Alladi Ramakrishnan Hall

Exoplanets: The Search for Unintelligent Life

Sujan Sengupta

Indian Institute of Astrophysics

The systematic scientific quest for “habitable” planets and hence a possible answer to the eternal query of mankind - if we are alone or if life is a common phenomenon in the Universe, rekindled with the discovery of a Jupiter size planet orbiting a Sun-like star in 1995 by Michel Mayor and Didier Queloz of Geneva Observatory. Soon, astronomers of various countries started hunting for new planets by using all available ground-based telescopes as well as dedicated telescopes in space. Consequently, a large number of Extra-solar planets orbiting stars of various kinds were discovered and the diversity in the physical properties of these planets revolutionized our concept on planets, planetary systems and their formation. In particular rocky planets in the habitable zone of a star where the ambient temperature can support water to exist in liquid form have become the main focus. It is also speculated that a rocky natural satellite or exo-moon around a giant planet in the habitable zone may also harbor life under appropriate conditions. While exo-moons still remain elusive, a good number of rocky planets orbiting within the habitable zones of low-mass stars are discovered and the upcoming next generation ground and space-bound observing facilities will enable discovery of rocky planets in the habitable zone of Sun-like stars. Therefore, the next step is to probe the atmosphere of such “Habitable” planets and search for bio-signature in their spectra. In this lecture I shall present the background as well as the current status of research on exoplanets with an emphasis on the habitable planets.