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]

Orbit and classification

Hal is a non- family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. ^[3] Based on osculating Keplerian orbital elements, the asteroid has also been classified as a member of the Flora family ( 402), a giant asteroid family and the largest family of stony asteroids in the main-belt. ^[4]

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]

Rotation period

In August 2008, a rotational lightcurve of Hal was obtained from photometric observations by Slovak astronomers Adrián Galád, Jozef Világi, Leonard Kornoš and Štefan Gajdoš at Modra Observatory. ^[9] Lightcurve analysis gave an exceptionally long rotation period of 908 hours with a high brightness variation of 0.9 magnitude ( U=2+). This makes Hal one of the slowest rotators known to exist. In addition, the body's high brightness amplitude is indicative of a non-spherical shape.

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]

Naming

This minor planet was named after the fictional supercomputer Hal 9000, featured in both Arthur C. Clarke's novel and Stanley Kubrick's movie 2001: A Space Odyssey (1968). ^[1] HAL stands for Heuristically programmed Algorithmic computer. It is one of the best-known artificial intelligence characters in modern movies. The official naming citation was published by the Minor Planet Center on 4 May 1999 ( M.P.C. 34628). ^[11] The asteroid 4923 Clarke and 10221 Kubrick were named after the writer and movie director, respectively.

References

External links

• Asteroid Lightcurve Database (LCDB), query form ( info Archived 16 December 2017 at the Wayback Machine)
• Dictionary of Minor Planet Names, Google books
• Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
• Discovery Circumstances: Numbered Minor Planets (5001)-(10000) – Minor Planet Center
• 9000 Hal at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 9000 Hal at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters