outpost on the summit of Hawaiis dormant Mauna Kea volcano,
the worlds two most powerful telescopes, located at the W.
M. Keck Observatory, are probing the deepest regions of the universe.
Thanks to a Lawrence LivermoreKeck team of scientists and
engineers, astronomers are obtaining images on the 10-meter Keck
telescopes with resolution greater than that of other land-based
telescopes or even the orbiting Hubble Space Telescope.
Many of the Keck images,
together with those from the smaller Shane telescope at the University
of Californias Lick Observatory near San Jose, are being taken
by Lawrence Livermore astronomers working with colleagues from University
of California (UC) campuses and the California Institute of Technology
(Caltech). The images are shedding new light on the formation of
stars and galaxies, revealing unexpected features on planets and
moons in our solar system, and yielding new information on black
holes in the centers of distant galaxies.
The key to the unsurpassed
image clarity is adaptive optics that remove the blurring of starlight
caused by turbulence in Earths atmosphere, resulting in a
tenfold improvement in resolution. Adaptive optics measure the distortions
of light from a natural star or one manufactured by a powerful laser,
and then remove the distortions by reflecting the light off a deformable
mirror that adjusts several hundred times per second to sharpen
A Livermore-designed adaptive
optics system was installed on Licks 3-meter Shane telescope
in 1994, and Livermores sodium-layer laser guide star system
was added in 1996. In September 1996, Lick obtained the first significant
image improvement using adaptive optics with a laser guide star.
Routine astronomical observation with the laser guide star began
in August 2001, and the guide star was turned over to the observatory
for operation in spring 2002.
Kecks adaptive optics
system, for which Livermore scientists and engineers working with
their Keck colleagues provided the wavefront control system, made
its first observations in 1998 and began general use in late 1999.
Its laser guide star, a LivermoreKeck project, was installed
in fall 2001 and achieved first light on December 23,
2001. We asked for an early present this year, and just before
Christmas, we were given a virtual star that will dramatically increase
the research capabilities of the worlds largest telescope,
announced Frederic Chaffee, director of the Keck Observatory. The
laser guide star should be fully integrated with the adaptive optics
system by autumn 2002, with the first astronomical observation following
optics sharply increase the resolution of images taken at
the Lick Observatory near San Jose, California.
are reporting exceptional results from the adaptive optics systems
installed at the two observatories. At Lick, roughly 50 percent
of images are taken using adaptive optics, and about half of those
images are made with the laser guide star. At Keck, reports Livermore
laser scientist Deanna Pennington, People are extremely pleased
with the adaptive optics systems.
Pennington, who served as
laser guide star project leader at both Lick and Keck, says astronomers
are clamoring to use the Keck laser guide star because It
makes possible entirely new kinds of observations that astronomers
simply couldnt access before.
Livermore astronomers have
been among the first to use the adaptive optics systems. Most of
them are part of the Livermore branch of the University of Californias
Institute of Geophysics and Planetary Physics. Since its establishment
in 1983, the Livermore branch has been the focus of most astronomical
activities at the Laboratory.
Claire Max, Bruce Macintosh, and Seran Gibbard have been observing
objects within our solar system using both Lick and Keck adaptive
optics. At Lick, they have been aided by Livermores Don Gavel,
lead engineer for the adaptive optics system. The Livermore efforts
focused on observations of Io, Jupiters largest moon; Titan,
Saturns largest moon; the planets Uranus and Neptune; and
photograph of the Lick Observatory and the laser guide star.
Astronomers using Kecks adaptive optics have obtained
the best pictures yet of the planet Neptune. The images show
bands encircling the planet and what appear to be fast-moving
storms of haze. (b) The same image without adaptive optics.
Storms on Neptune
using the Keck telescopes have obtained the best pictures yet of
the planet Neptune, the eighth planet from the Sun. Thanks to adaptive
optics, the images reveal a wealth of small-scale features in Neptunes
atmosphere, including narrow, bright bands encircling the planet,
similar to those observed on Jupiter. There appear to be waves within
the bands and regions where the bands move apart and come together
as if they are separated by a vortex.
The images suggest violent
methane storms with wind speeds reaching more than 1,770 kilometers
per hour. The imaging team, which has included astronomers from
the UC campuses at Berkeley and Los Angeles (UCLA) and from Caltech,
is working to understand what might be the source of the energy
driving the extreme weather.
Working with UC Berkeleys
Imke de Pater, the team has also captured near-infrared pictures
of the planet Uranus, which mark the first ground-based detection
of the faint rings around that planet. Also clearly visible is a
layer of methane haze on Uranuss south polar cap, tiny cloud
features at high northern latitudes, and, inside the planets
bright epsilon ring, three fainter rings.
