917 Lyka ('' prov. designation: '' ''or'' ) 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 The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...

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 Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

asteroid of the main belt's background population when applying the hierarchical clustering method to its

proper orbital elements __NOTOC__ The proper orbital elements or proper elements of an orbit are constants of motion of an object in space that remain practically unchanged over an astronomically long timescale. The term is usually used to describe the three quantitie ...

. It orbits the Sun in the

inner Interior may refer to: Arts and media * ''Interior'' (Degas) (also known as ''The Rape''), painting by Edgar Degas * ''Interior'' (play), 1895 play by Belgian playwright Maurice Maeterlinck * ''The Interior'' (novel), by Lisa See * Interior de ...

main-belt at a distance of 1.9–2.9 AU once every 3 years and 8 months (1,342 days;

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...

of 2.38 AU). Its orbit has an eccentricity of 0.20 and an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

of 5 ° with respect to the ecliptic. The body's

observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...

begins at Simeiz on 1 September 1926, eleven years after to its official discovery observation.

Naming

This

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor ...

was named after Lyka, a friend of the sister of discoverer Grigory Neujmin.

Lutz Schmadel Lutz Dieter Schmadel (2 July 1942, in Berlin – 21 October 2016) was a German astronomer and a prolific discoverer of asteroids, who worked at the Astronomisches Rechen-Institut (ARI) of the University of Heidelberg. His special interest was t ...

, 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 Nikolai Stepanovich Chernykh (russian: Никола́й Степа́нович Черны́х) (6 October 1931 – 25 May 2004Казакова, Р.К. Памяти Николая Степановича Черных'. Труды Государст ...

Physical characteristics

In both the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), ''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

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 This is a list of minor-planet discoverers credited by the Minor Planet Center with the discovery of one or several minor planets (such as near-Earth and main-belt asteroids, Jupiter trojans and distant objects). , the discovery of 612,011 numb ...

() 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 Infrared Astronomical Satellite (Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten mo ...

, the Japanese Akari satellite, and the NEOWISE mission of NASA's

WISE WISE may refer to: Arts, entertainment, and media * WISE (AM), a radio station licensed to Asheville, North Carolina *WISE-FM, a radio station licensed to Wise, Virginia * WISE-TV, a television station licensed to Fort Wayne, Indiana Education * ...

telescope (WISE), ''Lyka'' measures (), () and () kilometers in diameter and its surface has an

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

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 Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

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.

References

External links

Lightcurve Database Query
(LCDB), at ''www.minorplanet.info''
Dictionary of Minor Planet Names
Google books

– ''Geneva Observatory'', Raoul Behrend
Discovery Circumstances: Numbered Minor Planets (1)-(5000)
– Minor Planet Center * * {{DEFAULTSORT:Lyka 000917 Discoveries by Grigory Neujmin Named minor planets 19150905