NASA's Kepler telescope, set to blast into space from Cape Canaveral, Fla., Friday night, will look for Earth-like planets orbiting sun-like stars.
Smaller than the Hubble telescope—measuring 15.3 feet versus Hubble's 43.5—Kepler carries just one main piece of scientific hardware, a light imager known as a charged couple device that detects fluctuations in light so tiny they're measured by counting the electrons they produce on a silicon surface.
This will allow Kepler to spot planets by the previously invisible change in luminosity they cause as their orbit carries them around the facing side of their parent star.
Source: Time, Kepler Telescope to Take a Census of the Galaxy