NASA’s Kepler Mission Launches Next Week
By Edna DeVore
Co-I, Education and Public Outreach, Kepler Mission
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 KSC at 10:48 PM 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 star.
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.