| Discovery | |
|---|---|
| Discovered by | O. Struve |
| Discovery site | Williams Bay |
| Discovery date | 24 October 1922 |
| Designations | |
| MPC designation | (991) McDonalda |
| Alternative designations | 1922 NB, 1949 PF, 1950 WG, 1953 GT1, 1975 EE6 |
| Orbital characteristics | |
| 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) |
| Semi-major axis | 3.1419 AU (470.02 Gm) |
| Eccentricity | 0.15791 |
| Orbital period (sidereal) | 5.57 yr (2034.2 d) |
| Mean anomaly | 351.48° |
| Mean motion | 0° 10 37.092 / day |
| Inclination | 2.0696° |
| Longitude of ascending node | 63.255° |
| Argument of perihelion | 254.682° |
| Physical characteristics | |
| Mean radius | 15.705±1.05 km |
| Geometric albedo | 0.0638±0.009 |
| Spectral type | C |
| Absolute magnitude (H) | 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.
References
- "991 McDonalda (1922 NB)". JPL Small-Body Database. NASA/Jet Propulsion Laboratory. Retrieved 2 May 2016.
- Lutz D. Schmadel (2011). Dictionary of Minor Planet Names. Addendum to Fifth Edition: 2006–2008. Springer. ISBN 978-3-642-01966-1.
External links
- 991 McDonalda at AstDyS-2, Asteroids—Dynamic Site
- 991 McDonalda at the JPL Small-Body Database
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