Keck images of Io have revealed
many glowing volcanoes. Macintosh took the images in the infrared
band to detect sources of heat on the moon. Other striking images,
taken by Gavel, are of the asteroid Kalliope with its own moon.
Gibbard has been using Keck to obtain images of Titan, the only
solid body in the solar system besides Earth to have a substantial
atmosphere (mostly nitrogen, with about 3 percent methane). Some
astronomers believe that Titans atmosphere may be similar
to that of Earths during our planets early development.
Methane haze in the upper atmosphere obscures Titans surface
features at visible wavelengths. However, in some narrow transparency
windows in the near-infrared band, surface features can be
seen through the haze.
Without adaptive optics,
says Gibbard, Titan looks like a fuzzy star. She has
been analyzing a large series of images to assemble the first map
of Titans surface. By taking many images over time,
we can see which features do not change, and these belong to the
surface, she says. The use of adaptive optics has replaced
a process called speckle imaging, which involved taking hundreds
of very fast exposures and assembling them. Adaptive optics
is much simpler, Gibbard says.
light from the laser guide star on the Keck II telescope,
December 23, 2001.
Benefits from Laser Advances
Since their invention, ground-based telescopes have
suffered from blurred images caused by Earths
fast-moving and turbulent atmosphere. However, advances
in optics and computer technology have made it possible
to sharply reduce this blurring by the use of adaptive
optics that correct atmospheric distortions and allow
ground-based telescopes to reach their theoretical maximum
systems have traditionally required the astronomer to
find a bright star as a reference point of light. However,
less than 1 percent of the sky contains stars sufficiently
bright to be of use as a reference light. To extend
the usefulness of adaptive optics, Livermore scientists
developed a laser system that creates a virtual reference
star high above Earths surface to guide the adaptive
optics system. The laser guide star is created by projecting
light from a dye laser on a layer of sodium atoms that
are in the atmosphere 90 to 100 kilometers above Earth.
The main components
of an adaptive optics system using a laser guide star
are a wavefront sensor camera equipped with a charge-coupled
device detector, a control computer, a deformable mirror,
a pulsed dye laser that is tuned to the atomic sodium
resonance line at a wavelength of 589 nanometers, and
a set of solid-state lasers to pump, or energize, the
dye laser. The dye laser, similar to that pioneered
at Livermore for its Atomic Vapor Laser Isotope Separation
program, creates a glowing star of sodium atoms measuring
less than 1 meter in diameter at an altitude of about
100 kilometers above Earths surface. This artificial
reference can be created as close to the astronomical
target as desired so that the light from the laser star
and the observed object pass through the same small
part of the atmosphere.
At the telescope,
wavefront sensors measure distortions due to atmospheric
turbulence, using light from the guide star as a reference.
The sensors relay this information to a computer, which
in turn controls the movements of tiny actuators attached
to the back of a deformable mirror. The mirror changes
its shape hundreds of times per second to cancel out
images obtained with the adaptive optics systems on
the telescopes at the W. H. Keck Observatory in Hawaii
are superior to images obtained with the Hubble Space
Telescope because Hubbles light-gathering mirror
is much smaller. (Adaptive optics will not, however,
replace space-based observatories, many of which are
designed to sample certain bands of electromagnetic
radiation such as ultraviolet light that are blocked
by Earths atmosphere.)
dye laser projects light into the sky through a 30-centimeter
refractive telescope that is mounted on the side of
the main telescope. The laser was designed and built
by Livermores Herbert Friedman. The deformable
mirror has 127 actuators to raise or lower a tiny part
of the front surface by up to 4 micrometers.
laser guide star at the Keck II telescope uses a 20-watt
dye laser, the most powerful laser in use at a
telescope. The laser light is projected onto the sky
with a 50-centimeter lens attached to the side of the
10-meter Keck II telescope. A 15-centimeter-diameter
deformable mirror is adjusted continuously by 349 actuators.
guide star was built at Livermore and then reassembled
at the observatorys headquarters in Waimea, Hawaii,
which is slightly less than 1 kilometer above sea level.
The observatorys telescopes are located at the
summit of the Mauna Kea volcano, over 4 kilometers above
sea level. Scientists observe on these telescopes remotely
from the Waimea headquarters to avoid the risk of sickness
from extended exposure to Mauna Keas high altitude.
