5642 Bobbywilliams

"Bobbywilliams" redirects here. For other uses, see Bobby Williams (disambiguation).

5642 Bobbywilliams, provisional designation 1990 OK₁, is an eccentric, stony asteroid and Mars-crosser from the inner regions of the asteroid belt, approximately 4.7 kilometers in diameter.

5642 Bobbywilliams

Discovery[1]
Discovered by	H. E. Holt
Discovery site	Palomar Obs.
Discovery date	27 July 1990
Designations
MPC designation	(5642) Bobbywilliams
Named after	Bobby G. Williams (JPL engineer)[2]
Alternative designations	1990 OK1
Minor planet category	Mars-crosser[1][3][4]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	41.97 yr (15,330 days)
Aphelion	3.0867 AU
Perihelion	1.5454 AU
Semi-major axis	2.3161 AU
Eccentricity	0.3327
Orbital period (sidereal)	3.52 yr (1,287 days)
Mean anomaly	235.13°
Mean motion	0° 16m 46.56s / day
Inclination	24.956°
Longitude of ascending node	310.12°
Argument of perihelion	39.038°
Physical characteristics
Dimensions	4.71 km (calculated)[4]
Synodic rotation period	4.8341±0.0003 h[5]
Geometric albedo	0.20 (assumed)[4]
Spectral type	S[4]
Absolute magnitude (H)	14.0[1][4] · 14.24±0.23[6]

It was discovered on 27 July 1990, by American astronomer Henry E. Holt at Palomar Observatory in California, United States.^[3] The asteroid was named for JPL engineer Bobby Williams.^[2]

Orbit and classification

Bobbywilliams orbits the Sun in the inner main-belt at a distance of 1.5–3.1 AU once every 3 years and 6 months (1,287 days). Its orbit has an eccentricity of 0.33 and an inclination of 25° with respect to the ecliptic.^[1] A first precovery was taken at the Australian Siding Spring Observatory in 1975, extending the body's observation arc by 15 years prior to its official discovery at Palomar.^[3]

Physical characteristics

Rotation period

In July 2011, a rotational lightcurve of Bobbywilliams was obtained from photometric observations by astronomer Julian Oey at both the Australian Kingsgrove (E19) and Leura (E17) observatories. Lightcurve analysis gave a well-defined rotation period of 4.8341 hours with a brightness variation of 0.05 magnitude (U=3).^[5]

Diameter and albedo

The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 4.71 kilometers with an absolute magnitude of 14.0.^[4]

Naming

This minor planet was named for Jet Propulsion Laboratory engineer Bobby G. Williams (born 1951), specialized in celestial mechanics and the navigation of space probes. He has been a leading navigation manager when NEAR Shoemaker had its rendezvous with the asteroids 253 Mathilde and 433 Eros,^[2] The official naming citation was published by the Minor Planet Center on 28 July 1999 (M.P.C. 35483).^[7]