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2571 Geisei, provisional designation 1981 UC, is a stony Florian asteroid from the inner regions of the asteroid belt, approximately 6 kilometers in diameter. It was discovered by Japanese astronomer Tsutomu Seki at Geisei Observatory on 23 October 1981, and named for the Japanese village of Geisei.[2][10]

2571 Geisei
Discovery [1]
Discovered byT. Seki
Discovery siteGeisei Obs.
Discovery date23 October 1981
MPC designation(2571) Geisei
Named after
Geisei (Japanese village)[2]
1981 UC · 1931 TA4
1934 NV · 1944 OD
1961 XG · 1981 WR6
A911 UC
main-belt · Flora[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc85.64 yr (31,280 days)
Aphelion2.6607 AU
Perihelion1.7953 AU
2.2280 AU
3.33 yr (1,215 days)
0° 17m 47.04s / day
Physical characteristics
Dimensions5.21±0.95 km[4]
5.23±1.07 km[5]
6.582±0.035 km[6][7]
6.81 km (calculated)[3]
7.823±0.005 h[8]
0.24 (assumed)[3]
12.9[5] · 13.0[1][3][6] · 13.32±0.26[9] · 13.38[4]

Classification and OrbitEdit

Geisei is a member of the Flora family, one of the largest families of stony asteroids. It orbits the Sun in the inner main-belt at a distance of 1.8–2.7 AU once every 3 years and 4 months (1,215 days). Its orbit has an eccentricity of 0.19 and an inclination of 3° with respect to the ecliptic.[1]

In October 1911, Geisei was first identified as A911 UC at Heidelberg Observatory. The asteroid's observation arc begins 50 years prior to its discovery, with a precovery taken at Lowell Observatory in 1931.[10]

Physical characteristicsEdit


A rotational lightcurve for this asteroid was obtained from photometric observations made at the Australian Oakley Southern Sky Observatory (E09) in September 2014. The lightcurve gave a rotation period of 7.823±0.005 hours with a brightness variation of 0.50 in magnitude (U=3-).[8]

Diameter and albedoEdit

According to the 2015/16 NEOWISE mission results of NASA's space-based Wide-field Infrared Survey Explorer, Geisei measures 5.21 and 5.23 kilometers in diameter and its surface has an albedo of 0.34 and 0.38, respectively.[4][5] Preliminary WISE results gave a diameter of 6.582 kilometers and an albedo of 0.275.[6][7]

The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from 8 Flora, the largest member and namesake of the Flora family – and calculates a diameter of 6.81 kilometers using an absolute magnitude of 13.0.[3]


This minor planet is named after the small Japanese village of Geisei, where the discovering observatory is located. Geisei is situated near the city of Kōchi, after which Tsutomu Seki's first discovery, the asteroid 2396 Kochi, is named.[2] The approved naming citation was published by the Minor Planet Center on 6 June 1982 (M.P.C. 6956).[11]


  1. ^ a b c d "JPL Small-Body Database Browser: 2571 Geisei (1981 UC)" (2017-06-02 last obs.). Jet Propulsion Laboratory. Retrieved 3 July 2017.
  2. ^ a b c Schmadel, Lutz D. (2007). "(2571) Geisei". Dictionary of Minor Planet Names – (2571) Geisei. Springer Berlin Heidelberg. p. 210. doi:10.1007/978-3-540-29925-7_2572. ISBN 978-3-540-00238-3.
  3. ^ a b c d e f "LCDB Data for (2571) Geisei". Asteroid Lightcurve Database (LCDB). Retrieved 17 May 2016.
  4. ^ a b c d 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 3 July 2017.
  5. ^ a b c d Nugent, C. R.; Mainzer, A.; Masiero, J.; Bauer, J.; Cutri, R. M.; Grav, T.; et al. (December 2015). "NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos". The Astrophysical Journal. 814 (2): 13. arXiv:1509.02522. Bibcode:2015ApJ...814..117N. doi:10.1088/0004-637X/814/2/117. Retrieved 3 July 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. Retrieved 17 May 2016.
  7. ^ 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 6 December 2016.
  8. ^ a b Bohn, Lucas; Hibbler, Brianna; Stein, Gregory; Ditteon, Richard (April 2015). "Asteroid Lightcurve Analysis at the Oakley Southern Sky Observatory: 2014 September". The Minor Planet Bulletin. 42 (2): 89–90. Bibcode:2015MPBu...42...89B. ISSN 1052-8091. Retrieved 17 May 2016.
  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 17 May 2016.
  10. ^ a b "2571 Geisei (1981 UC)". Minor Planet Center. Retrieved 17 May 2016.
  11. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 17 May 2016.

External linksEdit