Where are humans in the universe? What else is there that hasn't been discovered? Is the map of the solar system completely filled in now? Questions like this are asked everyday, and most of them cannot be easily answered. However, another part of the solar system has recently been discovered. The Kuiper Belt is a ring of icy objects that extends beyond Neptune.
The Kuiper Belt was originally discovered by two scientists in 1992 by Dave Jewitt and Jane Luu. However, the idea that there might be a belt of icy objects past Neptune was proposed in 1943 by Kenneth E. Edgeworth. In 1951, Gerard Kuiper explained the proposition in much more detail. The search for objects beyond Neptune was not easy. Jewitt and Luu first started looking in 1987, but it was not until 5 years later that they found the first KBO (Kuiper Belt Object), which appeared as a reddish speck, 44 AU (Astronomical Unit- The average distance between the Sun and Earth) from the sun, using the University of Hawaii's 2.2m telescope. This object was later named “1992 QB1”.
The Kuiper Belt was formed about 4.6 billion years ago, from the leftover pieces after the formation of the planets. The inner parts of the “pre-planetary disk” (objects before planets were formed) formed into the major planets in just a few million years. However, since the outer parts were less dense, they formed slower, and many small objects were formed. Some larger KBOs were also formed when smaller objects collided. Although the objects formed in the outer areas, any objects seen beyond Neptune today were actually formed much closer to the Sun, and moved outward as planet formation ended.
Most objects in the Kuiper Belt consist mainly of ice and rock. Objects are generally about the size of small asteroids, with a few being 30-50% as large as Pluto. The Kuiper Belt starts at about 30 AU away from the sun, and ends at about 50 AU. There are currently at least 70,000 objects that have diameters larger than 100km in the area of 30-50 AU. The orbits of these KBOs are extremely similar to that of Pluto's. These objects are extremely dark, making it more difficult for them to be seen. “Although they're icy, most KBOs reflect as much sunlight (4-7%) as a lump of charcoal,” explains Dave Jewitt. “It's because of cosmic ray bombardment, which darkens and reddens their surfaces by breaking the bonds of molecules in the ice-molecules that reform as complex carbon-based compounds,” says scientists from Science@NASA.
The Kuiper Belt, although discovered only over a decade ago, is a remnant from when the solar system formed. Like fossils, it contains primitive traces of when the planets were created. This has provided much needed information, allowing mankind to learn about the early evolution of the solar system.
