Is Nereid in Chaotic Rotation?

Both Caltech and Non-Caltech students will be considered

Project Title:

Project Description:

As recently as 20 years ago, the dynamical state of the Solar System was believed to be fully described by a well-ordered array of bodies tracing Keplerian orbits. With the advent of chaos theory, it was realized that even the motions of the planets and satellites could in some cases be described by this theory. The most startling example is given by Hyperion, the outer, irregular Saturnian satellite, which was theoretically predicted to be in chaotic rotation. Subsequent observations confirmed this view.
Satellites tend to divide into bodies that rapidly despin to a synchronous state and those that retain their primordial spin state (Peale, 1977). The few satellites that dwell in the dynamical zone between these two states are important to study because they may be in chaotic rotation, and because a description of their dynamical state yields constraining data on the theory of tidal evolution of planetary satellites. The factors contributing favorably to the possibility of a chaotic state of rotation are high orbital eccentricity, non-sphericity, and a large distance from the primary. The prime candidate for a satellite in chaotic rotation is Neptune's satellite Nereid, which has by far the highest eccentricity (0.75) of any known satellite. Previous observations of Nereid show huge variations in its brightness (Schaefer and Schaefer, 1988; Williams et al., 1991), which were not confirmed by Voyager observations (Thomas et al. 1991) or by our own recent telescopic observations (Buratti et al., 1995).
During 1996, a set of well-placed photometric observations with the 200-inch Hale telescope on Palomar Mountain will enable us to determine whether Nereid is in simple rotation, synchronous rotation, or chaotic rotation. Our observing run will occur on June 15-17, and it will include observations of the nuclei of distant comets as well. If Nereid is a captured object (as appears very likely), it may share some characteristics and a common origin with some comets, although comets are much smaller bodies.

Background Information:

This SURF position entails participating in the astronomical observations in June and analyzing the data. The requirements for the position are familiarity with the Unix operating system and Sun computers, and an interest in data analysis and astronomy. Some knowledge of IDL or IRAF and astronomical observing techniques would be helpful, but not essential.

Literature references or articles that may provide more information on the project:

Buratti, B. et al., 1995. B.A.A.S. 27.
Peale, S., in "Planetary Satellites", U. of A Press, 1977.
Schaefer, M. and Schaefer, B. 1988. Nature 333, 436.
Thomas, P. et al., 1991. J. Geophys. Res. 96, 19,253.
Williams et al. 1991. M.N.R.A.S. 250,

Requirements (skills, specific coursework, academic major, year in school, etc.):

Research Sponsor Name: Bonnie Buratti
E-Mail: buratti@jplpds.jpl.nasa.gov
Division: JPL - Earth and Space Sciences
Telephone: (818) 394-7427
Address: M/C 183-501

For further information contact Dr. Buratti

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