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NASA Space Science News
Proving
that two telescopes are better than one, NASA astronomers
have combined starlight from a pair of Hawaiian 10-meter
(33-foot) telescopes, creating an "optical interferometer"
with the resolving power of a huge single telescope 85 meters
wide -- nearly the size of a football field.
This
successful test at the W.M. Keck Observatory on Mauna Kea
makes the linked telescopes, which together are called the
Keck Interferometer, the world's most powerful optical observing
system. The project will eventually search for planets around
nearby stars and help NASA design future space-based missions
that can search for habitable, Earth-like worlds.
Right:
At the summit of Mauna Kea, Hawaii,
NASA astronomers have linked the two 10-meter (33-foot)
telescopes at the W.M. Keck Observatory.
"Successfully
combining the light from the two largest telescopes on Earth
is a fabulous technical advance," said Anne Kinney, director
of NASA's Astronomical Search for Origins program, which
includes the Keck Interferometer project.
Paul
Swanson, the Keck Interferometer project manager at NASA's
Jet Propulsion Laboratory (JPL) agreed. "This is a major
step in the creation of a whole new class of astronomical
telescopes. Historically, breakthrough technologies like
the Hale 200-inch and the Hubble Space telescopes have made
discoveries way beyond the purpose for which they were originally
built."
Since
1995, astronomers have discovered almost 50 planets orbiting
other stars. With current technology, which relies mainly
on radial velocity (or "Doppler Shift") techniques to detect
planets in an indirect fashion, they can find very large
worlds, 300 times as massive as Earth, that are located
close to their parent stars. Such planets -- called "Hot
Jupiters" -- are not likely to harbor life as we know it.
Using
a technique called interferometric nulling, scientists hope
to directly detect Hot Jupiters with the Keck Interferometer.
The powerful pair of telescopes might also reveal planets
farther from their parent stars, which means their reflected
light would be dimmer and harder to detect.
Left:
Nulling is a process that reduces
the light recorded from the central star of a planetary
system, while leaving the planet's light undimmed. Credit:
Terrestrial Planet Finder.
Nulling
might also reveal faint dusty disks surrounding nearby stars,
a telltale sign of planetary systems. Our own solar system
is permeated with space dust. (The elusive Zodiacal Light,
which sharp-eyed sky watchers can spot in the night sky,
are sunlight reflected from interplanetary dust.) These
tiny particles are leftovers from the formation of the planets
billions of years ago, along with bits of debris from comets
and asteroids. The amount of such dust orbiting other stars
is poorly known, but perhaps not for long. The Keck Interferometer
can sense clouds of so-called "exozodiacal dust" comparable
in size to the dust swarm in our own solar system.
Exozodiacal
dust is a noise source for future space missions like the
Terrestrial Planet Finder (TPF), an interferometer that
will seek out Earth-like planets by looking directly for
their infrared emissions. By probing exozodiacal dust around
nearby stars and by testing key technologies, the Keck Interferometer
will be an important pathfinder for the TPF.
Above:
This dusty disk, viewed edge on
surrounding Beta Pictoris, a star only 50 lightyears distant,
may signal the presence of an infant solar system. Credit:
Hubble Space Telescope.
On Monday,
March 12, 2001, starlight from HD61294, a faint star in
the constellation Lynx, was captured by both Keck telescopes
and transported across a sophisticated optical system spanning
the 85 meters (275 feet) separating the two telescopes.
In an underground tunnel the collected light waves were
combined and processed with a beam combiner and camera.
In order to properly phase the two telescopes, adaptive
optics removed the distortion caused by the Earth's atmosphere.
"This
first light from the Keck Interferometer marks a dramatic
step forward and will help us accomplish the ultimate goal
of the Origins Program -- to search for signs of life beyond
by examining the light from 'Earths' orbiting nearby stars,"
said Charles Beichman, the Origins chief scientist at JPL.
Testing
will continue for the next several months. Limited science
operations, including the search for planets, are expected
to begin this fall. Scientists around the world will soon
be invited to propose studies they would like to conduct
using the Keck Interferometer. Their proposals will undergo
a formal review and selection process.
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