 Adaptive Optics observations of (87) Sylvia, showing its two satellites, Remus andRomulus. | |
| Discovery[1] | |
|---|---|
| Discovered by | Franck Marchis,Pascal Descamps, Daniel Hestroffer,Jérôme Berthier |
| Discovery date | August 9, 2004 |
| Designations | |
| Sylvia II | |
| Pronunciation | /ˈriːməs/ |
Named after | Rēmus |
| |
| Main belt (Cybele) | |
| Adjectives | Remian/ˈriːmiən/[2] |
| Orbital characteristics[3] | |
| 706 ± 5km | |
| Eccentricity | 0.016 ± 0.011 |
| 1.3788 ± 0.0007d | |
Averageorbital speed | 37.2 m/s |
| Inclination | 2.0 ± 1.0° (with respect to Sylvia equator) |
| Satellite of | 87 Sylvia |
| Physical characteristics | |
| Dimensions | 7 ± 2 km[3][a] |
| Mass | ~ 2×1014 kg(estimate)[b] |
Equatorialescape velocity | ~ 4 m/s(estimate) |
| unknown, probablysynchronous[c] | |
| unknown, zero expected | |
| 11.1[3] | |
Remus, formal designation87 Sylvia II, is the inner and smaller moon of themain-belt asteroid87 Sylvia. It follows an almost-circular and close-to-equatorial orbit around the parent asteroid. In this respect it is similar to the other Sylvian moonRomulus.
Remus was discovered several years after Romulus on images taken starting on August 9, 2004, and announced on August 10, 2005. It was discovered byFranck Marchis ofUC Berkeley, andPascal Descamps,Daniel Hestroffer, andJérôme Berthier of theObservatoire de Paris, France, using the Yepun telescope of theEuropean Southern Observatory (ESO) inChile. Marchis, the project leader, was waiting for the completion of the image acquisition programme before starting to process the data. Just as he was set to go on vacation in March 2005, Descamps sent him a brief note entitled "87 Sylvia est triple ?" pointing out that he could see two moonlets on several images of Sylvia. The entire team then focused quickly on analysis of the data, wrote a paper, submitted an abstract to the August meeting in Rio de Janeiro and submitted a naming proposal to the IAU.
Its formal designation is(87) Sylvia II; before receiving its name, it was known asS/2004 (87) 1.The moon is named afterRemus, twin of the mythological founder ofRome, one of the children ofRhea Silvia raised by a wolf.
87 Sylvia has a low density, which indicates that it is probably arubble pile asteroid formed when debris from a collision between its parent body and another asteroid re-accreted gravitationally. Thus it is likely that both Remus and Romulus 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.[3]
Remus's orbit is expected to be quite stable: it lies far inside Sylvia'sHill sphere (about 1/100 of Sylvia'sHill radius), but also far outside thesynchronous orbit.[3]
From Remus's surface, Sylvia appears huge, taking up an angular region roughly 30°×18° across, while Romulus's apparent size varies between 1.6° and 0.5° across.