Editing 85 Io

{{Short description|Main-belt asteroid}}
{{About|the asteroid|the satellite of Jupiter|Io (moon)|other uses|Io (disambiguation)}}
{{Use dmy dates|date=October 2019}}
{{Infobox planet
 | minorplanet     = yes
 | background      = #D6D6D6
 | name            = 85 Io
 | image           = 85Io (Lightcurve Inversion).png
 | image_scale      =
 | caption         = [[Lightcurve]]-based 3D-model of ''Io''
 | discoverer      = [[Christian Heinrich Friedrich Peters|C. H. F. Peters]]
 | discovered      = 19 September 1865
 | mpc_name        = (85) Io
 | alt_names       = A899 LA{{·}}A899 UA
 | pronounced      = {{IPAc-en|ˈ|aɪ|.|oʊ}}<ref>Noah Webster (1884) ''A Practical Dictionary of the English Language''</ref>
 | adjective       = Ionian {{IPAc-en|aɪ|ˈ|oʊ|n|i|ə|n}}
 | named_after     = [[Io (mythology)|Io]]
 | mp_category     = [[main-belt]]{{·}}{{small|([[Kirkwood gap|middle]])}}<br />[[Eunomia family#Interlopers|Eunomian interloper]]
 | orbit_ref       = &thinsp;<ref name="jpldata" />
 | epoch           = 4 September 2017 ([[Julian day|JD]] 2458000.5)
 | uncertainty     = 0
 | observation_arc = 151.35 yr (55,280 days)
 | aphelion        = 3.1679 [[Astronomical unit|AU]]
 | perihelion      = 2.1379 AU
 | semimajor       = 2.6529 AU
 | eccentricity    = 0.1941
 | period          = 4.32 [[Julian year (astronomy)|yr]] (1,578 days)
 | mean_anomaly    = 83.678[[Degree (angle)|°]]
 | mean_motion     = {{Deg2DMS|0.2281|sup=ms}} / day
 | inclination     = 11.961°
 | asc_node        = 203.12°
 | arg_peri        = 123.11°
 | dimensions      = 180 × 160 × 160 km<ref name="Torppa2003" /><ref name="Erikson99" />
 | mass            = (5.034 ± 0.999/1.406){{e|18}} kg<ref name="FiengaEtAl2020"/>
 | density         = 2.14 ± 0.425/0.598 g/cm<sup>3</sup><ref name="FiengaEtAl2020"/>{{efn|Assuming a diameter of 165 ± 3 km.}}
 | rotation        = 0.2864 d (6.875 h)<ref name=jpldata />
 | albedo          = 0.0666 ± 0.003<ref name=jpldata />
 | spectral_type   = [[F-type asteroid|F]][[C-type asteroid|C]] {{small|(Tholen)}}<ref name="jpldata" /><br />[[B-type asteroid|B]] {{small|(SMASSII)}}<ref name="jpldata" />
 | abs_magnitude   = 7.96<ref name=jpldata />
}}

'''85 Io''' is a [[Carbonaceous chondrite|carbonaceous]] [[asteroid]] in the central region of the [[asteroid belt]], approximately 170 kilometers in diameter. It is an identified [[Eunomia family#Interlopers|Eunomian interloper]].

== Discovery and naming ==

It was discovered by [[Christian Heinrich Friedrich Peters|C. H. F. Peters]] on 19 September 1865, and named after [[Io (mythology)|Io]], a lover of [[Zeus]] in [[Greek mythology]]. [[Io (moon)|Io]] is also the name of the [[volcanic]] [[natural satellite|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 [[Prograde and retrograde motion|retrograde]] rotator, with its pole pointing towards one of [[ecliptic coordinate system|ecliptic coordinates]] (β, λ) = (-45°, 105°) or (-15°, 295°) with a 10° uncertainty.<ref name="Torppa2003" /> This gives an [[axial tilt]] of about 125° or 115°, respectively. Its shape is quite regular.{{citation needed|date=August 2022}}

In the [[SMASS classification]], ''Io'' is a carbonaceous [[C-type asteroid]], which means that it is probably a primitive body composed of [[carbonate]]s. Like [[141&nbsp;Lumen]] it is an [[Interloper (asteroid)|interloper]] that orbits within the [[Eunomia family|Eunomia asteroid family]] but it is not related to the shattered parent body.{{citation needed|date=August 2022}}

An Ionian diameter of 178 kilometres was measured from an [[occultation]] of a [[star]] on 10 December 1995.<ref name="Erikson99" /> 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).<ref>http://www.asteroidoccultation.com/2009_03/0312_85_20455.htm {{dead link|date=September 2015}}</ref>

{| class="wikitable" style="align: center; font-size: 0.9em;"
|- 
! 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 
|}

== See also ==
* [[List of Solar System objects by size]]

== Notes ==
{{notelist}}

== References ==
{{reflist
|refs=

<ref name="jpldata">{{cite web
 |title=JPL Small-Body Database Browser: 85 Io
 |url=https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=85
 |publisher=[[Jet Propulsion Laboratory]]
 |access-date=1 November 2017}}</ref>

<ref name="Torppa2003">{{cite journal
 |last=Torppa |first=J.
 |display-authors=etal
 |journal=Icarus
 |volume=164 |page=346
 |url=http://www.rni.helsinki.fi/~mjk/thirty.pdf
 |title=Shapes and rotational properties of thirty asteroids from photometric data
 |date=2003
 |issue=2
 |doi=10.1016/s0019-1035(03)00146-5|bibcode = 2003Icar..164..346T }}</ref>

<ref name="Erikson99">{{cite journal
 |last1=Erikson |first1=A.
 |last2=Berthier |first2=J. |last3=Denchev |first3=P.V. 
 |bibcode=1999P&SS...47..327E
 |title=Photometric observations and modelling of the asteroid 85 Io in conjunction with data from an occultation event during the 1995-96 apparition
 |journal=Planetary and Space Science
 |volume=47 |pages=327–330
 |date=1999
 |issue=3–4
 |doi=10.1016/S0032-0633(98)00128-7}}</ref>

<ref name="FiengaEtAl2020">{{Cite journal 
  |last=Fienga |first=A.
  |last2=Avdellidou |first2=C.
  |last3=Hanuš |first3=J.
  |date=February 2020
  |title=Asteroid masses obtained with INPOP planetary ephemerides
  |url=https://academic.oup.com/mnras/article/492/1/589/5658701
  |journal=Monthly Notices of the Royal Astronomical Society
  |volume=492
  |issue=1
  |doi=10.1093/mnras/stz3407
  |doi-access=free}}</ref>

}} <!-- end of reflist -->

== External links ==
*[http://www.rni.helsinki.fi/~mjk/thirty.pdf Shapes and rotational properties of thirty asteroids from photometric data, Torppa (2003) ]
* {{AstDys|85}}
* {{JPL small body}}

{{Minor planets navigator |84 Klio |number=85 |86 Semele}}
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{{DEFAULTSORT:Io}}
[[Category:Eunomia asteroids|000085]]
[[Category:Discoveries by Christian Peters]]
[[Category:Named minor planets]]
[[Category:Objects observed by stellar occultation|000085]]
[[Category:FC-type asteroids (Tholen)|000085]]
[[Category:B-type asteroids (SMASS)|000085]]
[[Category:Astronomical objects discovered in 1865|18650919]]