Comet Bowell 1980b

Abstract

The authors have carried out optical filter photometry and optical and ultraviolet spectrophotometry of Comet Bowell over the period November 1980 - June 1982. They have observed emission by OH at heliocentric distances to nearly 5 AU preperihelion with the OH emission implying a production rate which decreased, but with outbursts, as the comet approached perihelion. CN, however, did not appear until the comet was close to perihelion. The grains exhibited a larger back-scattering peak than has been observed in other comets and showed evidence for two populations and outbursts. The reflectivity of the grains was determined from 2600 Å to 2.2 μ and shows steep slopes in two regions, 3200 - 4000 Å and 1.2 - 1.6 μ, with shallower or negligible slopes in other regions. A self-consistent model is developed. All observations are quantitatively consistent with a nucleus of radius several kilometers and a pre-existing halo of grains corresponding to a layer of a few meters if spread on the nucleus.