The Silicates in the Disk of beta Pictoris

We have obtained intermediate-resolution (R ≍ 50) infrared (2.6-13.5 μm) spectra of the particles in the circumstellar disk of β Pic. The silicate dust feature near 10 microns is broader and contains more structure than interstellar and most circumstellar emission features. The silicate feature in β Pic is remarkably similar to those in comets Halley, Bradfield 1987s, and Levy 1990 XX which have emission features characteristic of crystalline silicates. This result supports the inference based on IRAS results that cometary bodies resupply the grains in the β Pic disk. Detailed models of the dust disk and grains are used to derive plausible disk temperature and density gradients. We discuss implications of these results on the history and state of dust in disks and the solar system.