From: yee@trident.arc.nasa.gov (Peter E. Yee)
Subject: NASA satellite detects new, extreme ultraviolet sources [Release 92-138] (Forwarded)
Apparently-To: sci-space-news@ames.arc.nasa.gov
Followup-To: sci.space
Organization: NASA Ames Research Center, Moffett Field, CA
Date: Thu, 3 Sep 1992 19:51:49 GMT

Michael Braukus
Headquarters, Washington, D.C.                                 August 31, 1992
(Phone:  202/358-0872)

Randee Exler
Goddard Space Flight Center, Greenbelt, Md.
(Phone:  301/286-7277)


RELEASE:  92-138

NASA SATELLITE DETECTS NEW, EXTREME ULTRAVIOLET SOURCES

	An object emitting extreme ultraviolet light located outside the Milky
Way galaxy was detected by a NASA satellite through interstellar gas and dust,
once thought to block this source of radiation.  This discovery assures that
astronomers will have a new tool to probe the universe.

	Also, EUVE has detected a new source of extreme ultraviolet radiation
(EUV) from the corona of a star much like the sun, located about 16 light
years from Earth.  A white dwarf companion star also appears in the
photograph released today.

	On July 8 and 9, NASA's Extreme Ultraviolet Explorer (EUVE)
measured an outburst from a "cataclysmic variable," a closely orbiting pair of
stars in which gravitational forces pull matter from the outermost layers of a
normal star onto the surface of a white dwarf companion.  The hot,
compressed stellar material generates an explosive burst of extreme
ultraviolet radiation as the material falls into the deep gravitational
field of the white dwarf.

	Other explosive events are flares on stars.  These are unpredictable,
giant versions of eruptions known to occur on a smaller scale on our own sun.
EUVE caught two such events on the red dwarf stars called AT Microscopium
and AU Microscopium.

	Also, EUVE astronomers were surprised when they detected an object
located outside our own Milky Way galaxy that was emitting extreme
ultraviolet radiation (EUV).  At one time, astronomers had thought that the
interstellar medium, the gas and dust spread throughout the galaxy,
effectively would block their view of even nearby objects, because it is highly
opaque to EUV radiation.

	Each first view in a new spectral band gives astronomers a new tool to
probe the universe.  The EUV window is one of the last unexplored spectral
regions.

	EUVE Principal Investigators Professor Stuart Bowyer and Dr. Roger
Malina, of the University of California at Berkeley's Center for Extreme
Ultraviolet Astrophysics (CEA), presented the findings today to space
scientists at the World Space Congress in Washington, D.C.

	According to Professor Bowyer, initiator of the EUV program at
Berkeley, "Years ago a lot of our colleagues thought we were crazy to observe
in the EUV.  Everyone "knew" that trying to look through the interstellar
medium at these wavelengths would be like trying to use a telescope in a San
Francisco fog."

	Extreme ultraviolet (EUV) radiation is visible only to instruments
above Earth's atmosphere.  Radiation at these energies is emitted by
multi-million degree coronae on stars, by giant eruptions on novae, by the hot
surfaces of white dwarfs and by other exotic sources in the cosmos.

	The EUVE was launched June 7, 1992, to study the extreme ultraviolet,
the part of the electromagnetic spectrum lying between optical and x-ray
wavelengths.  It represents NASA's 67th Explorer mission.  The first Explorer
was launched on Jan. 31, 1958, and it discovered the Van Allen radiation
belts.

	The EUVE satellite, now 6 weeks into a survey of the entire sky, will
provide astronomers with their first detailed maps in multiple EUV energy
bands.

	Officials at NASA's Goddard Space Flight Center, Greenbelt, Md., report
that the satellite has functioned smoothly since its launch.  All instruments
are performing at or above expected levels, and data analysis is 50-percent
ahead of schedule.

	The EUVE Science Operations Center, based at CEA, operates around
the clock, sending commands to point the instruments at selected
astronomical sources and recording the findings of the satellite's four
telescopes and three spectrometers.  The CEA has adopted a novel approach
for operating the project with a staff that includes more than two dozen
undergraduate students who are getting a unique hands-on educational
experience.

	Researchers and engineers are studying the calibration and check-out
data obtained during the first 6 weeks of the mission.  These data serve a dual
purpose.  They verify the instrument performance and at the same time, give
astronomers valuable new measurements to test their models.

	NASA's Guest Observer Program begins at the conclusion of the
6-month sky survey.  Scientists from around the world have applied to NASA
to use the capabilities of the EUVE spectrometers.  Stiff competition will
assure that only the very best of the 140 submitted proposals will result in
allocated observing time.

	Goddard is responsible for the design, construction, integration,
checkout and operation of EUVE.  The spacecraft's science instrumentation
was designed, constructed and calibrated by the Space Science Laboratories
of the University of California, Berkeley.  The EUVE is managed by Goddard
for NASA's Office of Space Science and Applications, Washington, D.C.

- end -

	Editors Note:  A photograph is available to media representatives by
calling NASA's Broadcast And Imaging Branch on 202/453-8373.

     Color                            B&W
     92-HC-597                        92-H-653