1447 Utra

1447 Utra, provisional designation 1938 BB, is a stony asteroid, slow rotator and suspected tumbler from the central region of the asteroid belt, approximately 12 kilometers in diameter. It was discovered on 26 January 1938, by Finnish astronomer Yrjö Väisälä at Turku Observatory in Southwest Finland.^[9] The asteroid was named for the Finnish town of Utra (now a part of Joensuu).^[2]

1447 Utra

Discovery[1]
Discovered by	Y. Väisälä
Discovery site	Turku Obs.
Discovery date	26 January 1938
Designations
MPC designation	(1447) Utra
Named after	Utra (Finnish town)[2]
Alternative designations	1938 BB · 1936 SB 1951 KO · A918 FA
Minor planet category	main-belt · (middle)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	98.67 yr (36,038 days)
Aphelion	2.6404 AU
Perihelion	2.4299 AU
Semi-major axis	2.5352 AU
Eccentricity	0.0415
Orbital period (sidereal)	4.04 yr (1,474 days)
Mean anomaly	285.64°
Mean motion	0° 14m 39.12s / day
Inclination	4.7865°
Longitude of ascending node	35.528°
Argument of perihelion	64.085°
Physical characteristics
Dimensions	11.83±0.86 km[4] 11.834±0.122 km[5] 12.634±0.103 km[6] 13.26±0.53 km[7] 13.58 km (calculated)[3]
Synodic rotation period	257±30 h[a]
Geometric albedo	0.20 (assumed)[3] 0.303±0.038[7] 0.3381±0.0591[6] 0.381±0.058[4]
Spectral type	S[3]
Absolute magnitude (H)	11.30[4][6][7] · 11.60±0.44[8] · 11.7[1][3]

Orbit and classification

Utra is a S-type asteroid. It orbits the Sun in the central main-belt at a distance of 2.4–2.6 AU once every 4.04 years (1,474 days). Its orbit has an eccentricity of 0.04 and an inclination of 5° with respect to the ecliptic.^[1] Utra was first identified as A918 FA at Heidelberg Observatory in 1918. The body's observation arc begins with its official discovery observation at Turku in 1938.^[9]

Physical characteristics

Slow rotator

In March 2011, a rotational lightcurve of Utra was obtained from photometric observations by astronomer Luis E. Martinez. Lightcurve analysis gave a long rotation period of 257 hours with a brightness variation of 0.63 magnitude (U=2). This slow rotator is also a suspected tumbler (T0).^[a]

Diameter and albedo

According to the surveys carried out by the Japanese Akari satellite and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Utra measures between 11.83 and 13.26 kilometers in diameter, and its surface has an albedo between 0.303 and 0.381.^[4][5][6][7] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 13.58 kilometers with an absolute magnitude of 11.7.^[3]

Naming

This minor planet was named for Utra, a northeastern Finnish town and birthplace of the discoverer.^[2] The official naming citation was published by the Minor Planet Center on 30 January 1964 (M.P.C. 2277).^[10]

Notes

1. Martinez (2011) web: rotation period 257±30 hours with a brightness amplitude of 0.63 mag. Summary figures for (1447) Utra at Collaborative Asteroid Lightcurve Link (CALL). The referenced website was a non-recoverable dead link.