STAR FACTORY NEAR GALACTIC CENTER BATHED IN HIGH-ENERGY X-RAYS
Dolores Beasley, Steve Roy, Megan Watzke
Near the crowded core of the Milky Way galaxy, where stars
are so plentiful and shine so brightly that planets there would
never experience nighttime, astronomers have found a new
phenomenon: a cauldron of 60-million degree gas enveloping a
cluster of young stars.
Professor Farhad Zadeh of Northwestern University, Evanston, IL,
and his collaborators used NASA’s Chandra X-ray Observatory to
trace the gas around the Arches cluster, a well-studied region
of star formation that is home to some of our galaxy’s largest
and youngest stars.
“This is the first time we have seen a young cluster of stars
surrounded by such a halo of high-energy X-rays,” said Zadeh in
a news conference at the American Astronomical Society in
Pasadena, CA. “This supports theoretical predictions that
stellar winds from massive stars can collide with each other and
generate very hot gas.”
Massive stars, newborn stars and stellar winds have long been
known to emit X-rays. The Chandra results are significant
because they identify this new mechanism of stellar winds
colliding to generate X-rays as energetic as those seen in
distant starburst galaxies, which are known for their furious
pace of star production.
The Arches cluster is about 25,000 light-years from Earth and
only about one-to-two million years old. It is also less than
100 light-years from what is thought to be a supermassive black
hole in the center of our galaxy. The cluster contains 150 hot,
young stars, known as “O” stars, concentrated within a diameter
of one light-year, making it the most compact cluster known in
the Milky Way galaxy.
The density of stars makes the region in and around the Arches
cluster a microcosm of what is likely occurring in starburst
galaxies.
“The Arches cluster is one of the best ‘local’ analogues of
starburst galaxies — the most prodigious stellar nurseries
known,” said Casey Law of the Harvard-Smithsonian Center for
Astrophysics, Cambridge, MA. “Yet the Arches cluster is in our
backyard, not millions of light-years away.”
Starburst galaxies are known for creating huge hot bubbles of
gas that escape from the galaxy. In a similar way, Chandra
observations of the Arches clusters may provide clues to the
origin of a much larger cloud of hot gas known to exist in the
galaxy’s center.
“Our data suggest that the gas within the Arches cluster may get
so hot that it escapes from the cluster,” said Cornelia Lang of
the University of Massachusetts, Amherst. “The Arches and other
clusters like it may contribute to the reservoir of mysterious
hot gas long observed near the Milky Way.”
Zadeh and his collaborators intend to search for X-ray emissions
from other clusters of stars near the galactic center and
compare this to newer, longer Chandra observations of the Arches
cluster.
Chandra observed the Arches cluster region with its Advanced CCD
Imaging Spectrometer (ACIS). The research team for this
investigation included Casey Law and Antonella Fruscione from
the Harvard-Smithsonian Center for Astrophysics; Cornelia Lang
and Daniel Wang from University of Massachusetts; Mark Wardle of
the University of Sydney, Australia; and Angela Cotera from
University of Arizona, Tucson.
The ACIS X-ray camera was developed for NASA by The Pennsylvania
State University, University Park, and the Massachusetts
Institute of Technology, Cambridge. NASA’s Marshall Space Flight
Center in Huntsville, AL, manages the Chandra program for the
Office of Space Science, Washington, DC. TRW, Inc., Redondo
Beach, CA, is the prime contractor for the spacecraft. The
Smithsonian’s Chandra X-ray Center, Cambridge, MA, controls
science and flight operations.
Images associated with this release are available at:
http://chandra.harvard.edu
and
http://chandra.nasa.gov
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