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Sunday 1 January 2012

Moons of asteroid 87 Sylvia -- (87) Sylvia I Romulus

Sylvia is orbited by two small moons. They have been named Romulus and Remus [(87) Sylvia I Romulus and (87) Sylvia II Remus].

Discovery

Romulus was discovered in 18 February 2001 from the Keck II telescope by Michael E. Brown and Jean-Luc Margot.

Naming

The moon was given the temporary designation S/2001 (87) 1.

In 2005, the moon is named after Romulus, the mythological founder of Rome, one of the twins of Rhea Silvia raised by a wolf.

Stats

Diameter (mean): 18 km

Semi-major axis: 1356 ± 5 km

Orbital Period: 3.65 days

Rotation period: ?

Orbit

Romulus' orbit is expected to be quite stable − it lies far inside Sylvia's Hill sphere (about 1/50 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 Romulus, 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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