THE AGE OF THE HD 15407 SYSTEM AND THE EPOCH OF FINAL CATASTROPHIC MASS ACCRETION ONTO TERRESTRIAL PLANETS AROUND SUN-LIKE STARS

From optical spectroscopic measurements we determine that the HD 15407 binary system is ∼80 Myr old. The primary star, HD 15407A (spectral type F5 V), exhibits strong mid-infrared excess emission indicative of a recent catastrophic collision between rocky planetary embryos or planets in its inner planetary system. The synthesis of all known stars with large quantities of dust in their terrestrial planet zone indicates that for stars of roughly solar mass this warm dust phenomenon occurs at ages between 30 and 100 Myr. In contrast, for stars of a few solar masses, the dominant era of the final assembling of rocky planets occurs earlier, between 10 and 30 Myr age. The incidence of the warm dust phenomenon, when compared against models for the formation of rocky terrestrial-like bodies, implies that rocky planet formation in the terrestrial planet zone around Sun-like stars is common.