85 Io

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85 Io
85Io (Lightcurve Inversion).png
A three-dimensional model of 85 Io based on its light curve.
Discovery
Discovered by C. H. F. Peters
Discovery date September 19, 1865
Designations
Named after Io
Alternative names A899 LA; A899 UA
Minor planet category 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)
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°
Physical characteristics
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 (H) 7.61

85 Io (/ˈ./ 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] Another asteroid occultation of Io (magnitude 13.2) occurred on March 12, 2009, from the eastern USA, with the star 2UCAC 35694429 (magnitude 13.8).[1]

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.

Conjunction to sun stationary, then retrograde Opposition Minimal distance (AE) Maximum brightness (mag) stationary, then prograde
27. April 2004 31.October 2004 23. December 2004 1,92017 AE 12,3 mag 11. February 2005
3.August 2005 9. . January 2006 5. March 2006 2,14389 AE 11,8 mag 25. April 2006
17.October 2006 26. April 2007 9.June 2007 1,38393 AE 12,1 mag 26.July 2007
7. March 2008 6.October 2008 22.November 2008 1,61470 AE 10,7 mag 9. . January 2009
8.July 2009 17. December 2009 12. February 2010 2,19864 AE 11,1 mag 3. April 2010
21.September 2010 15. March 2011 30. April 2011 1,68623 AE 12,2 mag 20.June 2011
7. . January 2012 31.August 2012 12.October 2012 1,28465 AE 11,1 mag 19.November 2012
9.June 2013 25.November 2013 20. . January 2014 2,13519 AE 10,1 mag 12. March 2014
29.August 2014 10. February 2015 1. April 2015 1,95222 AE 12,2 mag 22.May 2015
22.November 2015 30.June 2016 14.August 2016 1,16222 AE 11,6 mag 17.September 2016
3.May 2017 3.November 2017 26. December 2017 1,95048 AE 10,2 mag 15. February 2018
6.August 2018 13. . January 2019 9. March 2019 2,12957 AE 11,8 mag 28. April 2019
21.October 2019 2.May 2020 14.June 2020 1,34977 AE 12,0 mag 30.July 2020

References[edit]

  1. PDS lightcurve data
  2. 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).
  3. G. A. Krasinsky et al. Hidden Mass in the Asteroid Belt, Icarus, Vol. 158, p. 98 (2002).


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