Hydrogen cyanide (HCN) was detected in Comet Hale-Bopp at infrared wavelengths near 3.0 μm on four dates between Feb 24.0 and May 1.0 1997 using high-resolution spectroscopy. The average rotational temperature retrieved for the (001) vibrational level on UT 1997 April 29.9 was (95±6) K near the nucleus, increasing to (122±8) K in the intermediate coma (4″-10″ off the nucleus). The HCN production rate on April 29.9 was (3.09±0.13)×1028 molecules s-1. When compared with the water production rate obtained from direct measurements of the H2O 100-010 band on common observation dates using the same instrument and data processing algorithms, the weighted average (for the four dates) of the relative abundance (HCN/H2O) was (0.40±0.05)%. The measured spatial distribution for HCN is consistent with its release at the nucleus - no significant contribution from a distributed source is required within 10,000 km of the nucleus.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science