9000 Hal, provisional designation 1981 JO, is a stony background asteroid and slow rotator from the inner regions of the asteroid belt, approximately 4 kilometers (2.5 miles) in diameter. It was discovered on 3 May 1981, by American astronomer Edward Bowell at Lowell's Anderson Mesa Station near Flagstaff, Arizona, in the United States.[1] The likely elongated S-type asteroid has an exceptionally long rotation period of 908 hours.[4] It was named after the homicidal supercomputer HAL 9000, featured in the 1968 film 2001: A Space Odyssey.[1]
Hal orbits the Sun in the inner asteroid belt at a distance of 1.8–2.7 AU once every 3 years and 4 months (1,216 days; semi-major axis of 2.23 AU). Its orbit has an eccentricity of 0.21 and an inclination of 6° with respect to the ecliptic.[2] The asteroid was first observed as 1975 VH3 at Crimea–Nauchnij in November 1975. The body's observation arc begins with its official discovery observation at Anderson Mesa in May 1981.[1]
Physical characteristics
Hal is an assumed stony S-type asteroid, based on the Collaborative Asteroid Lightcurve Link's (CALL) classification into the Flora family.[4]
An alternative measurement by French amateur astronomers Pierre Antonini and René Roy gave a much shorter period of 22.68 hours.[8] The result, however, is considered of poor quality by CALL (U=1).[4]
Diameter and albedo
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Hal measures between 3.61 and 4.134 kilometers in diameter and its surface has an albedo between 0.26 and 0.375.[5][6][7] CALL assumes an albedo of 0.24 – derived from 8 Flora, the Flora family's parent body – and calculates a diameter of 4.11 kilometers based on an absolute magnitude of 14.1.[4]
^ abGalad, Adrian; Vilagi, Jozef; Kornos, Leonard; Gajdos, Stefan (July 2009). "Relative Photometry of Nine Asteroids from Modra". The Minor Planet Bulletin. 36 (3): 116–118. Bibcode:2009MPBu...36..116G. ISSN1052-8091.
^Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. S2CID53493339.