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Contact:  JPL/Jane Platt  (818) 354-0880 
Space Telescope Science Institute/Ray Villard (410) 338-4514          
       
IMAGE ADVISORY                              March 6, 2002

HUBBLE EYES BOW SHOCK NEAR A YOUNG STAR

     Astronomers using NASA's Hubble Space Telescope have 
found a bow shock around a very young star in the nearby Orion 
nebula, an intense star-forming region of gas and dust.  

     A picture, from the Hubble Heritage team, is available at 
http://heritage.stsci.edu or 
http://oposite.stsci.edu/pubinfo/pr/2002/05 or 
http://www.jpl.nasa.gov/images/wfpc .  It was taken in 
February 1995 as part of the Hubble Orion Nebula mosaic by 
Hubble's Wide Field and Planetary Camera 2, designed and built 
by NASA's Jet Propulsion Laboratory, Pasadena, Calif.  

     Named for the crescent-shaped wave a ship makes as it 
moves through water, a bow shock can form in space when two 
gas streams collide. In this case, the young star, LL Ori, 
emits a vigorous wind, a stream of charged particles moving 
rapidly outward from the star. Our own Sun has a less 
energetic version of this wind that is responsible for auroral 
displays on the Earth.

     The material spewed from LL Ori collides with slow-moving 
gas evaporating away from the center of the Orion nebula, 
located to the lower right of the image. The surface where the 
two winds collide is seen as the crescent-shaped bow shock.
 
     Unlike a water wave from a ship, this interstellar bow 
shock is three-dimensional. The filamentary emission has a 
distinct boundary on the side facing away from LL Ori, but is 
diffuse on the side closest to the star, a trait common to 
many bow shocks.

     A second, fainter bow shock can be seen around a star 
near the upper right-hand corner of the image. Astronomers 
have identified numerous shock fronts in this complex star-
forming region and are using this data to understand the 
complex phenomena associated with star birth.

     The Orion nebula is a close neighbor in our Milky Way 
galaxy, at only 1,500 light-years from Earth. The filters used 
in this color composite represent oxygen, nitrogen, and 
hydrogen emissions.

Image Credit: NASA and the Hubble Heritage Team (STScI/AURA)
Acknowledgment: C. R. O'Dell (Vanderbilt University)

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03/05/02  JP        2002-055