Here is the latest work published by him as coauthor.
Available online 3 April 2012
In Press, Corrected Proof
Explaining why the uranian satellites have equatorial prograde orbits despite the large planetary obliquity
* A. Morbidelli a,
* K. Tsiganis b,
* K. Batygin c,
* A. Crida a,
* R. Gomes d,
* a Laboratoire Lagrange, UMR7293, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, Boulevard de l’Observatoire, 06304 Nice Cedex 4, France
* b Department of Physics, Section Astrophysics, Astronomy and Mechanics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
* c California Institute of Technology, Division of Geological & Planetary Sciences, MC 170-25 1200 E. California Blvd., Pasadena, CA 91125, United States
* d Observatório Nacional José Cristino, Rua General José Cristino 77, CEP 20921-400 Rio de Janeiro, RJ, Brazil
* Received 16 November 2011. Revised 23 March 2012. Accepted 27 March 2012. Available online 3 April 2012.
We show that the existence of prograde equatorial satellites is consistent with a collisional tilting scenario for Uranus. In fact, if the planet was surrounded by a proto-satellite disk at the time of the tilting and a massive ring of material was temporarily placed inside the Roche radius of the planet by the collision, the proto-satellite disk would have started to precess incoherently around the equator of the planet, up to a distance greater than that of Oberon. Collisional damping would then have collapsed it into a thin equatorial disk, from which the satellites eventually formed. The fact that the orbits of the satellites are prograde requires Uranus to have had a non-negligible initial obliquity (comparable to that of Neptune) before it was finally tilted to 98°.
* Uranus, Satellites;
* Satellites, Formation;
* Satellites, Dynamics