BERKELEY — When NASA’s Kepler telescope rockets into the night sky on Friday, March 6, from Cape Canaveral Air Force Station in Florida, two University of California, Berkeley, astronomers - key members of the Kepler team - will be watching its fading contrail, hoping that the telescope will reveal Earth’s and humanity’s place in the universe.
Kepler in the classroom: LHS’s Alan Gould has been gearing up for years for the Kepler mission, hoping its search for habitable planets will galvanize student interest in science.
Habitable planets are often said to be in the "Goldilocks zone," where it is not too hot, not too cold, but just right. This zone is far from a hot, blue star, so any habitable planet around a hot star would have a long-period orbit. For cooler, redder stars, a planet in the zone would be close-in and would orbit in several weeks or months. Short-period planets are easier for Kepler to detect because they transit their star more frequently. (Images courtesy NASA)
Kepler’s main goal is to discover Earth-size planets outside our solar system with conditions conducive to life, but it also will tell us how common rocky planets like Earth are in our Milky Way Galaxy. Of the 300-plus extrasolar planets discovered to date, fewer than a handful are thought to be rocky like the Earth and none are Earth-size. The rest are gas giants like Jupiter or ice giants like Neptune.
"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," said astronomy professor Geoff Marcy, a Kepler scientific advisor who, with Paul Butler and a large international planet-hunting team, have discovered nearly half of all known planets outside our solar system. "We learn a little bit about home, ironically, by studying the stars."
Gibor Basri, a UC Berkeley professor of astronomy and co-investigator for the Kepler mission, gave the mission a thumbs-up even before Marcy and others discovered the first extrasolar planet in 1995. Back then, Bill Borucki of NASA Ames Research Center in Mountain View, Calif., now principal investigator for the Kepler mission, was known for nagging astronomers to search for planets by looking for a slight decrease in a star’s brightness as a planet crosses in front of the star - a so-called transit.
Basri was asked to be part of a blue-ribbon panel convened to determine whether Borucki should, as Basri put it, "stop tilting at windmills." At the time, Basri said, "most people didn’t appreciate why a transit is a good way to find planets," mainly because astronomers weren’t sure that planets are common enough to make such a search fruitful.
According to Marcy, who first started working on a sensitive Doppler technique for finding planets in 1984, "it was considered lunatic to look for any planets. When I first started looking, people were embarrassed for me. They would look down at their shoes and wonder why I had abandoned a perfectly good career to look for planets."
But Basri and others judged that Borucki’s transit technique might just work - a conclusion bolstered by the steady stream of newly discovered exoplanets that soon began emerging from Marcy’s group and a rival group led by Michel Mayor and Didier Queloz in Switzerland. However, the Doppler technique can’t easily detect Earth-size planets orbiting at Earth’s distance from a star. The transit technique should. Basri subsequently joined a team of astronomers with Borucki in proposing the Kepler mission, approved in 2001, to put a space-borne telescope in orbit to search for transiting Earth-like planets.
NASA is emphasizing Kepler’s potential to discover new habitable rocky planets. In a media briefing held at NASA headquarters in Washington, D.C., on Feb. 19, Marcy collaborator and San Francisco State University astronomer Debra Fischer said that "the ultimate goal of NASA, in 15 years or so, it to take an image of a blue ball. Kepler will tell us how to get (to that goal)."