The Probability of an Earth Analog

Title: The Occurrence Rate of Earth Analog Planets Orbiting Sunlike Stars

Authors: Joseph Catanzarite and Michael Shao, Jet Propulsion Laboratory, California Institute of

Technology

Summary paragraph

Kepler is a space telescope that searches Sun-like stars for planets. Its major goal is to determine ߟா௔௥௧௛, the fraction of Sunlike stars that have planets like Earth. When a planet ‘transits’ or moves in front of a star, Kepler can measure the concomitant dimming of the starlight. From analysis of the first four months of those measurements for over 150,000 stars, Kepler’s science team has determined sizes, surface temperatures, orbit sizes and periods for over a thousand new planet candidates. Here, we show that 1.4% to 2.7% of stars like the Sun are expected to have Earth analog planets, based on the Kepler data release of Feb 2011. The estimate will improve when it is based on the full 3.5 to 6 year Kepler data set. Accurate knowledge of ߟா௔௥௧௛ is necessary to plan future missions that will image and take spectra of Earthlike planets. Our result that Earths are relatively scarce means that a substantial effort will be needed to identify suitable target stars prior to these future missions.

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