Mapping Orion's winds (Forwarded)

News Service
Vanderbilt University

Contact:
David F. Salisbury, (615) 343-6803

1-10-2006

Mapping Orion's winds

NASHVILLE, Tenn. -- For the past few months, Bob O'Dell has been mapping
the winds blowing in the Orion Nebula, the closest stellar nursery
similar to the one in which the sun was born.

New data from the Hubble Orion Heritage Program, a major observational
effort by the Hubble Space Telescope in 2004 and 2005, have given the
Vanderbilt astronomer the information he needs to measure the stellar
winds with unprecedented detail, and he reported his early results on
Jan. 11 at the annual meeting of the American Astronomical Society in
Washington D.C.

"Determining how stellar winds interact with the ambient material in
stellar nurseries like Orion is a critical factor in understanding the
process of star creation," says O'Dell, distinguished research professor
of astrophysics and an international authority on Orion.

All stars, including the Sun, give off a stream of particles as they
burn. In young, hot stars like those that form the "Trapezium" at the
heart of Orion this stream of particles is millions of times more dense
and energetic than the solar wind. Newborn stars, which are still
shrouded in thick veils of dust and gas, often eject gas and dust from
their polar regions in narrow jets, rather than broadcasting them
outward in all directions. When these stellar winds impact floating
clouds of dust and gas, they produce shock waves that erode and shape
the clouds in a fashion similar to the way in which terrestrial winds
sculpt sand dunes. When they are strong enough, such shock waves also
can compress the free-floating clouds of dust and gas, triggering the
formation of new stars.

O'Dell is using these shock waves as celestial "wind socks" to plot the
direction of these winds in different parts of the nebula. By
back-tracking older, more distant shock waves to their likely points of
origin, the astronomer can also get an idea of how long major currents
have been flowing.

"When you look closely enough, you see that the nebula is filled with
hundreds of visible shock waves," the astronomer says.

In his analysis, O'Dell has identified three different types of shock waves:

* Bow-shocks are stationary shock waves that are formed by the collision
of two steady winds and are excellent indicators of wind direction. They
are present near the hottest stars in the center of the nebula where
they show winds flowing outward at velocities of thousands of kilometers
per second. They are also present in the outer nebula where they are
produced by low velocity stellar winds of tens of kilometers per second.

* Jet-driven shocks are produced when narrow streams of gas and
particles traveling at hundreds of kilometers per second pass through
gas that is relatively stationary. There are many shockwaves of this
type in the nebula that are produced by jets of material ejected by
newly formed stars.

* Warped shocks are jet-driven shocks located in areas where the ambient
gas is not stationary but is moving in a cross current. This bends the
jets and shocks into bow-like shapes.

Using these markers, the astronomer has mapped the outflow from two of
the three regions of star formation in the nebula. Both of these
regions, labeled BN-KL and Orion-South, are located behind the glowing
region of the nebula where the light from the central stars ionizes the
outer layers of the parent molecular cloud. The specific objects that
are producing these winds in the two regions are not visible to optical
telescopes but they stand out as hot spots in infrared images.

By tracking back the farthest shockwaves produced by these outflows,
O'Dell has established that the winds blowing from BN-KL have been doing
so for 900 to 1,100 years, while those from Orion-South have been going
on for 200 to 1,500 years.

These observations were made during 104 orbits of the Hubble and provide
the most comprehensive picture ever obtained of the Orion Nebula. The
data will be combined with other Hubble and ground-based telescope
observations to create a widely available archive for research
scientists interested in this region, in addition to acting as a base
for a detailed study that should provide new insights into the
conditions required for creating stars like the sun.

For more news about Vanderbilt research, visit Exploration, Vanderbilt's
online research magazine, at
http://www.exploration.vanderbilt.edu

IMAGE CAPTIONS:

[Image 1:
http://www.newswise.com/images/uploa...ion_insert.jpg
(528KB)]
The area of the Orion Nebula in the white box is enlarged on the left to
show some of the hundreds of shock waves that crisscross the region.

Courtesy of C. Robert O'Dell

[Image 2:
http://www.newswise.com/images/uploa...rped_shock.jpg
(50KB)]
The young star at the center of the image is ejecting material in narrow
jets from both poles. The presence of a strong cross-flow is shown by
the bright bow-shock on the star's left. As a result of this
cross-current, both jets bend to the right.

Courtesy of C. Robert O'Dell