After the opening of the asteroid, Ida Satellite of Dactil in 1993, the detection of satellites around other small bodies in the belt of asteroids was the question of time. Already in 2001, the Sylvia asteroid was discovered the first satellite, and in 2004 the second. Thus, Sylvia became the first asteroid that two satellites were discovered.
Asteroid Sylvia (87 Sylvia in the Catalog of the Small Planet Center) was opened by the English astronomer in the Normon Potson in 1866 in the Madras of the Observatory in India and was named after Romulus’s Legendary Brothers (Romulus) and Remus (Remus), Rome Founders . In 2005, their names will be called open asteroid satellites.
Asteroid Sylvia refers to the Kibel family. This is a group of asteroids located in the outer part of the main belt of asteroids at a distance of 3.3-3.7 AE. from the sun. The family is named after the largest representative – asteroid Kibel.
Sylvia with an average diameter of 253 km is the eighth largest asteroid in the main belt. It is a rather dark asteroid with a high content of carbon and a very low density constituting on average 1.2 g / cm³, which indicates a high degree of porosity of this object. Probably, Sylvia is not a monolithic body, but represents the so-called “rubble pile” (eng. Rubble Pile) – an unofficial term in planetology to designate nonmonic objects consisting of debris held together with their own attraction.
Perhaps the asteroid system with two satellites was formed as a result of the collision of the initial asteroid with another body with their subsequent complete destruction, after which a part of the debris gathered into the body of the asteroid, and the other part formed satellites. For now, other asteroids with two satellites are also known.