991 McDonalda

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]

991 McDonalda

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[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)
Semi-major axis	3.1419 AU (470.02 Gm)
Eccentricity	0.15791
Orbital period	5.57 yr (2034.2 d)
Mean anomaly	351.48°
Mean motion	0° 10^m 37.092^s / 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

References

1. "991 McDonalda (1922 NB)". JPL Small-Body Database. NASA/Jet Propulsion Laboratory. Retrieved 2 May 2016.
2. 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
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 991 McDonalda at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters