Michael Braukus Headquarters, Washington, D.C. January 14, 1992 (Phone: 202/453-1549 ) 12:30 p.m. EST John Loughlin II Goddard Space Flight Center, Greenbelt, Md. (Phone: 301/286-5565) RELEASE: 92-6 GAMMA RAY OBSERVATORY MAKES NEW SCIENCE DISCOVERIES NASA's Compton Gamma Ray Observatory found three new gamma-ray quasars, detected more than 200 cosmic gamma ray bursts and captured the best ever observation of the glow of gamma radiation from the disk of the Milky Way galaxy. Dr. Carl Fichtel, Goddard Space Flight Center, Greenbelt, Md., Principal Investigator for the Energetic Gamma Ray Experiment Telescope (EGRET), one of four instruments on the Compton Observatory, says his instrument appears to have detected "still more distant and very luminous gamma-ray sources, even more distant than the massive quasar 3C 279." The EGRET team reported three sources of intense localized gamma radiation, quasars Q0208-512, 4C38.41 and PKS0528+134, detected between May 16, 1991 and Sept. 18, 1991, located in the constellations of Eridanus, Hercules and near the Crab Nebula, approximately 10 to 20 billion light years from Earth. "The sources are emitting an extraordinary flux of gamma rays, each gamma-ray photon with an energy greater than 100 million electron volts. In contrast, a visible light photon has an energy of only a few electron volts, and an X-ray photon has an energy of 1000 electron volts." Fichtel said, "The luminosity or total energy emitted by these sources is approximately 10 to 100 million times the total gamma-ray emission of the Milky Way galaxy." - more - - 2 - In addition to the quasar observations, EGRET scientists released an image today of the June 11, 1991, solar flare made by the telescope. "It is very unusual to see the high energy gamma-ray emissions from a solar flare," Fichtel said. "We were very surprised by this observation." Dr. Gerald Fishman, Principal Investigator for the Burst and Transient Source Experiment (BATSE), reports that his team has detected more than 200 cosmic gamma-ray bursts since Compton's launch. BATSE is designed to study the mysterious phenomenon of gamma-ray bursts. BATSE scientists announced last September indications of an apparent random distribution of the bursts in the sky. More recent observations by the BATSE team have further confirmed the earlier observation with almost twice as many bursts as the original report. In addition to their work on the enigmatic gamma-ray bursts, BATSE scientists have revealed the presence of gamma-ray pulses from a previously known radio and x-ray pulsar. The object is known as PSR 1509-58 or the Circinus Pulsar. "This is only the third known example of a gamma-ray pulsar and only the second one to be observed in the low energy gamma-ray region," Fishman said. Pulsars are rotating neutron stars which are thought to be formed from the core of a massive exploding star or supernova. A neutron star is composed of super dense matter, a cubic centimeter (about the size of an ordinary sugar cube) which would weigh over 10 million tons. Scientists theorize that a neutron star, only 10 miles in diameter, would have about 1-1\2 times the mass of Earth's sun. The Oriented Scintillation Spectrometer Experiment (OSSE) captured, in September of this year, the best ever observation of the glow of gamma radiation from the disk of the Milky Way galaxy. The glow was caused by matter and antimatter annihilating each other. "OSSE continues to operate very successfully. During the first nine months of the mission, OSSE has achieved excellent observations of several galactic sources as well as a number of other galaxies that may be associated with the centers of these distant galaxies," according to Dr. James Kurfess Principal Investigator for OSSE, Naval Research Laboratory, Washington, D.C. "OSSE has shown, with unprecedented sensitivity, the gamma- ray glow from matter-antimatter annihilation. One surprise is that the observations are not providing strong evidence that the emissions may be coming from some unknown compact objects located somewhere toward the center of the galaxy," Kurfess said. - more - - 3 - OSSE also has acquired observations of many solar flares, often following a solar flare trigger signal from the BATSE which results in an automatic re-pointing of OSSE's detectors toward the sun. The Imaging Compton Telescope (COMPTEL) continues to operate very well. "We are extremely pleased with the operation of our instrument, and we currently are making a very accurate gamma-ray map of our galactic plane," according to COMPTEL Principal Investigator Volker Schoenfelder, Max Planck Institute, Germany. "The overall operation of the observatory has been nothing short of superb," according to Paul Pashby, Project Manager, Goddard Space Flight Center, Orbiting Satellite Project. Pashby went on to say that the massive observatory "is extremely responsive and a joy to work with." The Compton Observatory, built by TRW Inc., Redondo Beach, Calif., is the second of NASA's "Great Observatories." The first was the Hubble Space Telescope, launched in April 1990. The third will be the Advanced X-ray Astrophysics Facility, expected to be launched in 1998. Deployed April 7, 1991, from the Space Shuttle Atlantis, Compton currently orbits Earth at an altitude of 268 by 262 miles. The Compton Observatory was developed and is managed and operated by Goddard Space Flight Center, Greenbelt, Md., for NASA's Office of Space Science and Applications. - end - A video (B roll GRO general info.) is available to media representatives by calling NASA Headquarters Audio/Video Branch on 202/453-8594. Photographs to illustrate this story are available by calling 202/453-8375. Photo Nos. Color B&W 92-HC-18 92-H 20 92-HC-19 92-H-21 92-HC-20 92-H-22