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This star, with the prosaic
name of OH231.8+4.2, is seen in these infrared pictures blowing out gas
and dust in two opposite directions. So much dust has been cast off and
now surrounds the star that it cannot be seen directly, only its starlight
that is reflected off the dust. The flow of gas is very fast, with a velocity
up to 700 000 km/h. With extreme clarity, these Hubble Near Infrared Camera
and Multi-Object Spectrometer (NICMOS) images reveal that the fast-moving
gas and dust are being collimated into several thin streamers (on the right)
and a jet-like structure (on the left), which can be seen extending away
from the centers of both pictures. On the right, wisps of material in jet-like
streamers appear to strike some dense blobs of gas. This interaction must
produce strong shock waves in the gas.
The pictures represent two
views of the object. The colour image is a composite of four images taken
with different NICMOS infrared filters on 28 March, 1998. It shows that
the physical properties of the material, both composition and temperature,
vary significantly throughout the outflowing material. The black-and-white
image was taken with one NICMOS infrared filter. That image is able to
show more clearly the faint detail and structure in the nebula than can
be achieved with the colour composites.
Observations by radio astronomers
have found many unusual molecules in the gas around this star, including
many containing sulphur, such as hydrogen sulphide and sulphur dioxide.
These sulphur compounds are believed to be produced in the shock waves
passing through the gas. Because of the large amount of sulphur compounds,
this object has earned the nickname "The Rotten Egg" Nebula. It resides
in the constellation Puppis.
These NICMOS data pose a
serious challenge to astrophysical theorists: How can a star generate such
tightly collimated streams of gas and dust and accelerate them to such
very high velocities? William B. Latter from the California Institute of
Technology and his group are using these data to obtain a better understanding
of the detailed structure in the outflowing material, look for evidence
for the origin of the thin streamers and jets, and learn more about the
star itself. This information will give astronomers a more complete understanding
of the final stages in the life of stars like our Sun.
These results were presented
at a conference called "Asymmetrical Planetary Nebulae II: From Origins
to Microstructures," Aug. 3 to 6, 1999 at the Massachusetts Institute of
Technology. The results will also be published in the Astrophysical Journal.
This news note has been prepared
in collaboration with Office of Public Outreach at ST ScI (Ray Villard).
Contacts:
Lars Lindberg Christensen,
ST-ECF, Garching, Germany
(phone: +49-89-3200-6306,
fax: +49-89-3200-6480, e-mail: lars@eso.org) or
William B. Latter
SIRTF Science Center/California
Institute of Technology
(phone: 626-395-8568, fax:
626-568-0673)
The Hubble Space Telescope
is a project of international cooperation between NASA and ESA. |
