The Optical Path in the Kepler Photometer

December 29, 2009
CreditNASA Kepler Mission/Dana Berry
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Kepler does not directly observe the image of a planet. Rather it observes the effect the planet has on its parent star. If the orbit of the planet is aligned along Kepler's line of sight to the star, it will block a very tiny amount of light coming from the star to the Kepler telescope. The telescope will image the light from many stars at once. It uses 42 CCDs, charge coupled devices, detectors similar to those in commercial digital cameras, but much larger, having at total of 95 mega-pixels. With the CCDs Kepler is capable of observing over 100,000 stars all at once and measuring their brightness to an accuracy of better than 1 part in 100,000, or ten parts per million. This is equivalent to looking at the Rose Bowl from the Goodyear blimp and detecting every time just one person walks in or out of the stadium.