SETI bioastro: Fw: Hubble Reveals Oddball "Backwards" Spiral Galaxy

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Date: Thu Feb 07 2002 - 18:26:13 PST

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Subject: Hubble Reveals Oddball "Backwards" Spiral Galaxy

PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011

Contact: JPL/Jane Platt (818) 354-0880
   Space Telescope Science Institute/Ray Villard (410) 338-4514

IMAGE ADVISORY February 7, 2002


     Astronomers using NASA's Hubble Space Telescope have found a spiral galaxy that may
rotate in the opposite direction from what was expected.

     A picture of the oddball galaxy is available at or or . It was taken
in May 2001 by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet
Propulsion Laboratory, Pasadena, Calif.

     The picture showed which side of galaxy NGC 4622 is closer to Earth; that information
helped astronomers determine that the galaxy may be spinning clockwise. The image shows NGC
4622 and its outer pair of winding arms full of new stars, shown in blue.

     Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral
arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But
this galaxy has two "leading" outer arms that point toward the direction of the galaxy's clockwise
rotation. NGC 4622 also has a "trailing" inner arm that is wrapped around the galaxy in the
opposite direction. Based on galaxy simulations, a team of astronomers had expected that the galaxy
was turning counterclockwise.

     NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions.
Astronomers suspect this oddity was caused by the interaction of NGC 4622 with another galaxy.
Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image
suggests that NGC 4622 consumed a smaller companion galaxy.

     Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many
stars in our Milky Way galaxy, completes a circuit around the Milky Way every 250 million years.
NGC 4622 lies 111 million light-years away in the direction of the constellation Centaurus.

     The science team, consisting of Drs. Ron Buta and Gene Byrd from the University of
Alabama, Tuscaloosa, and Tarsh Freeman of Bevill State Community College in Alabama,
observed NGC 4622 in ultraviolet, infrared, and blue and green filters. Their composite image and
science findings were presented at the January 2002 American Astronomical Society meeting.

     Image Credit: NASA and the Hubble Heritage Team (STScI/AURA) Acknowledgment: Dr. Ron
Buta (U. Alabama), Dr. Gene Byrd (U. Alabama) and Tarsh Freeman (Bevill State Comm. College)
# # # # #
02/07/02 JP 2002-033

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