Astro-2 Public Affairs Status Report #28
6:00 p.m. CST (13/17:22 MET), March 15, 1995
Spacelab Mission Operations Control
Marshall Space Flight Center
Huntsville, Ala.

   With about a day and a half remaining for Astro-2 observations,
lead scientists for each of the telescope teams vied for superlatives
to describe the mission in a midday air-to-ground conversation with
the STS-67 crew.

   Hopkins Ultraviolet Telescope (HUT) Principal Investigator
Dr. Arthur Davidsen said, "For all of us, the Astro-2 mission has been
like a dream come true.  We've observed more than 100 different HUT
targets and had more than 300 pointings with two days to go, and we're
absolutely thrilled."

   "We're really pleased down here," Ultraviolet Imaging Telescope
(UIT) Principal Investigator Ted Stecher told the crew, quipping, "We
never thought we'd run out of film, but now we're a little worried
about it."  He said all the team's top priorities have been achieved,
with just a few secondary programs left to complete, and they have
photographed essentially all the objects they had originally planned
to view.

   Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE)
Principal Investigator Dr. Arthur Code agreed.  "We're delighted with
mission results, too.  Reality has exceeded our fondest dreams, and
we've obtained about three times as much data as we did on Astro-1 --
a whole treasure chest of goodies."

   Observations continued to stack up at a steady pace throughout the
day, interrupted only by a planned hour of orbiter flight control
system tests in preparation for Friday's landing.

   All three telescopes took ultraviolet data during a UIT-led
observation of M 87, a spectacular elliptical galaxy in the
constellation Virgo.  "We can get information for several of our
favorite scientific programs by viewing M 87," said UIT team member
Dr. Susan Neff.  The galaxy is thought to have grown to its large size
by swallowing up smaller neighbors in the Virgo galaxy cluster.  A
1994 Hubble Space Telescope observation of M 87 revealed a
spiral-shaped disk of gas swirling at an immense speed in the galaxy's
center, providing the first almost irrefutable evidence that
supermassive black holes do exist in the universe.  A fantastic jet of
material, moving at a large fraction of the speed of light, emanates
from the area of the black hole.  UIT's wide field of view allows it
to photograph some 12 to 14 Virgo cluster galaxies in the same frame.
UIT team members are studying the stellar populations in M 87 and also
the jet.  HUT concentrated on the gas around the black hole to find
out how it is stimulated by radiation from heated matter falling
toward hole.  WUPPE made ultraviolet polarization measurements to
determine the structure of the swirling gas.

   The Astro-2 telescopes made the mission's first observation of
Omega Centauri , a giant globular star cluster which is easily visible
in the southern hemisphere to the naked eye. Its brightness is due
both to its relative closeness to Earth (17,000 light years) and its
immense size (150 light years across and containing more than one
million stars).  UIT's single five-minute exposure of this star
cluster during Astro-1 was the first ever made in ultraviolet
wavelengths.  Even that brief snapshot showed an unusual number of
stars that did not conform to the theoretical pattern of stellar
evolution.  Also, since all stars in a globular cluster are formed at
the same time, it should follow that they would have the same chemical
composition, but this is not the case in Omega Centauri.  The longer
Astro-2 observation of this globular cluster, along with those of
other clusters throughout the mission, should give scientists more
clues for solving this stellar mystery.

   The telescopes also observed M 92, a much smaller globular cluster,
and UIT made photographs of the galaxies NGC 1512 and NGC 1365 for Dr.
Wendy Freedman's spiral galaxy atlas.

   The majority of WUPPE-led observations today centered on the team's
study of interstellar dust in our Milky Way and in its neighboring
galaxy, the Large Magellanic Cloud.  A lower abundance of heavy
elements in the Large Magellanic Cloud causes both the stars and dust
to be different from those in our galaxy, and that dissimilarity is
most apparent in the ultraviolet.  Comparison of the two galaxies
could help astronomers define the extent of differences and perhaps
determine the reasons for them.

   The WUPPE team also viewed the star 51 Ophiuchi, for their study of
luminous spinning "Be" stars, whose outer layers show evidence of
being pulled off by their stellar winds.  Dr. Regina Schulte-Ladbeck
used WUPPE to observe HD 51285, a star between the Earth and one of
the Wolf-Rayet stars she has been studying.  She will use results to
subtract polarization in the interstellar medium from her Wolf-Rayet
measurements.

   The HUT team revisited their prime calibration target, the white
dwarf star HZ 43, for end-of-mission instrument verification.  They
also viewed another portion of the Vela supernova remnant and made the
mission's first observation of LSV 46-21, a white dwarf at the center
of a planetary nebula.  The active galaxy NGC 4151 was observed for
the sixth time during this flight.

   Another study of Jupiter, along with its moons Io and Callisto,
begins this evening's observations.  Tonight's viewing choices are
fairly evenly divided among the three ultraviolet telescope teams,
with targets again ranging from tiny white dwarf stars to surveys of
large sky areas.

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"