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.
Discovery [1] | |
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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]
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]
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]
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]
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]
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