Debris discs and comet populations around Sun-like stars: the Solar system in context

Numerous nearby FGK dwarfs possess discs of debris generated by collisions among comets. Here, we fit the levels of dusty excess observed by Spitzer at 70 mu m and show that they form a rather smooth distribution. Taking into account the transition of the dust removal process from collisional to Poynting-Robertson drag, all the stars may be empirically fitted by a single population with many low-excess members. Within this ensemble, the Kuiper Belt is inferred to be such a low-dust example, among the last 10 per cent of stars, with a small cometary population. Analogue systems hosting gas giant planets and a modest comet belt should occur for only a few per cent of Sun-like stars, and so terrestrial planets with a comparable cometary impact rate to the Earth may be uncommon. The nearest such analogue system presently known is HD 154345 at 18 pc, but accounting for survey completeness, a closer example should lie at around 10 pc.