Explanation : Observational astronomy has recently provided evidence of the existence of massive Jupiter-sized planets orbiting distant suns, protoplanetary disks of gas and dust surrounding newly formed stars, and planetary bodies orbiting exotic stellar corpses known as pulsars . Indeed, the formation of planets seems to be a broader and more varied phenomenon than previously imagined. Are there nearby solar systems with Earth-sized planets as well? Many would answer yes, but small, relatively low mass planets orbiting sunlike stars - which might be capable of supporting life - are extremely difficult to detect. One possible approach to this daunting observational problem is to regularly monitor the light from many solar-type stars, searching for the slight decrease in brightness which signals the transit of a small planet in front of the stellar disk. A proposal for a space-based instrument to engage in such a program, the Kepler Mission , is illustrated above. In this concept , the monitoring space telescope orbits the Sun, slowly drifting away from Earth. The goal of this mission would be to discover Earth-sized planets in the habitable zone of solar-type stars , taking a step toward answering the profound question - Does life exist on other worlds beyond our Solar System?
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Credit: Ball Aerospace, The Kepler Mission, NASA/Ames Research Center