85 Io
From Wikipedia, the free encyclopedia
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Discovery
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| Discovered by | C. H. F. Peters |
| Discovery date | September 19, 1865 |
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Designations
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| Alternative names | A899 LA; A899 UA |
| Minor planet category |
Main belt |
| Epoch March 6, 2006 (JD 2453800.5) | |
| Aphelion | 473.341 Gm (3.164 AU) |
| Perihelion | 320.334 Gm (2.141 AU) |
| Semi-major axis | 396.837 Gm (2.652 AU) |
| Eccentricity | 0.193 |
| Orbital period | 1578.081 d (4.32 a) |
| Average orbital speed | 18.12 km/s |
| Mean anomaly | 206.947° |
| Inclination | 11.967° |
| Longitude of ascending node | 203.440° |
| Argument of perihelion | 122.293° |
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Physical characteristics
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| Dimensions | 180×160×160 km[1][4] |
| Mass | ~3.4×1018 (estimate) |
| Mean density | ~1.4 g/cm³ (estimate)[5] |
| Equatorial surface gravity | ~0.028 m/s² (estimate) |
| Escape velocity | ~0.07 km/s (estimate) |
| Rotation period | 0.2864 d (6.875 h) [2] |
| Albedo | 0.067 [3] |
| Temperature | ~172 K max: 272K (-2° C) |
| Spectral type | C |
| Absolute magnitude | 7.61 |
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[1]. 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 [4].
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.
[edit] External links
[edit] References
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J. Torppa et al Shapes and rotational properties of thirty asteroids from photometric data, Icarus, Vol. 164, p. 346 (2003).
- PDS lightcurve data
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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).
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G. A. Krasinsky et al Hidden Mass in the Asteroid Belt, Icarus, Vol. 158, p. 98 (2002).
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