Английская Википедия:909 Ulla

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909 Ulla is a large and dark asteroid from the outermost regions of the asteroid belt, that measures approximately Шаблон:Convert in diameter. It is the parent body and namesake of the Ulla family, which belongs to the larger group of Cybele asteroids. It was discovered on 7 February 1919, by German astronomer Karl Reinmuth at the Heidelberg Observatory in southwest Germany. The X-type asteroid has a rotation period of 8.7 hours and a notably low value for its Jupiter Tisserand's parameter. It was named after Ulla Ahrens, daughter of a friend of the discoverer.

Orbit and classification

Ulla is the parent body of the Ulla family (Шаблон:Small), a very small asteroid family of less than 30 known bodies. It orbits the Sun in the outermost asteroid belt at a distance of 3.2–3.9 AU once every 6 years and 8 months (2,435 days; semi-major axis of 3.54 AU). Its orbit has an eccentricity of 0.09 and an inclination of 19° with respect to the ecliptic.

Naming

This minor planet was named after Ulla Ahrens, a daughter of a friend of the discoverer. Karl Reinmuth also named the asteroid 950 Ahrensa for the Ahrens family, who was a donor of the Heidelberg Observatory. The official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (Шаблон:Small).

Physical characteristics

In the SMASS classification, Ulla is an X-type asteroid.

Rotation period

A rotational lightcurve of Ulla was obtained from photometric observations in 2000. Lightcurve analysis gave a rotation period of 8.73 hours with a brightness amplitude between 0.13 and 0.24 magnitude (Шаблон:Small). Other photometric period determinations gave concurring results.

Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite IRAS and the Japanese Akari satellite, Ulla measures Шаблон:Val and Шаблон:Val kilometers in diameter and its surface has an albedo between Шаблон:Val and Шаблон:Val. The Collaborative Asteroid Lightcurve Link uses an albedo of 0.0450 and derives a diameter of 116.66 kilometers based on an absolute magnitude of 8.65.

External links

• Lightcurve Database Query (LCDB), at www.minorplanet.info
• Dictionary of Minor Planet Names, Google books
• Asteroids and comets rotation curves, CdR – Geneva Observatory, Raoul Behrend
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• Шаблон:AstDys
• Шаблон:JPL small body