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20000 Varuna

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20000 Varuna
Artist's idea of what Varuna may look like

Artist's idea of what Varuna may look like
Discovered byR. McMillan (Spacewatch)
Discovery time28 November 2000
Name20000 Varuna
Other names2000 WR106
GroupTNO (cubewano)[1]
Reference date 14 July 2004 (JD 2453200.5)
Longest distance from the Sun6 781.985 Gm (45.335 AU)
Shortest distance from the Sun6 120.810 Gm (40.915 AU)
Longest distance from the center of its orbital path
("semi-major axis")
6 451.398 Gm (43.129 AU)
How egg-shaped its orbit is
How long it takes to complete an orbit103 440.6 d (283.20 a)
Average speed4.53 km/s
Mean anomaly89.673°
Angle above the reference plane
Longitude of where it comes up through the reference plane97.296°
Angle between its shortest distance from what it orbits around and where it comes up through the reference plane
("argument of periapsis")
Size and Other Qualities
Measures800 km (avg of thermals)[2]
(scalene ellipsoid)?[3][4]
Mass≈3.7×1020? kg[3][5]
Average density0.992 g/cm³[3]
Gravity at its surface0.15 m/s²
Slowest speed able to escape into space
("escape velocity")
0.39 km/s
How long it takes to turn around one time
(in relation to the stars)
0.132 16 d (3.17 h)
How much light it reflects0.037–0.26[2]
Avg. surface temp.≈43–41 K
Light-band group
("spectral type")
(moderately red) B-V=0.93 V-R=0.64[6]
Seeming brightness
("apparent magnitude")
19.9 (opposition)[7]
True brightness
("absolute magnitude")

20000 Varuna is a big Kuiper belt object (KBO) and could be a dwarf planet. Before it was named Varuna, it had the provisional designation 2000 WR106.

Varuna is named after the Hindu deity Varuṇa.

Physical characteristics

Varuna completes one rotation in about 3.17 hours (or 6.34 hours, depending on whether the light curve is single or double-peaked). Given the fast rotation, which is not common for objects so big, Varuna is thought to be a stretched spheroid, with a density around 1g/cm³ (close to the density of water).[4]

The surface of Varuna is somewhat red and small amounts of water ice have been found on its surface.[9]


  1. Marc W. Buie (2007-01-12). "Orbit Fit and Astrometric record for 20000". SwRI (Space Science Department). Retrieved 2008-09-19.
  2. 2.0 2.1 Stansberry (2008). "TNO/Centaur diameters and albedos". Retrieved 2006-11-08.
  3. 3.0 3.1 3.2 Lightcurves Lacerda P., Jewitt D. Dentisities Of Solar System Objects From Their Rotational Lightcurves", accepted to AJ Dec. 2006 Preprint
  4. 4.0 4.1 Jewitt D, Sheppard S (2002). "Physical Properties Of Trans-Neptunian Object (20000) Varuna". Astronomical Journal 123 (April): 2110–2120. doi:10.1086/339557 . Preprint on arXiv.
  5. Calculated using Lacerda and Jewitt (2007) diameter of 900 km and density of 0.992 g/cm³.
  6. "TNO and Centaur Colors". Retrieved 2006-11-08.
  7. "HORIZONS Web-Interface". JPL Solar System Dynamics. Retrieved 2008-07-02.
  8. "JPL Small-Body Database Browser: 20000 Varuna (2000 WR106)". 2007-11-17 last obs. Retrieved 2008-07-02.
  9. Licandro J, Oliva E, Di Martino M (2001). "NICS-TNG infrared spectroscopy of trans-neptunian objects 2000 EB173 and 2000 WR106". Astronomy & Astrophysics 373 (July): 29–32L. doi:10.1051/0004-6361:20010758 .

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