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Kepler's Big News

Paul Kohlmiller


At the beginning of February, NASA’s Kepler mission finally spilled the beans on their big news. It wasn’t like they were withholding information on exoplanet discoveries. But it takes a while to get enough data to make sure-footed announcements. And although Kepler was launched mid-2009, the scientists have only been able to analyze 4 months worth of scientific data. Think about that for a moment. Kepler is detecting planets by measuring the drop in a star’s apparent magnitude caused by the planet passing between its star and us. That requires that three points, the star, the planet, and us be close to colinear. And the timing has to be right. You would need 2-3 years in order to see Earth pass in front of the Sun 3 times. If, so far, you see it transit 2 times you could call it a “candidate”.

And that was the big news: 1235 planetary candidates around 997 stars based on observations taken between May 2, 2009 and September 16, 2009. 68 of these candidates are 1.25 Earth’s radius or less. 288 are called super-Earth size, between 1.25 and 2 Earth radii. Most of the candidates are in the category of Neptune-size (2-6 Earth radii) but 74% are less than the actual size of Neptune. 17% of the stars have more than 1 planet. Indeed, at the same time as this announcement, NASA also announced the discovery of a 6 planet system that is surprisingly compact. Please see the diagrams on page 3 and more information in our Astronomy news section on page 6.


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