摘要：Samarasinha & Mueller related changes of cometary rotation to other physical parameters for four Jupiter-familycomets defining a parameter X, which is approximately constant within a factor of two irrespective of the activefraction of a comet. In this paper two additional comets are added to the original sample, and the claim of a nearlyconstant parameter X for these six comets is confirmed, albeit with a larger scatter. Taking the geometric mean ofX for all of the comets above excluding 2P/Encke (as X for each comet was determined with respect to that of2P/Encke), the expected changes in the rotation periods for a sample of 24 periodic comets are derived. From thissample we identify the comets that are most likely to show observationally detectable changes in their rotationperiods. Using these 24 comets and including the six comets used to determine X, we find a correlation between theparameter ζ (i.e., the total water production per unit surface area per orbit approximated by that inside of 4au) andthe perihelion distance q; specifically, we derive ζ ∝q −0.8 and provide a theoretical basis for this in the Appendix.This relationship between ζ and q enables ready comparisons of activity due to insolation between comets.Additionally, a relationship between the nuclear radius R and the rotation period P is found. We find that onaverage smaller nuclei have smaller rotation periods compared to the rotation periods of larger nuclei. This isconsistent with expectations for the rotational evolution and spin-up of comet nuclei, providing strongobservational evidence for sublimation-driven rotational changes in comets.
