ACTIVITY OF COMET HALE-BOPP (1995-O1) BEYOND 6 AU FROM THE SUN

The physical evolution of comet Hale-Bopp is investigated along the pr eperihelic are of its orbit at heliocentric distances larger than 6 AU . The comet's considerable intrinsic brightness and activity are expla ined by the existence of a relatively large area on its nucleus surfac e that is a reservoir of both carbon monoxide and dust particulates. T hree recurring dust emission events observed in August-October 1995 ar e studied in some detail. The characteristic shape of the features pro duced in the course of these episodes is interpreted as a product of a sharply peaked temporal profile of the dust emission and suggests a p robable common source to all the three events. The timing of these eve nts is shown to exhibit a periodicity that may indicate the state of r otation of the comet, which apparently is not pure spin. The total mas s of dust ejected during one of the episodes is calculated from report s of the comet's ''nuclear magnitudes'' at pertinent times to be on th e order of 10(11) grams. Estimates of the dust production rate are com pared with the published production rates of carbon monoxide and it is concluded that the mass loading of the CO gas flow by dust was enormo us, certainly much greater than a factor of 15. Finally, comet Hale-Bo pp is compared with other comets known to have experienced activity at large heliocentric distances. Most similarities are found with the du st emission pattern of comet 29P/Schwassmann-Wachmann 1.