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January 12, 2000
FOR IMMEDIATE RELEASE
FUSE Spacecraft Observes Interstellar
The extended halo of half-million-degree gas that surrounds the
was generated by thousands of exploding stars, or supernovae, as
galaxy evolved, according to new observations by NASA's
Spectroscopic Explorer (FUSE) spacecraft.
Lifeblood of Galaxies
The spacecraft has nearly completed its shakedown phase, and its
results are already providing a wealth of new information to
about the material that becomes stars, planets, and ourselves.
The new findings confirming the nature of the Milky Way halo are
presented today in Atlanta at the 195th meeting of the American
Astronomical Society (AAS).
The roughly football-shaped hot gas halo which surrounds our
about 5,000-10,000 light years above and below the galactic plane
and thins with distance. One light year is almost 6 trillion
"The hot gas halo has been known for some time, but we weren't
sure how it
got there or stayed hot," said FUSE co-investigator Blair Savage
University of Wisconsin in Madison. "The new FUSE observations
extensive amount of oxygen VI (oxygen atoms that have had five
eight surrounding electrons stripped away) in the halo. Some
thought that ultraviolet radiation from hot stars could produce
but the only way to make the observed amount of oxygen VI is
collision with the blast waves from exploding stars, called
"Stars destined to explode don't live long, compared to stars
like our Sun,
so star explosions are actually a record of star formation,"
Sonneborn, FUSE project scientist at NASA's Goddard Space Flight
Greenbelt, Md. "By comparing supernova generated halos among
may be able to compare their star formation histories."
"FUSE measures the pulse of the lifeblood of our galaxy, the thin
between stars," said
Warren Moos (pictured at right), FUSE principal
investigator at Johns
Hopkins University in Baltimore. "This interstellar gas courses
our veins, because dense clouds of it collapsed to form new
planets, including our solar system."
The FUSE observatory is now "open for business," Moos said.
extended on-orbit checkout and debugging period, common for
observatories, we are now performing observations on a routine
both members of the Principal Investigator Team and the 62 guest
investigators from around the world selected by NASA for the
first year of
"We are continuing to tune the instrument," Moos added. "In the
expect to begin a comprehensive study of the abundance of
fossil atom left over from the Big Bang. As our team becomes
practiced, we need less time to optimize the instrument, and the
time we can spend on scientific observations will go up. This
FUSE is able to detect interstellar gas and determine its
velocity and distance by viewing bright celestial objects further
intervening gas selectively absorbs the light from these objects
unique pattern of colors, depending on the composition of the
spectrograph on FUSE separates the light into its component
similar to the way a prism separates white light into a rainbow.
resulting patterns identify the gas like optical fingerprints.
patterns shift to different colors, velocity and distance
The FUSE spectrograph is at least 100 times more powerful than
instruments, helping it reveal a large number of new atomic and
features in interstellar gas that could only be guessed at
ultraviolet light analyzed by FUSE is invisible to the human
FUSE scientists are also reporting early results at the AAS
investigations into two other components of the galactic
system:" cold clouds of molecular hydrogen where new stars are
presented by Michael Shull of the University of Colorado, and hot
"winds" from stars so bright they nearly blow themselves apart,
by John Hutchings of the National Research Council of Canada.
Editor's Note: New images related to this
science, and more information about FUSE, can be found on the
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