Four
centuries after Johannes Kepler first described how planets orbit the Sun,
NASA's Kepler mission launches in search of Earth-size planets around distant
stars.
Kepler will
seek
evidence of planets by observing more than 100,000 stars continuously,
looking for the tiny dip in brightness caused by a planetary transit. I'm sure
that Johannes would be amazed; I know that I am. The launch is scheduled from Cape
Canaveral, Fla., at 10:48 p.m. EST on Thursday, March 5. That's one week from
now, and the countdown in underway. The excitement is palpable.
Kepler is
the first spacecraft capable of discovering Earth-size planets in the habitable
zone of distant stars. ESO's COROT spacecraft is finding "super-Earths" which
are planets several times the mass of Earth. COROT's planets are in short
period orbits, which means that the planets are close to their stars and are
high temperature orbs. The latest
COROT discovery is roughly twice the size of Earth. Ground-based telescopes
search for exo-planets using spectroscopy, and have discovered a bounty of
giant planets. More than 340
planets have been discovered, including 37 systems with multiple planets.
Altogether, planets have been found orbiting more than 280 nearby stars.
Amazing!
So far, planets
as small as Earth have not been found. The Kepler mission is specifically
designed to search for Earths in the habitable zone of other stars. This will
take time. One transit is not sufficient. Discoveries must be confirmed by at
least two additional transits, for a minimum of three transits. For a planet
like Earth in orbit around a Sun-like star, the transits would be about a year
apart. Thus, confirmation would require three years. The initial observation
period for Kepler is 3.5 years, and it may be extended.
Bill
Borucki, the Principal Investigator for the Kepler mission, has worked on the
idea of finding Earths for more than 20 years. At first, he had to convince
NASA that seeking small, terrestrial-type planets using the transit method was
feasible. Could equipment be designed and launched that could actually
accomplish the very precise observations needed to detect small planets?
Borucki and his team proposed the Kepler mission four times to the Discovery
Program. Following the third proposal in 1998, Dave Koch the Deputy Principal
Investigator was granted research funds to build a CCD camera and Bill Borucki
was granted funds to build a testbed. Together they formed the proof of
concept. They built a physical simulator in the labs at NASA's Ames Research
Center and successfully demonstrated that the transit method could detect
Earth-size planets. In the next round of Discovery proposals, two years later,
the Kepler Mission made the first cut and was ultimately selected in December
2001 as the tenth Discovery mission. Today, a large team of scientists and
engineers at NASA Ames Research Center, Jet Propulsion Laboratory,
non-profit organizations (including the SETI Institute) and several
universities are working together on Kepler, which was constructed by BATC (Ball Aerospace
& Technologies Corporation) in Boulder, CO.
Next week,
Kepler launches. Of course, the big question is whether "Earths" are common or
rare. We don't know, but the Kepler mission should be able to answer this question.
You can follow the mission via the NASA
website as we seek other worlds that could be like our own.
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