NASA's
planet-hunting Kepler space telescope is set for a planned March 5 launch to
begin searching for alien worlds the size of Earth and bigger, mission leaders said
Thursday.
"We're
only two weeks from launch and there's a lot of activities going on down at the
Kennedy Space Center right now," said Jon Morse, director of the
Astrophysics Division at NASA Headquarters in Washington, D.C.
The probe,
which is slated to blast off from the Cape Canaveral Air Force Station in Florida aboard a Delta 2 booster, will be searching
for Earth-sized planets orbiting other stars in the region where liquid
water - essential to life as we know it - might exist. The spacecraft is
expected to move to its launch pad today, mission managers said.
Over the
last two decades, scientists have spotted more than 300 extrasolar
planets circling other stars in our Milky Way galaxy. Most of these planets
have been about the size of Jupiter or larger, making it unlikely they would
harbor life.
"Most
of these planets do not have Earth-like sizes or orbits," Morse said.
Over the
course of its planned 3 1/2-year mission, Kepler will search the skies for
planets 30 to 600 times smaller than Jupiter - closer to an Earthly girth. After
launch, Kepler will enter a 372.5-day orbit around the sun, trailing in Earth's
wake. It is expected to be the first to find truly Earth-sized planets orbiting
stars like our own sun.
"I
call it our planetary census-taker," Morse said.
Astrophysicist
Alan Boss, of the Carnegie Institution in Washington, D.C., recently estimated
that there are about ten thousand billion billion habitable planets in the
observable universe, with some of those being Earth-like worlds.
Kepler will
also be looking for Earth-like
planets, rocky bodies that orbit what is called a star's "habitable
zone," the region where liquid water, and perhaps life, could exist.
"Kepler's
designed to find hundreds of Earth-like planets if they're common around stars,"
said Kepler principal investigator William Borucki of NASA's Ames Research Center in Moffett Field, Calif.
While
Kepler will be looking for planets that
could support life, it won't actually find any little green men.
"Kepler
is not hoping to find E.T., it's hoping to find E.T.'s home," Borucki
said.
Kepler
won't yield any spectacular Hubble-esque images, but its 0.95-meter diameter
telescope and array of 42 charge-coupled devices (light-sensitive microchips
also found in standard digital cameras) will search for planets by measuring
the change in brightness that occurs when a planets moves in front of its star
(from the perspective of Earth).
By
measuring the amount of fluctuation in light and how long it lasts, scientists
can estimate the size of the planet, the size of its orbit and potentially even
the planet's temperature.
This same
transit technique is responsible for finding most
of the known exoplanets to date.
The
potential planets Kepler spots will later be further examined by Earth-based
telescopes, to rule out false-positives and gather more observations.
Kepler, a
Discovery-class mission, was selected by NASA in 2001. Its original price tag
has risen over the last eight years, now reaching nearly $600 million.
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