(87) Sylvia

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(87 ) Sylvia is an asteroid that is moving in the outer region of the main asteroid belt. The celestial body was discovered on May 16, 1866 by Norman Robert Pogson at the Observatory of Madras in India.

The asteroid was named after Rhea Silvia, mother of Romulus and Remus in Roman mythology.

Sylvia moves between 3.2 AU ( perihelion ) and 3.8 AU ( aphelion ) in around 6.5 years of the sun. The orbital eccentricity is 0.08, the orbit is inclined by about 11 ° to the ecliptic.

With an average diameter of 260 km, it is the eighth-largest object in the main belt. In about five hours and eleven minutes he rotates around its own axis. It has a dark surface with an albedo of around four percent.

On 23 February 2001 it was discovered at the Keck Observatory using adaptive optics a companion to Sylvia. Through further observations with the Very Large Telescope in 2004, another companion could still be found: Sylvia is thus the first known asteroid with two moons. The first, Romulus, has a diameter of 18 km and orbits Sylvia at a distance of 1,356 km in the 3.65 days. The second, Remus is just 7 km tall and moves at a distance of 710 km in 33 hours around the asteroid. Both objects orbit the asteroid in a quasi- circular (eccentricity = 0.001 and 0.016 ) and nearly equatorial ( orbital inclination ≈ 1 ° ) orbits. As a fitting name for the two satellites of the names of Romulus and Remus by the International Astronomical Union ( IAU) have been set.