On this day......

On March 7th 2009, the Kepler space observatory, designed to discover Earth-like habitable planets orbiting other stars, is launched.  The spacecraft is named after the Renaissance astronomer Johannes Kepler who is best known for his laws of planetary motion.

Kepler is designed to survey a portion of our region of the Milky Way to discover dozens of Earth-size extrasolar planets in or near the habitable zone and estimate how many of the billions of stars in our galaxy have such planets.

Kepler uses a photometer that continually monitors the brightness of over 145,000 main sequence stars in a fixed field of view. This data is transmitted to Earth and analysed to detect periodic dimming caused by extrasolar planets that cross in front of their host star.

As of July 2013^[update], Kepler had found 134 confirmed exoplanets in 76 stellar systems, along with a further 3,277 unconfirmed planet candidates. In November 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of sun-like stars and red dwarf stars within the Milky Way Galaxy.  11 billion of these estimated planets may be orbiting sun-like stars.  The nearest such planet may be 12 light-years away, according to the scientists.

For more information visit:-
http://en.wikipedia.org/wiki/Kepler_(spacecraft)
http://kepler.nasa.gov/