Abundant Circumstellar Silica Dust and SiO Gas Created by a Giant Hypervelocity Collision in the ~12 Myr HD172555 System - Astrophysics > Solar and Stellar AstrophysicsReport as inadecuate




Abundant Circumstellar Silica Dust and SiO Gas Created by a Giant Hypervelocity Collision in the ~12 Myr HD172555 System - Astrophysics > Solar and Stellar Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: The fine dust detected by IR emission around the nearby Beta Pic analoguestar HD172555 is very peculiar. The dust mineralogy is composed primarily ofhighly refractory, non-equilibrium materials, with approximately three-quartersof the Si atoms in silica SiO2 species. Tektite and obsidian lab thermalemission spectra non-equilibrium glassy silicas found in impact and magmaticsystems are required to fit the data. The best-fit model size distribution forthe observed fine dust is dn-da = a-3.95 +- 0.10. This steep a sizedistribution, with abundant micron-sized particles, argues for a fresh sourceof material within the last 0.1 Myr. The location of the dust with respect tothe star is at 5.8 +- 0.6 AU equivalent to 1.9 +- 0.2 AU from the Sun,within the terrestrial planet formation region but at the outer edge of anypossible terrestrial habitability zone. The mass of fine dust is 4 x 10^19 - 2x 10^20 kg, equivalent to a 150 - 200 km radius asteroid. Significant emissionfeatures centered at 4 and 8 um due to fluorescing SiO gas are also found.Roughly 10^22 kg of SiO gas, formed by vaporizing silicate rock, is alsopresent in the system, and a separate population of very large, cool grains,massing 10^21 - 10^22 kg and equivalent to the largest sized asteroid currentlyfound in the Solar System-s main asteroid belt, dominates the solidcircumstellar material by mass. The makeup of the observed dust and gas, andthe noted lack of a dense circumstellar gas disk, strong primary x-rayactivity, or an extended disk of Beta-meteroids argues that the source of theobserved circumstellar materials is a giant hypervelocity > 10 km sec^-1impact between large rocky planetesimals, similar to the ones which formed theMoon and which stripped the surface crustal material off of Mercury-s surface.



Author: C.M. Lisse, C. H. Chen, M. C. Wyatt, A. Morlok, I. Song, G. Bryden, P. Sheehan

Source: https://arxiv.org/







Related documents