STS-67 Day 7 Highlights
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- On Thursday, March 9, 1995 at 6 a.m. CST, STS-67 Payload Status Report # 15
reports: (7/5:22 MET) Mission Specialist Wendy Lawrence
maneuvered the Space Shuttle Endeavour into a position where Payload
Commander Tammy Jernigan could align the Ultraviolet Imaging Telescope
(UIT) with M33, a nearby spiral galaxy in the constellation
Triangulum. This galaxy, also called the Pinwheel galaxy, is
approximately 2.4 million light years away, but is bright enough to be
seen with binoculars at night. "We are looking at this neighboring
spiral galaxy during Astro-2 to learn more about what goes on in that
galaxy and compare this information to what we already know about the
Milky Way," said Mission Scientist Dr. John Horack.
- Payload Specialist Ron Parise aligned the three onboard telescopes,
allowing UIT to make deep, wide-field images of a globular cluster of
stars known as NGC 362. Globular clusters, massive spherical
concentrations of extremely old stars, are generally located outside
the plane of the galaxy and form a halo around the center. These old
stars (possibly 10 billion years old) provide astronomers with
knowledge about the latter part of stellar evolution.
- Another type of star cluster, an open cluster, was imaged by UIT
last night. An open star cluster is moderate in size, containing from
only a few dozen to a few hundred stars. The age of the stars in an
open cluster can range from very young stars to older stars. UIT
scientists are particularly interested in searching the heavens for
white dwarfs and other faint, hot stars to be used as backlighting to
study interstellar medium Ð the gas and dust between stars. These
data will also provide highly accurate distance measurements and add
to astronomers' understanding of the chemical evolution of galaxies.
- The Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE)
telescope examined a supergiant, one of the largest, most radiant
stars in the sky. The largest of these massive stars may measure
1,000 times the radius of the sun, but their enormous size is coupled
with their voracious consumption of nuclear fuel, leading supergiant
stars through speedy evolutions and spectacular deaths in the form of
stellar explosions called supernovae.
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- The three Astro-2 ultraviolet telescopes were pointed at Jupiter's
moon Io, the most volcanically active body in our solar system. A
recent volcanic eruption on that moon, just before the Astro-2 mission
began, ejected material onto Io's surface and into Io's atmosphere.
Dr. Paul Feldman, co-investigator for the Hopkins Ultraviolet
Telescope (HUT) observed Io last night to detect possible changes in
the number of sulfur and oxygen ions in Io's atmosphere. As Io orbits
Jupiter once every 42 hours, some of this material is left behind,
forming a donut-shaped torus of sulfur and oxygen plasma around Io's
orbit. This plasma torus will be observed in a separate Jupiter
pointing during Astro-2.
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- Parise next pointed HUT at a starburst galaxy. While most galaxies
appear to have developed their stars billions of years ago, some are
forming new stars at an enormous rate in a process known as a
starburst. The massive, hot young stars emit strong ultraviolet
light, detectable by the telescopes onboard the Space Shuttle
Endeavour.
- Parise also aligned HUT to observe WX Hydri, a dwarf nova in a
binary star system. The dwarf nova for this observation, WX Hydri,
undergoes irregularly spaced outbursts, approximately once every 10
days. Scientists for HUT and WUPPE are interested in a process
associated with binary stars called accretion, where matter is
transferred from the smaller star to the larger star, causing the
interstellar gas to heat up and create bright ultraviolet emissions.
- HUT observed a very hot, massive blue star for Guest Investigator
Dr. Nolan Walborn. The star known as NGC 346 #3 is located in a
cluster of stars in the Small Magellanic Cloud. This star is being
studied because of its strong stellar winds. Data from this Astro-2
observation will be combined with observations made by the Hubble
Space Telescope and the European Southern Observatory's CASPEC
satellite, giving scientists a better understanding of this star,
which has a relatively brief life from 3 to 6 million years.
Several other stars in the NG 346 cluster will also be observed during
Astro-2.
- On Thursday, March 9, 1995 at 8 a.m. CST, STS-67 MCC Status Report # 14
reports: Looking out of the Shuttle's window, Wendy Lawrence
recorded volcanic activity on an island south of Burma and replayed
the brief video at about 5:45 a.m. CST. An alignment of the inertial
measurement units and a water dump through the flash evaporator system
were successfully performed this morning. Earlier this morning
Commander Stephen Oswald downlinked video of the Middeck Active
Control Experiment showing the effects of vibrations on spacecraft.
Through this experiment, researchers want to learn how to actively
control flexible structures in space. Lawrence continued maneuvering
the orbiter while Jernigan and Sam Durrance continued the Astro-2
observations of the ultraviolet universe.
- On Thursday, March 9, 1995 at 5 p.m. CST, STS-67 MCC Status Report # 15
reports: Oswald worked with the Middeck Active Control Experiment
as Gregory pointed the shuttle so that the payload bay telescopes
could acquire their targets. Gregory also flew another simulation on
the PILOT landing trainer. Grunsfeld and Parise directed the trio of
Astro-2 telescopes toward its targets. Oswald, Grunsfeld and Gregory
were interviewed by Glen Farley of KING-TV in Seattle at 4:30 p.m.
