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 μm excess emission toward Sun-like stars. Our unbiased sample is composed of 309 stars with masses 0.7-2.2 M⊙ and ages from <3 Myr to >3 Gyr that lack excess emission at wavelengths ≤8 μm. We identify 30 stars that exhibit clear evidence of excess emission from the observed 24 μm/8 μm flux ratio. The implied 24 μm 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 μm 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.
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