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2975 Spahr, provisional designation 1970 AF1, is a bright background asteroid from the Flora region of the inner asteroid belt, approximately 6 kilometers (3.7 miles) in diameter. It was discovered on 8 January 1970, by Russian astronomers Hejno Potter and A. Lokalov at the Cerro El Roble Station near Santiago, Chile.[1] The S- or A-type asteroid has a rotation period of 11.9 hours.[5] It was named for Timothy Spahr, an American astronomer and former director of the Minor Planet Center.[12]

2975 Spahr
Discovery [1]
Discovered byH. Potter
A. Lokalov
Discovery siteCerro El Roble Stn.
Discovery date8 January 1970
MPC designation(2975) Spahr
Named after
Timothy Spahr[1]
(MPC director)
1970 AF1 · 1957 HU
1967 GH · 1970 AK1
1970 CB · 1978 PF4
main-belt[1][2] · (inner)
background[3][4] · Flora[5]
Orbital characteristics[2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc61.07 yr (22,304 d)
Aphelion2.4621 AU
Perihelion2.0351 AU
2.2486 AU
3.37 yr (1,232 d)
0° 17m 32.28s / day
Physical characteristics
Mean diameter
5.919±0.107 km[6]
6.032±0.082 km[7]
6.51 km (calculated)[5]
11.946±0.006 h[8]
0.24 (assumed)[5]
S (Pan-STARRS)[5][10]
A (S3OS2-TH)[11]
A (S3OS2-BB)[11]


Orbit and classificationEdit

Spahr is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[3][4] 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.[5]

It orbits the Sun in the inner asteroid belt at a distance of 2.0–2.5 AU once every 3 years and 4 months (1,232 days; semi-major axis of 2.25 AU). Its orbit has an eccentricity of 0.09 and an inclination of 7° with respect to the ecliptic.[2]

The asteroid was first observed as 1957 HU at the Johannesburg-Hartbeespoort Observatory (076) on April 1957. The body's observation arc begins as 1967 GH at Crimea-Nauchnij in April 1967, nearly 3 years prior to its official discovery observation at Cerro El Roble.[1]

Physical characteristicsEdit

In the SDSS-based taxonomy, Spahr is a stony S-type asteroid.[9] Pan-STARRS' survey also characterizes the body as an S-type,[5][10] while in both, the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), Spahr is an uncommon A-type asteroid.[4][11]

Rotation periodEdit

In December 2009, a first rotational lightcurve of Spahr was obtained from photometric observations by French amateur astronomer René Roy. Lightcurve analysis gave a rotation period of 11.946 hours with a relatively high brightness amplitude of 0.47 magnitude (U=3-).[5][8]

Diameter and albedoEdit

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Spahr measures between 5.919 and 6.032 kilometers in diameter and its surface has a high albedo between 0.4044 and 0.419.[6][7] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from 8 Flora, the parent body of the Flora family – and consequently calculates a larger diameter of 6.51 kilometers using an absolute magnitude of 13.1.[5]


This minor planet was named after Timothy Bruce Spahr (born 1970), a discoverer of minor planets and comets such as 171P/Spahr and 242P/Spahr, as well as a co-discoverer of Callirrhoe and Albiorix (moon), satellites of Jupiter and Saturn, respectively. Spahr was with the photographic Bigelow Sky Survey, which searched for high-latitude minor planets using the 0.41-m Catalina Schmidt telescope. (This survey was superseded by the Catalina Sky Survey). Spahr also headed the Minor Planet Center (MPC) form 2000 to 2014.[13] The asteroid's name was proposed by his MPC-colleges Brian Marsden, Gareth Williams and Stephen Larson,[12] and published by the MPC on 3 May 1996 (M.P.C. 27124).[14]


  1. ^ a b c d e f "2975 Spahr (1970 AF1)". Minor Planet Center. Retrieved 5 June 2018.
  2. ^ a b c d "JPL Small-Body Database Browser: 2975 Spahr (1970 AF1)" (2018-05-24 last obs.). Jet Propulsion Laboratory. Retrieved 5 June 2018.
  3. ^ a b "Asteroid (2975) Spahr". AstDyS-2, Asteroids – Dynamic Site. Retrieved 5 June 2018.
  4. ^ a b c "Asteroid 2975 Spahr". Small Bodies Data Ferret. Retrieved 5 June 2018.
  5. ^ a b c d e f g h i j "LCDB Data for (2975) Spahr". Asteroid Lightcurve Database (LCDB). Retrieved 5 June 2018.
  6. ^ 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 5 June 2018.
  7. ^ 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. (catalog)
  8. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (2975) Spahr". Geneva Observatory. Retrieved 5 June 2018.
  9. ^ a b Carvano, J. M.; Hasselmann, P. H.; Lazzaro, D.; Mothé-Diniz, T. (February 2010). "SDSS-based taxonomic classification and orbital distribution of main belt asteroids". Astronomy and Astrophysics. 510: 12. Bibcode:2010A&A...510A..43C. doi:10.1051/0004-6361/200913322. Archived from the original on 2 May 2018. Retrieved 5 June 2018.
  10. ^ a b c 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. ^ a b c Lazzaro, D.; Angeli, C. A.; Carvano, J. M.; Mothé-Diniz, T.; Duffard, R.; Florczak, M. (November 2004). "S3OS2: the visible spectroscopic survey of 820 asteroids" (PDF). Icarus. 172 (1): 179–220. Bibcode:2004Icar..172..179L. doi:10.1016/j.icarus.2004.06.006. Retrieved 5 June 2018.
  12. ^ a b Schmadel, Lutz D. (2007). "(2975) Spahr". Dictionary of Minor Planet Names – (2975) Spahr. Springer Berlin Heidelberg. p. 245. doi:10.1007/978-3-540-29925-7_2976. ISBN 978-3-540-00238-3.
  13. ^ "Tim Spahr of the Minor Planet Center – Planetary Radio". The Planetary Society. Retrieved 5 June 2018.
  14. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 5 June 2018.

External linksEdit