Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005hia....13..482k&link_type=abstract
Highlights of Astronomy, Vol. 13, as presented at the XXVth General Assembly of the IAU - 2003 [Sydney, Australia, 13 - 26 July
Astronomy and Astrophysics
Astronomy
Scientific paper
Since the first determination of ortho-to-para ratio (OPR) of cometary water in comet Halley the real meaning of OPR has been discussed so far. The OPR of cometary ammonia in comet C/1999 S4 (LINEAR) was inferred from the observation of NH2 at the first time. NH2 is a photodissociation product of ammonia and OPR of NH2 is simply related to that of ammonia. Now we know OPRs of water in three comets and OPRs of ammonia in four comets (comet Hale-Bopp is included in both samples). All data show the spin temperature of about 30 K (26 -- 34 K) although there are variety in periods water production rates origins (Oort cloud or Kuiper belt origins) for these comets. It should be noted that the spin temperature of both water and ammonia are similar to each other 28 K in comet Hale-Bopp. It is an interesting result that the spin temperatures of different molecular species are consistent with each other. The spin temperature is possibly related to the temperature at grains where the molecules formed or their OPRs were re-equilibrated.
Furusho Reiko
Fuse Tetsuharu
Kawakita Hideyo
Watanabe Jun'ichi
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