November 28 – Discovery of KBO 20000 Varuna (2000)

We hurtle way beyond the asteroid belt today, for a change, to celebrate the discovery of TNO (or KBO) 20000 Varuna, first spotted for what it is on November 28th 2000 by Robert S Macmillan, despite appearing on photographic plates dating back to the 1950s.

Varuna is a fairly large classical Kuiper belt object (KBO). Estimates of its size varied widely at the time of discovery from 600 to 1000km. More recent calculations seem to be bringing it down to the lower end of that range, but it still ranks highly in the KBO pecking order.

Varuna has a very rapid rotation (one full turn every 6.34 hours) and a double-peaked light curve. it is thought to be an elongated spheroid, about half as wide again across the equator as from pole to pole.

A recent report in Astrophysical Journal Letters (883 (1)) suggests the possibility of a close-in satellite orbiting Varuna, but there’s nothing conclusive, so we will have to wait and see.

Varuna pacifying Sri Rama.
Varuna pacifying Sri Rama.

The Hindu deity Varuna, after whom this particular oblate spheroid is named, has similar qualities to the Roman god Neptune, making it a good choice for what at the time was the largest known trans-Neptunian object.


Asteroid 235 Carolina was also discovered today, in 1883. It is one of Johann Palisa‘s collection of 122 asteroids, and came while he was going through (by his standards) a dry patch in his rock hunting career. Having discovered nine in 1882, he “only” managed two in 1883, before hitting his stride again in 1884 with six. Part of the reason for this relative scarcity was probably that Palisa spent a good portion of the year 1883 travelling to watch a total solar eclipse. The spot chosen for the expedition was near to Tahiti, in the chain of coral atolls known as the Line Islands. More specifically . . . .

Caroline Island, Kiribati (image credit: NASA)
Caroline Island, Kiribati (image credit: NASA)

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