AAS 202nd Meeting, May 2003
Session 34 When Do Planets Form?
Topical Associated Poster, Tuesday, May 27, 2003, 10:00am-6:30pm, West Exhbit Hall

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[34.02] Prediction of Paradoxical Late-epoch Brightening of Planetary Debris Disks

S. M. Mehmud, D. E. Backman (Franklin and Marshall College)

The asteroid belt contains a population of planetesimals remnant from the formation of our solar system. It loses mass with time both via planetary perturbations removing asteroids, and also via collisions of asteroids that produce dust which is then removed from the system. The asteroid belt and its associated zodiacal dust cloud now have low density such that grains large enough not to be ejected by radiation pressure spiral toward the Sun under the influence of Poynting-Robertson (P-R) radiation drag. In a denser belt, mutual collisions of grains and direct ejection of tiny fragments would dominate over the P-R process.

It can be inferred that the asteroid belt was as much as 1000x more massive when the planets finished forming than it is at present. We calculate that asteroidal/zodiacal grain evolution originally produced relatively little warm zodiacal dust but rather a spray of small grains exiting the solar system. Thus, the young solar system’s thermal infrared spectral energy distribution (SED) would have been quite different from what it is now. We have estimated the time during the 4.5 Gyr history of the solar system when the dust cloud associated with the asteroid belt crossed the threshold between high-density (collisional, “blowout”, cold SED) and low-density (P-R drag, inward drift, warm SED) regimes. At the time of that transition the solar system’s IR emission should have suddenly brightened and shifted to shorter wavelengths. This has implications for interpreting SIRTF observations of planetary debris disks around young solar-type stars.

We are grateful for funding from the NASA SIRTF Legacy program plus Franklin and Marshall College’s William Hackman summer undergraduate research program.

The author(s) of this abstract have provided an email address for comments about the abstract: dana.backman@fandm.edu

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.