85 Io
.png) Lightcurve-based 3D-model of Io | |
| Discovery | |
|---|---|
| Discovered by | C. H. F. Peters |
| Discovery date | 19 September 1865 |
| Designations | |
| (85) Io | |
| Pronunciation | /ˈaɪ.oʊ/[1] |
Named after | Io |
| A899 LA · A899 UA | |
| main-belt · (middle) Eunomian interloper | |
| Adjectives | Ionian /aɪˈoʊniən/ |
| Orbital characteristics [2] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 151.35 yr (55,280 days) |
| Aphelion | 3.1679 AU |
| Perihelion | 2.1379 AU |
| 2.6529 AU | |
| Eccentricity | 0.1941 |
| 4.32 yr (1,578 days) | |
| 83.678° | |
| 0° 13m 41.16s / day | |
| Inclination | 11.961° |
| 203.12° | |
| 123.11° | |
| Physical characteristics | |
| Dimensions | 180 × 160 × 160 km[3][4] |
| Mass | (5.034 ± 0.999/1.406)×1018 kg[5] |
Mean density | 2.14 ± 0.425/0.598 g/cm3[5][a] |
| 0.2864 d (6.875 h)[2] | |
| 0.0666 ± 0.003[2] | |
| FC (Tholen)[2] B (SMASSII)[2] | |
| 7.96[2] | |
85 Io is a carbonaceous asteroid in the central region of the asteroid belt, approximately 170 kilometers in diameter. It is an identified Eunomian interloper.
Discovery and naming
[edit]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
[edit]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.[citation needed]
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.[citation needed]
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 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
[edit]Notes
[edit]- ^ Assuming a diameter of 165 ± 3 km.
References
[edit]- ^ Noah Webster (1884) A Practical Dictionary of the English Language
- ^ a b c d e f "JPL Small-Body Database Browser: 85 Io". Jet Propulsion Laboratory. Retrieved 1 November 2017.
- ^ a b 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.
- ^ a b 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.
- ^ a b Fienga, A.; Avdellidou, C.; Hanuš, J. (February 2020). "Asteroid masses obtained with INPOP planetary ephemerides". Monthly Notices of the Royal Astronomical Society. 492 (1). doi:10.1093/mnras/stz3407.
- ^ http://www.asteroidoccultation.com/2009_03/0312_85_20455.htm [dead link]
External links
[edit]- Shapes and rotational properties of thirty asteroids from photometric data, Torppa (2003)
- 85 Io at AstDyS-2, Asteroids—Dynamic Site
- 85 Io at the JPL Small-Body Database
