
From this he concluded that "the outer region of the solar system, beyond the orbits of the planets, is occupied by a very large number of comparatively small bodies" : xii and that, from time to time, one of their number "wanders from its own sphere and appears as an occasional visitor to the inner solar system", : 2 becoming a comet.

In 1943, in the Journal of the British Astronomical Association, Kenneth Edgeworth hypothesized that, in the region beyond Neptune, the material within the primordial solar nebula was too widely spaced to condense into planets, and so rather condensed into a myriad smaller bodies. Leuschner suggested that Pluto "may be one of many long-period planetary objects yet to be discovered." Īstronomer Gerard Kuiper, after whom the Kuiper belt is named
#Querious ice belt series#
Soon after Pluto's discovery by Clyde Tombaugh in 1930, Leonard pondered whether it was "not likely that in Pluto there has come to light the first of a series of ultra-Neptunian bodies, the remaining members of which still await discovery but which are destined eventually to be detected". The first astronomer to suggest the existence of a trans-Neptunian population was Frederick C. 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. It was only in 1992 that the first direct evidence for its existence was found. The region now called the Kuiper belt was hypothesized in various forms for decades. Īfter the discovery of Pluto in 1930, many speculated that it might not be alone.

The Kuiper belt and Neptune may be treated as a marker of the extent of the Solar System, alternatives being the heliopause and the distance at which the Sun's gravitational influence is matched by that of other stars (estimated to be between 50 000 AU and 125 000 AU). It is compositionally similar to many other objects of the Kuiper belt, and its orbital period is characteristic of a class of KBOs, known as " plutinos," that share the same 2:3 resonance with Neptune. Originally considered a planet, Pluto's status as part of the Kuiper belt caused it to be reclassified as a dwarf planet in 2006. Pluto is the largest and most massive member of the Kuiper belt and the largest and the second-most-massive known TNO, surpassed only by Eris in the scattered disc. The objects within the Kuiper belt, together with the members of the scattered disc and any potential Hills cloud or Oort cloud objects, are collectively referred to as trans-Neptunian objects (TNOs). The Kuiper belt is distinct from the hypothesized Oort cloud, which is believed to be a thousand times more distant and mostly spherical. 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. The Kuiper belt was initially thought to be the main repository for periodic comets, those with orbits lasting less than 200 years. Since its discovery, the number of known KBOs has increased to thousands, and more than 100,000 KBOs over 100 km (62 mi) in diameter are thought to exist.

In 1992, minor planet (15760) Albion was discovered, the first Kuiper belt object (KBO) since Pluto (in 1930) and Charon (in 1978). The Kuiper belt was named after Dutch astronomer Gerard Kuiper, although he did not predict its existence. Some of the Solar System's moons, such as Neptune's Triton and Saturn's Phoebe, may have originated in the region. The Kuiper belt is home to most of the objects that astronomers generally accept as dwarf planets: Orcus, Pluto, Haumea, Quaoar, and Makemake. 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. Like the asteroid belt, it consists mainly of small bodies or remnants from when the Solar System formed. It is similar to the asteroid belt, but is far larger-20 times as wide and 20–200 times as massive.

The Kuiper belt ( / ˈ k aɪ p ər/) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun.
