Debris discs are a consequence of the planet formation process and constitute the fingerprints of planetesimal systems. Their solar system's counterparts are the asteroid and Edgeworth-Kuiper belts. The main goal of our survey was to detect extra-solar analogues to the Edgeworth-Kuiper belt around solar-type stars, putting in this way the solar system into context. This survey allows us then to address some questions related to the prevalence and properties of planetesimal systems.
We have used the unique photometric capabilities provided by Herschel/PACS to observe a sample of nearby FGK stars. Data at 100 and 160 µm were obtained, complemented in some cases with observations at 70 µm, and at 250, 350 and 500 µm using SPIRE. The observing strategy was to integrate as deep as possible at 100 µm to detect the stellar photosphere and therefore obtain an unbiased, statistical sample of Edgeworth-Kuiper belt analogs (and more luminous disks) around nearby FGK main-sequence stars. Our sample is volume-limited (distances < 20 pc) and spans a broad range of stellar ages – from ~0.1 to ~10 Gyr. All stars with known extrasolar planets within that distance were included; additionaly, some M- and A-type stars were observed in collaboration with the DEBRIS Herschel OTKP, so that the whole sample covers a decade in stellar mass from 0.2 to 2 solar masses.
Our survey provides an unprecedented lower limit to the fractional abundance of planetesimal systems, and acts as a proxy to assess the presence of giant planets resembling the roles played by Neptune and Jupiter in the solar system. The Herschel observations are providing new and unique evidence for the presence of mature planetary systems in the solar neighbourhood and, in turn, are addressing the universality of planets/planetary systems formation in disks around young stars.