During the two-year
temporary installation at headquarters, the Livermore
team of Deanna Pennington, Curtis Brown, Pam Danforth,
and Holger Jones made extensive improvements. We
installed a significant level of automation and diagnostics
on the laser guide star system to make it more reliable
and robust and permit it to be operated remotely from
Waimea, says Pennington, laser scientist and systems
engineer at both Lick and Keck. She notes that installing
the adaptive optics system and laser guide star at Lick
gave the Livermore team valuable experience in designing
the larger system at Keck. The laser system was installed
and activated on the telescope at the 122-kilometer
summit over a 6-month period, culminating in the first
light demonstration on December 23, 2001.
adaptive optics and laser guide star embody more than
two decades of Livermore experience in adaptive optics
technology. Adaptive optics systems with adjustable
mirrors have been used on a succession of increasingly
powerful lasers at Livermore, and they will be used
on the National Nuclear Security Administrations
National Ignition Facility (NIF), under construction
Claire Max and
Friedman started Livermores work on laser guide
stars in the early 1990s. Feasibility tests conducted
at Livermore in 1992 demonstrated the first laser guide
star at usable power levels and determined the requirements
for a telescope version.
are working on the next generations of adaptive optics.
About 20 Livermore employees belong to the Adaptive
Optics program within the Physics and Advanced Technologies
Directorate. One team is developing more reliable deformable
mirrors based on microelectromechanical technology.
from the Center for Adaptive Optics (see the box below)
and the European Southern Observatory in Chile, Pennington
will lead another group of Livermore scientists within
the NIF Programs Directorate who are investigating fiber
lasers to replace the current dye laser. Fiber lasers,
widely used in the telecommunications industry, will
be part of the NIF front end and will produce the laser
beam before it is amplified. Pennington says that fiber
lasers provide an elegant solution for generating
589-nanometer light because they are compact, efficient,
Macintosh and astronomers
from UCLA are using adaptive optics on Lick and Keck to study the
formation and evolution of planetary systems in the Trapezium (sword)
region of the constellation of Orion. This region, the closest large-scale
star formation to our Sun, serves as a stellar nursery.
One of the most fundamental
questions in modern astronomy is the possibility of the existence
of other solar systems like our own, those with potentially habitable
planets, Macintosh says. He notes that although planetary
systems have been detected through indirect methods, all are different
from our solar system because they have massive, Jupiter-like planets
occupying the inner part where Earth is located in our system. It
is unclear which type of system is more common in the universe,
astronomers first use Lick to scout for promising young stellar
systems and then travel to Keck to obtain high-resolution images.
Bright stars found in the constellation serve as handy natural guide
stars for the adaptive optics system.
Macintosh says that large
planets (about the size of Jupiter) that are 10 million years old
or younger radiate significant near-infrared light. Kecks
adaptive optics system can detect these planets even though they
are a million times dimmer than the star they orbit. Macintosh has
also imaged several of the Orion proplydsprotoplanetary disk
envelopes surrounding young starsthat are being disrupted
by intense radiation from nearby supermassive stars.
Keck could be the first
telescope to image a planet orbiting a star outside of our solar
system, Macintosh says. He adds, Kecks adaptive
optics system represents the most significant advance in astronomical
capabilities since the launch of the Hubble Space Telescope.
Jennifer Patience is studying
the binary star systems that are found among the young stars in
Orions Trapezium. We want to know how common it is for
planets to form in binary systems, she says. Astronomers believe
that the presence of a nearby companion star may disrupt circumstellar
disks surrounding young stars (circumstellar disks provide the raw
materials for planet formation). Working with astronomers from UC
Berkeley and UCLA, she uses Keck and Lick adaptive optics systems
to look at star systems in the near-infrared spectrum and to see
through clouds of galactic dust and gas that mask images in visible
The team has imaged 150 stars
in Orion with resolution never before attained. Kecks adaptive
optics make it possible to resolve binaries with separations comparable
to the distance between our Sun and Uranus, a distance that is less
than the diameter of circumstellar disks. We now have the
capability of resolving most binary systems, including a range inaccessible
to previous surveys, Patience says. She notes that with the
resolving power of Kecks adaptive optics system, a person
standing on Mauna Kea, located on the big island of Hawaii, could
see objects as small as 1 centimeter tall on the island of Oahu,
approximately 400 kilometers away.
image of Io, Jupiters largest moon, reveals volcanic
activity. (Image courtesy of Keck Observatory.)
