Triaxial equilibrium ellipsoids among the asteroids? |
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| Authors: | P Farinella P Paolicchi EF Tedesco V Zappalà |
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| Institution: | Osservatorio Astronomico di Brera, Merate Como, Italy;Lunar and Planetary Laboratory, The University of Arizona, Tucson, Arizona 85721, USA;Osservatorio Astronomico di Torino, 10025 Pino Torinese, Torino, Italy |
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| Abstract: | We present a physical model to explain the existence of a class of large-lightcurve-amplitude, rapidly rotating asteroids found most commonly among objects in the size range 100–300 km diameter. A significant correlation between rotation period and lightcurve amplitude exists for asteroids in this size range in the sense that those with larger amplitudes spin more rapidly and hence these objects have high rotational angular momenta. Since this is a property of Jacobi ellipsoids, we have investigated whether these asteriods might be examples of triaxial equilibrium ellipsoids. We find that objects rotating with periods of 6 hr must have densities between 1.1 and 1.4 g cm?3, while those rotating in 4 hr would have densities between 2.4 and 3.2 g cm?3. If this model is valid then at least some of these asteroids have rather low mean densities. The reality of this result and its interpretation in terms of collisional evolution of the asteroids is discussed. |
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