پیوند به بیرون[ویرایش]
Orbit and classification
Öpik orbits the Sun in the inner main-belt at a distance of 1.5–3.1 AU once every 3 years and 6 months (1,277 days). Its orbit has an eccentricity of 0.36 and an inclination of 27° with respect to the ecliptic. The first used precovery was taken at the discovering observatory in 1970, extending the asteroid's observation arc by 7 years prior to its discovery.
Originally, the asteroid's spectral type was that of a bright S-type asteroid in the Tholen classification. More recently, it has been characterized as a dark Ch-type, a hydrated subtype of the carbonaceous C-type asteroids in the SMASS classification, which is in agreement with its low albedo (below).
Diameter and albedo
According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Öpik measures 5.17 kilometers in diameter and its surface has an albedo of 0.05. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous asteroids of 0.057 and calculates a diameter of 5.12 kilometers with an absolute magnitude of 15.18.
In 2005, a photometric lightcurve analysis by several astronomers including Pierre Antonini, rendered a rotation period of 6.4430±0.0002 hours and with a brightness amplitude of 0.21 in magnitude (U=2), superseding the results of an observation from the 1990s that gave a longer period of 9.3 hours (U=2).
This minor planet was named after Estonian astronomer and astrophysicist, Ernst Öpik (1893–1985), who has influenced many fields of astronomy during his 60-year long career. He is noted for developing the discipline of statistical celestial mechanics and for methods to estimate the lifetimes of planet-crossing asteroids. In the early 1950s, he calculated the impact probability of Mars-crossing asteroids with Mars, and concluded that a search for impact craters on Mars would be a fruitful. Fourteen years later, Martian craters were discovered by Mariner 4. The official naming citation was published by the Minor Planet Center on 1 November 1978 (M.P.C. 4548).