85 Io is a
carbonaceous asteroid
An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
in the central region of the
asteroid belt
The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...
, approximately 170 kilometers in diameter. It is an identified
Eunomian interloper.
Discovery and naming
It was discovered by
C. H. F. Peters on 19 September 1865, and named after
Io, a lover of
Zeus
Zeus (, ) is the chief deity of the List of Greek deities, Greek pantheon. He is a sky father, sky and thunder god in ancient Greek religion and Greek mythology, mythology, who rules as king of the gods on Mount Olympus.
Zeus is the child ...
in
Greek mythology
Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...
.
Io is also the name of the
volcanic satellite
A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...
of
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
. With a two-digit number and a two-letter name, 85 Io has the shortest designation of all minor planets.
Orbit and physical characteristics
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
In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orbita ...
of about 125° or 115°, respectively. Its shape is quite regular.
In the
SMASS classification, ''Io'' is a carbonaceous
C-type asteroid
C-type (carbonaceous ) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...
, which means that it is probably a primitive body composed of
carbonate
A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...
s. Like
141 Lumen it is an
interloper that orbits within the
Eunomia asteroid family but it is not related to the shattered parent body.
An Ionian diameter of 178 kilometres was measured from an
occultation of a
star
A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...
on 10 December 1995.
Another
asteroid occultation of Io (magnitude 13.2) occurred on 12 March 2009, from the eastern
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
, with the star 2UCAC 35694429
(magnitude 13.8).
[http://www.asteroidoccultation.com/2009_03/0312_85_20455.htm ]
See also
*
List of Solar System objects by size
Notes
References
External links
Shapes and rotational properties of thirty asteroids from photometric data, Torppa (2003) *
*
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000085
Discoveries by Christian Peters
Named minor planets
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