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 a semi-major axis of 30.1 astronomical units (AU).
Sedna (minor-planet designation 90377 Sedna) is a dwarf planet in the outer reaches of the Solar System that is in the innermost part of its orbit; as of 2022 it is 84 astronomical units (1.26×1010 km; 0.00041 pc) from the Sun, almost three times farther than Neptune. Spectroscopy has revealed that Sedna's surface composition is similar to those of some other trans-Neptunian objects, being largely a mixture of water, methane, and nitrogen ices with tholins. Its surface is one of the reddest among Solar System objects. To within estimated uncertainties, Sedna is tied with Ceres as the largest planetoid not known to have a moon.
(148209) 2000 CR105 is a trans-Neptunian object and the tenth-most-distant known object in the Solar System as of 2015. Considered a detached object, it orbits the Sun in a highly eccentric orbit every 3,305 years at an average distance of 222 astronomical units (AU).
The scattered disc (or scattered disk) is a distant circumstellar disc in the Solar System that is sparsely populated by icy small solar system bodies, which are a subset of the broader family of trans-Neptunian objects. The scattered-disc objects (SDOs) have orbital eccentricities ranging as high as 0.8, inclinations as high as 40°, and perihelia greater than 30 astronomical units (4.5×109 km; 2.8×109 mi). These extreme orbits are thought to be the result of gravitational "scattering" by the gas giants, and the objects continue to be subject to perturbation by the planet Neptune.
(42301) 2001 UR163, prov. designation: 2001 UR163, is a resonant trans-Neptunian object and possible dwarf planet located in the outermost region of the Solar System. The object measures approximately 352 kilometers (220 miles) in diameter with a high albedo and stays in an uncommon orbital resonance (4:9) with Neptune. It has the reddest color (RR-U) of any object in the Solar System. It was discovered on 21 October 2001 by astronomers of the Deep Ecliptic Survey program at Kitt Peak National Observatory near Tucson, Arizona, United States. As of 2021, it has not been named.
(309239) 2007 RW10, provisionally known as 2007 RW10, is a temporary quasi-satellite of Neptune. Observed from Neptune, it would appear to go around it during one Neptunian year but it actually orbits the Sun, not Neptune.
(613766) 2007 NC7, also written as 2007 NC7, is a trans-Neptunian object and centaur from the outer Solar System, approximately 106 kilometers in diameter. It was first observed on 11 July 2007, by American astronomers Megan Schwamb, Michael Brown and David Rabinowitz at Palomar Observatory in California.
229762 Gǃkúnǁʼhòmdímà, provisional designation 2007 UK126, is a trans-Neptunian object and binary system from the extended scattered disc, located in the outermost region of the Solar System. It was discovered on 19 October 2007 by American astronomers Megan Schwamb, Michael Brown, and David Rabinowitz at the Palomar Observatory in California and measures approximately 600 kilometers (400 miles) in diameter. This medium-sized TNO appears to be representative of a class of mid-sized objects under approximately 1000 km that have not collapsed into fully solid bodies. Its 100-kilometer moon was discovered by Keith Noll, Will Grundy, and colleagues with the Hubble Space Telescope in 2008, and named Gǃòʼé ǃHú.
Detached objects are a dynamical class of minor planets in the outer reaches of the Solar System and belong to the broader family of trans-Neptunian objects (TNOs). These objects have orbits whose points of closest approach to the Sun (perihelion) are sufficiently distant from the gravitational influence of Neptune that they are only moderately affected by Neptune and the other known planets: This makes them appear to be "detached" from the rest of the Solar System, except for their attraction to the Sun.
