We discuss the transneptunian objects and Centaur rotations, shapes, and densities as determined through analyzing observations of their short-term photometric lightcurves. The lightcurves are found to be produced by various different mechanisms including rotational albedo variations, elongation from extremely high angular momentum, as well as possible eclipsing or contact binaries. The known rotations are from a few hours to several days with the vast majority having periods around 8.5 h, which appears to be significantly slower than the main-belt asteroids of similar size. The photometric ranges have been found to be near zero to over 1.1 mag. Assuming the elongated, high-angular-momentum objects are relatively strengthless, we find most Kuiper belt objects appear to have very low densities (<1000 kg m-3) indicating high volatile content with significant porosity. The smaller objects appear to be more elongated, which is evidence of material strength becoming more important than self-compression. The large amount of angular momentum observed in the Kuiper belt suggests a much more numerous population of large objects in the distant past. In addition we review the various methods for determining periods from lightcurve datasets, including phase dispersion minimization (PDM), the Lomb periodogram, the Window CLEAN algorithm, the String method, and the Harris Fourier analysis method.
The Solar System Beyond Neptune
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