A Comet Model. II. Physical Relations for Comets and Meteors.

It has been shown previ6usly that the icy conglomerate model for comets explains the anomalous accelerations of certain comets and also possible reductions in the effective attraction by the sun. These effects depend upon a moderate loss of matter, AM/M per period. This loss measures the loss of radius, AR/R, while the solar radiation determines the maximum loss of radius by sublimation. By this means an upper limit of radius for seven comets has been determined. Numerical values in kilometers are: Encke, 4; Pons-Winnecke, 82; Biela, 1.7; D'Arrest, 1.4; Brooks,1.2; Wolf 1,19; and 1905 III, 0.2. The smaller values are the most significant and are generally greater than the expected values derived from the reflected light at great solar distances. The model predicts a large excess of unobserved hydrides, H20, NH3, and CH4 molecules, as compared to the observed CO+, C2, and CN. For Halley's Comet, using Wurm's calculations for the rate of loss of CO+ and C2 and using the total loss of ices calculated from solar radiation for a nucleus of radius 10 km, the relative abundances of CO+ and C3 to the combined hydrides are 10- and 10- , respectively. These abundances are roughly consistent with certain of ter Haar's calculations for molecules formed from interstellar atoms. Calculations show that the predicted excess of hydrides will produce no appreciable Rayleigh scattering in comets and also little electron scattering, should all atoms become singly ionixed by photoionixation. Little visible radiation from the hydrides of C, N, and 0 would be expected. The comet model requires that a large cometary nucleus eject visual or photographic meteoroids with greater velocities than a small nucleus at the same perihelion distance (velocity proportional to the square root of the radius). Hence the meteor streams from the greater comets should generally be more dispersed and more uniform from year to year than streams from lesser comets with comparable orbits. Confirming examples of streams from greater comets are the Perseids and the Orionids and Eta Aquarids, if the latter streams arise from Halley's Comet; the Leonids and Bielids represent debris from dying comets. Qualitatively, the model predicts well for the meteor streams from known comets.