32532 Thereus

32532 Thereus (/θɪˈriːəs/; provisional designation 2001 PT₁₃) is a centaur from the outer Solar System, approximately 80 kilometers (50 miles) in diameter. It was discovered on 9 August 2001, by astronomers of the Near-Earth Asteroid Tracking program at the Palomar Observatory in California, United States.^[5] This minor planet was named for the phrase thēreios bia 'beastly strength', used to describe centaurs in Greek mythology.^[2][3]

32532 Thereus

Discovery[1]
Discovered by	NEAT
Discovery site	Palomar Obs.
Discovery date	9 August 2001
Designations
MPC designation	(32532) Thereus
Pronunciation	/θɪˈriːəs/
Named after	θήρειος βία thēreios bia[2][3]
Alternative designations	2001 PT13 · 1995 MM6 1999 NE2
Minor planet category	centaur[1][4] · distant[5]
Symbol	(astrological)
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 1
Observation arc	21.57 yr (7,879 days)
Aphelion	12.745 AU
Perihelion	8.5345 AU
Semi-major axis	10.640 AU
Eccentricity	0.1979
Orbital period (sidereal)	34.70 yr (12,676 days)
Mean anomaly	192.91°
Mean motion	0° 1m 42.24s / day
Inclination	20.353°
Longitude of ascending node	205.33°
Argument of perihelion	86.322°
Physical characteristics
Mean diameter	62±3 km[6] 77.19 km (derived)[4] 80±5 km[7] 86.500±1.900 km[8]
Synodic rotation period	8.30 h[9] 8.3091 h[10] 8.335 h[11] 8.338±0.002 h[12] 8.3386±0.0006 h[13]
Geometric albedo	0.057 (assumed)[4] 0.059±0.013[8] 0.083±0.016[6] 0.0975±0.0125[7]
Spectral type	BR[14] B–V = 0.770±0.020[14] B–V = 0.810±0.050[15] B–V = 0.763±0.072[16] V–R = 0.490±0.010[14] V–R = 0.501±0.016[16] V–I = 0.940±0.010[14] V–I = 0.900±0.130[15] V–I = 0.917±0.035[16]
Absolute magnitude (H)	9.1[1] · 9.29[11][4] · 9.32[17] · 9.36[10] · 9.365±0.038 (R)[18] · 9.40±0.16[6] · 9.42±0.01[13]

Orbit and classification

Thereus orbits the Sun at a distance of 8.5–12.7 AU once every 34 years and 8 months (12,676 days). Its orbit has an eccentricity of 0.20 and an inclination of 20° with respect to the ecliptic.^[1]

The body's observation arc begins with a precovery taken by Spacewatch at Kitt Peak Observatory in June 1995, more than 6 years prior to its official discovery observation by NEAT at Palomar.^[5]

Naming

This minor planet was named after Thereus, a centaur from Greek mythology. He is described as a hunter who captured bears and carried them home, alive and struggling.^[2] The official naming citation was published by the Minor Planet Center on 14 June 2003 (M.P.C. 49102).^[19]

Physical characteristics

Rotation period

Since the early 2000s, several rotational lightcurves of Thereus were obtained from photometric observations with a period between 8.30 and 8.3386 hours.^{[9][10][11][12][13]} Analysis of the consolidated, best-rated lightcurve gave a rotation period of 8.335 hours and a brightness amplitude of 0.38 magnitude (U=3).^[4]

Diameter and albedo

According to observations made by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, ESA's Herschel Space Observatory with its PACS instrument, and the Spitzer Space Telescope, Thereus measures between 62 and 86.5 kilometers in diameter and its surface has an albedo between 0.059 and 0.0975.^[6][7][8]

The Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous minor planets of 0.057 and derives a diameter of 77.19 kilometers based on an absolute magnitude of 9.29.^[4]

See also

• List of centaurs (small Solar System bodies) § 32532