BY DR EMILY BALDWIN
Posted: 06 March, 2009
NASA’s Kepler mission to seek out other Earth-like planets is on the launch pad and ready for liftoff from Cape Canaveral tonight.
Kepler’s goal is to seek out the first Earth-sized planets orbiting stars in habitable zones, where liquid water could prevail on their surfaces. Of the 342 extrasolar planets discovered to date, the majority are gas giants, with very few rocky planets, let alone Earth-sized planets.
“This mission attempts to answer a question that is as old as time itself: are other planets like ours out there?” says Ed Weiler, associate administrator for NASA’s Science Mission Directorate at NASA Headquarters in Washington. “It’s not just a science question, it’s a basic human question.”
A scientist inspects Kepler's primary mirror. Image: NASA and Ball Aerospace.
The spacecraft will launch on a Delta II rocket, and after sixty-two minutes will separate from the rocket and arrive in its final Earth-trailing orbit around the Sun, an orbit similar to that of NASA’s Spitzer Space Telescope. After a commissioning period of roughly two months, Kepler will begin its three and a half year job of surveying over 100,000 stars in the region of sky near the Cygnus and Lyra constellations, using its 95 megapixel camera.
“We will monitor a wide range of stars; from small cool ones, where planets must circle closely to stay warm, to stars bigger and hotter than the Sun, where planets must stay well clear to avoid being roasted,” says William Borucki, science principal investigator for the mission at NASA’s Ames Research Center. “Everything about the mission is optimized to find Earth-size planets with the potential for life, to help us answer the question: are Earths bountiful or is our planet unique?”
Kepler will find planets by looking for periodic dips in starlight as the planet transits in front of its parent star. “Trying to detect Jupiter-size planets crossing in front of their stars is like trying to measure the effect of a mosquito flying by a car’s headlight,” says Fanson. “Finding Earth-sized planets is like trying to detect a very tiny flea in that same headlight.”
Kepler will search in this region of the Milky Way for Earth-like planets. Each rectangle represents a CCD element of Kepler's photometer. Image: Carter Roberts/Eastbay Astronomical Society.
If the mission does find Earth-size planets in the habitable zones of stars, it should find them first around stars that are smaller than our Sun because the habitable zone is closer for small stars. In this scenario, a planet would take less time to complete one lap of the star and therefore would take less time for Kepler to find and for other ground-telescopes to confirm its existence. Any Earth-size planets orbiting in the habitable zones of stars like our Sun - the true Earth analogues - would take at least three years to be confirmed.
“In part, learning about other Earths -- the frequency of them, the environment on them, the stability of the environment on other Earths, their habitability over the eons -- is going to teach us about our own Earth, how fragile and special it might be,” says astronomy professor Geoff Marcy at Berkeley and a Kepler scientific advisor. “We learn a little bit about home, ironically, by studying the stars.”
But even finding planets outside of a star's habitable zone will be of interest, since collating an inventory of all extrasolar, Earth-like planets in Kepler’s field of view will help provide clues to the commonality of terrestrial planets.
The mission has two launch opportunities from 10:49 to 10:52 p.m EST and 11:13 to 11:16 p.m EST (corresponding to the early hours of Saturday morning in the UK). For mission updates tonight and over the weekend, stay tuned to http://spaceflightnow.com