9617 Grahamchapman, provisional designation 1993 FA5, is a binary[4] Florian asteroid from the inner regions of the asteroid belt, approximately 2.8 kilometers in diameter.
Grahamchapman is a member of the Flora family, one of the largest collisional groups of stony asteroids. It orbits the Sun in the inner main-belt at a distance of 2.0–2.5 AU once every 3 years and 4 months (1,211 days). Its orbit has an eccentricity of 0.11 and an inclination of 6° with respect to the ecliptic.[1]
A first precovery was taken at Palomar Observatory in 1951, extending the body's observation arc by 42 years prior to its official discovery observation at La Silla.[11]
Physical characteristics
Diameter and albedo
According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Grahamchapman measures 2.84 kilometers in diameter and its surface has an albedo of 0.245.[6] The Collaborative Asteroid Lightcurve Link agrees with Petr Pravec's revised NEOWISE data and gives an albedo of 0.224 with a diameter of 2.85 kilometers with an absolute magnitude of 14.97.[3][8]
Asteroid moon
In February 2006, observations by the Ondřejov NEO Photometric Program determined that Grahamchapman is orbited by a minor-planet moon. The satellite is about a quarter the size of Grahamchapman, and orbits it about once every 19 hours, 23 minutes, and 5 seconds.[4][5]
Rotation period and shape
The lightcurve study also showed that Grahamchapman itself has a rotation period of 2.28561 hours with a brightness variation of 0.10 magnitude (U=3).[9] A second photometric observation in December 2008, gave an identical period with an amplitude of 0.11 magnitude (U=3).[9] A low brightness amplitude typically indicates that the body has a nearly spheroidal shape.