How Fast the Nucleus of Comet Hale–Bopp was Rotating? |
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Authors: | Shulman L. M. Kidger M. Serrat-Ricart M. Torres-Chico R. |
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Affiliation: | (1) Instituto Astrofisico de Canarias, La Laguna, Tenerife, Spain |
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Abstract: | 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 11.35h 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. |
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Keywords: | Comet Hale– Bopp cometary nucleus axial rotation jet activity of distant comets |
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