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This image of the Crab Pulsar was taken with
CHIMERA, an instrument at the Palomar Observatory, which is operated by
the California Institute of Technology. Credit: NASA/JPL-Caltech.› Full image and caption
At the Palomar Observatory near San Diego, astronomers are busy
tinkering with a high-tech instrument that could discover a variety of
objects both far from Earth and closer to home.
The Caltech HIgh-speed Multi-color camERA (CHIMERA) system is looking
for objects in the Kuiper Belt, the band of icy bodies beyond the orbit
of Neptune that includes Pluto. It can also detect near-Earth asteroids
and exotic forms of stars. Scientists at NASA's Jet Propulsion
Laboratory and the California Institute of Technology, both in Pasadena,
are collaborating on this instrument.
"The Kuiper Belt is a pristine remnant of the formation of our solar
system," said Gregg Hallinan, CHIMERA principal investigator at Caltech.
"By studying it, we can learn a large amount about how our solar system
formed and how it's continuing to evolve."
The wide-field telescope camera system allows scientists to monitor
thousands of stars simultaneously to see if a Kuiper Belt object passes
in front of any of them. Such an object would diminish a star's light
for only one-tenth of a second while traveling by, meaning a camera has
to be fast in order to capture it.
"Each of CHIMERA's cameras will be taking 40 frames per second,
allowing us to measure the distinct diffraction pattern in the
wavelengths of light to which they are sensitive," said Leon Harding,
CHIMERA instrument scientist at JPL. "This high-speed imaging technique
will enable us to find new Kuiper Belt objects far less massive in size
than any other ground-based survey to date."
Astronomers are particularly interested in finding Kuiper Belt
objects smaller than 0.6 miles (1 kilometer) in diameter. Since so few
such objects have ever been found, scientists want to figure out how
common they are, what they are made of and how they collide with other
objects. The CHIMERA astronomers estimate that in the first 100 hours of
CHIMERA data, they could find dozens of these small, distant objects.
Another scientific focus for CHIMERA is near-Earth asteroids, which
the instrument can detect even if they are only about 30 feet (10
meters) across. Mike Shao of JPL, who leads the CHIMERA group's
near-Earth asteroid research effort, predicts that by using CHIMERA on
the Hale telescope at Palomar, they could find several near-Earth
objects per night of telescope observation.
Transient or pulsing objects such as binary star systems, pulsing white dwarfs and brown dwarfs can also be seen with CHIMERA.
"What makes CHIMERA unique is that it does high-speed, wide-field,
multicolor imaging from the ground, and can be used for a wide variety
of scientific purposes," Hallinan said. "It's the most sensitive
instrument of its kind."
CHIMERA uses detectors called electron multiplying charged-coupled
devices (EMCCDs), making for an extremely high-sensitivity, low-noise
camera system. One of the EMCCDs picks up near-infrared light, while the
other picks up green and blue wavelengths, and the combination allows
for a robust system of scanning perturbations in starlight. The
detectors are capable of running at minus 148 degrees Fahrenheit (minus
100 degrees Celsius) in order to avoid noise when imaging fast objects.
"Not only can we image over a wide field, but in other modes we can
also image objects rotating hundreds of times per second," Harding said.
One of the objects the CHIMERA team used in testing the instrument's
imaging and timing abilities was the Crab Pulsar. This pulsar is the end
result of a star whose mass collapsed at the end of its life. It weighs
as much as our sun, but spins 32 times per second. The instrument
focused on the pulsar for a 300-second exposure to produce a color
"Our camera can image the entire field of view at 40 frames per
second," Hallinan said. "We zoomed in on the pulsar and imaged it very
fast, then imaged the rest of the scene slowly to create an
Highlighting CHIMERA's versatility, the instrument also imaged the
globular cluster M22, located in the constellation Sagittarius toward
the busy center of our galaxy. A single 25-millisecond image captured
more than 1,000 stars. The team will be observing M22, and other fields
like it, for 50 nights over three years, to look for signatures of
Kuiper Belt objects.