20000 Varuna

20000 Varuna ("VAR oo na") is a Kuiper Belt object about 1060 km in diameter, estimated from a combination of thermal and optical measurements (Lellouch et al., 2002).

It is named after the Hindu god Varuna. It previously had the provisional designation and has been precovered in plates dating back to 1953.

Orbit

Varuna is classified as a classical trans-Neptunian object and follows a near-circular orbit with a semi-major axis of ~43 AU, similar to that of 50000 Quaoar but more inclined. The graph shows the polar view (top; Varuna’s orbit in blue, Pluto’s in red, Neptune in grey). The spheres illustrate the current (April 2006) positions, relative sizes and colours. The perihelia (q), aphelia (Q) and the dates of passage are also marked. Interestingly, the orbits of Varuna and Pluto have similar inclination and are similarly oriented (the nodes of both orbits are quite close).

At 43 AU and on a near-circular orbit, unlike Pluto which is in 2:3 orbital resonance with Neptune, Varuna is free from any significant perturbation from Neptune. The ecliptic view illustrates the comparison of Varuna's near-circular orbit with that of Pluto (highly eccentric, e=0.25), both similarly inclined.

Physical characteristics

Varuna has a rotational period of approximately 3.17 hours (or 6.34 hours, depending on whether the light curve is single or double-peaked). Given the rapid rotation, unknown at this time (2002) for objects so large, (Jewitt & Sheppard, 2002) consider possible models for the shape and density concluding that the most probable interpretation fitting the data is an elongated spheroid (ratio of axis 2:3), composed from a porous mixture of rock, with a mean density around 1g/cm³ (roughly the density of water ice). Since then, another even larger, rapidly rotating (3.9 h) object has been discovered. An elongated shape was also suggested in that case (see references there).

The surface is moderately red (similar to 50000 Quaoar) but exceptionally dark (albedo<0.04) compared with other large classical Kuiper Belt objects indicating it is largely devoid of ice. (Jewitt, et al., 2001)

References

Preprint on arXiv.
Preprint on arXiv.
PMID 11373669. Reprint on the Author's site.

External links

Site updated Reretrived on 2006-07-10
Orbit simulation from NASA JPL site

Trans-Neptunian objects

Gourt Home::Gourt :: 20000 Varuna

Orbit

Physical characteristics

References

External links