The Kuiper belt 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. It is similar to the asteroid belt, but is far larger—20 times as wide and 20–200 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, such as methane, ammonia, and water. The Kuiper belt is home to most of the objects that astronomers generally accept as dwarf planets: Orcus, Pluto, Haumea, Quaoar, and Makemake. Some of the Solar System's moons, such as Neptune's Triton and Saturn's Phoebe, may have originated in the region.
A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has an orbital semi-major axis of 30.1 astronomical units (au).
Pluto is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest known trans-Neptunian object by volume, by a small margin, but is slightly less massive than Eris. Like other Kuiper belt objects, Pluto is made primarily of ice and rock and is much smaller than the inner planets. Pluto has only one sixth the mass of Earth's moon, and one third its volume.
28978 Ixion (, provisional designation 2001 KX76) is a large trans-Neptunian object and a possible dwarf planet. It is located in the Kuiper belt, a region of icy objects orbiting beyond Neptune in the outer Solar System. Ixion is classified as a plutino, a dynamical class of objects in a 2:3 orbital resonance with Neptune. It was discovered in May 2001 by astronomers of the Deep Ecliptic Survey at the Cerro Tololo Inter-American Observatory, and was announced in July 2001. The object is named after the Greek mythological figure Ixion, who was a king of the Lapiths.
New Horizons is an interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI), with a team led by Alan Stern, the spacecraft was launched in 2006 with the primary mission to perform a flyby study of the Pluto system in 2015, and a secondary mission to fly by and study one or more other Kuiper belt objects (KBOs) in the decade to follow, which became a mission to 486958 Arrokoth. It is the fifth space probe to achieve the escape velocity needed to leave the Solar System.
Marc William Buie is an American astronomer and prolific discoverer of minor planets who works at the Southwest Research Institute in Boulder, Colorado in the Space Science Department. Formerly he worked at the Lowell Observatory in Flagstaff, Arizona, and was the Sentinel Space Telescope Mission Scientist for the B612 Foundation, which is dedicated to protecting Earth from asteroid impact events.
15810 Arawn, provisional designation 1994 JR1, is a trans-Neptunian object (TNO) from the inner regions of the Kuiper belt, approximately 133 kilometres (83 mi) in diameter. It belongs to the plutinos, the largest class of resonant TNOs. It was named after Arawn, the ruler of the underworld in Welsh mythology, and discovered on 12 May 1994, by astronomers Michael Irwin and Anna Żytkow with the 2.5-metre Isaac Newton Telescope at Roque de los Muchachos Observatory in the Canary Islands, Spain.
Quaoar is a ringed dwarf planet in the Kuiper belt, a region of icy planetesimals beyond Neptune. A non-resonant object (cubewano), it measures approximately 1,086 km (675 mi) in diameter, about the size of Saturn's moon Dione or half the size of Pluto. The object was discovered by American astronomers Chad Trujillo and Michael Brown at the Palomar Observatory on 4 June 2002. Signs of water ice on the surface of Quaoar have been found, which suggests that cryovolcanism may be occurring on Quaoar. A small amount of methane is present on its surface, which can only be retained by the largest Kuiper belt objects.
The exploration of Pluto began with the arrival of the New Horizons probe in July 2015, though proposals for such a mission had been studied for many decades. There are no plans as yet for a follow-up mission, though follow-up concepts have been studied.
486958 Arrokoth (provisional designation 2014 MU69; formerly nicknamed Ultima Thule) is a trans-Neptunian object located in the Kuiper belt. Arrokoth became the farthest and most primitive object in the Solar System visited by a spacecraft when the NASA space probe New Horizons conducted a flyby on 1 January 2019. Arrokoth is a contact binary 36 km (22 mi) long, composed of two planetesimals 21 and 15 km (13 and 9 mi) across, that are joined along their major axes. With an orbital period of about 298 years and a low orbital inclination and eccentricity, Arrokoth is classified as a cold classical Kuiper belt object.
