85 Io
Lightcurve-based 3D-model of Io
Discovery
Discovered byC. H. F. Peters
Discovery date19 September 1865
Designations
(85) Io
Pronunciation/ˈaɪ.oʊ/[1]
Named after
Io
A899 LA · A899 UA
main-belt · (middle)
Eunomian interloper
AdjectivesIonian /aɪˈoʊniən/
Orbital characteristics [2]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc151.35 yr (55,280 days)
Aphelion3.1679 AU
Perihelion2.1379 AU
2.6529 AU
Eccentricity0.1941
4.32 yr (1,578 days)
83.678°
0° 13m 41.16s / day
Inclination11.961°
203.12°
123.11°
Physical characteristics
Dimensions180×160×160 km[3][4]
Mean density
1.4 g/cm3 (estimate)[5]
0.2864 d (6.875 h)[2]
0.067[2]
FC (Tholen)[2]
B (SMASSII)[2]
7.61[2]

    Io (minor planet designation: 85 Io) is carbonaceous asteroid in the central region of the asteroid belt, 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 in Greek mythology. 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.

    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.[3] This gives an axial tilt of about 125° or 115°, respectively. Its shape is quite regular.

    In the SMASS classification, Io is a carbonaceous C-type asteroid, which means that it is probably a primitive body composed of carbonates. 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 on 10 December 1995.[4] Another asteroid occultation of Io (magnitude 13.2) occurred on 12 March 2009, from the eastern United States, with the star 2UCAC 35694429 (magnitude 13.8).[6]

    Conjunction to sunstationary, then retrogradeOppositionMinimal distance (AE)Maximum brightness (mag)stationary, then prograde
    27. April 200431.October 200423. December 20041,92017 AE12,3 mag11. February 2005
    3.August 20059. January 20065. March 20062,14389 AE11,8 mag25. April 2006
    17.October 200626. April 20079.June 20071,38393 AE12,1 mag26.July 2007
    7. March 20086.October 200822.November 20081,61470 AE10,7 mag9. January 2009
    8. July 200917. December 200912. February 20102,19864 AE11,1 mag3. April 2010
    21. September 201015. March 201130. April 20111,68623 AE12,2 mag20.June 2011
    7. January 201231.August 201212.October 20121,28465 AE11,1 mag19.November 2012
    9.June 201325.November 201320. January 20142,13519 AE10,1 mag12. March 2014
    29.August 201410. February 20151. April 20151,95222 AE12,2 mag22.May 2015
    22.November 201530.June 201614.August 20161,16222 AE11,6 mag17.September 2016
    3.May 20173.November 201726. December 20171,95048 AE10,2 mag15. February 2018
    6.August 201813. January 20199. March 20192,12957 AE11,8 mag28. April 2019
    21.October 20192.May 202014.June 20201,34977 AE12,0 mag30.July 2020

    See also

    References

    1. ↑ Noah Webster (1884) A Practical Dictionary of the English Language
    2. 1 2 3 4 5 6 "JPL Small-Body Database Browser: 85 Io". Jet Propulsion Laboratory. Retrieved 1 November 2017.
    3. 1 2 Torppa, J.; et al. (2003). "Shapes and rotational properties of thirty asteroids from photometric data" (PDF). Icarus. 164 (2): 346. Bibcode:2003Icar..164..346T. doi:10.1016/s0019-1035(03)00146-5.
    4. 1 2 Erikson, A.; Berthier, J.; Denchev, P.V. (1999). "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. 47 (3–4): 327–330. Bibcode:1999P&SS...47..327E. doi:10.1016/S0032-0633(98)00128-7.
    5. ↑ Krasinsky, G. A.; Pitjeva, E. V.; Vasilyev, M. V.; Yagudina, E. I. (2002). "Hidden Mass in the Asteroid Belt". Icarus. 158 (1): 98. Bibcode:2002Icar..158...98K. doi:10.1006/icar.2002.6837.
    6. ↑ http://www.asteroidoccultation.com/2009_03/0312_85_20455.htm
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