Gonggong (formally 225088 Gonggong; provisional designation 2007 OR10) is a dwarf planet, a member of the scattered disc beyond Neptune. It has a highly eccentric and inclined orbit during which it ranges from 34–101 astronomical units (5.1–15.1 billion kilometers; 3.2–9.4 billion miles) from the Sun. As of 2019, its distance from the Sun is 88 AU (13.2×10^9 km; 8.2×10^9 mi), and it is the sixth-farthest known Solar System object. Gonggong is in a 3:10 orbital resonance with Neptune, in which it completes three orbits around the Sun for every ten orbits completed by Neptune. Gonggong was discovered in July 2007 by American astronomers Megan Schwamb, Michael Brown, and David Rabinowitz at the Palomar Observatory, and the discovery was announced in January 2009.
(470308) 2007 JH43, provisional designation 2007 JH43, is a trans-Neptunian object in the outer regions of the Solar System, approximately 500 kilometers in diameter. It was discovered on 10 May 2007, by the U.S. Palomar Observatory in California. The team of unaccredited astronomers at Palomar consisted of Megan E. Schwamb, Michael E. Brown and David L. Rabinowitz
(528381) 2008 ST291, provisional designation 2008 ST291, is a 1:6 resonant trans-Neptunian object located in the outermost region of the Solar System that takes almost a thousand years to complete an orbit around the Sun. It was discovered on 24 September 2008 by American astronomers Megan Schwamb, Michael Brown and David Rabinowitz at the Palomar Observatory in California, with no known earlier precovery images.
A sednoid is a trans-Neptunian object with a perihelion well beyond the Kuiper cliff at 47.8 AU. Only three objects are known from this population: 90377 Sedna, 2012 VP113, and 541132 Leleākūhonua (2015 TG387), but it is suspected that there are many more. All three have perihelia greater than 64 AU. These objects lie outside an apparently nearly empty gap in the Solar System and have no significant interaction with the planets. They are usually grouped with the detached objects. Some astronomers, such as Scott Sheppard, consider the sednoids to be inner Oort cloud objects (OCOs), though the inner Oort cloud, or Hills cloud, was originally predicted to lie beyond 2,000 AU, beyond the aphelia of the three known sednoids.
An extreme trans-Neptunian object (ETNO) is a trans-Neptunian object orbiting the Sun well beyond Neptune (30 AU) in the outermost region of the Solar System. An ETNO has a large semi-major axis of at least 150–250 AU. Its orbit is much less affected by the known giant planets than all other known trans-Neptunian objects. They may, however, be influenced by gravitational interactions with a hypothetical Planet Nine, shepherding these objects into similar types of orbits. The known ETNOs exhibit a highly statistically significant asymmetry between the distributions of object pairs with small ascending and descending nodal distances that might be indicative of a response to external perturbations.
Megan E. Schwamb is an American astronomer and planetary scientist, and lecturer at Queen's University, Belfast. Schwamb has discovered and co-discovered several trans-Neptunian objects, and is involved with Citizen science projects such as Planet Four and Planet Hunters.
The Outer Solar System Origins Survey (OSSOS) is an astronomical survey and observing program aimed at discovering and tracking trans-Neptunian objects located in the outermost regions of the Solar System beyond the orbit of Neptune. OSSOS is designed in way that observational biases can be characterized, allowing the numbers and orbits of detected objects to be compared using a survey simulator to the populations predicted in dynamical simulations of the emplacement of trans-Neptunian objects. Conducted at the Canada-France-Hawaii telescope at Mauna Kea Observatories in Hawaii, the survey has discovered 39 numbered objects as of 2018, with potentially hundreds more to follow. The survey's first numbered discovery was the object (496315) 2013 GP136 in 2013.
541132 Leleākūhonua, provisionally designated 2015 TG387, is an extreme trans-Neptunian object and sednoid in the outermost part of the Solar System. It was first observed on 13 October 2015, by astronomers at the Mauna Kea Observatories, Hawaii. Based on its discovery date near Halloween and the letters in its provisional designation 2015 TG387, the object was informally nicknamed "The Goblin" by its discoverers and later named Leleākūhonua, comparing its orbit to the flight of the Pacific golden plover. It was the third sednoid discovered, after Sedna and 2012 VP113, and measures around 220 kilometers (140 miles) in diameter.
