991 McDonalda

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991 McDonalda
Discovery
Discovered by O. Struve
Discovery site Williams Bay
Discovery date 24 October 1922
Designations
1922 NB, 1949 PF, 1950 WG, 1953 GT1, 1975 EE6
Orbital characteristics[1]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc 80.10 yr (29255 days)
Aphelion 3.6381 AU (544.25 Gm)
Perihelion 2.6458 AU (395.81 Gm)
3.1419 AU (470.02 Gm)
Eccentricity 0.15791
5.57 yr (2034.2 d)
351.48°
0° 10m 37.092s / day
Inclination 2.0696°
63.255°
254.682°
Earth MOID 1.63297 AU (244.289 Gm)
Jupiter MOID 1.65546 AU (247.653 Gm)
Jupiter Tisserand parameter 3.190
Proper orbital elements
0.1768 deg / yr
2036.1991 yr
(743721.719 d)
Physical characteristics
Mean radius
15.705±1.05 km
0.0638±0.009
Temperature 144-167 K
C
11.12

991 McDonalda is a Themistian asteroid. It was discovered by Otto Struve in 1922 at the Yerkes Observatory in Williams Bay, Wisconsin, United States. It is named after the McDonald Observatory, which Struve helped found in 1939.[2]

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