Remus is the inner and smaller moon of the main belt asteroid 87 Sylvia. It follows an almost-circular close-to-equatorial orbit around the parent asteroid. In this respect it is similar to the other moon Romulus. August 9 is the 221st day of the year in the Gregorian Calendar (222nd in leap years), with 144 days remaining. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... Moons of the Solar System scaled to Earths Moon A natural satellite is an object that orbits a planet or other body larger than itself and which is not man-made. ... 87 Sylvia (sil-vee-a) is one of the largest main belt asteroids. ... In geometry, the semi-major axis (also semimajor axis) a applies to ellipses and hyperbolas. ... A kilometer (Commonwealth spelling: kilometre), symbol: km is a unit of length in the metric system equal to 1,000 metres (from the Greek words χίλια (khilia) = thousand and μέτρο (metro) = count/measure). ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... Inclination in general is the angle between a reference plane and another plane or axis of direction. ... Space Shuttle Atlantis launches on mission STS-71 In physics, for a given gravitational field and a given position, the escape velocity is the minimum speed an object without propulsion, at that position, needs to have to move away indefinitely from the source of the field, as opposed to falling... In astronomy, synchronous rotation is a planetological term describing a body orbiting another, where the orbiting body takes as long to rotate on its axis as it does to make one orbit; and therefore always keeps the same hemisphere pointed at the body it is orbiting. ... Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... Albedo is a ratio of scattered to incident electromagnetic radiation power. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ... The asteroid belt is a region of the solar system falling roughly between the planets Mars and Jupiter where the greatest concentration of asteroid orbits can be found. ... 253 Mathilde, a C-type asteroid. ... 87 Sylvia (sil-vee-a) is one of the largest main belt asteroids. ...

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. 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. August 9 is the 221st day of the year in the Gregorian Calendar (222nd in leap years), with 144 days remaining. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... August 10 is the 222nd day of the year (223rd in leap years) in the Gregorian Calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... The University of California, Berkeley (also known as Cal, UC Berkeley, UCB, or simply Berkeley) is a prestigious, public, coeducational university situated in the foothills of Berkeley, California to the east of San Francisco Bay, overlooking the Golden Gate and its bridge. ... The Paris Observatory (in French, Observatoire de Paris or Observatoire de Paris-Meudon) is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. ... The European Southern Observatory (ESO) is an international astronomical organisation, composed and supported by ten countries from the European Union plus Switzerland. ...

Its full designation is (87) Sylvia II Remus; before receiving its name, it was known as S/2004 (87) 1. The moon is named after Remus, twin of the mythological founder of Rome, one of the children of Rhea Silvia raised by a wolf. Romulus (c. ... Nickname: The Eternal City Motto: SPQR: Senatus PopulusQue Romanus Location of the city of Rome (yellow) within the Province of Rome (red) and region of Lazio (grey) Coordinates: Region Lazio Province Province of Rome Founded 21 April 753 BC  - Mayor Walter Veltroni Area    - City 1285 km²  (580 sq mi)  - Urban... Rhea Sylvia (also written as Rea Silvia), and also known as Ilia, was the mythical mother of the twins Romulus and Remus, who founded the city of Rome. ...

87 Sylvia, has a low density, which indicates that it is likely a rubble pile asteroid formed when debris from a collision between its parent body and another asteroid re-accreted gravitationally. It is likely then, 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 ^[2]. In astronomy, rubble pile is the informal name for an asteroid that is not a monolith, consisting instead of numerous pieces of rock that have coalesced under the influence of gravity. ...

Remus' 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^[2]. A Hill sphere approximates the gravitational sphere of influence of one astronomical body in the face of perturbations from another heavier body around which it orbits. ... A synchronous orbit is an orbit in which an orbiting body (usually a satellite) has a period equal to the average rotational period of the body being orbited (usually a planet), and in the same direction of rotation as that body. ...

From Remus' surface, Sylvia appears huge, taking up an angular region roughly 30°×18° across, while Romulus' apparent size varies between 1.6° and 0.5° across.

See also

• Romulus (moon)

References

1. ^ IAUC 8582, announcing the discovery of S/2004 (87) 1 and naming Romulus and Remus.
2. ^ ^{a b c d e} F. Marchis et al (2005). "Discovery of the triple asteroidal system 87 Sylvia". Nature 436: 822.
3. ^ Assuming the same albedo as Sylvia
4. ^ Assuming same density and albedo as Sylvia
5. ^ Based on a rough tidal locking timescale of several tens of My.

Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. ...

External links

• 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
• IAUC 8582, reporting discovery of S/2004 (87) 1 and naming Romulus and Remus