Kepler

Johannes . 1571--1630, German astronomer. As discoverer of Kepler's laws of planetary motion he is regarded as one of the founders of modern astronomy

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

1 see table at craters.

2 A space telescope planned for launch by NASA in 2007 for the purpose of searching for Earth-sized extrasolar planets. The Kepler mission, to be managed by NASA's Jet Propulsion Laboratory, will seek to locate planets indirectly by watching for transits. The transit of a planet across the face of its parent star is only detectable if the planet is in direct line with the star and its orbit appears edge-on to the observer's line of sight. A transit should cause a minute decrease in the star's brightness, and Kepler will be designed to detect such dimming using a 1-meter telescope-photometer equipped with highly sensitive CCD technology. Using a relatively wide field of view, Kepler will measure the brightness of several thousand stars and check for brightness variations. Three transits, all with a consistent period, duration and change in brightness, provide strong confirmation of a planet's existence. From this information and the nature of the star concerned, Kepler's science team hopes to be able to measure the planet's orbit and work out whether it is in the habitable zone, the region of space around the star at the right distance for water to exist on the planet's surface. This will help determine whether or not the planet is like the Earth and can perhaps support life. Statistically it is estimated that the transit method is likely to detect only 0.5% of the number of planets there could possibly be in the Milky Way Galaxy.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006