Kuiper-belt objects: Getting the measure of Varuna

There are at least 70,000 'trans-Neptunian' bodies in the Kuiper Belt, orbiting the outer reaches of the Solar System. They are so distant that it is difficult to determine their physical properties. But a recently discovered body, minor planet number 20000, now known as Varuna, has provided a suitably bright target for closer examination. After Pluto, Varuna is the largest known trans-Neptunian body and by measuring its thermal omissions and reflected optical light simultaneously, both its size and albedo have been be determined. Varuna's diameter is about 900 km and its surface is brighter than previously assumed for Kuiper Belt Objects, but darker than Pluto's, suggesting that it is largely devoid of fresh ice.

The size and albedo of the Kuiper-belt object (20000) Varuna
DAVID JEWITT, HERVE AUSSEL & AARON EVANS
Nature 411, 446-447 (24 May 2001)
| Summary | Full Text | PDF (152 K) |

Almost Planet X
S. C. TEGLER & W. ROMANISHIN
Optical and infrared observations of a bright object in the outer Solar System reveal it to be surprisingly large — almost as big as Pluto's moon. It could be the first of many such discoveries.
Nature 411, 423-424 (24 May 2001)
| Full Text | PDF (101 K) |

space: Pluto has big shiny colleague

24 May 2001 table of contents