Paula Cleggett-Haleim Headquarters, Washington, D.C. July 25, 1991 (Phone: 202/453-1549) Randee Exler Goddard Spaceflight Center, Greenbelt, Md. (Phone: 301/286-7277) RELEASE: 91-117 NASA OBSERVATORY DETECTS STRONGEST GAMMA RAY SOURCE The Goddard Space Flight Center's Energetic Gamma Ray Experiment Telescope (EGRET), one of four instruments aboard NASA's Gamma Ray Observatory (GRO), has detected "the most distant and by far, the most luminous gamma-ray source ever seen," according to EGRET Principal Investigator Dr. Carl Fichtel. The EGRET team, led by Fichtel, reported in a telegram to the International Astronomical Union, Cambridge, Mass., that a source of intense localized gamma radiation, was detected between June 15 and 28. The source of this radiation has been identified with the variable Quasar 3C279, located in the constellation Virgo, approximately 7 billion light years from Earth. Fichtel says that the quasar is emitting a large 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 a thousand electron volts. The luminosity or total energy emitted by this quasar is approximately 10 million times that of the total emission of the Milky Way galaxy, according to the Goddard scientist. "Quasar 3C279 is a variable quasar, meaning that its intensity changes over time," Fichtel explained. At its present intensity, this source should have been visible to two previous gamma ray missions -- NASA's Small Astronomy Satellite and the European Celestial Observation Satellite. In the telegram, the EGRET team states that "neither reported a detection during 1972/73 and 1975-82, respectively." - more - - 2 - Summarizing, Fichtel said, "Between 1982 and 1991, this quasar has gone from being undetectable to being one of the few brightest objects in the gamma ray sky. Because of its large distance, this observation is dramatic confirmation of the dynamic nature of the gamma ray sky and an example of the most energetic processes in nature." GRO, the second of NASA's Great Observatories, was launched April 5, 1991, aboard the Space Shuttle Atlantis to study high-energy radiation from deep space. EGRET is the largest instrument ever assembled in-house by the Goddard Space Flight Center, Greenbelt, Md. The 7.3 feet by 5.4 feet, 4,001 pound EGRET is between 10 to 20 times larger and more sensitive than any high-energy gamma-ray telescope ever to orbit the Earth. Co-principal investigators for EGRET are Dr. Carl Fichtel, Goddard Space Flight Center, and Dr. Klaus Pinkau, Max Planck Institute, Federal Republic of Germany. EGRET is the result of a joint effort by scientists and engineers at Goddard; Stanford University, Calif.; Max Planck Institute; and Grumman Aerospace Corp., Bethel, N.Y. The Gamma Ray Observatory was developed, managed and operated by the Goddard Space Flight Center for NASA's Office of Space Science and Applications, Washington, D.C. - end -