Institute for Advanced Study/Princeton University Joint Astrophysics Colloquium

Planetesimals are the building blocks of planets. They can be traced by the dust they produce in collisions or sublimation that forms a debris disk. In the solar system, such a dust disk is produced by the asteroids, comets and Kuiper Belt objects, with a dust production rate that has changed significantly with time, being higher in the past when the planetesimal belts were more densely populated. The Herschel DEBRIS, DUNES, and GT programs observed 37 extrasolar planetary systems within 25 pc. With a sensitivity to detect far-infrared excess emission at flux density levels only an order of magnitude greater than that of the current solar system’s Kuiper belt, these surveys identified 11 debris disks, indicating the presence of planetesimals. We discuss the general characteristics of these Kuiper belt-like disks and the correlations between the stellar, planetary, and debris components. We also present results from an unbiased subsample of the Herschel surveys consisting of 204 FGK stars, located at distances <20 pc, with ages > 100 Myr, and with no binary companions at <100 AU, and discuss whether the presence of planets affect the frequency and properties of extrasolar Kuiper belts. Is there evidence that debris disks are more common, or more dusty, or have a different characteristic temperature around stars harboring high-mass or low-mass planets compared to a control sample without identified planets? Are debris disks more or less common, or more or less dusty, around stars harboring multiple planets compared to single-planet systems? The study of extrasolar Kuiper belt-like disks can shed light on planet formation and migration scenarios. It can also help assess whether terrestrial planet detection might be feasible in these systems. The debris dust can cause an important observational issue for direct detection, with the level of zodiacal light being one of the parameters that defines the design of future telescopes like ATLAST, that have a goal of detecting biosignatures. From our unbiased subsample, we find that 14% of solar-type stars harbor dust-producing planetesimals at 10s of AU from the star with a distribution of fractional luminosity (Ldust/Lstar) that can be reproduced by a Gaussian centered at the solar-system’s level. A Gaussian distribution centered at 10× the solar-system’s value can be ruled out. Because this dust would drift into the terrestrial planet region under PR drag, this indicates that there are good prospects for finding a large number of debris-disk systems—with evidence of harboring planetesimals—with zodi emission low enough to be appropriate targets for terrestrial-planet searches.