- On Thursday, March 9, 1995 at 6 p.m. CST, STS-67 Payload Status Report # 16
reports: (7/17:22 MET) The Astro-2 observatory teamed up
with NASA's Hubble Space Telescope today for a close examination of
the planet Jupiter's "northern lights." Though Jupiter is always in
daylight from Earth's perspective, ultraviolet photographs reveal a
glowing circle of charged particles in its upper atmosphere,
comparable to the beautiful aurora borealis visible in our far
northern latitudes. Payload Specialist Sam Durrance, whose
astronomical specialty is Jupiter, carefully centered the Hopkins
Ultraviolet Telescope's (HUT) view on the northern region of the
planet. The Astro telescopes made high-quality spectral and
polarimetric measurements, as well as wide-field, far- ultraviolet
images. At the same time, Hubble's Wide Field/Planetary Camera 2
obtained high resolution, far-ultraviolet images of the auroral
region. Dr. Paul Feldman, professor of physics at The Johns Hopkins
University, is the lead scientist for both the HUT and Hubble
observations.
- "We're very interested in whether the recent volcanic eruption on
Jupiter's moon Io produced more ions in the planet's magnetosphere and
led to a brighter aurora. There is some debate as to whether
atmospheric ionization in the Jovian system is created primarily by
sunlight, as it is in Earth's atmosphere, or by volcanic activity on
Io," said Feldman. "We obtained a very nice spectrum of molecular
hydrogen, the dominant component of Jupiter's upper atmosphere, which
we will analyze in correlation with the Hubble images. By combining
the two, we will get a scientific product that is greater than the sum
of the two individual observations."
- Several of today's observations were for scientific programs
designed by Astro-2 guest investigators. As mission planning began,
NASA invited astronomers to suggest experiments and observations that
could be conducted using one or more of the ultraviolet telescopes. A
committee of astronomers reviewed the proposals and selected ten to be
included in the observation schedule.
- Dr. John Raymond, of the Smithsonian Institution Astrophysical
Observatory, used the Hopkins telescope to view two supernova
remnants, the Cygnus Loop and Vela F. Both are relatively nearby,
with little foreground matter to block a clear view. Raymond is
studying the products of supernova explosions -- outwardly moving
shock waves containing more energy than most galaxies radiate in a
year. As the shock wave and debris from the explosion moves outward,
it heats the interstellar medium in its path and may trigger the
formation of new stars rich with the elements ejected in the
explosion. Scattered long ago by these immense blasts, some of the
iron and other heavy elements helped form the world in which we live.
- Dr. Claus Leitherer, from the Space Telescope Science Institute,
took spectral measurements of the starburst galaxy 1050+40, one where
rapid star formation is taking place. Leitherer's colleague,
Dr. Nolan Walborn, viewed O-type star SK-61837 in the Large Magellanic
Cloud, the nearest galaxy to our own Milky Way. Walborn is studying O
stars, the hottest and most massive of the "normal" stars, in a
far-ultraviolet portion of the spectrum where they had not been
studies previously. Both Leitherer and Walborn used the Hopkins
telescope for their investigations.
- Guest Investigator Dr. Gregory Bothun, of the University of Oregon,
used the Ultraviolet Imaging Telescope (UIT) to observe galaxy VCC
530, one of a recently recognized class of astronomical objects.
"They are called "low- surface-brightness" galaxies because they are
fainter than the dark night sky. It has only been in recent years,
with improvements in telescopes, that we have been able to detect
them," said Dr. Barry Madore, another UIT guest investigator. "The
most fascinating thing about this class of galaxies is that
ground-based observations show some of them are blue. This could be
due to an absence of dust, or because they are made up of very
metal-poor stars, or maybe they are a new type we're not been aware of
before. By viewing them in ultraviolet light, we can get a better
understanding of where they came from and what their properties are."
- UIT Principal Investigator Ted Stecher, of the Goddard Space Flight
Center, chose a cluster of galaxies known as Abell 1367 for
observation. The galaxies in this cluster are primarily spirals, like
our own Milky Way. Examining photographs of spiral-rich clusters
gives astronomers a better understanding of the spatial structure and
development of spiral galaxies. UIT made images of Abell 1367 during
Astro 1 as well. Stecher also selected NGC 6946, a rapid-
star-formation galaxy. Ultraviolet radiation emphasizes the hot stars
and dust features associated with spiral arms and suppresses the cool
star background of the galactic bulge and underlying disc.
- Other observations today spanned the life cycle of stars, from
studies of the elderly Schweizer-Middleditch white dwarf star to
another search for intergalactic helium left over from the birth of
the universe. The Astro telescopes are currently in the midst of a
nearly four-hour-long observation series to study the magnetic
cataclysmic variable binary star, AM Herculis.
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