9000 Hal

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 movie 2001: A Space Odyssey.[1]

This article is about the real-life asteroid. For the fictional computer in 2001: A Space Odyssey, see HAL 9000.
9000 Hal
Discovery [1]
Discovered byE. Bowell
Discovery siteAnderson Mesa Stn.
Discovery date3 May 1981
Designations
(9000) Hal
Pronunciation/ˈhæl/
Named after
HAL 9000 [1]
(Fictional supercomputer)
1981 JO · 1975 VH3
1981 JJ3 · 1995 US3
main-belt [1][2] · (inner)
background [3] · Flora [4]
Orbital characteristics [2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc41.49 yr (15,156 d)
Aphelion2.6955 AU
Perihelion1.7648 AU
2.2301 AU
Eccentricity0.2087
3.33 yr (1,216 d)
328.38°
0° 17m 45.24s / day
Inclination6.2618°
226.61°
79.871°
Physical characteristics
Mean diameter
3.61±0.78 km[5]
4.11 km (calculated)[4]
4.134±0.935 km[6][7]
22.68±0.02 h (poor)[8]
908 h[9]
0.24 (assumed)[4]
0.26±0.13[5]
0.375±0.184[6][7]
S (assumed)[4]
13.6[7]
14.0[2]
14.1[4]
14.35±0.66[10]
14.42[5]

    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
    1. "9000 Hal (1981 JO)". Minor Planet Center. Retrieved 16 May 2018.
    2. "JPL Small-Body Database Browser: 9000 Hal (1981 JO)" (2017-05-01 last obs.). Jet Propulsion Laboratory. Retrieved 16 May 2018.
    3. "Asteroid 9000 Hal". Small Bodies Data Ferret. Retrieved 15 May 2018.
    4. "LCDB Data for (9000) Hal". Asteroid Lightcurve Database (LCDB). Retrieved 16 May 2018.
    5. Nugent, C. R.; Mainzer, A.; Bauer, J.; Cutri, R. M.; Kramer, E. A.; Grav, T.; et al. (September 2016). "NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos". The Astronomical Journal. 152 (3): 12. arXiv:1606.08923. Bibcode:2016AJ....152...63N. doi:10.3847/0004-6256/152/3/63.
    6. Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68.
    7. Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. (catalog)
    8. Behrend, Raoul. "Asteroids and comets rotation curves – (9000) Hal". Geneva Observatory. Retrieved 16 May 2018.
    9. Galad, 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. ISSN 1052-8091.
    10. 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.
    11. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 16 May 2018.

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