Upon reaching the outskirts of our solar system, we begin exploring a large disk-shaped region, a reservoir of dormant comets called the Edgeworth-Kuiper Belt. Commonly referred to as the Kuiper Belt, the region extending past Neptune’s orbital range is similar in appearance to an asteroid belt, but it is composed of icy masses rather than rock and metal objects. The objects comprising the Kuiper Belt are aptly called Kuiper Belt Objects, or KBOs, and are similar in composition to comets. They are often composed of ammonia, frozen water, and various hydrocarbons such as methane.
The belt is located 4.5 to 7.4 billion kilometers from the sun, and was first discovered in 1992 by David Jewitt and Jane Luu. Despite its recent discovery, the belt’s existence was predicted by both Kenneth Edgeworth and Gerard P Kuiper in 1943 and 1951 respectively. Both astronomers predicted that at the outskirts of the solar system, the space beyond Neptune could hold a reservoir of innumerable small icy bodies or potential comets.
The large amounts of dust, icy masses, and dwarf planets surrounding our solar system have led astronomers to presume that the Kuiper Belt and its distant yet akin neighbour, the Oort cloud, are the last remnants of the nebula from which our solar system emerged. It is believed that the size of the Kuiper Belt has decreased over time, having to withstand both the sun’s solar wind, and Neptune’s gravitational effect — whose interaction can cause KBOs to change their orbital trajectory and travel across the solar system as comets.
Among the objects believed to have originated from Kuiper’s Belt are Neptune’s satellite Triton, along with Pluto and its moon Charon. The belt is also home to the newest planetary addition to our solar system, Eris, which was discovered in 2005 using the Samuel Oschin telescope at the Palomar Observatory. Eris is 97 times as far from the sun as Earth, and is an ordinary member of the belt. Although astronomers are unsure of how much light Eris reflects away from the sun, Eris’ brightness had led them to suspect that it is at least as big as Pluto, if not larger.
While the Kuiper Belt possesses many mysteries yet to be discovered, its most mysterious aspects are the characteristics of its KBOs. Surprisingly, since their first observation in 2001, eight of the 500 KBOs detected have had orbiting satellites. In many of these cases, the Hubble Space Telescope has indicated that the KBO satellites are almost as large as the objects they orbit. This development violates the standard model for large satellite formation, in which collision between two objects must occur in order to form a satellite system. Since great magnitude collisions required for large satellite formation are energetically improbable in the Kuiper Belt, the only possibility for the standard model to hold is for the KBOs and their satellites to be more reflective than previously analyzed. In such a situation, the objects would be smaller and would require less energetic collisions to create a satellite system.
Due to its recent discovery and great distance from the sun, the Kuiper Belt has yet to be thoroughly analyzed. NASA’s latest mission New Horizons, launched in January 2006, hopes to provide the first detailed study of both Pluto and the Kuiper Belt, as it leaves the solar system. After having passed by Jupiter in February 2007, and having reached the half-way point to Pluto in February 2010, New Horizons is expected to reach Pluto by July 2015, and explore the Kuiper Belt from 2018 to 2022.
Whereas the New Horizons mission has at least five years until its interaction with Pluto, next week we will embark on a space probe, which has long completed its mission, and continues to make interstellar discoveries. Until then, your wonderland space ventures await.
