How Fast the Nucleus of Comet Hale–Bopp was Rotating?     

Shulman  L. M.  Kidger  M.  Serrat-Ricart  M.  Torres-Chico  R. 《Earth, Moon, and Planets》2002,90(1-4):109-117

At the First International Conference on Comet Hale–Bopp(Canaries, 1998) many astronomers agreed with the value of theperiod of axial rotation of its nucleus, which was obtained byobservers by a comparison of the two sequential patterns of thedust arcs. It was noted that the pattern had been repeated each∼12 hours. The value 11.35^h was taken as the periodof axial rotation. However, alternative periods of 4 and 8 days havealso been suggested. The possible reasons for thisdiscrepancy are discussed. It is shown that a short period could be obtained by a misidentification of the same arc on twosequential images and, as a result, an overestimate of theradial velocity of dust in the arcs. To obtain the half day period one must take the projected velocity of the arc ∼ 1.6 km/s,which exceeds the H₂O gas expansion velocity. If one takes a lower expansion velocity a longer period would be obtained.  相似文献