57868 Pupin (provisional designation 2001 YD) is a dark Erigonian asteroid and slow rotator from the inner regions of the asteroid belt, approximately 3.5 kilometers in diameter. It was discovered on 17 December 2001, by astronomers of Near-Earth Asteroid Tracking (NEAT) at the Palomar Observatory in California, United States. The asteroid was named after Serbian–American physicist Mihajlo Pupin.^[2]

Pupin is a member of the Erigone family, named after 163 Erigone.^[4] It orbits the Sun in the inner main-belt at a distance of 1.8–3.0 AU once every 3 years and 8 months (1,342 days). Its orbit has an eccentricity of 0.25 and an inclination of 4° with respect to the ecliptic.^[1] The body's observation arc begins with its first identification as 1997 WU₄₆ at Lincoln Laboratory ETS in November 1997.^[2]

Based on PanSTARRS photometric survey, Pupin is a carbonaceous C-type asteroid,^[9] while the Erigone family's overall spectral type is that of a C- and X-type (CX).^[10]: 23

In September 2015, a first rotational lightcurve of Pupin was obtained by astronomer Vladimir Benishek at Sopot Astronomical Observatory (K90), Serbia, and by American astronomer Frederick Pilcher at his Organ Mesa Observatory (G50) in New Mexico. It showed a rotation period of 108.10±0.04 hours with a brightness amplitude of 0.93 in magnitude (U=3-).^[8] This makes it a slow rotator, as asteroids of this size typically rotate within less than 20 hours once around their axis.

According to the survey carried out by the NEOWISE mission of NASA's space-based Wide-field Infrared Survey Explorer, Pupin measures 3.42 and 5.7 kilometers in diameter and its surface has an albedo of 0.045 and 0.09, respectively.^[6] However, the Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20, and calculates a diameter of 2.6 kilometers using an absolute magnitude of 15.3.^[3]

This minor planet was named in honor of Serbian–American physicist and humanitarian, Mihajlo Pupin (1858–1935). He greatly improved long-distance telephone transmission and the sensitivity of X-ray detection, and worked for Serbian emigres. The asteroid's name was suggested by the above-mentioned astronomers Vladimir Benishek and Frederick Pilcher.^[2] The official naming citation was published by the Minor Planet Center on 23 March 2016 (M.P.C. 99354).^[11]

• 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 (55001)-(60000) – Minor Planet Center
• 57868 Pupin at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 57868 Pupin at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters