85 Io
| Discovery | |
|---|---|
| Discovered by | C. H. F. Peters |
| Discovery date | September 19, 1865 |
| Designations | |
| A899 LA; A899 UA | |
| Main belt | |
| Orbital characteristics | |
| Epoch March 6, 2006 (JD 2453800.5) | |
| Aphelion | 473.341 Gm (3.164 AU) |
| Perihelion | 320.334 Gm (2.141 AU) |
| 396.837 Gm (2.652 AU) | |
| Eccentricity | 0.193 |
| 1578.081 d (4.32 a) | |
Average orbital speed | 18.12 km/s |
| 206.947° | |
| Inclination | 11.967° |
| 203.440° | |
| 122.293° | |
| Physical characteristics | |
| Dimensions | 180×160×160 km[1][4] |
| Mass | ~3.4×1018 (estimate) |
Mean density | ~1.4 g/cm³ (estimate)[5] |
| ~0.028 m/s² (estimate) | |
| ~0.07 km/s (estimate) | |
| 0.2864 d (6.875 h) [2] | |
| Albedo | 0.067 [3] |
| Temperature | ~172 K max: 272K (-2° C) |
Spectral type | C-type asteroid |
| 7.61 | |
85 Io is a big, dark Main belt asteroid of the C spectral class. It is probably a primitive body made 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 spherical.
It was found by C. H. F. Peters on September 19, 1865 and named after Io, a lover of Zeus in Greek mythology.
A 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 moon of Jupiter. With a two-digit number and a two-letter name, 85 Io has the shortest designation of all minor planets.
Other websites
References
- J. Torppa et al. Shapes and rotational properties of thirty asteroids from photometric data, Icarus, Vol. 164, p. 346 (2003).
- PDS lightcurve data
- 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).
- G. A. Krasinsky et al. Hidden Mass in the Asteroid Belt, Icarus, Vol. 158, p. 98 (2002).