Press Release

Laser Vision Gives New Eyes to Keck Telescope

By SpaceRef Editor
September 17, 2004
Filed under , ,
Laser Vision Gives New Eyes to Keck Telescope

The Laser Guide Star Adaptive Optics
system at the W. M. Keck Observatory is exceeding performance expectations
and is poised to revolutionize many fields of astronomy. The new guide star
system, the only one of its kind on a very large telescope, allows
astronomers to use adaptive optics to study astronomical objects with
unprecedented resolution anywhere in the night sky. The system also opens
the door to wide-field imaging with adaptive optics.

“We are just thunderstruck with this new capability,” said Dr. Frederic
Chaffee, director of the W. M. Keck Observatory in Hawaii. “Laser guide
stars on large telescopes are a remarkable breakthrough for ground-based
astronomy and we look forward to providing this astonishing capability to
Keck astronomers as quickly as possible.”

The dramatic boost in telescope performance is due to a new laser system
that allows adaptive optics (AO) to make precise atmospheric corrections to
a scientific target. Before the laser guide star (LGS) system, Keck
astronomers had to rely on the availability of a relatively bright,
naturally-occurring star to measure and correct for atmospheric distortions.
However, such relatively bright stars are available in only about one
percent of the sky. The new astronomical laser removes these limitations and
gives almost full access to the sky for study with adaptive optics.

“It is a tremendous achievement to turn one of the most technically complex
prototypes in astronomy into a facility-class instrument on an operational
telescope, said Dr. Peter Wizinowich, head of the Adaptive Optics group at
the W. M. Keck Observatory. “It is a significant accomplishment for the

Image blurring has plagued astronomy since the invention of the telescope
nearly 400 years ago and has prevented ground-based astronomers from
studying structural details of faint objects such as spiral arms in distant
old galaxies.

“Telescopes in space and on the ground have analyzed the light from galaxies
for years, but now we can actually see the structure and stellar population
inside those galaxies,” said Dr. David Le Mignant, instrument scientist for
the adaptive optics system at the W. M. Keck Observatory. “It is as if the
Keck telescope were in space!”

With the atmospheric blurring removed by the Keck adaptive optics system,
and the large diameter of a 10-meter mirror, the Keck II telescope is now
more powerful than even the largest space-based telescope for looking at the
cosmos in the near infrared.

“Keck’s achievement in bringing this new technology to fruition marks
nothing less than a renaissance in ground-based infrared astronomy,
equivalent to the day Galileo first turned his telescope to look at the
night sky,” said Dr. Matt Mountain, director of the Gemini Observatory,
which operates twin 8-meter telescopes. “A profound impact of these results
is that it can enable a whole new class of extremely large 30 meter to 100
meter telescopes to obtain diffraction-limited images from the ground.”

Studying the center of our home galaxy, the Milky Way, is another of the key
scientific drivers for developing adaptive optics systems and improving
their performance. “The center of our galaxy is a very difficult region to
study from Hawaii because it rises only about 44 degrees above the horizon,”
said Dr. Antonin Bouchez, adaptive optics researcher at the W. M. Keck
Observatory. “The Galactic Center is also a region in the sky heavily
obscured by interstellar dust, and only a few dim stars are available in
that area for us to use as reference stars to guide the adaptive optics

Despite these observing difficulties, which limited the ability to correct
the image blur, astronomers were previously able to use a guide star 30
arcseconds away from the Galactic Center to study the motion of individual
stars in the very central region. This work helped confirm the presence of a
massive black hole at the center of our galaxy.

“With the laser guide star, we can place a far brighter reference star right
on top of the black hole and suddenly we’ve removed that 30 arcsecond
penalty,” added Dr. Bouchez.

The new guide star images show many more point sources in the central region
of the Galactic Center, and these stars are much better resolved (Figure 1).
Now, the black hole at the center of our galaxy is easy to distinguish from
other sources, even allowing scientists to witness a giant flare as plasma
material fell into the black hole (Figure 2). The new system can also be
used to generate large, panoramic views of the sky because it creates its
own reference star in any given field. For the Galactic Center, AO-corrected
images over a large field of view were assembled to study stars within five
light years of the central black hole region (Figure 3).

“Past studies have shown that several of the stars orbiting the black hole
seem surprisingly young, yet this is a paradox because stars cannot be born
in such a violent, turbulent region,” said Andrea Ghez, head of the Galactic
Center group and professor of physics and astronomy at the University of
California, Los Angeles. “This wide-field image lets us study how the young
and old stars are distributed in relation to their position to the black
hole. With the laser guide star, we can do this on a much larger scale than

The new images of the Galactic Center were obtained July 26, 2004 under
average turbulence conditions for Mauna Kea (0.4 arcseconds). Team members
responsible for the observations are Peter Wizinowich, team lead, and
Antonin Bouchez, Randy Campbell, Jason Chin, Scott Hartman, Erik Johansson,
Robert Lafon, David Le Mignant, Paul Stomski, Doug Summers and Marcos van
Dam, all from W. M. Keck Observatory.

Shared risk observations by a small number of astronomers will continue on
the LGS/AO system through July 2005. General observing with the LGS/AO
system will begin August 2005.

The laser guide star adaptive optics system was funded by the W. M. Keck
Foundation. The artificial laser guide star system was developed and
integrated in a partnership between the Lawrence Livermore National Labs
(LLNL) and the W. M. Keck Observatory. The laser was integrated at Keck with
the help of Dee Pennington, Curtis Brown and Pam Danforth. The NIRC2
near-infrared camera was developed by Caltech, UCLA and the W. M. Keck
observatory (P.I. Keith Matthew from CalTech).

The W. M. Keck Observatory is managed by the California Association for
Research in Astronomy (CARA), a non-profit 501 (c) 3 corporation whose board
of directors includes members from the California Institute of Technology,
the University of California and the National Aeronautics and Space
Administration (NASA). For more information and accompanying figures, please
visit .

SpaceRef staff editor.