87 Sylvia

Sylvia's shape is very stretched at 385×265×230 ± 10 km

The asteroid has a lot of empty spaces; From 25% to as much as 60% of it may be empty space.

Mass 1.478±0.006×1019 kg

Mean density 1.2 ± 0.1 g/cm³

Surface gravity 0.027 m/s²

Escape velocity 0.10 km/s

Rotation period 0.2160 d (5.183642 h)

Moons

87 Sylvia has Two small Moons Romulus and Remus

Romulus (moon)

The largest of two Moons of asteroid 87 Sylvia is about 18 km in diameter and orbits at a distance of 1356±5 km, taking 3.6496±0.0007 days (87.59 h) to complete an orbit of Sylvia

Remus (moon)

It is 7±2 km in diameter and orbits at a distance of 706±5 km, taking 1.3788±0.0007 days (33.09 h) to complete an orbit of Sylvia.