A Survey of Water Production in 61 Comets from SOHO/SWAN Observations of Hydrogen Lyman-alpha: Twenty-One Years 1996-2016

TL;DR

This survey analyzes 61 comets observed over 21 years using SOHO/SWAN data, revealing water production rates, activity variations, and evolutionary evidence of cometary nuclei across different classes.

Contribution

It provides a comprehensive dataset of water production rates and activity variations for a large sample of comets, highlighting evolutionary trends and correlations with dynamical properties.

Findings

Water production rates vary exponentially with heliocentric distance.

Evidence of nucleus evolution in both long- and short-period comets.

Correlations between activity measures and dynamical classes.

Abstract

The Solar Wind Anisotropies (SWAN) instrument on the SOlar and Heliospheric Observatory (SOHO) satellite has observed 44 long period and new Oort cloud comets and 36 apparitions of 17 short period comets since its launch in December 1995. Water production rates have been determined from the over 3700 images producing a consistent set of activity variations over large parts of each comet's orbit. This has enabled the calculation of exponential power-law variations with heliocentric distance of these comets both before and after perihelion, as well as the absolute values of the water production rates. These various measures of overall water activity including pre- and post-perihelion exponents, absolute water production rates at 1 AU, active surface areas and their variations have been compared with a number of dynamical quantities for each comet including dynamical class, original semi-major axis, nucleus radius (when available), and compositional taxonomic class. Evidence for evolution of cometary nuclei is seen in both long-period and short-period comets.