Astro-2 Public Affairs Status Report #10 6:00 p.m. CST (4/17:22 MET), March 6, 1995 Spacelab Mission Operations Control Marshall Space Flight Center Huntsville, Ala. During another day of very smooth operations, the Astro-2 crew and science teams at Spacelab Mission Operations Control kept up a steady pace of ultraviolet astronomical observations. The Hopkins Ultraviolet Telescope (HUT) and Ultraviolet Imaging Telescope (UIT) teams selected the celestial objects viewed today, but all three Astro telescopes participated in the majority of the observations. Two cataclysmic variables were on today's menu of HUT targets. These are systems of two stars, orbiting extremely close together, where a white dwarf in the final stage of its life cycle is paired with a more "normal" star somewhat similar to our sun. Occasionally their interactions create an outburst, or sudden increase in energy emissions. This interchange of matter between stars, called accretion, is of great interest to the HUT and Wisconsin Ultraviolet Photo-Polarimeter Experiment teams because it is essential to many astrophysical situations such as the generation of energy by quasars. This morning, the Astro telescopes observed VW Hydri, a cataclysmic variable which undergoes outbursts of energy roughly every 20 days. Though it was in a relatively low state of activity today, VW Hydri will be monitored at intervals throughout the mission in hopes of getting measurements in both an outburst and a non-outburst stage. This afternoon, the teams viewed another variable, YZ Cancri, which is located in the constellation Cancer. The telescopes made two observations of elliptical galaxy M 105 in the constellation of Leo the Lion. HUT studied the nature of stars that put out an unexpected amount of ultraviolet light in this type of galaxy. HUT observations from Astro-1 indicate it comes from older, low mass stars in a previously unknown stage of their evolution. Individual stars chosen for viewing by HUT ranged from massive stars to compact white dwarfs. Observations of the hot, massive O-type star HD 94963, in the Southern Hemisphere constellation Carina, will be added to an "atlas" of hot stars which may assist in stellar population studies in galaxies. The white sub-dwarf star, Schweizer-Middleditch, was too close to the sun to be observed on Astro-1, so Astro-2 astronomers were particularly pleased to observe it today. It lies behind the supernova remnant SN1006, which is the debris of a star that exploded in 1006 A.D. HUT scientists are studying the star's spectrum for signs that its light is being absorbed by iron in the supernova remnant. Theories predict that a large quantity of iron was ejected by the exploding star. Other observations in the HUT time block included observations in two parts of the Cygnus Loop supernova remnant, the leftover gas from a stellar explosion some 20,000 year ago. Seyfert galaxy Markarian 3 also was studied. Such active galaxies have unusually bright centers that resemble the more distant and more luminous quasars, and they are believed to harbor massive black holes. The Ultraviolet Imaging Telescope (UIT) took images for an ultraviolet census of "Selected Area 57," a portion of the sky that has been intensively mapped at many other wavelengths. "This is one of two parts of the sky that astronomers all over the world have agreed to study as closely as possible with every new technology that comes along," said UIT Team Member Dr. Steve Maran. UIT's wide-field images should provide new information on faint objects that have not yet been catalogued. The UIT team will count galaxies down to faint ultraviolet magnitudes and search for quasars, for galaxies that are receding very quickly as the universe expands, and for distant clusters of star-forming galaxies. "If we see something we don't understand, we can go back and look at images made in other wavelengths to help define it," said UIT Principal Investigator Ted Stecher. "It's something like using the Rosetta stone to decipher something that was previously unknown . UIT made images for two other science programs that could shed light on the life cycles of stars. The instrument photographed a globular cluster known as NGC 6752. Ultraviolet images will pick out hot stars, at an unusual stage of their evolution, from the tightly grouped assembly of old stars in the cluster. UIT also viewed the spiral galaxy NGC 3351. The arms of spiral galaxies, which look something like cosmic pinwheels, are made up of interstellar matter and bright young stars. The images should be useful to ultraviolet astronomers in assessing the amount of star formation in progress within the galaxies. The Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) team reported that one of last night's observations seems to confirm a surprise finding from Astro-1. According to WUPPE Co-Investigator Dr. Geoff Clayton, the team again saw evidence of two types of polarized "dust" in an interstellar cloud. An Astro-1 observation had indicated that some parts of the dust were like grains of sand, while others were more like soot. Ultraviolet radiation reflected from both types of grains was polarized, or vibrating in a preferred direction, indicating that both were lined up to the magnetic field. But until last night, no other observation had detected polarization in the "soot." "Last night, we saw a 'bump' in our polarization measurements just where it was on Astro 1," said Clayton. "We hope to see more bumps on later observations. If we find out this is real, we'll have to go back to the drawing board and find out why these grains are aligned as they are." Observations scheduled for tonight include more supernova remnants, another globular cluster, and a variety of galaxies. 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"