Astro-2 Public Affairs Status Report #26 6:00 p.m. CST (12/17:22 MET), March 14, 1995 Spacelab Mission Operations Control Marshall Space Flight Center Huntsville, Ala. The majority of today's Astro-2 observations were of objects in the Large and Small Magellanic Clouds. These irregular galaxies, in the southern hemisphere sky, are satellites of our Milky Way galaxy. They are gravitationally bound with some 20 others that make up our "local group" of galaxies. The Ultraviolet Imaging Telescope made the mission's first photographs of Supernova 1987A. The February 1987 stellar explosion, in the Large Magellanic Cloud, was the first supernova explosion visible to the naked eye since 1604 A.D., six years before the first telescope was used to view the heavens. The supernova reached its brightest visible radiation level in May 1987, but scientists believe an intense flash of ultraviolet light occurred almost at the moment of the explosion, when the outer layers of the supernova lifted away. UIT is attempting to photograph the light "echo," or reflection of this maximum ultraviolet output, as it bounces off sheets of dust in space. UIT's Astro 1 photographs of Supernova 1987A indicate the echo is extremely faint, so UIT is making a number of long exposures to capture it. "If we see the same phenomenon in several exposures, we can not only add them together to improve the quality of our observations; the repeated evidence assures us that what we are seeing is real," said UIT team member Dr. Steve Maran. An observation of N 79 looked at young star formation in a Large Magellanic Cloud star grouping called an "OB Association." Unlike other types of star clusters, there is insufficient gravitational attraction to hold these groups of very young, hot O and B stars together. Though formed at the same time, the stars are rapidly drifting apart. Other targets in UIT's eight-observation time block included two Large Magellanic Cloud open star clusters which are surrounded by emission rings. N 51, in the southern constellation Dorado, is an unusual nebula which appears to be a bubble blown in the interstellar gas by wind from a very massive hot star. The imaging telescope made limited observations of the area during Astro-1, and the science team hopes to collect more extensive data on this flight. N 70, in the southern constellation Hydra, is a region of space where the gas has been ionized. The UIT team will compare images made at two different wavelengths to help determine what caused the ionization. UIT also photographed the bar structure of the Large Magellanic Cloud, an elongated linear accumulation of stars in the galaxy, as part of its study of young star populations. Dr. John Raymond, of the Smithsonian Institution's Astrophysical Observatory, added to his study of interstellar shock waves with an observation of LMC 519, an old supernova remnant also in the Large Magellanic Cloud. Dr. Nolan R. Walborn got another observation of a hot O star in the open star cluster NGC 346, for his study of the strong stellar winds produced by these stars in the Large and Small Magellanic Clouds. This evening, Dr. Geoffrey Clayton began another block of observations for his study of interstellar dust in the Large Magellanic Cloud. Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) Principal Investigator Dr. Arthur Code is researching the sizes and chemical compositions of dust grains in the Milky Way's interstellar medium. Clayton is extending the sample to the nearby Large Magellanic Cloud, where interstellar chemical abundances are known to be quite different from those in our own galaxy. All three telescopes participated in the third Astro-2 observation of 47 Tucanae, a metal-rich globular cluster in the southern Milky Way. The Astro telescopes also viewed Centaurus A, the nearest active galaxy to our own and one of the most prominent radio sources in the southern hemisphere. Earlier today, the WUPPE science team selected NGC 3132, a young planetary nebula in the constellation Vela, for observation. A planetary nebula is a bright cloud ejected by the star at its center, believed to be a phase in the life of certain lower mass stars when they expel large amounts of material in to space. Sometimes called the "Eight-Burst" Nebula because its elliptical disk looks like several oval rings superimposed and tilted at different angles, NGC 3132 is one the few planetary nebulae known to have a binary star system at its center. WUPPE scientists will examine the light scattered by dust in the cloud to study the nature of the dust, which will eventually return to the interstellar medium. Ultraviolet Imaging Telescope images will test ionization and temperature levels within the nebula. The Hopkins Ultraviolet Telescope (HUT) took spectra of the cloud itself and of its binary star. The WUPPE team led the Astro telescopes back to the Nova Aquilae 1995. This was the mission's third look at the nova whose outburst, or sudden increase in brightness, was first observed some three weeks before the STS-67 launch. Successive polarization measurements during Astro-2 will allow WUPPE scientists to look for changes in the shape of the gas disk and for possible clumps ejected during the outburst. The HUT team chose the quasar 1211+143 as one of their targets today. Team members will study the shape of the quasar's ultraviolet spectrum to learn more about the intrinsic qualities of the quasar itself. First discovered in the 1960s, quasars are the most luminous and energetic, as well as the most distant, objects in the universe. They are believed to be powered by supermassive black holes at their centers. HUT observations will test the current understanding of accretion disks, or disks of matter being whirlpooled and sucked into the black hole. WUPPE's Large Magellanic Cloud dust study will continue into this evening. UIT has chosen two galaxies and an open star cluster for imaging tonight. The HUT team will lead observations of two quasars, several individual stars, a planetary nebula, an elliptical galaxy, and another supernova remnant. To follow the mission in progress, visit Astro-2's home page on the Internet World Wide Web: URL "http://astro-2.msfc.nasa.gov"