20000 Varuna
20000 Varuna (provisional designation 2000 WR106) is a large trans-Neptunian object in the Kuiper belt. It was discovered in November 2000 by American astronomer Robert McMillan during a Spacewatch survey at the Kitt Peak National Observatory. It is named after the Hindu deity Varuna, one of the oldest deities mentioned in the Vedic texts.
Hubble Space Telescope image of Varuna, taken in 2005 | |
| Discovery | |
|---|---|
| Discovered by | Spacewatch (Robert McMillan) |
| Discovery date | 28 November 2000 |
| Designations | |
MPC designation | (20000) Varuna |
| Pronunciation | /ˈværənə/ VARR-ə-nə |
Named after | Varuna |
Alternative designations | 2000 WR106 |
Minor planet category | TNO · cubewano Scat-Ext |
| Adjectives | Varunian /vəˈruːniən/ |
| Symbol | (astrological) |
| Orbital characteristics | |
| Epoch 31 May 2020 (JD 2459000.5) | |
| Uncertainty parameter 2 | |
| Observation arc | 64.49 yr (23,555 days) |
| Earliest precovery date | 24 November 1954 |
| Aphelion | 45.117 AU (6.7494 Tm) |
| Perihelion | 40.319 AU (6.0316 Tm) |
Semi-major axis | 42.718 AU (6.3905 Tm) |
| Eccentricity | 0.05617 |
Orbital period (sidereal) | 279.21 yr (101,980 d) |
Average orbital speed | 4.53 km/s |
Mean anomaly | 119.121° |
Mean motion | 0° 0m 12.708s / day |
| Inclination | 17.221° |
Longitude of ascending node | 97.372° |
| 262.220° | |
| Neptune MOID | 12.040 AU (1.8012 Tm) |
| Physical characteristics | |
Mean diameter | 654+154 −102 km 668+154 −86 km |
Synodic rotation period | 6.343572±0.000006 h |
| 0.127+0.04 −0.042 | |
| IR (moderately red) B−V=0.88±0.02 V−R=0.62±0.01 V−I=1.24±0.01 | |
| 20.3 (opposition) | |
| 3.760±0.035, 3.6 | |
Varuna's light curve is compatible with the body being a Jacobi ellipsoid, suggesting that it has an elongated shape due to its rapid rotation. Varuna's surface is moderately red in color due to the presence of complex organic compounds on its surface. Water ice is also present on its surface, and is thought to have been exposed by past collisions which may have also caused Varuna's rapid rotation. Although no natural satellites have been found or directly imaged around Varuna, analysis of variations in its light curve in 2019 suggests the presence of a possible satellite orbiting closely around Varuna.