On the search for O2 in extrasolar planets

The present work is a first attempt to investigate the feasibility of the optical detection of absorption lines in the atmosphere of extrasolar planets. Two cases are considered: (1) the reflection case, where the planet is observed by imaging via the light coming from the parent star and re-emitted by the planet; and (2) the occultation case, where the planet makes a partial occultation of the star. I find only in the latter case that there are planetary configurations where the absorption lines can effectively be detected with existing or forthcoming telescopes. The discussion is basically made for the O₂ A-band, which is of interest for exobiology.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A.