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Title: RELATING CHANGES IN COMETARY ROTATION TO ACTIVITY: CURRENT STATUS AND APPLICATIONS TO COMET C/2012 S1 (ISON)

We introduce a parameter, X, to predict the changes in the rotational period of a comet in terms of the rotational period itself, the nuclear radius, and the orbital characteristics. We show that X should be a constant if the bulk densities and shapes of nuclei are nearly identical and the activity patterns are similar for all comets. For four nuclei for which rotational changes are well documented, despite the nearly factor 30 variation observed among the effective active fractions of these comets, X is constant to within a factor two. We present an analysis for the sungrazing comet C/2012 S1 (ISON) to explore what rotational changes it could undergo during the upcoming perihelion passage where its perihelion distance will be ∼2.7 solar radii. When close to the Sun, barring a catastrophic disruption of the nucleus, the activity of ISON will be sufficiently strong to put the nucleus into a non-principal-axis rotational state and observable changes to the rotational period should also occur. Additional causes for rotational state changes near perihelion for ISON are tidal torques caused by the Sun and the significant mass loss due to a number of mechanisms resulting in alterations to the moments of inertia ofmore » the nucleus.« less
Authors:
;  [1]
  1. Planetary Science Institute, 1700 East Fort Lowell Road, Suite 106, Tucson, AZ 85719 (United States)
Publication Date:
OSTI Identifier:
22215463
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 775; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BULK DENSITY; COMETS; DISTANCE; MOMENT OF INERTIA; ROTATION; ROTATIONAL STATES; SHAPE; STELLAR WINDS; SUN; TORQUE; VARIATIONS