Skip Navigation: Avoid going through Home page links and jump straight to content
spacer spacer spacer
spacer spacer spacer
spacer
NASA Logo    + View the NASA Portal  
Near Earth Object Program
spacer
spacer spacer spacer
spacer
NEO Basics Search Programs Discovery Statistics Accessible NEAs News Frequently Asked Questions
spacer
spacer spacer spacer
spacer
Orbit Diagrams Orbit Elements Close Approaches Impact Risk Images Related LInks
spacer
spacer spacer spacer
spacer

A KUIPER-BELT GIANT?

Sky & Telescope News Bulletin
December 1, 2000

Ordinarily the discovery of a 20th-magnitude blip wouldn't be much cause for excitement, but the one found early on November 28th is a special case. If preliminary calculations are borne out by further observations, the object now designated 2000 WR106 may prove to equal the size Ceres, the largest asteroid. Located about 1.5 deg. south of the star Epsilon Geminorum, the new find was spotted first by Robert S. McMillan and later by Jeffrey A. Larsen (University of Arizona) with the 0.9-meter Spacewatch telescope on Kitt Peak. They noticed its shifting position by eye in a computer display of successive frames -- the motion was too slow to be picked up by Spacewatch's automatic-detection software.

The object's actual size remains very uncertain in part because astronomers aren't yet sure of its distance from the Sun. Right now the best estimate is 43 astronomical units (6.4 billion kilometers), which means it is a Kuiper Belt object (KBO) beyond the orbit of Pluto. An object this far away takes nearly three centuries to circle the Sun, so astronomers will need to observe it over many weeks or months for its motion to betray the orbit's true character. However, according to Brian G. Marsden (IAU Minor Planet Center), the assumed distance is unlikely to change very much.

Another unknown is the albedo, or reflectivity, of the body's surface. If 2000 WR106 is bright, like Pluto or Charon, then its diameter might not exceed 250 km, something akin to Vesta in size. But just the opposite might be true. "Many people think KBOs have albedos closer to comet nuclei -- very dark," William J. Romanishin (University of Oklahoma) told members of the Minor Planet Mailing List. In that case, the Spacewatch discovery could exceed 1,200 km in diameter. Ceres, discovered almost exactly 200 years ago, is roughly 950 km across.

Apparently the object has escaped detection until now because it spent many years lurking among the stars of the northern Milky Way. With modern electronic detectors, it is actually within the detection range of many backyard telescopes.


Copyright 2000 Sky Publishing Corporation. S&T's Weekly News Bulletin and Sky at a Glance stargazing calendar are provided as a service to the astronomical community by the editors of SKY & TELESCOPE magazine. Widespread electronic distribution is encouraged as long as these paragraphs are included. But the text of the bulletin and calendar may not be published in any other form without permission from Sky Publishing (contact permissions@skypub.com or phone 617-864-7360). Updates of astronomical news, including active links to related Internet resources, are available via SKY & TELESCOPE's site on the World Wide Web at http://www.skypub.com/.

Menu
FIRST GOV   NASA Home Page Site Manager: Don Yeomans
Webmaster: Ron Baalke
Last Updated:
Feedback Credits Privacy Mailing List NASA