Photographic observations of comet Hale-Bopp at the Pulkovo Observatory: The detection of dust envelopes

The photographic observations of comet Hale-Bopp with the 26-inch Pulkovo Observatory refractor in March–April, 1998, revealed three hemispherical gas-dust envelopes and one spiral jet in the comet head. We determined the angular distances of these envelopes from the comet nucleus and estimated their velocities. The masses and sizes of dust grains were estimated. We conclude that submicron-sized grains dominate in the envelopes. We also estimated the time scale of the comet nuclear activity, which manifests itself in dust ejection, the initial velocity of the ejected dust grains, and the ratio of the radiation-pressure force exerted on dust grains to the force of their gravitational attraction to the Sun. Our observations yielded an estimate for the radius of the comet nucleus, ～30 km.