Exoplanet findings spark philosophical debate

How many worlds are there out there? Are we alone in the universe? What were once speculative and philosophical questions are now being tackled with real data, generated by NASA's planet-hunting space telescope, Kepler.

Discussion of both questions - you could call them the practical and the spiritual aspects of the huge amounts of planetary data from Kepler - took up several seminars at the American Association for the Advancement of Science meeting in Washington DC. 

First the hard data, which we heard about on Saturday. Launched in 2009, Kepler has been staring at a small patch of sky containing some 150,000 stars. By measuring the fluctuations in light from the stars, astronomers can deduce the existence of orbiting planets. So far some 1235 potential planets have been identified. Of these, 68 are Earth-sized, and 54 may be in the fabled Goldilocks zone, the habitable region of space not too close and not too far from its star.