120347 Salacia

120347 Salacia
	Keck Telescope image of Salacia (center) and its moon Actaea (left), taken by the NIRC2 near-infrared camera on 3 August 2010.
Discovery
Discovered by	H. G. Roe; M. E. Brown; K. M. Barkume
Discovery site	Palomar Obs.
Discovery date	22 September 2004
Designations
MPC designation	(120347) Salacia
Pronunciation	/səˈleɪʃə/ (sə-LAY-shə)
Named after	Salacia (Roman mythology)
Alternative designations	2004 SB60 (provisional designation)
Minor planet category	TNO · classical (hot); extended
Adjectives	Salacian
Symbol	or (rare)
Orbital characteristics
	Epoch 31 May 2020 (JD 2459000.5)
	Uncertainty parameter 3
Observation arc	37.16 yr (13,572 days)
Earliest precovery date	25 July 1982
Aphelion	46.670 AU
Perihelion	37.697 AU
Semi-major axis	42.184 AU
Eccentricity	0.10636
Orbital period (sidereal)	273.98 yr (100,073 days)
Mean anomaly	123.138°
Mean motion	0° 0m 12.951s / day
Inclination	23.921°
Longitude of ascending node	279.880°
Argument of perihelion	312.294°
Known satellites	1 (Actaea)
Physical characteristics
Mean diameter	838±44 km (2025); 846±21 km (2019); 866±37 km (2017);
Mass	4.861+0.076; −0.074×1020 kg (System mass)
Mean density	1.50±0.12 g/cm3; 1.26±0.16 g/cm3
Sidereal rotation period	5.49403±0.00016 d (synchronous)
Geometric albedo	0.041±0.004 (2025); 0.042±0.004 (2017)
Spectral type	Prominent water (H; 2O-type); BB (neutral); B−V = 0.66±0.06; V−R = 0.40±0.04;
Apparent magnitude	20.7
Absolute magnitude (H)	4.360±0.011 (Salacia+Actaea); 4.476±0.013 (Salacia); 4.15

Salacia (minor-planet designation: 120347 Salacia) is a large trans-Neptunian object (TNO) and possible dwarf planet in the Kuiper belt that is probably between 800 km (500 mi) and 875 km (544 mi) in diameter. It was discovered on 22 September 2004 by American astronomers Henry Roe, Michael Brown and Kristina Barkume at the Palomar Observatory in California, United States. Salacia orbits the Sun at an average distance that is slightly greater than that of Pluto. It was named after the Roman goddess Salacia and has a single known moon, Actaea. Salacia and Actaea form a binary system where both bodies are tidally locked to the other, similar to Pluto and Charon.