Astro-2 Public Affairs Status Report #17 6:00 a.m. CST (8/5:22 MET), March 10, 1995 Spacelab Mission Operations Control Marshall Space Flight Center Huntsville, Ala. The crew of STS-67 continued to gather science for the second Astro Observatory (Astro-2) mission throughout their eighth night aboard the Space Shuttle Endeavour. Payload Specialist Ronald Parise pointed the Hopkins Ultraviolet Telescope (HUT) at a binary star system called AM Herculis. This star system has a white dwarf and a normal low-mass companion star, locked in a tight orbit around each other. As these two stars move around each other, material from the low-mass star is transferred to the white dwarf. During this transfer, matter from the companion star is heated as it spirals down onto the white dwarf, generating a great deal of ultraviolet emission. Because of these outbursts (which may occur every couple of weeks to months or years), binary star systems such as these are called cataclysmic variables. Several Astro-2 observations have been made of the AM Herculis binary star system because of its unique characteristics. In this star system, the white dwarf star has a strong magnetic field. As material from the companion star is being transferred, the magnetic field of the white dwarf causes the matter to assemble around its magnetic poles. HUT astronomers are using observations of cataclysmic variables during this mission to learn more about how the magnetic transfer of matter differs from the normal transfer of matter between binary stars. In another study of cataclysmic variables, HUT observed EM Cygni, a dwarf nova which has no magnetic field. During the night portion of two separate orbits, Pilot William Gregory maneuvered Endeavour into the proper orbital position for Parise to align HUT for observations of quasar 1700+64. HUT scientists are using this quasar, located in the constellation Draco, to search the vast region of space between distant galaxies for evidence of helium left over from the primordial fireball that many scientists believe marked the birth of the universe. HUT Principal Investigator Dr. Arthur Davidsen is using the light from this extremely distant quasar as back lighting to shine through the intergalactic medium. Astronomers will use data from these Astro-2 observations to verify recent findings from the Hubble Space Telescope as well as measure the density and ionization state of the intergalactic helium. Parise also aligned HUT with two white dwarf stars for a study by HUT Guest Investigator Dr. David Finley. White dwarfs are one of the extremely dense remnants of normal stars like the sun. Those being studied with HUT are young and extremely hot stars. Finley is using these HUT observations to get very accurate measurements of the temperatures and surface gravity of white dwarf stars and determine the properties of hydrogen under conditions of extreme temperature and pressure. Another HUT investigation looked at a portion of a supernova remnant called the Cygnus Loop. Guest Investigator Dr. John Raymond observed this "middle-aged" supernova remnant to study the physics of collisionless shocks, the destruction of grains in shocked gas, instabilities behind radiative shocks, and shock wave parameters. Parise aimed HUT at Jupiter's moon Io again last night. A recent volcanic eruption on Io ejected material into Io's atmosphere and onto its surface. HUT scientists are observing Io to detect changes in the number of sulfur and oxygen ions in its atmosphere as a result of the volcanic eruption. The Ultraviolet Imaging Telescope (UIT) imaged two globular clusters last night a metal-poor cluster and a metal-rich cluster. The metal-poor globular cluster, known as NGC 2808, is made up of relatively old stars. The low metal content of these stars indicates they were formed early in the life of the Milky Way galaxy. Astronomers theorize that the metal-rich globular cluster, called 47 Tucanae, once belonged to a small metal-rich galaxy that was swallowed up by the Milky Way in the remote past. The UIT science team will use images from these two types of globular clusters to search for hot binaries that are transferring matter from the massive star to its low-mass companion (accretion), hot white dwarfs, planetary nebulae, and objects associated with X-ray sources in globular clusters. Payload Specialist Sam Durrance pointed the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) telescope at a young stellar object, still forming out of interstellar dust. WUPPE astronomers will analyze data about the polarization of the ultraviolet light in this object to learn more about the star- formation processes taking place there. WUPPE scientists also gathered data about hot stars with bright emission lines last night. Principal Investigator Dr. Arthur Code will use information about the orientation of light waves traveling through the circumstellar disk of this star, called 48 Persei, to understand more about the material around it. Although this type of star was first noted because of bright emission lines, over 100 years of study have shown stars like these to be unusual in many other respects. Each spectral region studied provides astronomers with information about a different part of the material around the star. During the next 12 hours, the Astro-2 crew will be aligning the HUT, UIT and WUPPE telescopes to observe cataclysmic variable stars, young star populations in galaxies, metal-poor star clusters and a 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"