1529 Oterma

1529 Oterma, provisional designation 1938 BC, is a reddish, rare-type Hildian asteroid from the outermost region of the asteroid belt, approximately 56 kilometers in diameter. It was discovered on 26 January 1938, by Finnish astronomer Yrjö Väisälä at Turku Observatory in Southwest Finland.^[8] It is named for Liisi Oterma.^[2]

1529 Oterma

Discovery[1]
Discovered by	Y. Väisälä
Discovery site	Turku Obs.
Discovery date	26 January 1938
Designations
MPC designation	(1529) Oterma
Named after	Liisi Oterma (astronomer)[2]
Alternative designations	1938 BC · 1950 PV 1959 RD1 · A912 VO
Minor planet category	main-belt · Hilda[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	66.76 yr (24,385 days)
Aphelion	4.7933 AU
Perihelion	3.1916 AU
Semi-major axis	3.9924 AU
Eccentricity	0.2006
Orbital period (sidereal)	7.98 yr (2,914 days)
Mean anomaly	50.497°
Mean motion	0° 7m 24.96s / day
Inclination	9.0582°
Longitude of ascending node	100.59°
Argument of perihelion	295.08°
Jupiter MOID	0.8116 AU
Physical characteristics
Dimensions	54.40 km (calculated)[3] 56.327±0.285[4] 60.16±1.11 km[5]
Synodic rotation period	15.75 h[6]
Geometric albedo	0.047±0.002[5] 0.054±0.003[4] 0.057 (assumed)[3]
Spectral type	Tholen = P[1] · P[3] B–V = 0.764[1] U–B = 0.386[1]
Absolute magnitude (H)	10.05[1][3][5] · 10.11±0.26[7]

Orbit and classification

Orbit of 1529 Oterma

Oterma is a member of the Hilda family (001), an asteroid family within the dynamical Hilda group, a large group of asteroids that orbit in resonance with the gas giant Jupiter. Hildian asteroids are thought to have originated from the Kuiper belt in the outer Solar System.

It orbits the Sun in the outer main-belt at a distance of 3.2–4.8 AU once every 7 years and 12 months (2,914 days). Its orbit has an eccentricity of 0.20 and an inclination of 9° with respect to the ecliptic.^[1]

It was first identified as A912 VO at Winchester Observatory in 1912 (799). The body's observation arc begins at Turku a few weeks after its official discovery observation.^[8]

Physical characteristics

Oterma belongs to an exclusive group of 33 known asteroids with a spectral P-type in the Tholen classification scheme.^[9]

Photometry

During a study of 47 Hilda asteroids in the 1990s, a rotational lightcurve of Oterma was obtained from photometric observations at the Swedish Uppsala Astronomical Observatory and other places. It gave a rotation period of 15.75 hours with a change in brightness of 0.18 magnitude (U=2).^[6]

Diameter and albedo

According to the space-based surveys carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission and by the Japanese Akari satellite, Oterma measures 56.33 and 60.1 kilometers in diameter and its surface has an albedo of 0.054 and 0.047, respectively.^[4][5] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous asteroids of 0.057 and calculates a diameter of 54.40 kilometers, with an absolute magnitude of 10.05.^[3]

Naming

Oterma was named for Liisi Oterma (1915–2001), first Finnish female astronomer with a PhD and a discoverer of minor planets and comets at the Turku observatory between 1939 and 1953.^[2] The official naming citation was published by the Minor Planet Center on 20 February 1976 (M.P.C. 3929).^[10]