date: 2010 December 1 (Wed) 16:00-17:00
room: Kobe University, Science and Technology Research Building #4-809
speaker: Aki Takigawa (University of Tokyo)
organizer: Hiroshi Kimura
title: Formation and evolution of circumstellar corundum grains
abstract: Infrared spectroscopy has revealed the presence of dust grains such as silicates and oxides in protoplanetary disks and around evolved stars. Dust grains have condensed from hot gas and possibly experienced chemical reaction or heating. Corundum (Al2O3) and spinel (MgAl2O4) initially condense from hot gas with the solar abundance, which constraints on the size and number density of dust species heterogeneously condensed on them at lower temperatures including major dust species like silicates and Fe-metal. An anisotropic crystal may have a specific morphology depending on the anisotropy in formation processes and conditions, and the morphologies of corundum grains in chondrites and those observed by infrared spectroscopy might contain their formation conditions.
It is important to measure the spectra of materials condensed at low pressure conditions, although there is experimental difficulty to obtain a sufficient quantity of of condensates. This time, I visited Friedrich-Schiller University in Germany supported by CPS Exchange Program to measure the absorption spectra of spinel produced from solid-gas reaction.
I will present the result of the infrared measurements of the spinel in Jena, and recent results of condensation experiments of corundum and spinel and shape analyses and oxygen isotropic measurements of corundum grains in ordinary chondrites.