(Proposal ID) S15B-126

(PI) Ootsubo, Takafumi

(Proposal Title)
Study of the diversity of dust properties in Oort cloud comets

(Abstract)
Crystalline silicate is sometimes observed in comets as an 11.3-mu m resonant 
emission feature, and may be used for probing the early solar nebula. Because 
the formation of the crystalline silicate grains requires high temperature, 
they are thought to be born from amorphous silicates at the inner region, and 
then transported toward the outer region where comets were born. This 
transportation can produce the difference in the fraction of crystalline 
silicate in the cometary dust between two dynamical types of comets, Oort-
cloud comets (OCs) and Ecliptic comets (ECs), due to the different 
heliocentric distances of their birth places. OCs usually have a higher 
fraction of crystalline silicate and a stronger silicate feature than ECs. 
Recently, however, we have several comets with a weak silicate feature and 
without a crystalline silicate feature, such as comet ISON. It is important to 
investigate the diversity of dust properties among Oort cloud comets. 
Fortunately, we can observe three comets C/2013 US10 (Catalina), C/2013 X1 
(PanSTARRS), P/2010 V1 (Ikeya-Murakami) in this semester. In particular, 
the comet C/Catalina is a bright and good target for this silicate peak 
feature study.