Astro-2 Public Affairs Status Report #29
6:00 a.m. CST (14/5:22 MET), March 16, 1995
Spacelab Mission Operations Control
Marshall Space Flight Center
Huntsville, Ala.


   All three ultraviolet telescopes were pointed at Jupiter and one of
its 16 moons, Io, as the second Astro Observatory (Astro-2) mission
continued aboard the Space Shuttle Endeavour last night.

   The science team for the Hopkins Ultraviolet Telescope (HUT)
recorded spectrographic data about ultraviolet emissions around Io.
HUT scientists are especially interested in how Jupiter's
magnetosphere and torus, a donut-shaped field of ionized particles
that follows Io's path around Jupiter, are affected by the reddish
particles erupting from Io's volcanoes.

   Astronomers with the Wisconsin Ultraviolet Photo-Polarimeter
Experiment (WUPPE) team observed Jupiter to learn more about the
polarization properties of its atmosphere.  The Ultraviolet Imaging
Telescope (UIT) scientists used one of their two wide-field cameras to
produce ultraviolet images of Jupiter to determine the planet's
reflectiveness and cloud structure and provide ultraviolet images of
the entire Jovian system.

   HUT continued the search for helium in the intergalactic regions of
space last night, using a quasar (Q 1542+54) as background lighting.
HUT scientists are looking for evidence of helium left over from the
primordial fireball that many believe marked the birth of the
universe.  Helium reveals itself as a telltale absorption line at a
certain extreme ultraviolet wavelength.  Principal Investigator Arthur
Davidsen will use HUT's spectrograph to search for the characteristic
signature created when helium atoms absorb light from this quasar.

   HUT was also used to observe Markarian 66, a starburst galaxy, for
Guest Investigator Dr. Claus Leitherer of the Space Telescope Science
Institute in Baltimore, Md.  Leitherer is using HUT's capacity to
detect short ultraviolet wavelengths to study the ionized radiation
that escapes from bright, relatively nearby starburst galaxies.  HUT
observations of the far ultraviolet radiation from these galaxies will
be used to determine whether they could play an important role in
ionizing the intergalactic medium.

   UIT imaged NGC 6318, a relatively old cluster of stars.  This
cluster of stars has a low metal content, indicating it was formed
early in the life of the Milky Way galaxy.  Since most hot stars emit
radiation in the ultraviolet and cooler stars emit in the lower
ultraviolet range, the UIT instrument is especially suited for making
images of these types of stars.  Astronomers will analyze these
Astro-2 images, looking for hot accreting binaries, hot white dwarfs,
planetary nebula, and objects associated with X-ray sources.

   As UIT made images of a faint dwarf galaxy known as IC 2574, HUT
made spectrographic recordings and WUPPE observed the orientation of
the ultraviolet energy being emitted from the galaxy.  Because this
type of galaxy emits such a faint trace of ultraviolet radiation, very
little is known about the formation of young stars there.  Astro-2
scientists are using their sensitive telescopes to explore this
little-known region of the universe.

   UIT was also pointed at the Baades Window, an unusually clear line
of sight towards the center of our Milky Way galaxy.  Because of the
relative lack of obscuring dust in this field of view, the UIT can
image stars and star clusters in the central bulge of the galaxy,
where stars are thought to be both ancient and rich in metals.

   WUPPE and HUT observed a reflection nebula near the star Eta
Carinae.  Reflection nebulae are colorful objects.  Starlight is
scattered by dust grains, producing brilliant illumination in the
cloud.  WUPPE scientists will analyze their data to learn more about
the chemical composition, size, distribution and shape of the dust
grains.  HUT astronomers observed the nucleus and surrounding region
of this nebula, searching for effects of the shock wave that was
created when the nova exploded.

   WUPPE and HUT also jointly observed AO Cassiopeia, a close binary
star system (two stars so close that they not only orbit each other
but actually influence each other's evolution).  Astronomers have
observed that the more evolved a star is (in a close binary system),
the less massive the star becomes because it donates material to the
younger star.  WUPPE scientists are studying the effects of the
dust-scattering processes in the distorted atmospheres of close
binaries.  These data will provide new information about the evolution
of these stars and help astronomers learn more about the mass transfer
of material between close binaries.

   The WUPPE telescope also gathered data about the orientation of
dust grains between the stars last night.  To help scientists study
this polarization of interstellar medium, WUPPE was pointed at three
stars, which served as background lights to illuminate the
interstellar dust.  As astronomers learn more about the polarization
of interstellar medium, they can make allowances for this intervening
matter when studying other celestial objects.

   During the next 12 hours, the Astro-2 ultraviolet telescopes will
be pointed at the moon, two Seyfert galaxies, and single and multiple
star systems to study electron scattering.  These astronomical
instruments will also observe interstellar medium and young star
populations in a galaxy.


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"