Romulus (moon)
- J.-L. Margot
- M. E. Brown
Romulus is the outer and larger of the two moons of main belt asteroid (87 ) Sylvia ( Cybele group). Its average diameter is about 18 kilometers, which corresponds to about 1/16 of Sylvia diameter.
Discovery and designation
Romulus was discovered in Hawaii on February 18, 2001 by Jean -Luc Margot and Michael E. Brown at the Keck Observatory on Mauna Kea II. Romulus was 0.59 arcsec distance to Sylvia found a difference in the apparent brightness of 6.24 ± 0.2. The discovery was announced on 23 February 2001; the moon was given the provisional designation S/2001 (87 ) 1
2004 saw the team of astronomers Franck Marchis ( University of California, Berkeley ) and Pascal Descamps, Daniel Hestroffer, and Jérôme Berthier ( Observatoire de Paris), another companion of Sylvia, what the system swelled to the first known asteroid triple system.
On August 11, both moons were officially named. Since Sylvia was named after Rhea Silvia, suggested the team to Franck Marchis, to name the two satellites by Sylvia- Romulus and Remus, the children of Rhea Sylvia and the god Mars, were raised by a she-wolf. In Roman mythology, Romulus is 753 BC founded the city of Rome, have given her the name and killed his twin brother Remus in anger before he became the first king of Rome.
Web properties
Romulus orbits Sylvia on a prograde, nearly perfect circular orbit at an average distance of 1356 kilometers to the center ( about 9.5 Sylvia radii ). The orbital eccentricity is not more than 0.001, the orbit is inclined 1.7 ° relative to the equator of Sylvia. The orbit of the inner moon Remus ' Orbit removed on average about 650 km from Romulus.
Romulus orbits Sylvia in 3 days, 15 hours and 35.4 minutes, resulting in a Sylvia- year equals about 652.6 rounds (about 6.52 Earth years ). From the orbit of Romulus, it is assumed that it is stable, because it is well within Sylvia's Hill sphere ( approximately 1/ 50 of the Hill radius of Sylvia ), but also far outside the synchronous orbit.
Physical Properties
The result, the system is probably due to a collision of two asteroids. From the large fragments of such a collision is accordingly formed the great mother asteroid, during the moons probably smaller debris are the collision that were attracted by the new asteroid. Romulus is therefore as the parent body of the type Rubble Pile; However, it appears in the spectrum of something bluer color.
Research
Immediately after the discovery, Sylvia system was observed with the Hubble Space Telescope. Five days after the discovery of the Romulus from the Hubble team could be confirmed by the visibility on six images. The second moon Remus was there but not detected.
Seen from the surface of Romulus from Sylvia covered a region of the sky of 16 ° x 10 °, while Remus ' apparent size between 0.62 ° and 0.19 ° varied.