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FOR IMMEDIATE RELEASE: Tuesday, January 10, 2006

UCLA Astronomers Provide New Insights Into Massive Black Hole at Center of
the Milky Way and Surrounding Region

UCLA astronomers can determine, for the first time, orbits of massive
young stars located a few light months from the enormous black hole at the
center of our Milky Way galaxy -- stars that hold an imprint of how they
were born. The origin of young stars at the center of our galaxy has
puzzled astronomers, but the orbits may be the key to unlocking the
mystery, UCLA astronomy graduate student Jessica Lu reported today at the
annual meeting of the American Astronomical Society in Washington, D.C.
The astronomers use a new laser virtual star at the W.M. Keck observatory
in Hawaii.

The hostile environment around the supermassive black hole should make it
extremely difficult for stars to form, but many young stars have been
detected around the black hole, said Lu, who reported that she and a UCLA
team are tracking a puzzling group of more than 30 massive young stars of
uncertain origins.

"How were these stars formed in such an inhospitable region?" Lu asked.
"My advisor, Andrea Ghez, calls this mystery 'the paradox of youth.' Using
the Keck's Laser Guide Star adaptive optics system, we expect to resolve
the paradox. We are able to measure how these young stars move across the
sky with an unparalleled precision (only two kilometers per second) and
determine, for the first time, the orbit of each of the young stars
located a few light months from the black hole.

"Just as a fingerprint can be used to identify a person, the information
encoded in the orbits of the young stars will tell us how and where they
formed," said Lu, a member of a UCLA research team including her advisor,
Ghez, a UCLA professor of physics and astronomy.

Lu added that these are the closest stars to the supermassive black hole
that have not had their orbits distorted by their inhospitable
environment.

"The orbits of these young stars suggest the stars were born far from the
black hole in a massive star cluster, which migrated in," Lu reported. "We
can now track the stars so precisely as they move around the black hole
that we can determine each star's exact orbit."

The research was conducted using the 10-meter Keck II Telescope, which is
the world's first 10-meter telescope with a laser on it. Laser Guide Star
allows astronomers to "generate an artificial bright star" exactly where
they want it, which reveals the atmosphere's distortions.

Black holes are collapsed stars so dense that nothing can escape their
gravitational pull, not even light. Black holes cannot be seen directly,
but their influence on nearby stars is visible, and provides a signature,
Ghez said.

The supermassive black hole, with a mass more than 3 million times that of
our sun, is in the constellation of Sagittarius. The galactic center is
located due south in the summer sky.

Co-authors on the research include fellow UCLA graduate student Seth
Hornstein; the adaptive optics team at W. M. Keck Observatory: David Le
Mignant, Marcos Van Dam and Peter Wizinowich; Antonin Bouchez (formerly
with the W. M. Keck Observatory) and Keith Matthews at Caltech; Mark
Morris, a UCLA professor of physics and astronomy; and Eric Becklin, a
UCLA professor of physics and astronomy.

This research is federally funded by the National Science Foundation.

More information and images of the galactic center are available at
http://www.astro.ucla.edu/research/galcenter/