2014 OS393, unofficially designated e31007AI, e3 and PT2, is a binary trans-Neptunian object in the classical Kuiper belt, the outermost region of the Solar System. It was first observed by the New Horizons KBO Search using the Hubble Space Telescope on 30 July 2014. Until 2015, when the object 486958 Arrokoth was selected, it was a potential flyby target for the New Horizons probe. Estimated to be approximately 42 kilometres (26 mi) in diameter, the object has a poorly determined orbit as it had been observed for only a few months.
2014 MT69 (internally designated 0720090F in the context of the Hubble Space Telescope, and 7 in the context of the New Horizons mission) is a cold classical Kuiper belt object (KBO) and was formerly a potential flyby target for the New Horizons probe. The object measures approximately 20–90 kilometers (12–56 miles) in diameter.
Long Range Reconnaissance Imager (LORRI) is a telescope aboard the New Horizons spacecraft for imaging. LORRI has been used to image Jupiter, its moons, Pluto and its moons, and Arrokoth since its launch in 2006. LORRI is a reflecting telescope of Ritchey-Chrétien design, and it has a main mirror diameter of 208 mm across. LORRI has a narrow field of view, less than a third of a degree. Images are taken with a CCD capturing data with 1024 × 1024 pixels. LORRI is a telescopic panchromatic camera integrated with the New Horizons spacecraft, and it is one of seven major science instruments on the probe. LORRI does not have any moving parts and is pointed by moving the entire New Horizons spacecraft.
REX or Radio Science Experiment is an experiment on the New Horizons space probe to determine various aspects of the atmosphere of Pluto during the 2015 flyby.
(516977) 2012 HZ84, provisional designation 2012 HZ84, is a small trans-Neptunian object from the Kuiper belt located in the outermost region of the Solar System, approximately 74 kilometers (46 miles) in diameter. It was discovered on 17 April 2012, by a team of astronomers using one of the Magellan Telescopes in Chile during the New Horizons KBO Search in order to find a potential flyby target for the New Horizons spacecraft. In December 2017, this classical Kuiper belt object was imaged by the spacecraft from afar at a record distance from Earth.
2012 HE85 is a small, resonant trans-Neptunian object from the Kuiper belt, located in the outermost region of the Solar System, approximately 74 kilometers (46 miles) in diameter. It was first observed by a team of astronomers using one of the Magellan Telescopes in Chile during the New Horizons KBO Search on 18 April 2012, in order to find a potential flyby target for the New Horizons spacecraft. The likely 5:9 resonant object was imaged by the spacecraft from afar at a record distance from Earth in 2017.
(523764) 2014 WC510 is a binary trans-Neptunian object discovered on 8 September 2011 by the Pan-STARRS survey at the Haleakalā Observatory in Hawaii. It was found by Pan-STARRS on 20 November 2014 and was announced later in July 2016 after additional observations and precovery identifications. It is in the Kuiper belt, a region of icy objects orbiting beyond Neptune in the outer Solar System. It is classified as a plutino, a dynamical class of objects in a 2:3 orbital resonance with Neptune. On 1 December 2018, a team of astronomers observed a stellar occultation by the object, which revealed that it is a compact binary system consisting of two separate components in close orbit around each other. The primary and secondary components are estimated to have diameters of around 180 km (110 mi) and 140 km (87 mi), respectively.
2011 JY31 is a binary trans-Neptunian object from the Kuiper belt, located in the outermost region of the Solar System. It was discovered on 4 May 2011, by a team of astronomers using one of the Magellan Telescopes in Chile during the New Horizons KBO Search for a potential flyby target for the New Horizons spacecraft. Distant observations by New Horizons from September 2018 revealed its binary nature, showing two 50 km (31 mi)-wide components in a tight, mutual orbit 200 km (120 mi) apart. The discovery adds support to streaming instability as the dominant mechanism in the formation of tight and contact binary planetesimals such as 486958 Arrokoth, which appear to be prevalent in the cold classical Kuiper belt population.
Timeline for the New Horizons interplanetary space probe lists the significant events of the launch, transition phases as well as subsequent significant operational mission events; by date and brief description.
