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TOPIC: 3d part

dafni

Date: Mar 8, 2008

3d part	Permalink

The Compton Gamma-Ray Observatorys primary mission was only two years long, but GRO continued to operate and send data for more than seven years. The Compton Gamma Ray Observatory was launched into an orbit 296 km (184 mi) above Earth by the space shuttle Atlantis. GRO then used its own rocket engine to climb to a 400-km (249-mi) orbit. Like most satellites, GRO gradually lost altitude because it was slowed by friction with very tiny particles orbiting above Earths atmosphere. To compensate for such altitude loss, GRO used its rocket engine to boost itself back up into its proper orbit once in 1993 and once in 1997. GRO observed the sky constantly for periods from a few days to a few weeks long, transmitting data to Earth continuously during those periods. Between viewing periods, ground controllers reoriented GRO to scan a new section of sky. GROs primary two-year mission was dedicated to providing a survey of gamma-ray sources over the entire sky. In its first nine months, GRO detected more than 200 gamma-ray bursts and provided astronomers with a clearer picture of the gamma-ray glow that the disk-shaped Milky Way Galaxy emits. Gamma-ray bursts are short-lived explosions of energy in gamma-ray wavelengths. Later work with GRO and other satellites allowed scientists to determine that at least some of the bursts originated several billion light-years (a light-year is a distance measurement equivalent to 9.5 trillion km or 5.9 trillion mi) from Earth. Astronomers now believe that gamma-ray bursts are caused by supernovasexplosions that occur at the end of the lives of extremely massive stars. GRO also observed high-energy gamma rays from a solar flare in June 1991. This observation showed that solar flares release gamma rays for a longer period than scientists had expected. During the initial two-year mission, the spacecraft also discovered three gamma-ray quasars (the energetic hearts of distant galaxies) and four gamma ray pulsars (the dense, spinning hearts of dead stars). On January 17, 1993, GRO detected the so-called 'Super Bowl Burst,' the highest energy gamma-ray burst ever observed. GRO continued to return important data after its minimum two-year mission was over. In December 1995, GROs BATSE instruments discovered the first of a new class of gamma-ray object called a bursting pulsara gamma-ray burst that pulses. GRO also detected an isotope of the element cobalt in space for the first time. The presence of this isotope in space helps confirm the theory that chemical elements heavier than hydrogen and helium form through nuclear processes in the hearts of large stars or in supernovas __________________

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