How common are extrasolar late heavy bombardments?
Recent infra-red surveys of FGK stars have shown that 4% of stars exhibit 24 Ám excess and 16% exhibit 70 Ám excess indicating the presence of debris discs. In many cases these discs occur 10s or even 100s of AU from the central star, analogous to our own Kuiper belt. Studies of the history of our own Solar System show that the primordial Kuiper belt was once much more massive than it is now. Interactions between the Kuiper belt and the outer planets caused the outer planets to migrate. The Nice model shows that this migration could have been the cause of the Late Heavy Bombardment (LHB) on the Moon, which occurred 3.8 Gya. Here we investigate whether LHB-like events may have occured in extrasolar systems. We develop a model of how the Solar System would have appeared to a distant observer during its history based on the Nice model. We show that the Solar System would have been amongst the brightest of systems with debris discs before the LHB at both 24 and 70 Ám. We find a significant increase in 24 Ám emission during the LHB, which rapidly drops off and becomes undetectable within 30 Myr, whereas the 70 Ám emission remains detectable until 360 Myr after the LHB. Comparison with the statistics of debris disc evolution shows that such heavy bombardment events must be rare occurring around less than 12% of Sun-like stars and with this level of incidence we would expect approximately one of the 413 Sun-like, field stars so far detected to have a 24 Ám excess to be currently going through an LHB.