Is Nereid a binary satellite? |
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| Authors: | Paolo Farinella A Cellino V Zappalà P Paolicchi |
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| Institution: | (1) Dipartimento di Mathematica, Università di Pisa, Pisa, Italy;(2) Osservatorio Astronomico di Torino, Pino Torinese, Italy;(3) Istituto di Astronomia, Università di Pisa, Pisa, Italy |
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| Abstract: | If real, Nereid's recently observed large photometric variations (Schaefer and Schaefer, 1988) can be explained by modelling this Neptunian satellite as a quasi-contact binary system made of two similar, ellipsoidal components distorted by their mutual tides. Both the amplitude and the likely periodicity of the observed luminosity changes are consistent with the binary model, provided Nereid's density is close to 1 g cm–3 (similar to that of most outer solar system satellites). The assumed binary would be probably stable against Neptune's gravitational perturbations, and its origin - as already suggested for a few suspected binary asteroids, like 624 Hektor (Weidenschilling, 1980; Farinella et al., 1982) - could be due to rotational fission following a catastrophic impact. During the Neptune encounter due for August, 1989, Voyager 2's cameras will provide images adequate to confirm, or disprove, the binary model. |
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