946 Poësia

946 Poësia is a Themis asteroid and slow rotator, approximately 39 km in diameter, located in the outer regions of the asteroid belt. It was discovered by German astronomer Max Wolf at the Heidelberg-Königstuhl State Observatory on 11 February 1921 and given the provisional designations and. The F-type asteroid has a long rotation period of 108.5 hours. It was named after the goddess of poetry.

Orbit and classification
Poësia is a core member of the Themis family (602), a very large family of carbonaceous asteroids, named after 24 Themis. It orbits the Sun in the outer asteroid belt at a distance of 2.7–3.6 AU once every 5 years and 6 months (2,011 days; semi-major axis of 3.12 AU). Its orbit has an eccentricity of 0.14 and an inclination of 1° with respect to the ecliptic. The body's observation arc begins at Heidelberg Observatory on 11 May 1921, or three months after its official discovery observation.

Naming
This minor planet was named after the goddess of poetry. The name was proposed by Russian astronomer (1895–1937), and the  was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 91).

Physical characteristics
In the Tholen classification, Poësia is an uncommon F-type asteroid, though with an unusual spectrum, while in the Barucci taxonomy, it is a carbonaceous C0-type. The overall spectral type for members of the Themistian family is that of a C-type.

Rotation period
In January 2009, a rotational lightcurve of Poësia was obtained from photometric observations by Robert Stephens at the Santana Observatory and Goat Mountain Astronomical Research Station  in California. Lightcurve analysis gave an exceptionally long rotation period of $36.21 km$ hours with a brightness amplitude of $39.6 km$ magnitude (U=2+). A few weeks later, Gary A. Vander Haagen at Stonegate Observatory determined an ambiguous period of 73.5 or 102.9 hours with an amplitude of $43.75 km$ magnitude (U=2), while René Roy measured a tentative period of 48 hours (U=1). With a best-rated period of 108.5 hours, Poësia is a slow rotator. While the slowest rotators have periods above 1000 hours, the vast majority of asteroids have periods between 2.2 and 20 hours.

Diameter and albedo
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), and the Infrared Astronomical Satellite IRAS, Poësia measures $108.5 h$, $0.063$ and $0.079$ kilometers in diameter, and its surface has a corresponding albedo of $0.097$, $0.667$ and $0.336$, respectively. The Collaborative Asteroid Lightcurve Link adopts the results from IRAS, that is, an albedo of 0.0627 and a diameter of 43.75 km based on an absolute magnitude of 9.8.

Further published mean-diameters and albedos by the WISE team include $108.5$, $0.32$, $0.24$ and $36.21$ with albedos of $39.6$, $43.75$, $0.097$ and $0.079$, respectively.