|Discovery and designation|
|Discovered by||Michael E. Brown and Jean-Luc Margot|
|Discovery date||February 18, 2001|
|MPC designation||S/2001 (87) 1|
|Minor planet category||Main belt (Cybele)|
|Semi-major axis||1356 ± 5 km|
|Eccentricity||0.001 ± 0.001|
|Orbital period||3.6496 ± 0.0007 d|
|Average orbital speed||27.0 m/s|
|Inclination||1.7 ± 1.0°
(with respect to Sylvia equator)
|Satellite of||87 Sylvia|
|Dimensions||18 ± 4 km|
|Mass||~ 4×1015 kg (estimate)|
|Equatorial escape velocity||~ 7 m/s (estimate)|
|Absolute magnitude (H)||10.7|
Romulus is the outer and larger moon of the main-belt asteroid 87 Sylvia, not to be confused with the directly Sun-orbiting asteroid 10386 Romulus. It follows an almost-circular close-to-equatorial orbit around the parent asteroid. In this respect it is similar to the other moon Remus.
Romulus was discovered in February 2001 from the Keck II telescope by Michael E. Brown and Jean-Luc Margot. Its full designation is (87) Sylvia I Romulus; before receiving its name, it was known as S/2001 (87) 1. The moon is named after Romulus, the mythological founder of Rome, one of the twins of Rhea Silvia raised by a wolf.
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 both Romulus and Remus, the second of Sylvia's moons, are smaller rubble piles which accreted in orbit around the main body from debris of the same collision. In this case their albedo and density are expected to be similar to Sylvia's.
From Romulus' surface, Sylvia takes up an angular region 16°×10° across, while Remus's apparent size varies between 0.62° and 0.19° (for comparison, Earth's Moon has an apparent size of about 0.5°).
See also 
- IAUC 7588, announcing the discovery of S/2001 (87) 1
- F. Marchis et al. (2005). "Discovery of the triple asteroidal system 87 Sylvia". Nature 436 (7052): 822–4. Bibcode:2005Natur.436..822M. doi:10.1038/nature04018. PMID 16094362.
- Assuming the same albedo as Sylvia
- Assuming same density and albedo as Sylvia
- Data on (87) Sylvia from Johnston's archive (maintained by W. R. Johnston)
- Rubble-Pile Minor Planet Sylvia and Her Twins (ESO news release, August 2005) Includes images and artists impressions
- Adaptive Optics System Reveals New Asteroidal Satellite (SpaceDaily.com, March 2001) Includes a discovery image.
- IAUC 7590, confirming the discovery of S/2001 (87) 1
- IAUC 8582, reporting discovery of S/2004 (87) 1 and naming Romulus and Remus