Leona (minor planet designation: 319 Leona), provisional designation A920 HE, is a dark asteroid and tumbling slow rotator from the outermost regions of the asteroid belt, approximately 70 kilometers in diameter. It was discovered on 8 October 1891, by French astronomer Auguste Charlois at Nice Observatory in southwestern France.[13] Any reference of its name to a person is unknown.[3] On 12 December 2023 Leona will occult Betelgeuse as seen from southern Europe.[14]
Leona orbits the Sun in the outer main-belt at a distance of 2.7–4.1AU once every 6 years and 3 months (2,295 days). Its orbit has an eccentricity of 0.22 and an inclination of 11° with respect to the ecliptic.[1]
The asteroid's observation arc begins at the discovering observatory, one night after its official discovery observation.[13]
Physical characteristics
Spectral type
Leona has been characterized as a dark and reddish P-type asteroid by the Wide-field Infrared Survey Explorer (WISE), and as an X-type asteroid by Pan-STARRS photometric survey.[6] The Collaborative Asteroid Lightcurve Link groups it to the carbonaceous C-type asteroids.[4]
Slow rotator and tumbler
In October 2016, a rotational lightcurve of Leona was obtained from photometric observations by astronomers Frederick Pilcher (see naming cite for 1990 Pilcher) at Organ Mesa Observatory (G50), United States, Lorenzo Franco at Balzaretto Observatory (A81), Italy, and Petr Pravec at the Ondřejov Observatory, Czech Republic. Lightcurve analysis gave a well-defined rotation period of 430±2 hours with a brightness variation of 0.5 magnitude (U=3).[11]
This makes Leona one of the Top 100 slowest rotators known to exist. The astronomers also detected a non-principal axis rotation seen in distinct rotational cycles in successive order. This tumbling also gives an alternative candidate period solution of 1084±10 hours, one of the longest periods ever measured.[11] It is the third-largest tumbler known to exists (also see List of tumblers).
Previous observations of Leona gave a much shorter period between 6 and 15 hours,[9][10] which demonstrates the intricacy when observing slow rotators, especially those with a tumbling motion. A detailed description of the procedure of the photometric measurement is given by Pilcher.[11]
Diameter and albedo
According to the surveys carried out by the Japanese Akari satellite and the NEOWISE mission of NASA's WISE space-telescope, Leona measures between 49.943 and 89.00 kilometers in diameter and its surface has an albedo between 0.02 and 0.085.[5][6][7][8] CALL derived an albedo of 0.0318 and a diameter of 67.97 kilometers based on an absolute magnitude of 10.2.[4]
Naming
The origin of this minor planet's name is unknown.[3]
Among the many thousands of named minor planets, Leona is one of 120 asteroids for which no official naming citation has been published. All of these low-numbered asteroids have numbers between 164 Eva and 1514 Ricouxa and were discovered between 1876 and the 1930s, predominantly by astronomers Auguste Charlois, Johann Palisa, Max Wolf and Karl Reinmuth (also see category).[15]
Noah Webster (1884) A Practical Dictionary of the English Language
Schmadel, Lutz D. (2007). "(319) Leona". Dictionary of Minor Planet Names – (319) Leona. Springer Berlin Heidelberg. p.42. doi:10.1007/978-3-540-29925-7_320. ISBN978-3-540-00238-3.
Schmadel, Lutz D. (2007). "Appendix 11 – Minor Planet Names with Unknown Meaning". Dictionary of Minor Planet Names – Fifth Revised and Enlarged revision. Springer Berlin Heidelberg. pp.927–929. ISBN978-3-540-00238-3.
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