The Kuiper belt is a region of the solar system that lies further beyond the orbit of Neptune. The Kuiper belt is populated by objects, including asteroids, comets and other ice dwarfs. The name with which these objects are collectively known is Kuiper belt objects (KBOs) or trans-Neptunian objects. The Kuiper belt is located in between 30-55 astronomical units (AU) from the Sun, and it is believed to be the region where short-period comets originate. The Kuiper belt took its name from Dutch-American astronomer Gerard Kuiper who was the first to predict its existence.
The Kuiper belt is believed to be composed of small fragments known as planetesimals which derived from the early formation of the solar system. During the formation of the solar system, these planetesimals failed to coalesce into planets, instead, they formed smaller bodies known as Kuiper belt objects (KBOs). KBOs are gigantic balls of ice and rock, varying in size, with some having only a few km in diameter, while others are as big as the planet Pluto. More than 70,000 KBOs of over 100 km (62 miles) are estimated to exist in the Kuiper belt. KBOs orbit the Sun in approximately 200 years or even longer.
The collective mass of the Kuiper belt is relatively low, despite its huge extent. Total mass is calculated to be in between one quarter and one tenth the mass of the Earth. The Kuiper belt extends to approximately 30 to 55 AU and is populated by thousands of icy objects some of which are larger than 100 km (62 miles) in diameter. In 1992 astronomers spotted for the first time a source of light coming from an object at about 42 AU from the Sun. since that time, over one thousand KBOs have been identified.
The objects in the Kuiper belt are primarily composed of a mixture of carbohydrates, ammonia and water ice. The same composition that comets are made. The Kuiper belt is an icy world with temperatures of about 50 K (-370°F). Compounds that would be gaseous closer to the inner solar system remain solid in the Kuiper belt. Due to the small size of the objects and vast distance from Earth, scientists are able to determine the chemical composition of KBOs through the use of spectroscopy.
The presence of Neptune exerts a deep effect on the structure of the Kuiper belt due to orbital resonances. Neptune’s gravitational pull destabilizes the orbits of objects lying in certain regions of the Kuiper belt either sending them in the direction of the inner solar system or out into interstellar space. This produces gaps in the layout of the Kuiper belt. For example, in the region situated between 40-42 AU, objects are not able to maintain stable orbits. It is thought that any object observed in that region must have travelled there recently.
Different kinds of KBOs have different orbits. Those that have orbits similar to Pluto are called plutinos, and those that have circular orbits are called cubewanos. Pluto and Eris (2003 UB 313), which was discovered on July 2005, are the best known icy dwarf planets in the Kuiper belt, although, there must hundreds of similar dwarf icy worlds there. Since the year 2000, various KBOs larger than Pluto have been discovered. 50000 Quaoar, measuring 1,200 km (124 miles) was discovered in 2002. Haumea and Makemake, which are larger still, were discovered in 2004 and 2005, respectively.
The outer edge of the solar system is not an empty region, scientists believe, there are many enormous spheres of rock and ice near the orbit of Pluto and beyond. It is hoped that a new space mission allow scientists to solve the mysteries of this distant region. NASA’s New Horizons spacecraft is travelling in space on its way to take the first close-up study of Pluto, as well as other icy objects in the Kuiper belt. The spacecraft is equipped with seven scientific high technology instruments to study Pluto and other objects. Horizons’ journey began in 2006, and will continue until 2015 when it is expected to approach Pluto.