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1685 Toro

1685 Toro
Discovery 
Discovered by C. A. Wirtanen
Discovery site Lick Obs.
Discovery date 17 July 1948
Designations
MPC designation 1685 Toro
Named after
Betulia Toro Herrick
(wife Samuel Herrick)
1948 OA
NEO · Apollo
Mars-crosser
Orbital characteristics
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc 67.99 yr (24,833 days)
Aphelion 1.9633 AU
Perihelion 0.7713 AU
1.3673 AU
Eccentricity 0.4359
1.60 yr (584 days)
48.623°
Inclination 9.3807°
274.34°
127.08°
Earth MOID 0.0507 AU
Physical characteristics
Dimensions 3.810±0.049 km
4.1 km
10.185±0.003 h
10.1862±0.0006 h
10.191±0.005 h
10.195 h
10.19540 h
10.196 h
10.199±0.003 h
10.1995±0.0004 h
10.203±0.003 h
0.247±0.049
0.29
0.38±0.33
B–V = 0.880
U–B = 0.470
S(Tholen) · S(SMASS) · S
13.90 · 14.02±1.11 · 14.23

1685 Toro, provisional designation 1948 OA, is an eccentric stony asteroid and near-Earth object of the Apollo group, approximately 4 kilometers in diameter. It was discovered on 17 July 1948, by American astronomer Carl A. Wirtanen at Lick Observatory on Mount Hamilton, California. It is named after the wife of astronomer Samuel Herrick.

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 1 years and 7 months (584 days). Its orbit has an eccentricity of 0.44 and an inclination of 9° with respect to the ecliptic.

The stony S-type asteroid is reported to be composed of L chondrite with a high albedo in the range of 0.24–0.34. It has an extremely well-measured rotation period of 10.2 hours.

Toro's orbit also shows a 5:8 resonance with Earth and in a near 5:13 resonance with Venus. 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 AD, and that it will enter the region of 5:13 resonance with Venus in 3470. 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.


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