STS-67 Day 9 Highlights
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- On Saturday, March 11, 1995 at 6 a.m. CST, STS-67 Payload Status Report # 19
reports: (9/5:22 MET) Pilot William Gregory maneuvered the
Endeavour into a position where Mission Specialist John Grunsfeld and
Payload Specialist Ronald Parise could align the Wisconsin Ultraviolet
Photo-Polarimeter Experiment (WUPPE) with Nova Centauri 1995. "The
WUPPE instrument has given us some spectacular spectral 'signatures'
of the elements (such as carbon, nitrogen or oxygen) that may be
present in the atmosphere following this very recent explosion," said
Guest Investigator Dr. Joni Johnson of the University of Wisconsin in
Madison. "We'll be analyzing these data for quite some time, looking
for clues about the atmospheric composition, as well as the structure,
of this new nova."
- Nova Centauri 1995, which occurred just two weeks before the
launch of Astro-2, is the result of a Red Giant, transferring material
to a compact white dwarf companion star. After a period of time
(perhaps 1,000 years or more) the material which accreted onto this
white dwarf reached extremely high temperatures and pressure, causing
a thermonuclear explosion. WUPPE scientists were excited to be able
to observe this rare new nova so soon after its beginning.
- Parise also pointed the WUPPE telescope to a massive star that is
known to have bright emission lines. Scientists are studying this
type of star to learn more about the composition of material
surrounding the star and how it is effected by stellar winds.
- WUPPE scientists also got another look at a rare Wolf-Rayet star
overnight. Wolf-Rayet stars are thought to represent one of the final
phases in the evolution of massive stars. This type of massive star
has powerful, eroding stellar winds carrying material outward. The
interaction between the star's light and this material causes the
radiation to be polarized (oriented in one particular direction)
rather than in all different directions. The polarization of light
coming from this Wolf-Rayet star can tell astronomers something about
the properties of the stellar winds around it.
- Mission Specialist Wendy Lawrence maneuvered the orbiter to
different positions last night, allowing the WUPPE science team to
observe two galaxies in the Local Group. Payload Commander Tammy
Jernigan operated the Instrument Pointing System, while Payload
Specialist Sam Durrance aimed the Astro-2 telescopes at the galaxies.
These two galaxies served as background lights for the study of
interstellar polarization, the direction that light travels between
- The Ultraviolet Imaging Telescope (UIT) imaged Holmberg 2 (a dwarf
galaxy) and a portion of the Andromeda spiral galaxy, M31, to help UIT
astronomers learn more about young stellar formations in galaxies.
One of the major science goals of the UIT is to map out our "twin
sister" galaxy, Andromeda (M31). UIT also imaged a galaxy known as
NGC 3310, allowing investigators to study the design of spiral
galaxies and related structures, the nature of stellar populations,
and learn more about the material between stars associated with bars,
irregular, and anemic (poor in structure) galaxies.
- The Hopkins Ultraviolet Telescope (HUT) observed two Seyfert 1
galaxies, Markarian 279 and NGC 3516. These targets are active
galaxies with bright, compact nuclei, radiating in wavelength ranges
from infrared to X- ray. HUT Project Scientist Dr. Gerard Kriss
arranged simultaneous X-ray observations of NGC 3516 using the
Japanese X-ray satellite ASCA (the Advanced Satellite for Cosmology
and Astrophysics). Astro-2 and ASCA will revisit NGC 3516 for another
observation in two days. UIT scientists observed these galaxies to
better understand how energy is transferred between the nuclei and
- Parise pointed HUT at a dwarf nova called Z Camelopardalis (Z CAM).
This stellar system has two stars locked in a tight orbit around each
other, with an orbital period of seven hours. The companion star to Z
CAM is a low mass star which transfers matter onto Z CAM, causing
outbursts of ultraviolet emissions.
