Search: Spectroscopy, Sodium
Scientists crossed a new frontier in exo-planet research just last year when, using the Hubble Space Telescope, they detected sodium by its characteristic orange colour in the atmosphere of a large alien world orbiting the star HD 209458. Perhaps we are seeing ETs street lighting from a distance?
Beginning in 2006, a new telescope, Kepler (approved recently by NASA) will monitor about 100,000 nearby stars, searching for the slight dimming that occurs when an orbiting planet blocks some of the parent star's light. Because Kepler will be sensitive enough to detect planets as small as Earth, this celestial survey will give scientists an idea of how common Earth-like planets are - and identify candidates for further study.
This space telescope will use a technique called interferometry to dramatically reduce the obscuring glare from the planet's parent star, allowing scientists to see the planet itself, and so perhaps be able to analyse the atmospheres of those planets - required to detect signs of life.