1998 WW31
1998 WW31, is a non-resonant trans-Neptunian object and binary system from the Kuiper belt located in the outermost region of the Solar System, approximately 148 kilometers (92 miles) in diameter. It was first observed on 18 November 1998, by American astronomer Marc Buie and Robert Millis at the Kitt Peak National Observatory in Arizona, United States. In December 2000, a minor-planet moon, designated S/2000 (1998 WW31) 1 with a diameter of 123 kilometers (76 miles), was discovered in its orbit. After Charon in 1978, it was the first of nearly 100 satellites since discovered in the outer Solar System.
| Discovery | |
|---|---|
| Discovered by | M. W. Buie R. L. Millis |
| Discovery site | Kitt Peak Obs. |
| Discovery date | 18 November 1998 (first observed only) |
| Designations | |
| 1998 WW31 | |
| TNO · cubewano (hot) distant · binary | |
| Orbital characteristics | |
| Epoch 31 May 2020 (JD 2459000.5) | |
| Uncertainty parameter 4 | |
| Observation arc | 20.94 yr (7,647 d) |
| Aphelion | 48.526 AU |
| Perihelion | 40.429 AU |
| 44.477 AU | |
| Eccentricity | 0.09102 |
| 296.63 yr (108,345 d) | |
| 141.847° | |
| 0° 0m 11.963s / day | |
| Inclination | 6.8171° |
| 237.138° | |
| 51.218° | |
| Known satellites | 1 (D: 123 km; P: 587 d) |
| Physical characteristics | |
Mean diameter | 148 km (est. primary) 192.1 km (cal. system) |
| Mass | (2.658±0.015)×1018 kg |
| 0.04 (est.) 0.10 (assumed) | |
| blue C (assumed) V–I = 0.910±0.020 | |
| 6.7 6.9 | |
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