1685 Toro

1685 Toro (prov. designation: 1948 OA) is an asteroid and near-Earth object of the Apollo group on an eccentric orbit. It was discovered on 17 July 1948, by American astronomer Carl Wirtanen at Lick Observatory on Mount Hamilton, California.[3][19] The stony S-type asteroid has a rotation period of 10.2 hours and measures approximately 4 kilometers (2.5 miles) in diameter. It is named for Betulia Toro Herrick, wife of astronomer Samuel Herrick.[2]

1685 Toro
001685-asteroid shape model (1685) Toro.png
Shape model of Toro from its lightcurve
Discovery [1]
Discovered byC. A. Wirtanen
Discovery siteLick Obs.
Discovery date17 July 1948
(1685) Toro
Named after
Betulia Toro Herrick
(wife Samuel Herrick)[2]
1948 OA
NEO · Apollo[1][3]
Orbital characteristics[1]
Epoch 31 May 2021 (JD 2459000.5)
Uncertainty parameter 0
Observation arc72.59 yr (26,512 days)
Aphelion1.9636 AU
Perihelion0.7715 AU
1.3676 AU
1.60 yr (584 days)
Earth MOID0.0507 AU · 19.7 LD
Physical characteristics
Mean diameter
3.810±0.049 km[4]
4.1 km[5]
10.185±0.003 h[6]
10.1862±0.0006 h[7]
10.191±0.005 h[8]
10.195 h[9]
10.19540 h[10]
10.196 h[11]
10.199±0.003 h[12]
10.1995±0.0004 h[13]
10.203±0.003 h[14]
13.90[5][17] · 14.02±1.11[18] · 14.23[1][4]

Classification and orbitEdit

Toro is an Apollo asteroid, a subgroup of near-Earth asteroids that cross the orbit of Earth. It orbits the Sun at a distance of 0.8–2.0 AU once every 584 days. Its orbit has an eccentricity of 0.44 and an inclination of 9° with respect to the ecliptic.[1]

This asteroid's orbit also shows a 5:8 resonance with Earth[20] and in a near 5:13 resonance with Venus. This near resonance results from Earth and Venus being in a near 8:13 resonance with each other. It was the third Apollo asteroid to be discovered. The current resonance with Earth will last for only a few thousand years. Calculations show that Toro will leave it in 2960 CE, and that it will enter the region of 5:13 resonance with Venus in 3470 CE. This is because the distance from Earth's orbit will become larger and that from Venus's orbit smaller. A study of long-term stability shows that the alternating resonances will possibly be broken roughly 3 million years from now because of close approaches between Toro and Mars.[21]

Based on orbital paths, Toro is the best candidate for the source of the Sylacauga meteorite, the first meteorite authenticated to have struck a human, Mrs. Ann Hodges of Sylacauga, Alabama on 30 November 1954.[22] Toro's Earth minimum orbit intersection distance of 0.0507 AU (7,580,000 km),[1] is just above the 0.05 AU requirement to be listed as a potentially hazardous asteroid. With an orbital uncertainty U = 0, its orbit and future close approaches are well determined.[1]


This minor planet was named after the maiden name of Betulia (née Toro) Herrick, wife of American astronomer Samuel Herrick. Herrick had studied the asteroid's orbit, and requested the name, along with the other asteroid, 1580 Betulia.[23][24] The official naming citation was published by the Minor Planet Center on 10 March 1966 (M.P.C. 2504).[25]

Physical characteristicsEdit

In the Tholen and SMASS taxonomic scheme, Toro is characterized as a stony S-type asteroid.[1] It is reported to be composed of L chondrite[26] with a high albedo in the range of 0.24–0.34. It has an extremely well-measured rotation period of 10.2 hours.[6][7][9][10][11][12][13]


