789 Lena
789 Lena, provisional designation , is a metallic asteroid from the middle region of the asteroid belt, approximately 24 kilometers in diameter. It was discovered on 24 June 1914, by Soviet–Russian astronomer Grigory Neujmin at Simeiz Observatory on the Crimean peninsula, and named after the discoverer's mother.
Orbit and classification
Lena orbits the Sun in the middle main-belt at a distance of 2.3–3.1 AU once every 4 years and 5 months. Its orbit has an eccentricity of 0.15 and an inclination of 11° with respect to the ecliptic. Lenas observation arc begins with its first used observation made at Yerkes Observatory in 1935, or 21 years after its official discovery observation at Simeiz.Although its orbital elements resemble those of the asteroids in the Eunomia family, true members of this family have a S-type composition, so it is almost certainly an unrelated interloper.
Physical characteristics
In the SMASS taxonomy, Lena is an X-type asteroid. It has also been characterized as a metallic M-type asteroid by NASA's Wide-field Infrared Survey Explorer.Rotation period
In 1993, a rotational lightcurve which was later proven incorrect, was obtained from photometric observations at the Félix Aguilar Observatory, Argentina. It gave an unusual lightcurve, indicating a very irregular shape and/or a relatively long rotation period of 22 hours with an exceptionally high amplitude of 1.5 in magnitude.In August and September 2007, two reliable lightcurves were obtained by Italian astronomer Silvano Casulli and by members at the U.S.Oakley Observatory. Lightcurve analysis gave a period of and hours, with a brightness variation of 0.50 and of 0.40 magnitude, respectively.