David Charbonneau

Harvard University

The Fast Track to Finding an Inhabited Exoplanet

When exoplanets are observed to transit their parent stars, we are granted direct estimates of their masses and radii, and we can undertake studies of their atmospheres. Such systems have profoundly impacted our understanding of giant exoplanets akin to Jupiter or Neptune, but the study of smaller rocky exoplanets has only just begun. The NASA Kepler Mission is conducting a space-based transit search for rocky planets orbiting large, Sun-like stars. Alternately, by targeting nearby low-mass stars, a ground-based transit search using modest equipment is capable of discovering planets as small as 1.5 Earth radii in their stellar habitable zones. The discovery of such planets would provide fundamental constraints on the physical structure of planets that are primarily rock and ice in composition. Moreover, by differencing spectra gathered when the planet is in view from those when it is occulted by the star, we can study the atmospheric chemistry of potentially habitable worlds.