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Contact: Mary Beth Murrill
FOR IMMEDIATE RELEASEJune 12, 1996
ASTRONOMERS FIND KEY TO LOCATING HOTBEDS OF STARBIRTH
A team of U.S. astronomers working with data from the European
Space Agency's Infrared Space Observatory (ISO) today announced
they have discovered a clear-cut infrared signature that reveals
hotbeds of star formation hidden within spiral galaxies.
Researchers presenting their results at a meeting of the American
Astronomical Society in Madison, WI, say the discovery will
streamline efforts to look at galaxies across the universe and
easily find the areas where unusually intense episodes of
starbirth are occurring.
"At the same time, the discovery may help explain why some areas
within a galaxy burst forth with new stars but other similar
regions remain comparatively quiescent," said Dr. George Helou,
NASA's ISO project scientist and an astronomer at the NASA/JPL
Infrared Processing and Analyis Center (IPAC) at Caltech in
Pasadena, CA. Helou leads a key ISO project to understand the
properties and evolution of the interstellar medium of normal
spiral galaxies such as our own Milky Way.
An infrared image of galaxy NGC 6946 produced with ISO data and
processed at IPAC clearly shows bright areas seen at 7 and 15
microns where star formation is taking place. The galactic
nucleus appears to be a hub of star birth, as are distinct areas
along the galaxy's spiral arms.
Starbirth commonly takes place behind curtains of galactic dust
and gas. ISO's infrared detectors, however, "see" the heat
emitted from behind those curtains. The color composite image of
NGC 6946 was made with data from ISO's mid-infrared camera (CAM).
The instrument was built by a consortium led by Dr. Catherine
Cesarsky of the CEA/Saclay Institute near Paris, France.
"We know from studying other galaxies that when they merge or
collide, they create a burst of star formation," said Helou. "But
in this case, there's no collision and no culprit to identify as
the catalyst for star formation. In the absence of galactic
collisions, why should there be any starburst at all?" More data
on this and other starburst regions from ISO and other infrared
studies will help answer this question," Helou said.
Members of Helou's team are Dr. David Hollenbach of the NASA/Ames
Research Center, Dr. Harley Thronson of the University of
Wyoming, Dr. Gordon Stacey of Cornell University, Dr. Robert
Rubin of NASA/Ames, Dr. Harriett Dinerstein of the University of
Texas, Austin, Dr. Steven Lord of the NASA/JPL Infrared
Processing and Analysis Center (IPAC) at Caltech, Dr. Michael
Werner of JPL, Dr. Diedre Hunter of the Lowell Observatory, Dr.
Kwok Yung Lo of the University of Illinois at Urbana-Champagne,
Dr. Charles Beichman (IPAC), Dr. Nanyao Lu (IPAC) and Sangeeta
Other key ISO experiments being conducted by U.S. astronomers are
studies of quasars (led by Dr. Belinda Wilkes of the
Harvard-Smithsonian Center for Astrophysics), investigations of
dust debris around Sun-like stars (led by Dr. Eric Becklin of the
University of California at Los Angeles) and the birth and death
of planetary systems (led by Dr. Robert Stencel of the University
of Denver). In addition to these, more than one hundred U.S.
astronomers are receiving observing time on ISO to conduct other
investigations. The ISO was launched into Earth orbit November