90 Antiope

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**90 Antiope**
Orbital elements
Eccentricity (orbit)>e
Inclination>i	°
Perihelion>q	~ on } Astronomical Unit>AU
Argument of perihelion>ω	°
Semi-major axis>a	AU
Longitude of the ascending node>ω	°
Aphelion>Q	~ on } Astronomical Unit>AU
Mean anomaly>M	°
Orbital period>P	years
Mean motion>n	°/day
Time of perihelion passage>TP

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 a character in Greek Mythology, called Antiope, though it is disputed as to which, there being more than one.

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

In 2000, using adaptive optics at the Keck Telescope on Mauna Kea it was discovered that Antiope is in fact a double asteroid, consisting 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.

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