6398 Timhunter

6398 Timhunter, provisional designation 1991 CD1, is a stony Phocaea asteroid from the inner regions of the asteroid belt, approximately 5.5 kilometers in diameter. It was discovered on 10 February 1991, by American astronomer couple Carolyn and Eugene Shoemaker, in collaboration with Canadian astronomer David H. Levy at Palomar Observatory in California, United States.[10] It was named for American amateur astronomer Tim Hunter.[2]

6398 Timhunter
Discovery [1]
Discovered byC. S. Shoemaker
E. M. Shoemaker
D. H. Levy
Discovery sitePalomar Obs.
Discovery date10 February 1991
Designations
(6398) Timhunter
Named after
Tim Hunter
(amateur astronomer)[2]
1991 CD1 · 1955 DB
1988 PG
main-belt · Phocaea [3][4]
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc62.19 yr (22,716 days)
Aphelion2.8684 AU
Perihelion1.8179 AU
2.3431 AU
Eccentricity0.2242
3.59 yr (1,310 days)
119.46°
0° 16m 29.28s / day
Inclination23.856°
128.98°
67.697°
Physical characteristics
Dimensions5.20±1.11 km[5]
5.528±0.112 km[6][7]
5.79 km (calculated)[3]
7.1074±0.0007 h[8]
14.55±0.01 h[lower-alpha 1]
0.23 (assumed)[3]
0.27±0.12[5]
0.333±0.049[6][7]
S [3]
13.1[6] · 13.4[1][3] · 13.59±0.81[9] · 13.63[5]

    Classification an orbit

    The stony S-type asteroid is a member of the Phocaea family (701),[4] a relatively small group of asteroids with similar orbital characteristics. Timhunter orbits the Sun in the inner main-belt at a distance of 1.8–2.9 AU once every 3 years and 7 months (1,310 days). Its orbit has an eccentricity of 0.22 and an inclination of 24° with respect to the ecliptic.[1] It was first identified as 1955 DB at Goethe Link Observatory in 1955, extending the body's observation arc by 36 years prior to its official discovery observation at Palomar.[10]

    Lightcurves

    In March 2009, a rotational lightcurve of Timhunter was obtained from photometric observations by astronomer Petr Pravec at the Ondřejov Observatory in the Czech Republic. Lightcurve analysis gave a well-defined rotation period of 14.55 hours with a brightness variation of 0.29 magnitude (U=3).[lower-alpha 1] One month later, another lightcurve was obtained by French amateur astronomers David Romeuf, Maurice Audejean and René Roy, which gave an alternative period solution of 7.1074 hours with an amplitude of 0.32 magnitude (U=2-).[8]

    Diameter and albedo

    According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Timhunter measures 5.20 and 5.528 kilometers in diameter, and its surface has an albedo of 0.333 and 0.27. respectively.[5][6][7] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.23 – derived from 25 Phocaea, the Phocaea family's namesake – and calculates a diameter of 5.79 kilometers, based on an absolute magnitude of 13.4.[3]

    Naming

    This minor planet was named after Tim Hunter, an American radiologist and amateur astronomer. Together with David Crawford he co-founded the non-profit International Dark-Sky Association with the aim to preserve and protect Earth's night sky from light pollution.[2] The approved naming citation was published by the Minor Planet Center on 1 June 1996 (M.P.C. 27330).[11]

    Notes
    1. Pravec (2009) web: lightcurve plot of (6398) Timhunter with a rotation period of 14.55±0.01 hours and a brightness amplitude of 0.29 mag. Summary figures at Collaborative Asteroid Lightcurve Link and Ondrejov Asteroid Photometry Project

    References
    1. "JPL Small-Body Database Browser: 6398 Timhunter (1991 CD1)" (2017-05-04 last obs.). Jet Propulsion Laboratory. Retrieved 4 July 2017.
    2. Schmadel, Lutz D. (2007). "(6398) Timhunter". Dictionary of Minor Planet Names – (6398) Timhunter. Springer Berlin Heidelberg. p. 529. doi:10.1007/978-3-540-29925-7_5841. ISBN 978-3-540-00238-3.
    3. "LCDB Data for (6398) Timhunter". Asteroid Lightcurve Database (LCDB). Retrieved 15 March 2017.
    4. "Asteroid 6398 Timhunter – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Retrieved 27 October 2019.
    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. Retrieved 15 March 2017.
    6. 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.
    7. 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. Retrieved 15 March 2017.
    8. Behrend, Raoul. "Asteroids and comets rotation curves – (6398) Timhunter". Geneva Observatory. Retrieved 15 March 2017.
    9. 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. Retrieved 15 March 2017.
    10. "6398 Timhunter (1991 CD1)". Minor Planet Center. Retrieved 15 March 2017.
    11. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 15 March 2017.

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