Infrared spectroscopy of comet Hale-Bopp

Abstract

High resolution (λ/δλ ~ 20,000) spectra of comet C/1995 01 (Hale-Bopp) in the 2-5 μm region were obtained during UT 2-5 March 1997 using CSHELL at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. The heliocentric and geocentric distances of the comet were ~1.1 AU and ~1.5 AU, respectively. We detected emission lines of the gas-phase molecules H2O, CH4, C2H6, C2H2, HCN, and CO and derived absolute production rates and relative abundances for all species. We also used the 2-dimensional nature of the CSHELL data to investigate the spatial distribution of the molecules and find evidence that CO was derived at least partly from an extended source in the coma.