Annealing of Silicate Dust by Nebular Shocks at 10 AU
By D. Harker, S. Desch. 2001
154 citations recorded by the source corpus.
Silicate dust grains in the interstellar medium are known to be mostly amorphous, yet crystalline silicate grains have been observed in many long-period comets and in protoplanetary disks. Annealing of amorphous silicate grains into crystalline grains requires temperatures of ≳1000 K, but exposure of dust grains in comets to such high temperatures is incompatible with the generally low temperatures experienced by comets. This has led to the proposal of models in which dust grains were thermally processed near the proto-Sun, then underwent considerable radial transport until they reached the gas giant planet region where the long-period comets originated. We hypothesize instead that silicate dust grains were annealed in situ by shock waves triggered by gravitational instabilities. We assume a shock speed of 5 km s-1, a plausible value for shocks driven by gravitational instabilities. We calculate the peak temperatures of micron and submicron amorphous pyroxene grains of chondritic composition under conditions typical in protoplanetary disks at 5-10 AU. Our results also apply to chondritic amorphous olivine grains. We show that in situ thermal annealing of submicron- and micron-sized silicate dust grains can occur, obviating the need for large-scale radial transport.
Subfields: Astronomy and Astrophysics
View Paper: https://www.semanticscholar.org/paper/4d1c47e9205ec08a774139d3ea3f4bbe25420a53
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In Astronomy and Astrophysics
Citations in the corpus
- CRYSTALLINE SILICATES AND DUST PROCESSING IN THE PROTOPLANETARY DISKS OF THE TAURUS YOUNG CLUSTER (2007, background): “…heating of the disk by accretion processes is substantial (Nuth et al. 2000; Gail 2001; Bockelée-Morvan et al. 2002; Wehrstedt & Gail 2002); or as can be produced over the central 10 AU by spiral density wave shocks which grow from fluid-mechanical instabilities in the disk (Harker & Desch 2002).”
- The origin of crystalline silicates in the Herbig Be star HD 100546 and in comet Hale-Bopp (2003, background): “Another possible mechanism for in situ production of crystalline silicates has been proposed by Harker & Desch (2002).”
- A 10 μm spectroscopic survey of Herbig Ae star disks: Grain growth and crystallization (2005, background): “…in the hot inner disk and subsequent radial transport of this material outward, and (2) local production of crystalline material at large distance from the star in transient heating events caused by shocks (e.g. Harker & Desch 2002) or lightning (e.g. Pilipp et al. 1998; Desch & Cuzzi 2000).”