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Published 2008 | public
Book Section - Chapter

Physical Properties of Kuiper Belt and Centaur Objects: Constraints from the Spitzer Space Telescope


Detecting heat from minor planers in the outer solar system is challenging, yet it is the most efficient means for constraining the albedos and sizes of Kuiper belt objects (KBOs) and their progeny, the Centaur objects. These physical parameters are critical. e.g., for interpreting spectroscopic data, deriving densities from the masses of binary systems, and predicting occultation tracks. Here we summarize Spitzer Space Telescope observations of 47 KBOs and Centaurs at wavelengths near 24 and 70 µm. We interpret the measurements using a variation of the standard thermal model (STM) to derive the physical properties (albedo and diameter) of the targets. We also summarize the results of other efforts to measure the albedos and sizes of K.BOs and Centaurs. The three or four largest KBOs appear to constitute a distinct class in terms of their albedos. From our Spitzer results, we find that the geometric albedo of KBOs and Centaurs is correlated with perihelion distance (darker objects having smaller perihelia), and that the albedos of KBOs (bur not Centaurs) are correlated with size (larger KBOs having higher albedos). We also find hints that albedo may be correlated with visible color (for Centaurs). Interestingly, if the color correlation is real, redder Centaurs appear to have higher albedos. Finally, we briefly discuss the prospects for future thermal observations of these primitive outer solar system objects.

Additional Information

© 2008 University of Arizona Press. Many of the results presented here are based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Support for this work was provided through multiple awards issued by JPL. Online resources offered by the Solar System Dynamics group at JPL and the Minor Planet Center of the International Astronomical Union were extremely valuable.

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August 22, 2023
January 13, 2024