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Posted by baalke on December 18, 2006, 5:27 pm
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NSF AWARDS $2 MILLION TO W. M. KECK OBSERVATORY IN HAWAII
Media Contact:
Laura K. Kinoshita
Public Information Officer
1-808-881-3827
newsletter@keck.hawaii.edu
KAMUELA, Hawaii (December 18, 2006) The National Science Foundation
(NSF) has awarded the W. M. Keck Observatory $2 million to improve the
sensitivity and resolution of the Keck Interferometer. The improvements
will enable the instrument to detect Jupiter-sized planets around other
stars and test predictions of Einstein's general theory of relativity
in
the chaotic core of our galaxy.
The three-year grant is from NSF's Major Research Instrumentation
Program (MRI), which each year funds more than 200 proposals to develop
or purchase scientific instrumentation. Typically, less than one-half
of
one percent of all submitted proposals receive the maximum award of $2
million, and only a couple go to astronomical observatories.
"The interferometer improvements will make Keck Observatory a unique
instrument for measuring the position, velocity and acceleration of
stars near the massive black hole at the center of our own galaxy,
allowing us to look for the distortions in space predicted by general
relativity," said Principal Investigator Dr. Peter Wizinowich, a senior
scientist at the W. M. Keck Observatory.
The money will be used to boost the sensitivity of the 85-m baseline
Keck Interferometer which combines the light from the two 10-meter
diameter Keck telescopes. Combined with Laser Guide Star Adaptive
Optics
on both Keck telescopes, the improvements will allow the linked Keck
telescopes to observe objects 100 times fainter than the existing
interferometer and measure the apparent positions of celestial objects
with 10 times more accuracy than a single Keck telescope working alone.
Observations near the black hole at the center of the galaxy "are at
the
core of the project and will be difficult and technically challenging,"
said Project Scientist James R. Graham, professor of astronomy at the
University of California, Berkeley.
Even before this goal is achieved, the upgrades will allow the Keck
Interferometer to help determine the mass of extra-solar planets by
measuring the periodic change in the position of parent stars caused by
the tug of unseen planets. Currently, more than 200 extra-solar planets
have been detected due to the radial velocity or "wobble effect" they
induce on their parent star. About two-thirds of all known extra-solar
planets have been confirmed at the W. M. Keck Observatory. The
Interferometer will add precise orbital measurements to the existing
catalogue of radial velocity data to help precisely determine the mass
of extra-solar planets the size of Jupiter and larger.
Extra-solar planets and dusty stellar disk observations were a major
goal of the interferometer when NASA's Origins program funded its
development in support of upcoming planet-finding missions. Now that
NASA has temporarily shelved these missions-the Space Interferometer
Mission and the Terrestrial Planet Finder- the Keck Interferometer will
be the only instrument in the world capable of measuring accurate
masses
for planets around distant stars.
The grant funds two major telescope improvements: installation of a
phase referencing system on the interferometer that will allow longer
exposures, and thus detection of fainter objects; and upgrading of the
interferometer to be able to perform accurate measurements of a star's
position.
Phase referencing is an interferometric technique in which two or more
receivers simultaneously look at the same reference star or galaxy and
compares signals. The process makes it possible for the instrument to
adjust the signal from each telescope just the right amount to cancel
out any wavelength differences caused by atmospheric turbulence, or
"seeing."
Phase referencing provides a stable image which will allow the Keck
Interferometer to track an object 100 to 500 times longer than before.
The extended exposure time will allow the instrument to study much
fainter objects, such as the cores of active galactic nuclei that
signal
the presence of a central black hole.
The second part of the project will develop the interferometer's
ability
to accurately measure positions of celestial objects. Improvements will
be made to the existing metrology systems and the instrument's ability
to accurately measure the relative positions of the two Keck
telescopes.
A key goal of the project, Dr. Wizinowich added, is to demonstrate the
power of combining laser guide star adaptive optics with interferometry
to observe faint science objects.
With the added improvements, the Keck Interferometer will resolve
objects on the sky to an accuracy of 30 microarcseconds, compared to
about 300-microarcsecond resolution of each telescope alone. Such fine
measurements will allow scientists to measure the velocities of stars
orbiting the black hole at the center of the galaxy.
The hope, Dr. Graham said, is to detect in the stellar orbits the
effect
of the dragging of "inertial reference frames" predicted to occur near
a
rapidly rotating black hole. This effect is predicted by Newton's laws
of motion for mass located very near a spinning black hole. Scientists
using the Keck Interferometer may be able to see this effect, which
would be major breakthrough in tests of general relativity and other
theories of gravity. The observations could also prove that black holes
spin, thus constraining theories of their formation.
"This is a major opportunity to show astronomers what interferometry
can
do for them," Wizinowich said. "Every time astronomers look in more
detail at the sky, they learn something new."
Scientific collaborators on the NSF proposal for development of the
Keck
Interferometer with Laser Guide Star Adaptive Optics for Microarcsecond
Astronmetry-from Exoplanets to Black Holes- include: Dr. Julien Woillez
at the W. M. Keck Observatory, Dr. Andrea Ghez at the University of
California at Los Angeles; Dr. Rachel Akeson and Dr. Lynne Hillenbrand
of the California Institute of Technology; Dr. Josh Eisner and Dr.
Eliot
Quataert of University of California at Berkeley; Dr. Nevin Weinberg,
University of California at Santa Barbara and Dr. John Monnier at the
University of Michigan.
The W. M. Keck Observatory is operated by the California Association
for
Research in Astronomy (CARA), a non-profit 501 (c) (3) corporation
whose
governing board consists of directors from the California Institute of
Technology and the University of California. In addition, the National
Aeronautics and Space Administration and the W. M. Keck Foundation each
have liaisons to the board. Construction of the twin Keck telescopes
and
domes was made possible with generous grants totaling more than $140
million from the W. M. Keck Foundation in Los Angeles.
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