also found that they come in two varieties: those lasting less than two seconds, and those lasting longer than two seconds.
Using observations from Compton and other observatories in space and on the ground, astronomers determined that the two varieties have different origins.
The short bursts appear to come from the violent collisions and mergers of neutron stars -- the ultradense "corpses" of once-mighty stars. The long bursts are caused by the collapse of a mighty star to form an even denser corpse: a black hole.
Compton operated until 2000, when one of its control systems failed. The observatory was sent plunging back to Earth, where it burned up over the Pacific Ocean -- ending a "great" mission of discovery.
Script by Damond Benningfield, Copyright 2011