A new image-processing algorithm has been devised to improve visibility of features in the head of Comet Halley on the high-resolution photographs taken at Mount Wilson in May - June 1910. The most striking features are spiral jets that "unwind" from the central condensation and evolve into expanding envelopes on a time scale of days. They consist of dust particles ejected continuously from discrete regions on the sunlit side of the rotating nucleus and are, in their early phase of development, essentially two-dimensional formations. The authors find ≡1 day as a crude lower limit to the comet's rotation period. The projected expansion velocities of the dust features are measured to range from 0.2 to 0.3 km/s. Relative photometry of a bright jet suggests that the column density of dust ejecta in the jet exceeds the density in the coma by a factor of ⪆2 and that, if narrow along the line of sight, the jet may have a particle number concentration several tens of times higher than the coma background. Numerous ion features are also seen on the photographs.
No takes yet. Share an insight, caveat, or question.
Larson et al. (1984) studied this question.