EMBARGOED UNTIL:    9:20 a.m. PDT, June 8, 1998

  NICMOS IMAGES A SPECTACULAR OUTFLOW IN THE ORION MOLECULAR CLOUD

The Hubble Space Telescope's Near-Infrared Camera and MultiObject
Spectrometer (NICMOS) has looked through the visible surface of the
Orion Nebula, a giant interstellar gas cloud, to view an explosive
pattern of molecular hydrogen emisssion underneath.  The pattern is
delineated by numerous gaseous streamers resembling the petals of a
flower.  The streamers were produced as relatively quiescent gas in
the cloud was impacted by gas ejected from a young star or stars
buried deep within the cloud.

Astronomers have found such outflows are often associated with massive
young stars, and expect the new observations to yield important
information about pre-natal and infant stars and their influence on
this stellar nursery.  The report is being presented today by
Dr. Edwin F. Erickson of NASA's Ames Research Center in Moffett Field,
CA, and his colleagues Drs. Angie Schultz, Sean Colgan, David
Hollenbach, Michael Kaufman (all of NASA-Ames), Erick Young, and Hua
Chen (of the University of Arizona) at the American Astronomical
Society meeting in San Diego, CA.

The great Orion Nebula, about 1500 light years away, is a familiar
sight to backyard astronomers.  Behind the optically visible nebula
lies the clear evidence of an outflow resulting from the birth of an
unseen star (or stars).  This outflow has produced streamers of
molecular hydrogen gas, observed here in infrared light at a
wavelength near two microns -- about four times longer wavelength than
that of visible light.  The infrared emission arises as the outflowing
gas collides with the surrounding cloud.  Dust in the molecular cloud
obscures most of the cloud volume from our (human) sight, but infrared
light is relatively unaffected by the dust.  The NICMOS images show
previously unknown delicate internal structures in the molecular
hydrogen petals or fingers.  Study of these features will improve
astronomers' understanding of the outflow mechanism, which is closely
linked to processes important in the early lives of stars.

``The HST and NICMOS give us unprecedented ability to see not only the
exquisite detail of these outflow features as revealed by the
molecular hydrogen emission, but also to image important features in
other spectral bands.", said Dr. Edwin F. Erickson, Astrophysicist at
NASA's Ames Research Center.  ``The lifetime of these molecular
hydrogen features is short compared with the duration of the outflows,
so although we see evidence for outflows in many sources, the structure
seen here is truly remarkable."

The distinctive shape of the molecular hydrogen emission may be produced
by the ejection of many small clumps of material, as in fireworks, or
it may be the result of turbulence formed when a fast expanding wind from
the young star catches up with a slower wind emitted previously.

These features were dubbed "fingers" when first discovered in 1993 by
Drs. David Allen and Michael Burton of the Anglo-Australian
Observatory.  Their observations uncovered only the fingers at the far
northern end of the outflow.  Earlier this year, the innermost fingers
were observed by Dr. Susan Stolovy of the University of Arizona and
her colleagues using NICMOS.

The outflow which the astronomers studied gives rise to chemical
changes in the cloud which produce vast amounts of water.  Team member
Michael Kaufman was part of another group which used the European
Infrared Space Observatory (ISO) to show that the outflow in Orion is
producing the equal of many Earth-oceans of water every day.
Dr. Kaufman states: "The ISO observations showed us the chemical
evidence; these new images reveal the magnificently complex structure
of the outflow."

Figure 1 shows a false-color image of the region observed by
Dr. Erickson and his team.  Red represents the molecular hydrogen gas.
Green is emission from a spectral feature of atomic hydrogen not
previously imaged in Orion.  This light is produced by absorption of
ultraviolet radiation coming from a hot star in a stellar quartet
called the "Trapezium", which is just off the bottom of the picture.
This infrared emission from the atomic hydrogen comes from much of the
same gas that is seen in visible light, and closely resembles the
images seen by Dr. Robert O'Dell of Rice University with the HST Wide
Field/Planetary Camera. The blue areas in the image are 2.15 micron
starlight directly emitted by stars (small blue dots) or reflected by
interstellar dust grains embedded in the gas.  The image is about 0.6
light years on a side.  Figure 2 is a diagram identifying the various
features in the image.

The different wavelengths of infrared light characterize a variety of
processes and penetrate the nebula to different depths.  The
observations will permit astronomers to assemble a more accurate model
of this nearest nursery of massive star birth.

For more information:
  Dr. Edwin F. Erickson (605) 604-5508   erickson@cygnus.arc.nasa.gov
  Dr. Angie Schultz     (605) 604-1841   schultz@cygnus.arc.nasa.gov

This press release is available over the internet at 
   http://web99.arc.nasa.gov/~kaufman/orion_nicmos.html