Institute of Astronomy

The impact of exo-Zodi on exo-Earth imaging

SpeakerTalk DateTalk Series
Grant Kennedy30 July 2014Across HR 2014 Talks


To directly image habitable Earth-like planets around other stars, a future New Worlds Mission will need to overcome background noise from warm ""exo-Zodi"" around the target stars. The occurrence rate of exo-Zodi of a given brightness (a.k.a the luminosity function) is unknown, and therefore so is the potential impact of exo-Zodi on future Earth-imaging attempts. With this motivation, I will present the first characterisation of the 12um exo-Zodi luminosity function around Sun-like stars. The dustiest old (>Gyr) systems are 1 in 10,000 occurrences, but warm dust is much more common around young (<120Myr) systems, with a 5% occurrence rate. These very different occurrence rates can be explained by two different models: in situ collisional evolution with a stochastic component, or comet delivery from exterior regions by planet scattering. Using the collision model, I will show predictions for the fraction of stars with exo-Zodi bright enough to cause problems for future exo-Earth imaging attempts. The prediction should be strongly tested by the Large Binocular Telescope Interferometer, for which I will present some initial results. The comet delivery model cannot yet make predictions, but I will present results from a study of two-temperature debris disks that test which of the collision or comet delivery scenarios is more likely.