SIX WHITE DWARFS WITH CIRCUMSTELLAR SILICATES

Spitzer Space Telescope spectra reveal 10 μm silicate emission from circumstellar dust orbiting six externally polluted white dwarfs. Micron-size glasses with an olivine stoichiometry can account for the distinctively broad wings that extend to 12 μm; these particles likely are produced by tidal disruption of asteroids. The absence of infrared polycyclic aromatic hydrocarbon features is consistent with a scenario where extrasolar rocky planets are assembled from carbon-poor solids.

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