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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