The Universe in X-rays.

Various programs and discoveries of X-ray astronomy from space-based instruments are reviewed. The first X-ray object discovered was Sco X-1 during a rocket flight in 1962. The Uhuru satellite identified dozens of X-ray sources, including Cyg X-1, which is a possible black hole. The HEAO-1 satellite carried detectors large enough to permit some resolution of the X-ray sources. X-ray telescopes were used on Skylab and on HEAO-2, employing a parabolic mirror at the aperture followed by a hyperbolic mirror which focused the original image onto a detector. The HEAO-2, also known as the Einstein Observatory, allowed discovery of a number of quasars. The X-ray telescope satellites Copernicus, Einstein, and Ariel VI were successively shut down, leaving only the Japanese spacecraft Hakucho detecting burster events. Future X-ray observing satellites such as AXAF, Exosat, and Rosat are outlined.