Hubble Space Telescope
Hubble, ROSAT yield dramatic space photos Dramatic new photographs taken with the Hubble Space Telescope (HST), far superior to previous, ground-based observations, were re leased earlier this month by the Na tional Aeronautics & Space Admin istration. NASA also released the first pictures taken by a n o t h e r spacecraft orbiting above Earth's at mospheric distortions, the Roentgen Satellite (ROSAT), launched by an unmanned rocket on June 1 to study cosmic x-ray emissions. The Hubble photos exemplify NASA's good news-bad news situa tion. The bad news is that the spher ical aberration in a mirror means HST, launched last April 25, will not yield the kind of results expected (C&EN, April 9, page 4) until repairs can be made by a space shuttle flight in 1993. Research plans are being re vamped accordingly. The good news, NASA associate administrator Lennard A. Fisk said recently, is that "we'll get outstand ing science from it, anyway." Most spectroscopy can still be done, he noted. Moreover, ultraviolet astron omy w o n ' t have the anticipated 10,000-fold advantage over previous work, but it still can yield a 1000fold advantage. And with image en hancement methods, HST also can give p h o t o s of u n p r e c e d e n t e d sharpness and clarity for objects with "reasonable contrast and brightness." For example (upper right), HST's faint-object camera, supplied by the
European Space Agency, has ob tained the clearest pictures ever of Pluto and its moon, Charon (below it in the photo). Pluto is the solar system's most distant object—now about 4.5 billion km away—and the only planet not visited by a fly-by spacecraft. The best ground-based image (middle right) can't clearly re solve the pair. Photos of Saturn (upper left), tak en by Hubble's wide field and plan etary camera at a distance of 1.4 bil lion km, also are better than from ground-based telescopes. The color was reconstructed by combining pictures in blue, green, and red light. In addition, HST's faint-object camera has obtained the most de tailed and highest-resolution optical images yet of the radio galaxy PKS 0521-36 (lower left), located about 1 billion light-years from Earth. A h i g h - e n e r g y "jet," about 30,000 light-years in length, streams out of the galaxy's nucleus.
One of the first photos from RO SAT—a cooperative program be tween the U.S., Germany, and the U.K.—shows the Abell 2256 cluster of galaxies (lower right). The image, taken by a High-Resolution Imager instrument, represents x-rays in the 0.4- to 2.5-keV range. Galaxy clusters are traditionally strong x-ray emit ters. Richard Seltzer October 22, 1990 C&EN