[en]

189 Phthia
Discovery
Discovered by	C. H. F. Peters
Discovery site	Clinton, New York
Discovery date	9 September 1878
Designations
MPC designation	(189) Phthia
Pronunciation	/ˈθaɪ.ə/
Alternative designations	A878 RA
Minor planet category	main-belt
Orbital characteristics
	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; 40.91 ± 1.36 km
Mass	(3.84 ± 0.81) × 1016 kg
Mean density	1.07 ± 0.25 g/cm3
Synodic rotation period	22.346 h (0.9311 d)
Geometric albedo	0.2310±0.027; 0.1566 ± 0.0349
Spectral type	S (Tholen)
Absolute magnitude (H)	9.33, 9.60

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.

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]

References

^ ^a ^b “Numbered Minor Planets 1–5000”, Discovery Circumstances, IAU Minor Planet center, retrieved 7 April 2013.
^ Noah Webster (1884) A Practical Dictionary of the English Language
^ ^a ^b ^c ^d ^e Yeomans, Donald K., “189 Phthia”, JPL Small-Body Database Browser, NASA Jet Propulsion Laboratory, retrieved 12 May 2016.
^ “The Asteroid Orbital Elements Database”. astorb. Lowell Observatory.
^ ^a ^b ^c Carry, B. (December 2012), “Density of asteroids”, Planetary and Space Science, vol. 73, pp. 98–118, arXiv:1203.4336, Bibcode:2012P&SS…73…98C, doi:10.1016/j.pss.2012.03.009. See Table 1.
^ ^a ^b Pilcher, Frederick (January 2009), “Period Determinations for 33 Polyhymnia, 38 Leda, 50 Virginia, 189 Phthia, and 290 Bruna”, The Minor Planet Bulletin, vol. 36, no. 1, pp. 25–27, Bibcode:2009MPBu…36…25P.
^ ^a ^b ^c Pravec, P.; et al. (May 2012), “Absolute Magnitudes of Asteroids and a Revision of Asteroid Albedo Estimates from WISE Thermal Observations”, Asteroids, Comets, Meteors 2012, Proceedings of the conference held May 16–20, 2012 in Niigata, Japan, no. 1667, Bibcode:2012LPICo1667.6089P. See Table 4.