Publication Date:
2001-11-03
Description:
A high-dispersion spectrum of Comet C/1999S4 (LINEAR) was obtained in the optical region with the high-dispersion spectrograph on the Subaru telescope when the comet was 0.863 astronomical units from the Sun before its disintegration. We obtained high signal-to-noise ratio emission lines of the cometary NH2 bands from which an ortho-to-para ratio (OPR) of 3.33 +/- 0.07 was derived on the basis of a fluorescence excitation model. Assuming that cometary NH2 mainly originates from ammonia through photodissociation, the derived OPR of NH2 molecules should reflect that of ammonia, which provides information on the environment of molecular formation or condensation and of the thermal history of cometary ices. Assuming that the OPR of ammonia in comets was unchanged in the nucleus, the derived spin temperature of ammonia (28 +/- 2 kelvin) suggests that a formation region of the cometary ammonia ice was between the orbit of Saturn and that of Uranus in the solar nebula.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kawakita, H -- Watanabe, J -- Ando, H -- Aoki, W -- Fuse, T -- Honda, S -- Izumiura, H -- Kajino, T -- Kambe, E -- Kawanomoto, S -- Noguchi, K -- Okita, K -- Sadakane, K -- Sato, B -- Takada-Hidai, M -- Takeda, Y -- Usuda, T -- Watanabe, E -- Yoshida, M -- New York, N.Y. -- Science. 2001 Nov 2;294(5544):1089-91.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Gunma Astronomical Observatory, 6860-86 Nakayama, Takayama, Agatsuma, Gunma 377-0702, Japan. kawakita@astron.pref.gunma.jp〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11691989" target="_blank"〉PubMed〈/a〉
Keywords:
*Ammonia
;
Ice
;
*Meteoroids
;
Spectrum Analysis
;
Temperature
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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