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9971 Ishihara (prov. designation: 1993 HS) is a stony Flora asteroid from the inner regions of the asteroid belt, approximately 5 kilometers (3.1 miles) in diameter. It was discovered by Japanese amateur astronomers Kin Endate and Kazuro Watanabe at Kitami Observatory on 16 April 1993,[1] and named after Takahiro Ishihara, president of the astronomical society at Hiroshima.[2]

Orbit and classification

Orbit of Ishihara (blue), inner planets and Jupiter (outermost)

Ishihara is a member of the Flora family, one of the largest families of stony asteroids in the asteroid belt. It orbits the Sun in the inner main-belt at a distance of 1.9–2.4 AU once every 3 years and 3 months (1,177 days). Its orbit has an eccentricity of 0.12 and an inclination of 3° with respect to the ecliptic.[3] It was first identified as 1991 YC2 at Karl Schwarzschild Observatory in 1991, extending the body's observation arc by approximately 2 years prior to its official discovery at Kitami.[1]

Naming

This minor planet was named after Takahiro Ishihara (born 1961), an observer of comets, communicator of astronomy, and former president of the astronomical society at Hiroshima (1987–1997).[2] The official naming citation was published by the Minor Planet Center on 6 January 2003 (M.P.C. 47298).[9]

Physical characteristics

Rotation and poles

In January 2012, a rotational lightcurve of Ishihara was obtained from photometric observations by astronomers at the Palomar Transient Factory in California. Lightcurve analysis gave a rotation period of 6.715±0.0036 hours with a brightness amplitude of 1.06 in magnitude, which indicates that the body has a non-spheroidal shape (U=2).[7]

A 2016-published lightcurve, using modeled photometric data from the Lowell Photometric Database (LPD), gave a concurring period of 6.71574 hours (U=n.a.), as well as a spin axis of (42.0°, 76.0°) in ecliptic coordinates (λ, β).[8]

Diameter and albedo

According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Ishihara measures 4.986 and 5.012 kilometers in diameter and its surface has an albedo of 0.235 and 0.2328, respectively.[5][6] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from 8 Flora, a S-type asteroid and the family's largest member and namesake – and calculates a diameter of 3.74 kilometers with an absolute magnitude of 14.3.[4]

References

  1. ^ a b c d "9971 Ishihara (1993 HS)". Minor Planet Center. Retrieved 10 April 2017.
  2. ^ a b c Schmadel, Lutz D. (2006). "(9971) Ishihara [2.18, 0.12, 2.7]". Dictionary of Minor Planet Names – (9971) Ishihara, Addendum to Fifth Edition: 2003–2005. Springer Berlin Heidelberg. p. 49. doi:10.1007/978-3-540-34361-5_391. ISBN 978-3-540-34361-5.
  3. ^ a b c d "JPL Small-Body Database Browser: 9971 Ishihara (1993 HS)" (2016-11-23 last obs.). Jet Propulsion Laboratory. Retrieved 22 June 2017.
  4. ^ a b c d "LCDB Data for (9971) Ishihara". Asteroid Lightcurve Database (LCDB). Retrieved 10 April 2017.
  5. ^ a b c 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 10 April 2017.
  6. ^ a b c d 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. ^ a b c Waszczak, Adam; Chang, Chan-Kao; Ofek, Eran O.; Laher, Russ; Masci, Frank; Levitan, David; et al. (September 2015). "Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry". The Astronomical Journal. 150 (3): 35. arXiv:1504.04041. Bibcode:2015AJ....150...75W. doi:10.1088/0004-6256/150/3/75. Retrieved 10 April 2017.
  8. ^ a b c Durech, J.; Hanus, J.; Oszkiewicz, D.; Vanco, R. (March 2016). "Asteroid models from the Lowell photometric database". Astronomy and Astrophysics. 587: 6. arXiv:1601.02909. Bibcode:2016A&A...587A..48D. doi:10.1051/0004-6361/201527573. Retrieved 10 April 2017.
  9. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 10 April 2017.

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