Ixion

Another KBO, called Ixion and found last year, has been estimated to be 745 miles wide (1,200 kilometers) -- nearly the same size as Quaoar. But that calculation was based on an estimate for how much sunlight Ixion might reflect, a figure called albedo. Researchers used a 4 percent albedo, once considered the standard for KBOs. The number is based on what scientists know about asteroids and comets they've actually seen.