1545 Thernöe

1545 Thernöe (prov. designation: ) is an elongated background asteroid from the central region of the asteroid belt. It was discovered on 15 October 1941, by Finnish astronomer Liisi Oterma at Turku Observatory in Southwest Finland. The uncommon K-type asteroid has a rotation period of 16.1 hours and measures approximately 18 km in diameter. It was later named after Danish astronomer Karl August Thernöe.

Orbit
Thernöe orbits the Sun in the central main-belt at a distance of 2.1–3.4 AU once every 4 years and 7 months (1,684 days). Its orbit has an eccentricity of 0.24 and an inclination of 3° with respect to the ecliptic. It was first identified as at Heidelberg Observatory in 1906, extending the body's observation arc by 35 years prior to its official discovery observation at Turku.

Naming
This minor planet was named after Karl August Thernöe (1911–1987), Danish astronomer and celestial mechanic at Østervold Observatory in Copenhagen. He was also a popularizer of astronomy and director of IAU's Central Bureau for Astronomical Telegrams during 1950–1964. The official was published by the Minor Planet Center on 20 February 1976 (M.P.C. 3930).

Spectral type
In the SMASS taxonomy, Thernöe is classified as a rare K-type asteroid, a newly introduced subtype that belongs to the broader S-complex of stony bodies. Conversely, CALL groups Thernöe into the carbonaceous C-complex.

Rotation period and pole
In December 2006, a rotational lightcurve of Thernöe was obtained from photometric observations by French amateur astronomer René Roy. Lightcurve analysis gave a well-defined rotation period of 17.20 hours with a brightness variation of 0.76 magnitude (U=3). The high lightcurve-amplitude of 0.76 indicates that the body has a non-spheroidal shape.

A 2016-published lightcurve, using modeled photometric data from the Lowell Photometric Database, gave a concurring period of 17.20321 hours, as well as a spin axis of (164.0°, −5.0°) in ecliptic coordinates (λ, β).

Diameter and albedo
According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Thernöe measures between 16.12 and 19.37 kilometers in diameter and its surface has an albedo between 0.092 and 0.13. The Collaborative Asteroid Lightcurve Link (CALL) adopts the results obtained by IRAS, that is, an albedo of 0.0962 and diameter of 18.71 kilometers with an absolute magnitude of 11.8.