917 Lyka


917 Lyka is a background asteroid, approximately in diameter, located in the inner region of the asteroid belt. It was discovered on 5 September 1915, by Russian astronomer Grigory Neujmin at the Simeiz Observatory on the Crimean peninsula. The X-type asteroid has a rotation period of 7.9 hours and is likely spherical in shape. It was named after Lyka, a friend of the discoverer's sister.

Orbit and classification

Lyka is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. It orbits the Sun in the inner main-belt at a distance of 1.9–2.9 AU once every 3 years and 8 months. Its orbit has an eccentricity of 0.20 and an inclination of 5° with respect to the ecliptic. The body's observation arc begins at Simeiz on 1 September 1926, eleven years after to its official discovery observation.

Naming

This minor planet was named after Lyka, a friend of the sister of discoverer Grigory Neujmin. Lutz Schmadel, the author of the Dictionary of Minor Planet Names learned about the meaning of the asteroid's name from private communications with long-time Simeiz astronomer Nikolai Chernykh.

Physical characteristics

In both the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey, Lyka is an X-type asteroid.

Rotation period

In January 2005, a rotational lightcurve of Lyka was obtained from photometric observations by Matthieu Conjat. Lightcurve analysis gave a well-defined rotation period of hours with a low brightness variation of magnitude, indicative of a rather spherical shape. In October 2018, the period was confirmed by Laurent Bernasconi and by Alfonso Carreño of OBAS with amplitudes of and, respectively.

Diameter and albedo

According to the survey carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and the NEOWISE mission of NASA's WISE telescope, Lyka measures, and kilometers in diameter and its surface has an albedo of, and, respectively. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0520 and a diameter of 27.89 km based on an absolute magnitude of 11.6. Further published mean-diameters by the WISE team include,, and with albedos between and. An asteroid occultation, observed on 4 March 2005, gave a best-fit ellipse dimension of 28.0 × 28.0 kilometers. These timed observations are taken when the asteroid passes in front of a distant star. However the quality of the measurement is rated poorly.