VARUNA, the biggest object spotted beyond Pluto, is nearly as big as Pluto鈥檚
moon Charon but much darker. This gives the first insight into the nature of the
surface of objects in the Kuiper Belt鈥攔emnants of the birth of our Solar
System that lie beyond Neptune.
Dave Jewitt of the University of Hawaii measured Varuna鈥檚 internal heat as
well as the sunlight it reflects. From this he calculated its diameter to be 900
kilometres, slightly smaller than the 1100-kilometre Charon. Although much
darker than icy Pluto or Charon, it is brighter than asteroids in the
main-belt.
鈥淚t鈥檚 not an ice or frost surface. At the very least it has a huge amount of
carbon-rich dirt,鈥� says Jewitt (Nature, vol 411, p 446).
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