SOHO/SWAN Observations of the Structure and Evolution of the Hydrogen Lyman-α Coma of Comet Hale–Bopp (1995 O1)

✍ Scribed by M.R. Combi; A.A. Reinard; J.-L. Bertaux; E. Quemerais; T. Mäkinen

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 262 KB
• Volume: 144
• Category: Article
• ISSN: 0019-1035
• DOI: 10.1006/icar.1999.6335

✦ Synopsis

The SWAN all-sky camera on the SOHO spacecraft observed the hydrogen Lyman-alpha coma of Comet Hale-Bopp (1995 O1) from January through May 1997. The observations covered heliocentric distances from 1.75 AU before perihelion to 1.29 AU after, showing the hydrogen coma to vary in brightness, shape, and orientation with the comet's orbital position. The water production rate of the comet was determined from an analysis of these images with a model that accounts for the detailed physics and chemistry. The model incorporates coma dynamics (expansion velocity and kinetic temperatures), which have been shown to be consistent with a variety of other observations. The distribution of brightness in the modeled images reproduces the absolute magnitude and distribution of brightness seen in the observations. We find that the maximum water production rate occurred about 2 weeks after perihelion, and that the magnitude and variation with time are consistent with other published observations which were analyzed in a consistent manner.