Center Spreads the Word
Lawrence Livermore is a major partner in the Center
for Adaptive Optics, which is headquartered at the University
of California (UC) at Santa Cruz. The center, funded
by the National Science Foundation, began operations
in November 2001. The 27 partner institutions in the
center also include several other UC campuses, the University
of Chicago, the California Institute of Technology,
the University of Rochester, the University of Houston,
Indiana University, and 17 other partners.
director is Jerry Nelson, professor of astronomy and
astrophysics at UC Santa Cruz. Nelson designed the twin
telescopes at the W. M. Keck Observatory in Hawaii.
Livermore scientists Claire Max and Scot Olivier are
associate directors, and Livermore scientists play important
roles in center activities and sponsored research.
The center coordinates
the efforts of researchers across the country involved
in the growing field of adaptive optics for astronomical
and vision science. The center also operates science
education and outreach programs for scientists and college
is to provide the sustained effort needed to bring adaptive
optics from promise to widespread use by astronomers
and vision researchers, says Max. She predicts
that most large ground-based telescopes will have adaptive
optics systems within the next few years. Relatively
few astronomers, however, have experience with adaptive
optics, let alone laser guide stars. We want to
inform the broader astronomical community about adaptive
optics through conferences and workshops, she
Max points out
that adaptive optics are also used in vision science
to compensate for aberrations in the eye that affect
vision and impede efforts to study the living retina.
Adaptive optics has made it possible to obtain images
of the living human retina with unprecedented resolution,
enabling researchers to see individual light receptors.
Adaptive optics may also provide normal eyes with supernormal
vision. A team of Livermore researchers led by Olivier
is developing a high-resolution liquid-crystal adaptive
optics system for human vision correction that will
be used at UC Davis to study the limits of human visual
into Black Holes
Max, her colleague Gaby Canalizo,
and astronomers from UC Santa Barbara, are using adaptive optics
on Lick and Keck telescopes and Licks laser guide star to
observe nearby active galactic nuclei, which are small, extremely
bright central regions in some galaxies. Very distant and bright
active galactic nuclei are known as quasars. Active galactic nuclei
are thought to contain black holes at their centers, which suck
up stars, planets, and gas from the surrounding galaxy in a process
called accretion. In some cases, the material is then shot out from
the region surrounding the black hole at high speeds in outflows
known as jets.
Max notes that for 30 years,
Department of Energy laboratories have been doing pioneering work
on the high-energy processes involved in black-hole formation and
emission. However, only in the past few years has direct evidence
for black holes begun to emergein the form of high-resolution
observations that probe the active galactic nuclei close to the
central black hole.
Max and Canalizos team
is observing energy outflow from the process of accretion of matter
into the most massive black holes in nearby galaxies. The images
enable astronomers to explore the region nearby and the evolution
of the central black holes. In the process, the astronomers have
found double active galactic nuclei suggestive of galaxy mergers,
which are believed to be a cause of black hole formation.
first map of the surface of Titan, Saturns largest moon,
is being assembled with the help of adaptive optics. Colors
denote reflectance, with 1.00 corresponding to the reflectance
of a perfect mirror. Data from current observations are filling
in the blank areas.
adaptive optics image of a protoplanetary disk envelope surrounding
a young star in the Trapezium region of the constellation
to the Future
When the Keck laser guide
star becomes available for viewing, Livermore scientists will be
among the first to use it and thereby help to make laser guide stars
a more accepted tool of astronomical research. Pennington notes
that a National Academy of Sciences panel has identified laser guide
stars as a key technology for advancing astronomy. Most experts
say that the next generation of giant telescopes will not be feasible
without adaptive optics systems equipped with laser guide stars.
However, as a telescope gets
larger, the requirements for an adaptive optics system become increasingly
rigorous. The proposed California Extremely Large Telescope (CELT),
a collaboration between UC and Caltech, is designed to have a 30-meter-diameter
mirror, three times the size of Kecks. CELTs adaptive
optics system will probably require multiple laser guide stars with
several mirrors working together to correct for different layers
of atmospheric turbulence. Each mirror may require about 5,000 actuators.
Thanks to increasingly powerful
telescopes, more capable adaptive optics systems, and advanced guide-star
lasers, the heavens are sure to be revealing more of their secrets
in the new millennium.
Key Words: active
galactic nuclei, adaptive optics, atomic vapor laser isotope separation,
binary star, black hole, California Extremely Large Telescope (CELT),
deformable mirror, dye laser, Hubble Space Telescope, laser guide
star, Lick Observatory, W. M. Keck Observatory.
information contact Deanna Pennington (925) 423-9234 (firstname.lastname@example.org).
information on the W. M. Keck Observatory:
information on the Lick Observatory:
information on the Center for Adaptive Optics: