DPS 34th Meeting, October 2002
Session 23. Other (than Io and Europa) Planetary Satellites
Oral, Chair(s): C.A. Hibbitts and W.M. Grundy, Wednesday, October 9, 2002, 9:20-10:30 and 11:00-11:20am, Room M

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[23.08] Another Yarkovsky effect for irregular satellites

M. Cuk, J. A. Burns, V. Carruba (Cornell U.), R.A. Jacobson (JPL), P.D. Nicholson (Cornell U.)

In the ``classical" Yarkovsky effect, so popular today, bodies orbiting the Sun experience forces because momentum-carrying, re-emitted thermal radiation leaves asymmetrically (relative to the orbit) due to the body's spin. Another variant of the Yarkovsky effect might be important for the orbital evolution of Jupiter's outer satellites: the absorbed (and thus the re-emitted) radiation is greater when the satellites are closer to the Sun. This gradient causes the thermal drag to be stronger on the solar-facing half of the satellite's orbit, leading to inward drift for satellites that rotate in the same sense as they orbit, and outward drift for bodies spinning in the opposite sense. Since the physical sizes of most irregular satellites are near those for which Yarkovsky accelerations are largest, and since the orbital sizes of these satellites are significant compared to that of their parent planet's, this effect may be important for the continuing orbital evolution of these satellites.

Based on previous results for main-belt asteroids (Bottke et al. 2001), we calculate the maximum change in semimajor axis (over several GY) for a 2-km (in radius) satellite of Jupiter orbiting at about 2x107 km to be on the order of 100,000 km, or about a percent. Although small, such drifts may allow capture into resonances. We note that Sheppard's recent discovery, S/2001 J10, may reside in the Kozai resonance, which induces its argument of pericenter to librate. Since S/2001 J10 is probably a member of Ananke's ``collisional family", we suspect that this object was pushed into resonance by the form of Yarkovsky effect described above, after the family-creating collision.

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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.