SUBMILLIMETER CONTINUUM EMISSION FROM COMETS

We report submillimeter continuum observations of five comets obtained at the James Clerk Maxwell Telescope on Mauna Kea. Two of the five comets (P/Brorsen-Metcalf and Okazaki-Levy-Rudenko) were detected at 800-μm wavelength while physically significant upper limits were placed on the other three (Austin 1989c1, P/Faye, and Levy 1990c). We compare the JCMT data with millimeter continuum measurements of Comets Austin 1989c1, IRAS-Araki-Alcock, and P/Halley from the published literature. The submillimeter and millimeter signals are tentatively ascribed to thermal emission from porous particles in the coma, with total particle masses M ∼ 107-108 kg. Previous explanations in terms of ice grain halos and near-nucleus boulder-clouds are less plausible, as they require inordinately large particle masses. © 1992.