- Parise aligned HUT with a portion of the supernova remnant Cygnus
Loop D. HUT scientists are studying a very bright, radiative filament
on the western edge of the Cygnus Loop, to learn more about the shock
waves generated during the death of a star. Astronomers will analyze
these HUT data to determine temperatures, densities, and chemical
compositions of the gaseous filaments in the interstellar medium.
- On Saturday, March 11, 1995 at 6 p.m. CST, STS-67 Payload Status Report # 20
reports: ( 9/17:22 MET) On the tenth day of the STS-67
mission, Astro-2 scientists took their first look in the extreme
ultraviolet at what may be the most massive star in the known
universe. They also focused their observations on spiral galaxies,
elliptical galaxies, and star clusters.
- HD 269810, a faint O-class star located in the Large Magellanic
Cloud, is about 190 times as massive as Earth's sun and qualifies as a
candidate for the most massive star ever observed. Hopkins
Ultraviolet Telescope Guest Investigator Dr. Nolan R. Walborn, of the
Space Telescope Science Institute, used the HUT instrument to study
the star's unusually powerful stellar wind, or expanding outer layer,
like it has never been seen before. Although this star probably
possesses the most mass a star can have, its stellar wind is depleting
this mass at an accelerated rate. These observations provide crucial
information regarding the ultimate fate of the most massive stars.
- Dr. Walborn uses the HUT to study a sample of very hot O class
stars that are currently being observed in ultraviolet wavelengths of
1200 angstroms and above by the Hubble Space Telescope. However, only
HUT is able to take its unprecedented measurements of these stars in
the 900-1200 angstrom wavelength range. Commenting on what he called
the "beautiful" real-time data acquired from this observation,
Dr. Walborn said, "Now we have new information about a current
candidate for the most massive star known. This was the star I wanted
to see, and now we have it."
- Earlier this morning, Payload Specialist Sam Durrance successfully
pointed the Astro telescopes at a somewhat challenging target, the
elliptical galaxy M60, to enable the science teams to obtain an
overall average spectrum of stars in its core. A roughly
sphere-shaped galaxy with no clearly discernible internal structure,
M60 contains older, evolved stars and therefore represents a stable
stage of development. Due to the faintness of this galaxy and the
absence of suitable guide stars for automatic targeting, manual
acquisition of this target was necessary.
- The Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) also
observed the center of the M60 giant elliptical for polarized
radiation, or radiation preferentially oriented in one direction. M60
is part of rich cluster of galaxies in the Virgo constellation,
containing about 2500 galaxies, and has a notable ultraviolet excess.
- The Ultraviolet Imaging Telescope (UIT) viewed NGC 6791, an unusual
open cluster located 14,000 light years away in the Lyra
constellation. Open clusters are diffuse collections of 100 to 1,000
stars and are usually thought to be young systems, less than 10
million years old. As one of the oldest known open clusters, NGC 6791
is three billion years older than our solar system. Because UIT's
field of view is well matched to the sizes of these clusters, UIT
scientists are able to perform ultraviolet observations of many stars
at the same time.
- Another target for UIT, M101 in the Ursa Major constellation, was a
big spiral galaxy with arms that are wide and not very tightly wound.
A perfect example, or prototype, of spiral structure, it is the
highest priority spiral galaxy for UIT. This galaxy contains bright
regions, such as Searle 2 (named for Dr. Leonard Searle, the
astronomer who first discovered that region), of glowing hydrogen
ionized by hot blue stars. UIT's ultraviolet imaging offers a
powerful new tool for the study of these regions, especially since it
emphasizes these hot stars. Ultraviolet imaging also suppresses the
cool star background of the galaxy, allowing the young hot stars to
become more evident to astronomers studying the evolution of stars.
- On Saturday, March 11 1995 at 5 p.m. CST, STS-67 MCC Status Report # 19
reports: Gregory continued work with the Portable In-Flight
Landing Operations Trainer, PILOT, a laptop computer and hand
controller designed to simulate Shuttle landings. The device helps
Shuttle Commanders and Pilots to stay sharp during long duration
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