Predicting Planets in Known Extrasolar Planetary Systems. III. Forming Terrestrial Planets

Recent results have shown that many of the known extrasolar planetary systems contain regions that are stable for both Earth-mass and Saturn-mass planets. Here we simulate the formation of terrestrial planets in four planetary systems, 55 Cancri, HD 38529, HD 37124, and HD 74156, under the assumption that these systems of giant planets are complete and that their orbits are well determined. Assuming that the giant planets formed and migrated quickly, terrestrial planets may form from a second generation of planetesimals. In each case, Moon- to Mars-sized planetary embryos are placed in between the giant planets and evolved for 100 Myr. We find that planets form relatively easily in 55 Cnc, with masses up to 0.6 M ⊕ and, in some cases, substantial water content and orbits in the habitable zone. HD 38529 is likely to support an asteroid belt, but no terrestrial planets of significant mass. No terrestrial planets form in HD 37124 and HD 74156, although in some cases 1-2 lone embryos survive for 100 Myr. If migration occurred later, depleting the planetesimal disk, then massive terrestrial planets are unlikely to form in any of these systems.