Astro-2 Public Affairs Status Report #25 6:00 a.m. CST (12/5:22 MET), March 14, 1995 Spacelab Mission Operations Control Marshall Space Flight Center Huntsville, Ala. The second Astro Observatory (Astro-2) mission continues as STS-67 crew members aboard the Space Shuttle Endeavour pointed three ultraviolet telescopes at celestial objects last night. The Ultraviolet Imaging Telescope (UIT) imaged NGC 2300, a cluster of galaxies that emits large quantities of X-rays. The study of clusters can provide a wealth of information to astronomers. Astro-2 data may provide UIT scientists with a better understanding of the relationship between galaxies in a cluster, the relationships between different levels of clusters and star formation in clusters of galaxies. UIT also imaged a globular cluster, NGC 5272, that contains relatively old stars. The low metal content in this cluster of stars indicates they were formed early in the life of the Milky Way galaxy. The telescope, image intensifiers and cameras of the UIT instrument are helping astronomers search for hot accreting binaries, hot white dwarfs, planetary nebulae and objects associated with X-ray sources in globular clusters. The study of young stellar populations in galaxies continued when UIT was pointed at a galaxy field in the spiral galaxy Andromeda. Approximately half of UIT's Astro-2 science program is devoted to the study of star-forming galaxies such as this one. A unique feature of UIT is the identification of thousands of individual hot stars in other galaxies that shine brightly in the ultraviolet. These hot stars may be observed later by the Hubble Space Telescope. UIT imaged another spiral galaxy, NGC 925, to provide images for Guest Investigator Dr. Wendy Freedman's atlas of spiral galaxies. UIT and the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) were pointed at the moon again last night. UIT imaged the moon to help astronomers, such as Guest Investigator Dr. Randy Gladstone, learn more about the surface properties of the moon. Scientists will develop and analyze the UIT film after Endeavour returns to Earth to understand future ultraviolet images of asteroids and other planetary satellites. WUPPE scientists observed the moon, looking at the reflection of ultraviolet light for distinctive differences in the maria (dark areas of the lunar surface) and highlands (brighter surface features of the moon). The Hopkins Ultraviolet Telescope (HUT) was used to observe a radio- loud quasar in the far- and extreme-ultraviolet wavelengths. HUT Principal Investigator Dr. Arthur Davidsen will analyze the Astro-2 data of this quasi- stellar object (located in the constellation Eridanus) to understand more about the shape of its ultraviolet spectrum. Davidsen is looking for the region of the ultraviolet spectrum where the hydrogen becomes opaque to radiation. He will then compare what he learns from these observations with what astronomers already know about the disk-shaped structure of stellar matter surrounding a black hole, testing the theory that quasars are powered by supermassive black holes. Hopkins scientists also observed the Seyfert galaxy NGC 5548 with HUT last night. The ultraviolet absorption lines in the HUT spectrum will be used in conjunction with earlier X-ray observations to determine the physical conditions in the hot absorbing gas. The absorbing gas in this Seyfert 1 galaxy may be the "reflecting medium" that produces the polarized reflection spectrum seen in Seyfert 2 galaxies such as NGC 1068. Two elliptical galaxies were also observed by HUT last night. Elliptical galaxies, which are spherical with no clearly defined internal structure, contain older, more evolved stars. Galaxy M87, the central galaxy in the Virgo cluster, shows signs that star formation may be occurring even though elliptical galaxies do not have enough stellar matter for new star formation. Another galaxy, known as M60, is being observed during this mission because it has a very high "ultraviolet upturn" Ð an excess of ultraviolet output for an old star population. The UIT team is also very interested in these targets Ð UIT collected ultraviolet images of both galaxies in support of several science programs. The WUPPE telescope was calibrated during an observation of Beta- Ursa Majoris, a star that remains relatively constant in luminosity. The surrounding area of this star is virtually dust free, giving WUPPE scientists a good, clear target to determine if there have been any changes in the performance of their telescope during this mission. HUT and WUPPE scientists used their ultraviolet telescopes to study a binary star system known as a magnetic cataclysmic variable. This two-star system, called AM Herculis, has a white dwarf star that pulls material away from its companion red star. A strong magnetic field on the white dwarf causes stellar material from the red star to accumulate on the white star's poles. Information about the dynamics of mass transfer in a binary star system is important because accretion, or the accumulation of gas, is essential to many astrophysical situations, such as star and planetary formation. During the next 12 hours, the STS-67 crew will point the astronomical telescopes to a newly discovered nova, a young planetary nebula, supernova remnants, the Large Magellanic Cloud and ultraviolet-bright stars in globular clusters. 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"