8900 AAVSO, provisional designation 1995 UD₂, is a stony background asteroid from the central region of the asteroid belt, approximately 5.5 kilometers in diameter. It was discovered by American amateur astronomer Dennis di Cicco at the U.S Sudbury Observatory (817), Massachusetts, on 24 October 1995.^[8] The asteroid was named after the American Association of Variable Star Observers (AAVSO).^[2]

AAVSO is a non-family asteroid from the main belt's background population. It orbits the Sun in the central main-belt at a distance of 2.2–2.9 AU once every 4.04 years (1,475 days). Its orbit has an eccentricity of 0.15 and an inclination of 9° with respect to the ecliptic.^[1] The first precovery was obtained at Kleť Observatory in 1979, extending the asteroid's observation arc by 16 years prior to its discovery.^[8]

This minor planet was named after the American Association of Variable Star Observers (AAVSO), an astronomical pro-am organization that promotes the study of variable stars to both amateur and professional astronomers, maintaining the largest database of variable star observations in the world.^[2]

AAVSO was founded in 1911 by amateur astronomer William Tyler Olcott (1873–1936), based on a suggestion by Edward Charles Pickering's (1846–1919), after whom the minor planet 784 Pickeringia is named.^[2] The official naming citation was published by the Minor Planet Center on 1 May 2003 (M.P.C. 48388).^[9]