120347 Salacia
120347 Salacia, provisional designation 2004 SB60, is a large planetoid in the Kuiper belt, approximately 850 kilometers in diameter. As of 2018, it is located 44.8 astronomical units from the Sun, and reaches apparent magnitude 20.7 at opposition.
 Keck Telescope image of Salacia (bright, center) and its moon Actaea (faint, at left) | |
| Discovery[1][2] | |
|---|---|
| Discovered by | H. G. Roe M. E. Brown K. M. Barkume |
| Discovery site | Palomar Obs. |
| Discovery date | 22 September 2004 |
| Designations | |
| (120347) Salacia | |
| Pronunciation | /səˈleɪʃə/ (sə-LAY-shə) |
Named after | Salacia (Roman mythology)[2] |
| 2004 SB60 | |
| TNO[1] · Cubewano[3] Extended[4] | |
| Adjectives | Salacian |
| Orbital characteristics[1] | |
| 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 |
| 42.184 AU | |
| Eccentricity | 0.10636 |
| 273.98 yr (100,073 days) | |
| 123.138° | |
| 0° 0m 12.951s / day | |
| Inclination | 23.921° |
| 279.880° | |
| 312.294° | |
| Known satellites | 1 (Actaea) |
| Physical characteristics | |
Mean diameter | 846±21 km[5][lower-alpha 1] 854±45 km (equal albedos)[6] 866±37 km[7] |
| Mass | (4.922±0.071)×1020 kg (system)[5] (4.38±0.16)×1020 kg (system mass)[6][8] |
Mean density | 1.5±0.12 g/cm3[5] 1.29+0.29 −0.23 g/cm3 (system)[6] 1.26±0.16 g/cm3[7] |
| 6.09 h (0.254 d) | |
| 6.09 h[1] | |
| 0.044±0.004[6] 0.042±0.004[7] | |
| BB[9] B−V=0.66±0.06[9] V−R=0.40±0.04[9] V−I=0.83±0.04[9] | |
| 20.7 | |
| 4.360±0.011 (system)[8] 4.476±0.013 (Salacia)[8] 6.850±0.053 (Actaea)[8] 3.9[1] | |
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Salacia was discovered on 22 September 2004, by American astronomers Henry Roe, Michael Brown and Kristina Barkume at the Palomar Observatory in California, United States. It has been observed 124 times, with precovery images back to 25 July 1982.[2] 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.
Brown estimated that Salacia is nearly certainly a dwarf planet.[10] However, William Grundy et al. argue that objects in the size range of 400–1,000 km, with densities of ≈ 1.2 g/cm3 or less and albedos less than ≈ 0.2, have likely never compressed into fully solid bodies or been resurfaced, let alone differentiated or collapsed into hydrostatic equilibrium, and so are highly unlikely to be dwarf planets.[11] Salacia is at the upper end of this size range and has a very low albedo, though Grundy et al. later found it to have the relatively high density of 1.5±0.1 g/cm3.[5]