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“Detecting Exomoons through Imaging”

Brianna Lacy (U. Washington)
Wednesday, 1540, Lecture Room 106

Direct imaging of extrasolar planets with future space-based coronagraphic missions may provide a means of detecting companion moons for exoplanets with bands of strong atmospheric absorption. Although currently proposed telescopes will not have the angular resolution necessary to spatially resolve a planet and its moon, the angular shift of a point spread function centroid can be measured to precisions better than the angular resolution of the telescope yielding information at angular scales nearer to that of exoplanet-exomoon separation. At wavelengths of light where an exomoon outshines its host due to absorption in the planet's atmosphere, the centroid will shift towards the exomoon. We thus propose a detection strategy based on the variation of the center of light with wavelength, “spectroastrometry," which can both yield a detection of an exomoon and allow for characterization of the moon's orbit and mass of the exoplanet. To explore this detection method, we consider two model systems: an earth moon analogue and a warm Jupiter with earth as its moon. We discuss the instrumentation requirements for detection of these model systems around nearby stars, as well as characterization of the moon-planet systems that may be identified with this approach.