The shell of Comet Hale-Bopp

A film showing the shells in the coma of Comet Hale-Bopp, taken on March 4, 1997, is digitized and measured by means of a PDS. The method of fitting leads to the following results: (1)The first shell (innermost one), derived from a jet formation, is seen as an Archimedean spiral and the velocity of the ejecta from the cometary nucleus is 1.6 km/sec; (2)All of the 2nd, 3rd and 4th shells are parabolas or catenaries.