Evolution of mid-infrared excess around sun-like stars: constraints on models of terrestrial planet formation

We report observations from the Spitzer Space Telescope regarding the frequency of 24 mm excess emission toward Sun-like stars. Our unbiased sample is composed of 309 stars with masses 0.7-2.2 M-circle dot and ages from, < 3 Myr to > 3 Gyr that lack excess emission at wavelengths <= 8 mu m. We identify 30 stars that exhibit clear evidence of excess emission from the observed 24 mu m/8 mu m flux ratio. The implied 24 mu m excesses of these candidate debris disk systems range from 13% (the minimum detectable) to more than 100% compared to the expected photospheric emission. The frequency of systems with evidence for dust debris emitting at 24 mu m ranges from 8.5%-19% at ages < 300 Myr to < 4% for older stars. The results suggest that many, perhaps most, Sun-like stars might form terrestrial planets.