85 Io

Infobox Planet | discovery=yes | physical_characteristics = yes | bgcolour=#FFFFC0 | name=85 Io
discoverer=C. H. F. Peters
discovered=September 19, 1865
alt_names=A899 LA; A899 UA
mp_category=Main belt
epoch=March 6, 2006 (JD 2453800.5)
semimajor=396.837 Gm (2.652 AU)
perihelion=320.334 Gm (2.141 AU)
aphelion=473.341 Gm (3.164 AU)
eccentricity=0.193
period=1578.081 d (4.32 a)
inclination=11.967°
asc_node=203.440°
arg_peri=122.293°
mean_anomaly=206.947°
avg_speed=18.12 km/s
dimensions=180×160×160 km ^{[http://www.rni.helsinki.fi/~mjk/thirty.pdf] [#Erikson99| [4]}
mass=~3.4×10¹⁸ "(estimate)"
density=~1.4 g/cm³ "(estimate)" ^{[#Krasinsky| [5]}
surface_grav=~0.028 m/s² "(estimate)"
escape_velocity=~0.07 km/s "(estimate)"
rotation=0.2864 d (6.875 h) ^{[http://www.psi.edu/pds/archive/lc.html]}
spectral_type=C
abs_magnitude=7.61
albedo=0.067 ^{[http://www.psi.edu/pds/archive/astdata04/simps04/diamalb.tab]}
single_temperature=~172 K
"max:" 272K (-2° C)

85 Io (pronEng|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 ^{[#Torppa2003| [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 ^{[#Erikson99| [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.

External links

* [http://www.rni.helsinki.fi/~mjk/thirty.pdf shape model deduced from lightcurve]

References

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[http://www.rni.helsinki.fi/~mjk/thirty.pdf J. Torppa et al "Shapes and rotational properties of thirty asteroids from photometric data"] , Icarus, Vol. 164, p. 346 (2003).

# [http://www.psi.edu/pds/archive/lc.html PDS lightcurve data]
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[http://www.psi.edu/pds/archive/astdata04/simps04/diamalb.tab Supplemental IRAS Minor Planet Survey]

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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).