A184: The Kuiper Belt is a region of space in our solar system, shaped more like an ellipse than a circle, which is similar to an asteroid belt. While the asteroid belt is mostly metal and rock, the Kuiper Belt is composed almost entirely of icy chunks of various substances. Actually, the makeup of Kuiper Belt Objects is similar to the composition of comets – a mixture of frozen water, ammonia and various hydrocarbons, such as methane.
This region is located approximately 30 to 50 AU (astronomical units) from the Sun. Each astronomical unit is equivalent to the distance from the Earth to the Sun, so the region is 4.5 billion km to 7.4 billion km from the Sun. Scientists believe that there are over 70,000 objects in the Kuiper Belt, although astronomers have found a fraction so far. Some of these Kuiper Belt objects, KBOs, are massive. In fact, the dwarf planet Pluto is thought to be one of the objects in the Kuiper Belt. Pluto is the largest known KBO, but there are a number of other objects of substantial size. Quaoar is more than half the size of Pluto, and Makemake and Haumea are much closer in size to Pluto. A number of KBOs, including Pluto and Haumea, also have satellites.
The Kuiper Belt can be divided into smaller sections. The most densely populated section of the Kuiper Belt is called the classical Kuiper Belt and is located between 42 and 48 astronomical units from the Sun. The region is mostly unaffected by Neptune’s gravitational effect, so the objects there can remain stable in their orbits. The Kuiper Belt’s contents are included in what are known as Trans-Neptunian Objects (TNOs), which are objects that orbit farther from the Sun than Neptune does. Although most comets are thought to come from the Oort Cloud, some do come from the Kuiper Belt.
Although no spacecraft has yet studied the Kuiper Belt up close, NASA’s New Horizons will investigate the region after it has studied Pluto. Unfortunately, it will not reach Pluto until 2015 and other KBOs until even later. While scientists wait for the information provided by New Horizons, they study the information they have already gathered and try to prove theories about the region.