|Discovered by||Carl A. Wirtanen|
|Discovery date||17 July 1948|
|Alternative names||1948 OA|
|Minor planet category||Apollo, Mars crosser|
|Epoch 1 December 2005 (JD 2453705.5)|
|Semi-major axis||1.367 AU|
|Orbital period||583.957 d|
|Average orbital speed||24.217 km/s|
|Longitude of ascending node||274.355°|
|Argument of perihelion||127.037°|
|Rotation period||10.2 h|
|Absolute magnitude (H)||14.0–14.4|
1685 Toro is an Apollo asteroid that orbits the Sun in an 5:8 resonance with Earth, and a near 5:13 resonance with Venus. Because of this unusual orbit, it is sometimes referenced as "Earth's second satellite".
Toro was discovered by Carl A. Wirtanen at the Lick Observatory in 1948. It was the third Apollo asteroid to be discovered. The name honours Betulia Toro, wife of the astronomer Samuel Herrick. Herrick had studied the asteroid's orbit, and requested the name, along with that of 1580 Betulia.
Based on orbital paths, 1685 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.
Toro's Earth minimum orbit intersection distance of 0.0509 AU (7,610,000 km; 4,730,000 mi), is just above the 0.05-AU requirement to be listed as a potentially hazardous asteroid. With an orbital uncertainty of 0, its orbit and future close approaches are well determined.
- 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.
- Danielsson, L.; Ip, W.-H. (1972-05-26). "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. Retrieved 2012-06-09.
- Bruce Duensing (16 February 2009). "Ruminations On An Asteroid Named 1685 Toro". Intangible Materiality. Retrieved 4 August 2011.
- Schmadel, Lutz D. (2009). Dictionary of Minor Planet Names: Addendum to Fifth Edition: 2006–2008. Berlin: Springer Berlin. ISBN 978-3-642-01964-7. Retrieved 4 August 2011.
- University of California, Samuel Herrick, Engineering; Astronomy: Los Angeles
- H. Povenmire. The Sylacauga, Alabama Meteorite: The Impact Locations, Atmosphere Trajectory, Strewn Field and Radiant. H.Povenmire. Abstracts of the Lunar and Planetary Science Conference, volume 26, page 1133, (1995)
- Hartmann, W. K. (2005). Moons & Planets (5th ed.). Belmont, Calif.: Brooks/Cole.
- "JPL Small-Body Database Browser: 1685 Toro (1948 OA)". Jet Propulsion Laboratory. 2013-09-01 last obs. Retrieved 2014-02-02.
- telnet://ssd.jpl.nasa.gov:6775 telnet for JPL Horizons, easier and more comprehensive than web version