  1. ^ a b c d e f g h i j k l "JPL Small-Body Database Browser: 1685 Toro (1948 OA)" (2021-02-16 last obs.). Jet Propulsion Laboratory. Retrieved 18 February 2021.
  2. ^ a b Schmadel, Lutz D. (2007). "(1685) Toro". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 134. doi:10.1007/978-3-540-29925-7_1686. ISBN 978-3-540-00238-3.
  3. ^ a b "1685 Toro (1948 OA)". Minor Planet Center. Retrieved 22 December 2016.
  4. ^ a b c Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90.
  5. ^ a b c Harris, Alan W. (February 1998). "A Thermal Model for Near-Earth Asteroids". Icarus. 131 (2): 291–301. Bibcode:1998Icar..131..291H. doi:10.1006/icar.1997.5865.
  6. ^ a b Warner, Brian D. (January 2013). "Asteroid Lightcurve Analysis at the Palmer Divide Observatory: 2012 June - September" (PDF). Minor Planet Bulletin. 40 (1): 26–29. Bibcode:2013MPBu...40...26W. ISSN 1052-8091. Retrieved 17 March 2020.
  7. ^ a b Higgins, David; Pravec, Petr; Kusnirak, Peter; Hornoch, Kamil; Brinsfield, James W.; Allen, Bill; et al. (September 2008). "Asteroid Lightcurve Analysis at Hunters Hill Observatory and Collaborating Stations: November 2007 - March 2008" (PDF). Minor Planet Bulletin. 35 (3): 123–126. Bibcode:2008MPBu...35..123H. ISSN 1052-8091. Retrieved 17 March 2020.
  8. ^ Warner, Brian D. (July 2016). "Near-Earth Asteorid Lightcurve Analysis at CS3-Palmer Divide Station: 2016 January-April" (PDF). Minor Planet Bulletin. 43 (3): 240–250. Bibcode:2016MPBu...43..240W. ISSN 1052-8091. Retrieved 17 March 2020.
  9. ^ a b Torppa, J.; Aksnes, K.; Dai, Z.; Grav, T.; Hahn, G.; Laakso, T.; et al. (August 2005). "Spins and Shapes of Potentially Hazardous Asteroids". American Astronomical Society. 37: 643. Bibcode:2005DPS....37.1526T.
  10. ^ a b De Angelis, G. (May 1995). "Asteroid spin, pole and shape determinations". Planetary and Space Science. 43 (5): 649–682. Bibcode:1995P&SS...43..649D. doi:10.1016/0032-0633(94)00151-G.
  11. ^ a b Dunlap, J. L.; Gehrels, T.; Howes, M. L. (August 1973). "Minor planets and related objects. IX. Photometry and polarimetry of (1685) Toro". Astronomical Journal. 78: 491. Bibcode:1973AJ.....78..491D. doi:10.1086/111447.
  12. ^ a b Higgins, David (January 2011). "Period Determination of Asteroid Targets Observed at Hunters Hill Observatory: May 2009 - September 2010" (PDF). Minor Planet Bulletin. 38 (1): 41–46. Bibcode:2011MPBu...38...41H. ISSN 1052-8091. Retrieved 17 March 2020.
  13. ^ a b Higgins, David (March 2008). "Asteroid Lightcurve Analysis at Hunters Hill Observatory and Collaborating Stations: April 2007 - June 2007" (PDF). Minor Planet Bulletin. 35 (1): 30–32. Bibcode:2008MPBu...35...30H. ISSN 1052-8091. Retrieved 17 March 2020.
  14. ^ Oey, Julian (October 2011). "Lightcurve Analysis of Asteroids from Leura and Kingsgrove Observatory for the Second Half of 2009 and 2010" (PDF). Minor Planet Bulletin. 38 (4): 221–223. Bibcode:2011MPBu...38..221O. ISSN 1052-8091. Retrieved 17 March 2020.
  15. ^ Thomas, C. A.; Trilling, D. E.; Emery, J. P.; Mueller, M.; Hora, J. L.; Benner, L. A. M.; et al. (September 2011). "ExploreNEOs. V. Average Albedo by Taxonomic Complex in the Near-Earth Asteroid Population". The Astronomical Journal. 142 (3): 12. Bibcode:2011AJ....142...85T. doi:10.1088/0004-6256/142/3/85.
  16. ^ Thomas, Cristina A.; Emery, Joshua P.; Trilling, David E.; Delbó, Marco; Hora, Joseph L.; Mueller, Michael (January 2014). "Physical characterization of Warm Spitzer-observed near-Earth objects". Icarus. 228: 217–246. arXiv:1310.2000. Bibcode:2014Icar..228..217T. doi:10.1016/j.icarus.2013.10.004.
  17. ^ a b "LCDB Data for (1685) Toro". Asteroid Lightcurve Database (LCDB). Retrieved 22 December 2016.
  18. ^ Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 – Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007.
  19. ^ Waldemar Kaempffert (26 December 1948). "Science in Review: Research Work in Astronomy and Cancer Lead Year's List of Scientific Developments". The New York Times. p. 87. ISSN 0362-4331. Retrieved 4 August 2011.
  20. ^ Danielsson, L.; Ip, W.-H. (May 1972). "Capture Resonance of the Asteroid 1685 Toro by the Earth". Science. 176 (4037): 906–907. Bibcode:1972Sci...176..906D. doi:10.1126/science.176.4037.906. PMID 17829299.
  21. ^ Williams, J. G.; Wertherill, G. W. (August 1973). "Minor planets and related objects. XIII. Long-term orbital evolution of (1685) Toro". Astronomical Journal. 78: 510. Bibcode:1973AJ.....78..510W. doi:10.1086/111451.
  22. ^ Povenmire, H. (March 1995). "The Sylacauga, Alabama Meteorite: The Impact Locations, Atmosphere Trajectory, Strewn Field and Radiant". Abstracts of the Lunar and Planetary Science Conference. 26: 1133. Bibcode:1995LPI....26.1133P.
  23. ^ Schmadel, Lutz D. (2007). "(1580) Betulia". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 125. doi:10.1007/978-3-540-29925-7_1581. ISBN 978-3-540-00238-3.
  24. ^ "Samuel Herrick, Engineering; Astronomy: Los Angeles". Calisphere – University of California. Retrieved 22 December 2016.
  25. ^ Schmadel, Lutz D. (2009). "Appendix – Publication Dates of the MPCs". Dictionary of Minor Planet Names – Addendum to Fifth Edition (2006–2008). Springer Berlin Heidelberg. p. 221. doi:10.1007/978-3-642-01965-4. ISBN 978-3-642-01964-7.
  26. ^ Hartmann, W. K. (2005). Moons & Planets (5th ed.). Belmont, Calif.: Brooks/Cole. ASIN 0534493939

External linksEdit