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FOR AS long as humans have looked at the night sky we have speculated on the possibility that other planets harbour intelligent life. Now that we are capable of sophisticated scientific probing of the universe, the search for such planets is on in earnest. Nasa launched the Kepler telescope in March 2009 to search for potential life-supporting Earth-sized planets around other stars (kepler.nasa.gov).

The Kepler telescope orbits the sun in an Earth-trailing orbit so that its view of the stars is not blocked periodically by the Earth, moon or sun. The telescope looks fixedly at a star field in our region of the Milky Way in an effort to detect associated planets that are one-half to twice the size of Earth, particularly planets that orbit their stars in the “habitable zone”, where liquid water could exist and where life as we know it might reside.