Astro-2 Public Affairs Status Report #27
6:00 a.m. CST (13/5:22 MET), March 15, 1995
Spacelab Mission Operations Control
Marshall Space Flight Center
Huntsville, Ala.

   From their platform in the payload bay of the Space Shuttle
Endeavour, the three ultraviolet telescope of the second Astro
Observatory (Astro-2) mission continued to provide information about
the ultraviolet energy in our universe last night.

   STS-67 Pilot William Gregory placed the orbiter in the proper
attitudes for Mission Specialist John Grunsfeld to align the
Instrument Pointing System (IPS) to selected areas in the sky.
Payload Specialist Ronald Parise then aligned the Wisconsin
Ultraviolet Photo-Polarimeter (WUPPE), the Hopkins Ultraviolet
Telescope (HUT) and the Ultraviolet Imaging Telescope (UIT), allowing
them to lock on to four targets in the Large Magellanic Cloud (LMC).
	
   Guest Investigator Dr. Geoffrey Clayton of the University of
Colorado in Boulder will use WUPPE and HUT information about
ultraviolet polarization in the LMC, comparing these data to what
scientists already know about the nature of dust particles in the
interstellar medium of our own galaxy.  Using selected stars of the
LMC to back light the dust and gas, Clayton can examine the behavior
of the many dust grains found there.  In contrast, a bright, blue-hot
supergiant star, Sanduleak 67-90, was the target of one of last
night's four LMC observations to let astronomers study the dynamics of
ultraviolet emissions in an area where there was not a substantial
amount of stellar dust.  UIT takes images of all fields in the
Magellanic Clouds, and obtained excellent data in parallel with the
observations being made by HUT and WUPPE.

   In other observations over night, HUT scientists got another chance
to learn more about a halo of ultra-hot gases they believe surrounds
our Milky Way galaxy.  HUT was pointed at the brightest quasar in the
sky, 3C273, which is approximately two billion light years away.  As
ultraviolet light from the quasar shines through interstellar space,
it is absorbed by the halo that surrounds our galaxy.  Scientists at
the Johns Hopkins University in Baltimore, Md., will analyze these
data in the months following Astro-2, testing theories about whether
the halo actually exists, and if so, how hot the gas is and how far it
extends.

   Mission Specialist Wendy Lawrence maneuvered the orbiter into
position, Payload Commander Tammy Jernigan aligned the IPS and Payload
Specialist Sam Durrance pointed HUT to again record ultraviolet
spectrographic data of the "young" supernova remnant, SN 1006.  This
supernova remnant, first documented by Chinese astronomers in the year
1006, is giving HUT Guest Investigator Dr. John Raymond an opportunity
to study the physics of shock waves before they hit a substantial
amount of interstellar material (where the gas begins to cool off and
slow down).  Traveling at approximately 1,200 miles (2,000 kilometers)
per second, the shock waves from this young supernova remnant are
providing new insights into the characteristics of interstellar medium
surrounding the site of a supernova explosion.

   Parise also pointed HUT at elliptical galaxies called M60 and M89
last night.  These galaxies are part of the Virgo cluster, a huge
cluster of galaxies centered some 50 million light years from Earth.
Astronomers have long been interested in these galaxies because of
their very high ultraviolet upturn Ð an excessive output of
ultraviolet light for an old star population.  HUT and UIT scientists
are interested in these targets to learn more about what is causing
the excessive amount of ultraviolet light. The theory was that younger
star- formation galaxies produce more ultraviolet emissions than older
star populations.  However, observations of galaxies such as M60 and
M89 are leading scientists to believe that some of these old low mass
star populations may be in a more advanced stage of evolution.  UIT is
making a two- dimensional map of the ultraviolet upturn across the
face of the M60 galaxy.  Near the end of the M89 observation, WUPPE's
dedicated experiment computer experienced a brief software problem.
Durrance recycled power to the computer, which reset the software.
The WUPPE science team has reactivated their telescope from the ground
and resumed operations.

   Durrance and Parise pointed HUT at several other celestial objects
during the night.  HUT observed planetary nebula NGC 1360, a cloud of
gas and matter surrounding a star.  The nebula glows because the
ultraviolet radiation from the star ionizes the material in the
surrounding cloud, which, in turn, emits energy at a variety of
wavelengths.  HUT scientists will study the ultraviolet light from the
nebula and the star to learn more about the material making up the
nebula and the star at its core.
	
   UIT imaged NGC 752, an open star cluster, searching for hot
accreting binaries, planetary nebulae and X-ray sources.  UIT
scientists are particularly interested in probing star clusters such
as this for white dwarfs and other faint, hot stars.
	
   STS-67 crew members will spend the next 12 hours pointing the
Astro-2 telescopes to the heavens to observe Io (Jupiter's moon), a
star in the Small Magellanic Cloud, an elliptical galaxy, a globular
cluster, two galaxies for inclusion in the Atlas of Spiral Galaxies, a
Wolf-Rayet star and will continue observations of interstellar dust in
the Large Magellanic Cloud with all three instruments.


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"