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]

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) in 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]

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]}

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]}

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) from 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]

• Asteroid Lightcurve Database (LCDB), query form ( info Archived 16 December 2017 at the Wayback Machine)
• Dictionary of Minor Planet Names, Google books
• Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• 2975 Spahr at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 2975 Spahr at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters