The launch
of a European space telescope called COROT tomorrow could help planet hunting astronomers spot a bevy
of small, rocky worlds only a few times larger than Earth. But the detection of a true, Earth-like world--the holy
grail amongst planet seeking astronomers--will have to wait at least another two
years until the launch of NASA's space observatory, Kepler.
In just a
little over a decade, the number of known planets outside our solar system has
jumped from zero to over 200. But most of these extrasolar planets are so-called "hot-Jupiters," large, gassy worlds many times bigger than Jupiter which orbit very close to their stars.
Astronomers'
current catalogue of known exoplanets is heavily skewed towards these fast,
gaseous worlds because most of the exoplanets discovered to date were spotted
using a technique that watches for the slight gravitational pull that orbiting planets can have on
their parent stars. Because the planets would have to be large and orbiting
close to the star to exert any effect at all, these are the planets that are discovered.
Flying high
above the Earth's atmosphere, the Convection Rotation and planetary Transits
(COROT) satellite [[image] will use a different technique better suited to finding
smaller worlds. Called the "transit" technique [image], it will detect extrasolar planets by measuring the dip in
starlight their passage creates as they glide across the face of their parent
stars.
COROT's 27
centimeter (10.6 inch) lens will monitor the brightness of the stars, looking
for the slight dip in starlight caused by the planet's passage. COROT will be
able to monitor hundreds of thousands of stars simultaneously and will turn its
unblinking eye toward different parts of the sky for 150 days at a time. COROT
is expected to find between 10 to 40 rocky worlds over the course of its two
and a half year mission, along with tens of new gas giant planets.
As it's
observing a star for signs of a planet's passage, COROT will also watch for "starquakes," acoustical waves generated deep inside stars which
ripple across a star's surface, altering its brightness. This information can
be used to calculate a star's precise mass, age and chemical composition.
In 2008,
NASA will launch Kepler, a space telescope that works in the same way as COROT, but
which will be able to detect the first Earth-sized planets in similar orbits to
our own world.
"The goal
of Kepler is to find Earth-sized planets in habitable zones around equivalent
Suns, or slightly smaller," said Micheal Moore, NASA's program executive for
the mission. "We actually like them a bit smaller than our Sun itself, but basically the same thing."
Unlike
COROT, which will watch multiple targets over the course of its mission, Kepler
will continually stare at about 100,000 stars in Cygnus region for four years.
Cygnus is a prime viewing spot to look for rocky planets because it is outside
the plane of our solar system, so interference from the Sun's light is not a
problem. "If you pick an area where you don't have to look through the Sun to
get there, then you have twenty-four seven, 365 viewing of the sky," Moore said.
Kepler will
also be positioned in an Earth-trailing solar orbit so that its view is not
obstructed by Earth or the Moon. In
contrast, COROT will be positioned in a low Earth orbit. "Since the COROT guys
are going to be in a low Earth orbit, they don't have the opportunity to be
able to stare at one patch of sky for the entire mission of multiple years," Moore said.
COROT and
Kepler are only the first of many planned projects designed to look for planets
similar to Earth. ESA is also working on another project that will be capable
of chemically analyzing light reflected off a distant planet's atmosphere,
possibly revealing signs of life. Called Darwin, the planned satellite will be launched sometime around
2020.
The COROT
mission is led by the French national space agency (CNES) and supported by
other international partners, including the European Space Agency (ESA),
Austria Belgium, Germany, Spain and Brazil. The satellite is set to launch into
space on Dec. 27.
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