Orbiting Tribute to a Gamma-Ray Pioneer

THE United States National Aeronautics and Space Administration's orbiting Gamma Ray Observatory is no more. Long live the Arthur Holly Compton Gamma Ray Observatory.It's fitting that this second satellite in NASA's planned series of four "Great Observatories" should take the name of the late Nobel Prize laureate. As University of Chicago physicist John Simpson observed, "In one way or another, all the fundamental interactions of gamma rays with matter invoke the effects Compton studied." Renaming the satellite also focuses attention on what, so far, is one of NASA's outstandingly successful missions. Besides the Hubble Space Telescope and Compton satellite, the Great Observatory series is to include X-ray and infrared radiation observing vehicles. Hubble's troubles launched the series on a negative note. They have raised justified questions about NASA's management of the program. Yet working quietly since the space-shuttle Atlantis put it on orbit April 5, the $557-million, 17.5-ton Comp ton Observatory has already made discoveries of revolutionary importance. Surveying the sky from its 273-by-280 mile-high (440-by-450 kilometer) orbit, it has found enormously energetic split-second gamma-ray bursts appearing from all directions. Gamma rays are electromagnetic radiation that is more energetic even than X-rays. Astronomers had thought that these bursts, which appear without warning, probably come from objects within the plane of our Milky Way galaxy. Compton is detecting them in all parts of the sky at the rate of about one a day. It has detected more than 117 of them so far. The new data reflect unknown types of sources that are located either deep in the universe or close by our galaxy. Either way, the findings show that the cosmos still holds unsuspected mysteries for astronomers. Stephen Maran, spokesman for the American Astronomical Society, likens this revelation to discovery of the quasars in the 1960s. Quasars (quasi-stellar objects) are the most powerful objects known. Some of them also are the most distant objects yet detected. Compton's early observations of Quasar 3C279 confirm that reputation. Carl Fichtel, a Compton Observatory investigator at the NASA Goddard Space Flight Center in Greenbelt, Md., says that this quasar, located some 7 billion light years away, turns out to be "the most distant and, by far, the most luminous gamma-ray source ever seen." It is emitting 100 million times the gamma-ray power radiated by our own galaxy. Yet the object was undetectable before 1982. Dr. Fichtel calls this discovery "dramatic confirmation of the dynamic nature of the gamma-ray sky and an example of the most energetic processes in nature." Arthur Compton won the 1927 Nobel Prize for showing that high-energy photons (X-rays or gamma rays) bounce off electrons the way billiard balls bounce off each other. It reflects the dual nature of electromagnetic radiation, which sometimes acts like a wave and sometimes like a particle. Compton-scattering is a key process that helps astrophysicists understand cosmic gamma-ray activity and also helps the orbiting observatory "see" the sky in gamma-ray light. Let's cheer on the Compton Observatory. It honors a great scientist and shows the positive side of NASA's astronomical satellite series.