Astro-2 Public Affairs Status Report 9	
6:00 a.m. CST (4/5:22 MET), March 6, 1995	
Spacelab Mission Operations Control	
Marshall Space Flight Center	
Huntsville, Ala.

     The Astro-2 instruments spent the fourth night of the mission
viewing spiral, radio and other types of galaxies as well as two types
of binary star systems and some individual stars.  Also, the search
for intergalactic helium continued as these telescopes observed some
of the most distant objects in the known universe.  All the Astro-2
instruments, Spacelab, and the Instrument Pointing System continue to
perform well

     "I think we've just set a world record for acquisition,"
commented Mission Specialist John Grunsfeld upon the swift targeting
of GD394, a white dwarf star in the Cygnus constellation, for the
Hopkins Ultraviolet Telescope (HUT).  Earlier in the evening, an
edited StarView software package was uplinked to Space Shuttle
Endeavour.  This upgrade made what Alternate Payload Specialist Scott
D. Vangen called, "a world of difference" in improving acquisition
times for the Astro-2 instruments.

     White dwarf stars, such as GD394, have magnetic fields stronger
than any that can be formed in laboratories on the earth.  They are
interesting for astronomers because they provide a laboratory for
studying the effects of strong magnetic fields on radiation.  One such
effect is that the light coming from these objects is highly
polarized, or is vibrating in a single direction.

     HUT scientists made further ultraviolet observations of the
bright quasar 1700+64 in the hope of discovering intergalactic helium.
Astronomers have been searching for evidence of intergalactic matter
left over from the formation of the universe for 30 years, and HUT was
originally designed with this goal in mind.  If ionized helium is
present in the space in front of a quasar, it should block out the
helium signature in HUT's far ultraviolet spectrum of the quasar--
thus establishing the existence of the ionized helium in the
intergalactic medium.

     Binary star systems, or pairs of mutually orbiting stars, again
became prime objects for observations selected by the HUT science
team.  Earlier in the evening, the HUTand Wisconsin Ultraviolet Photo
Polarimeter Experiment (WUPPE) instruments looked at the symbiotic
binary Z Andromedae, located in the constellation Andromeda, as part
of the joint HUT/WUPPE investigator program.  Symbiotic stars are
binary systems in which the component stars have radically different
temperature ranges.  Guest Investigator Dr. Brian R.  Espey used HUT
and WUPPE to study the ultraviolet spectrum of Z Andromedae, in order
to improve measurements of the hotter star's temperature.

     The first ever ultraviolet observations of a very spectacular
binary star system, Nova Aquilae, were made early this morning by
members of the WUPPE science team.  This system, consisting of a white
dwarf and a more normal star, became a bright nova, or a new explosive
object, just about a week ago.  This binary's explosions occurred due
to the interactions between the two stars.  Specifically, hot gas from
the normal star was pulled by gravity toward the white dwarf star's
surface.  As this material collected on the white dwarf's surface,
thermonuclear fusion took place, resulting in sudden and extremely
bright explosions.  As WUPPE co-investigator Chris Anderson described
this process, "a week ago it was a faint, unobtrusive star....then it
suddenly became thousands of times brighter."

     Another target observation for WUPPE scientists last night
included one of the most beautiful and colorful types of objects
known.  Reflection nebula NGC7023 is the brightest of its kind, in
which starlight is scattered by dust grains, producing brilliant
illumination in its cloud.  The WUPPE team is using its observations
of this nebula to further study the nature of dust grains in
interstellar space.

     Celestial objects chosen for observation by the Ultraviolet
Imaging Telescope (UIT) last night included the spiral galaxy NGC1097
and the radio galaxy Centaurus A.  Centaurus A is the nearest active
galaxy to our own and is one of the most prominent radio sources in
the Southern Hemisphere.  UIT scientists are examining it to study
star formation processes and stellar evolution there.  Radio galaxies
like Centaurus A emit radiation a million times stronger than galaxies
like ours.  Many questions surround radio galaxies, including those
concerning the possible relationships between these galaxies, quasars
and other energetic sources.

     UIT scientists also selected a cluster in the Small Magellanic
Cloud, an irregular galaxy, as a target.  Eighteen targets within the
local group of galaxies are candidates for observation on Astro-2, and
UIT is conducting ultraviolet studies on their structures.  These
scientists are also studying the physics of star formation in
supernova remnants contained in these galaxies.  While UIT used its
large field of view to image regions of the Small Magellanic Cloud,
HUT observed the supernova remnants within it.  HUT's large
spectrograph apertures permit observations of the remnants'
temperature, density and chemical composition.

     The next twelve hour shift will begin with a variety of
observation targets, including an elliptical galaxy, a white dwarf
star, and a variable star as the Astro-2 mission enters its fifth day
of ultraviolet explorations.

     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"