Sylvia is orbited by two small moons. They have been named Romulus and Remus [(87) Sylvia I Romulus and (87) Sylvia II Remus].
Discovery
Remus was discovered several years after Romulus on images taken starting on August 9, 2004, and announced on August 10, 2005. It was discovered by Franck Marchis of UC Berkeley, and Pascal Descamps, Daniel Hestroffer, and Jérôme Berthier of the Observatoire de Paris, France, using the Yepun telescope of the European Southern Observatory (ESO) in Chile.
Naming
The moon was given the temporary designation S/2004 (87) 1.
In 2005, the moon is named after Remus, the mythological founder of Rome, one of the twins of Rhea Silvia raised by a wolf.
Stats
Diameter (mean): 7 km
Semi-major axis: 706 ± 5 km
Orbital Period: 1.38 days
Rotation period: ?
Orbit
Remus's orbit is expected to be quite stable − it lies far inside Sylvia's Hill sphere (about 1/100 of Sylvia's Hill radius), but also far outside the synchronous orbit.
Physical characteristics
87 Sylvia has a low density, which indicates that it is probably a rubble pile formed when debris from a collision between its parent body and another asteroid re-accreted gravitationally.
Therefore it is likely that Remus, Sylvia's moon, is smaller rubble pile which accreted in orbit around the main body from debris of the same collision. In this case the albedo and density are expected to be similar to Sylvia's.
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