The Kuiper belt, sometimes called the Edgeworth–Kuiper belt, is a circumstellar disc in the Solar System beyond the (known) planets, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun.
What is the Kuiper belt?
It is similar to the asteroid belt, but is far larger—20 times as wide and 20 to 200 times as massive. Like the asteroid belt, it consists mainly of small bodies or remnants from when the Solar System formed. While many asteroids are composed primarily of rock and metal, most Kuiper belt objects are composed largely of frozen volatiles (termed “ices”), such as methane, ammonia and water. The Kuiper belt is home to three officially recognized dwarf planets: Pluto, Haumea and Makemake. Some of the Solar System’s moons, such as Neptune’s Triton and Saturn’s Phoebe, are thought to have originated in the region.
The Kuiper belt was named after Dutch-American astronomer Gerard Kuiper, though he did not predict its existence. In 1992, 1992 QB1 was discovered, the first Kuiper belt object (KBO) since Pluto. Since its discovery, the number of known KBOs has increased to over a thousand and more than 100,000 KBOs over 100 km (62 mi) in diameter are thought to exist. The Kuiper belt was initially thought to be the main repository for periodic comets, those with orbits lasting less than 200 years. Studies since the mid-1990s have shown that the belt is dynamically stable and that comets’ true place of origin is the scattered disc, a dynamically active zone created by the outward motion of Neptune 4.5 billion years ago, scattered disc objects such as Eris have extremely eccentric orbits that take them as far as 100 AU from the Sun.
After the discovery of Pluto in 1930, many speculated that it might not be alone. The region now called the Kuiper belt was hypothesized in various forms for decades. It was only in 1992 that the first direct evidence for its existence was found. The number and variety of prior speculations on the nature of the Kuiper belt have led to continued uncertainty as to who deserves credit for first proposing it.
Extrasolar Kuiper Belts
By 2006, astronomers had resolved dust discs thought to be Kuiper belt-like structures around nine stars other than the Sun. They appear to fall into two categories: wide belts, with radii of over 50 AU, and narrow belts (tentatively like that of the Solar System) with radii of between 20 and 30 AU and relatively sharp boundaries. Beyond this, 15–20% of solar-type stars have an observed infrared excess that is suggestive of massive Kuiper-belt-like structures. Most known debris discs around other stars are fairly young, but the two images on the right, taken by the Hubble Space Telescope in January 2006, are old enough (roughly 300 million years) to have settled into stable configurations. The left image is a “top view” of a wide belt, and the right image is an “edge view” of a narrow belt. Computer simulations of dust in the Kuiper belt suggest that when it was younger, it may have resembled the narrow rings seen around younger stars.
Image: NASA / JHUAPL / SWRI
Text: Wikipedia contributors. “Kuiper belt.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 16 Jul. 2017. Web. 9 Aug. 2017.