Physical and Chemical Evolution of Dust Aggregate and their Physical Properties in the Primordial Solar Nebula

原始太阳星云尘埃聚集体的物理化学演化及其物理性质

基本信息

批准号：
07640640
负责人：
KOZASA Takashi
金额：
$ 1.22万
依托单位：
Kobe University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

The following subject had been investigated during the period supported by this grant.(1) Scattering properties and their dependence on the strusture and the chemical composition of dust aggregates : The discrete dipole approximation was applied to investigate the dependence of the scattering properties on the structure and the chemical composition of dust aggregates. The results show that the behavior of forward scattered light clearly reflects the overall size and the mean chemical composition of dust aggregates, otherwise the backward scattering is sensitive to the roughness of surface layr of dust aggregates.(2) Formation process of dust aggregates in the primordial solar nebula : A method was discussed to treat the formation process and the resulting structure of dust aggregates self-consistently in the primordial solar nebula, but the detailed calculation was not performed.(3) The crystallinity of silicate component in comet dust : On the basis of the Greenberg's interstellar dust model, the origin of crystalline silicate component in cometary dust was investigated ; in comparison with the observation of comet P/Halley the crystalline component was estimated to be the order of 10 to 20% in volume. The estimated value can be realized by the mechanism for the crystallization of silicate component developed in the framework of the evolution from interstellar dust to cometary dust.(4) Formation of dust grains in astrophysical environments ; The formation of dust grains was investigated in circumstellar envelopes of evolved stars. The formation process of core-mantle grains consisting of a SiC core and a carbon mantle was investigated to reproduce the 11.3mum feature observed towards carbon stars. In oxygen-rich AGB stars the observed 13mum feature can be attributed to dust grains consisting of a Al_2O_3 core and a silicate mantle. The possibility of the formation of dust grains in Ia supernovae was discussed.

在此资助期间，对以下课题进行了研究。（1）散射特性及其对粉尘聚集体结构和化学成分的依赖性：应用离散偶极近似研究散射特性对结构的依赖性以及粉尘聚集体的化学成分。结果表明,前向散射光行为清晰地反映了粉尘团聚体的整体尺寸和平均化学成分,而后向散射光对粉尘团聚体表层粗糙度较为敏感。(2)粉尘团聚体的形成过程。原始太阳星云：讨论了一种处理原始太阳星云中尘埃聚集体的形成过程和由此产生的结构自洽的方法，但没有进行详细的计算。（3）硅酸盐的结晶度彗星尘埃成分：基于格林伯格星际尘埃模型，研究了彗星尘埃中结晶硅酸盐成分的来源；与 P/Halley 彗星的观测结果相比，晶体成分的体积估计约为 10% 至 20%。该估计值可以通过在星际尘埃到彗星尘埃演化框架中发展起来的硅酸盐成分结晶机制来实现。(4)天体物理环境中尘埃颗粒的形成；在演化恒星的星周包层中研究了尘埃颗粒的形成。研究了由 SiC 核心和碳地幔组成的核幔颗粒的形成过程，以重现观察到的碳星的 11.3mum 特征。在富氧 AGB 恒星中，观察到的 13mum 特征可归因于由 Al_2O_3 核心和硅酸盐地幔组成的尘埃颗粒。讨论了 Ia 超新星中尘埃颗粒形成的可能性。