85 Io (pronounced /ˈaɪoʊ/ eye'-oh) is a large, dark Main belt asteroid of the C spectral class. It is probably a primitive body composed of carbonates. Like 70 Panopaea it orbits within the Eunomia asteroid family but it is not related to the shattered parent body.
Io is a retrograde rotator, with its pole pointing towards one of ecliptic coordinates (β, λ) = (-45°, 105°) or (-15°, 295°) with a 10° uncertainty. This gives an axial tilt of about 125° or 115°, respectively. Its shape is quite regular.
It was discovered by C. H. F. Peters on September 19, 1865 and named after Io, a lover of Zeus in Greek mythology.
An Ionian diameter of 178 kilometres was measured from an occultation of a star on December 10, 1995 .
Io is also the name of the volcanic satellite of Jupiter. With a two-digit number and a two-letter name, 85 Io has the shortest designation of all minor planets.
1. J. Torppa et al Shapes and rotational properties of thirty asteroids from photometric data, Icarus, Vol. 164, p. 346 (2003).
4. A. Erikson Photometric observations and modelling of the asteroid 85 Io in conjunction with data from an occultation event during the 1995-96 apparition, Planetary and Space Science, Vol. 47, p. 327 (1999).
5. G. A. Krasinsky et al Hidden Mass in the Asteroid Belt, Icarus, Vol. 158, p. 98 (2002).
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