189 Phthia

189 Phthia is a bright-coloured, rocky main belt asteroid that was discovered by German-American astronomer Christian Heinrich Friedrich Peters on September 9, 1878,^[1] in Clinton, New York, and named after Phthia, a region of ancient Greece.

189 Phthia

3D convex shape model of 189 Phthia
Discovery[1]
Discovered by	C. H. F. Peters
Discovery site	Clinton, New York
Discovery date	9 September 1878
Designations
MPC designation	(189) Phthia
Pronunciation	/ˈθaɪ.ə/[2]
Alternative designations	A878 RA
Minor planet category	main-belt
Orbital characteristics[3][4]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc	136.18 yr (49739 d)
Aphelion	2.5415 AU (380.20 Gm)
Perihelion	2.3597 AU (353.01 Gm)
Semi-major axis	2.4506 AU (366.60 Gm)
Eccentricity	0.037105
Orbital period (sidereal)	3.84 yr (1401.2 d)
Mean anomaly	336.98°
Mean motion	0° 15m 24.912s / day
Inclination	5.1774°
Longitude of ascending node	203.42°
Argument of perihelion	168.03°
Physical characteristics
Dimensions	37.66±2.0 km[3] 40.91 ± 1.36 km[5]
Mass	(3.84 ± 0.81) × 1016 kg[5]
Mean density	1.07 ± 0.25 g/cm3[5]
Synodic rotation period	22.346 h (0.9311 d)[3][6]
Geometric albedo	0.2310±0.027[3] 0.1566 ± 0.0349[7]
Spectral type	S[7] (Tholen)
Absolute magnitude (H)	9.33,[3] 9.60[7]

Photometric observations of this asteroid at the Organ Mesa Observatory in Las Cruces, New Mexico, during 2008 gave a light curve with a period of 22.346 ± 0.001 hours and a brightness variation of 0.26 ± 0.02 in magnitude.^[6]