1857 Parchomenko, provisional designation 1971 QS1, is a stony asteroid and suspected binary from the inner regions of the asteroid belt, approximately 8 kilometers in diameter.
Parchomenko orbits the Sun in the inner main-belt at a distance of 1.9–2.5 AU once every 3 years and 4 months (1,228 days). Its orbit has an eccentricity of 0.13 and an inclination of 4° with respect to the ecliptic.[1]
First identified as 1931 XT at Lowell Observatory, the body's first used observation was taken at Nice Observatory in 1939, extending its observation arc by 32 years prior to its official discovery observation at Nauchnyj.[8]
According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Parchomenko measures 7.99 and 9.84 kilometers in diameter, and its surface has an albedo of 0.295 and 0.333, respectively.[4][5] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 8.5 kilometers, based on an absolute magnitude of 12.4.[3]
Three possible occultation events were observed, suggesting that Parchomenko might be a binary asteroid, having a minor-planet moon as companion.[7] However, no new findings have been made since. In October 2008, Italian amateur astronomer Silvano Casulli measured a similar period of 3.08 hours with an amplitude of 0.27 magnitude (U=3).[6]