90 Antiope

90 Antiope ([æn ˈtaɪ o pe]) is an asteroid discovered on October 1, 1866 by Robert Luther. The 90th asteroid to be discovered, it is named after Antiope from Greek mythology, though it is disputed as to whether the namesake is Antiope the Amazon or Antiope the mother of Amphion and Zethus.

Antiope is classified as a member of the Themis family of asteroids.

One observed stellar occultation by Antiope has been reported, on June 11, 1980.

Adaptive optics image of Antiope.

[edit] Double asteroid

In 2000, using adaptive optics at the Keck Telescope on Mauna Kea it was discovered that Antiope is in fact a double asteroid. It consists of two individual bodies (the "secondary" is designated S/2000 (90) 1), each about 110±16 km across, separated by only 170 kilometers, orbiting around a common center. This means the gap separating the two halves is a mere 60±16 km. Additional studies by light curve variation and adaptive optics at ESO-VLT indicate that the lobes revolve around the centre of mass in ~16.5 hours. Using Kepler's third law, the mass and density of the components can be derived. The relatively low density (0.6±0.2 g/cm3) suggests a high porosity (>60%). Their composition is C-type, which means that they are dark in colouring with a carbonate composition.