Bright Company for Pluto

Scientists have found what appears to be the brightest object past Neptune except Pluto, bringing the total of known trans-neptunian objects (TNOs) to 348. Robert McMillan first spotted the new, slow-moving body, named 2000 WR₁₀₆, on November 28 using the Spacewatch 36-inch telescope. Jeffrey Larsen subsequently witnessed the target, which was discovered in a moderately rich star field, closer to the galactic equator than where TNOs are usually sought. Armed with observations spanning three days from both astronomers, the International Astronomical Union's Minor Planet Center at the Smithsonian Astrophysical Observatory in Cambridge, Mass., determined a preliminary orbit. As of December 1, that orbit suggests that 2000 WR ₁₀₆ is 43 times farther from the sun than Earth is. Follow-up observations will help scientists determine just how large 2000 WR ₁₀₆ really is. But they have taken a guess, assuming its reflectivity is like that of other minor planets. Given its brightness, 2000 WR ₁₀₆ could be between 330 and 750 miles in diameterwhich is quite sizeable, considering that Pluto measures 1,470 miles in diameter, and the largest known asteroid, Ceres, is 570 miles wide.