Intellifive - Kuiper Belt    Kuiper belt refers to the disc-shaped region beyond Neptune, named for astronomer Gerard Kuiper. It is presumed to be remnants from the formation of the solar system about 4.6 billion years ago.The Kuiper Belt extends from about 30 to 55 AU (One astronomical unit, or AU, is the mean distance of Earth from the Sun: about 150 million kilometers or 93 million miles.) and is probably populated with hundreds of thousands of icy bodies larger than 100 kilometers (62 miles) across and an estimated trillion or more comets. Because KBOs are so distant, their sizes are difficult to measure. The calculated diameter of a KBO depends on assumptions about how brightness relates to size. With infrared observations by the Spitzer Space Telescope, most of the largest KBOs have known sizes.