11:30 〜 11:45
[PCG21-10] Crystalline Fraction of Cometary Silicate Dust: Implications for the Origin and Evolution of Cometary Nuclei
キーワード：彗星、ダスト、結晶質シリケイト
The presence of crystalline silicate grains in comets is thought to indicate radial mixing of materials in the early solar nebula. The crystallinity of cometary silicate dust is expected to provide key insights into the formation processes of cometary nuclei and their subsequent orbital evolution. To investigate this, we have conducted mid-infrared spectroscopic observations of comets using COMICS on the Subaru Telescope.
We derived the crystalline fraction of silicate dust from the mid-infrared spectra of comets. In Shinnaka et al. (2018), we compared the crystalline fractions of seven comets (three short-period and four long-period). While a slight trend suggested that long-period comets may have a higher crystalline fraction than short-period comets, no further discussion was made.
This study expands on the previous analysis by incorporating mid-infrared observations of four additional comets: 4P/Faye, 144P/Kushida, C/2013 US10, and C/2014 S2. Although no clear silicate emission feature was detected for C/2013 US10, the other three comets exhibited distinct silicate features. By adding these new samples to those from Shinnaka et al. (2018), our dataset now includes ten comets. This expanded analysis further supports the trend that Oort Cloud comets tend to have a higher fraction of crystalline silicates than Jupiter-family comets. Additionally, even among short-period comets, variations in crystalline fractions are observed, with more recently discovered short-period comets potentially exhibiting higher crystalline fractions.
In this presentation, we will introduce our observational results obtained with COMICS and discuss possible scenarios for cometary nucleus formation based on the crystallinity of silicate dust in comets.
Reference: Shinnaka et al., 2018, AJ ,156, 242
We derived the crystalline fraction of silicate dust from the mid-infrared spectra of comets. In Shinnaka et al. (2018), we compared the crystalline fractions of seven comets (three short-period and four long-period). While a slight trend suggested that long-period comets may have a higher crystalline fraction than short-period comets, no further discussion was made.
This study expands on the previous analysis by incorporating mid-infrared observations of four additional comets: 4P/Faye, 144P/Kushida, C/2013 US10, and C/2014 S2. Although no clear silicate emission feature was detected for C/2013 US10, the other three comets exhibited distinct silicate features. By adding these new samples to those from Shinnaka et al. (2018), our dataset now includes ten comets. This expanded analysis further supports the trend that Oort Cloud comets tend to have a higher fraction of crystalline silicates than Jupiter-family comets. Additionally, even among short-period comets, variations in crystalline fractions are observed, with more recently discovered short-period comets potentially exhibiting higher crystalline fractions.
In this presentation, we will introduce our observational results obtained with COMICS and discuss possible scenarios for cometary nucleus formation based on the crystallinity of silicate dust in comets.
Reference: Shinnaka et al., 2018, AJ ,156, 242