Trans-Neptunian object

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A trans-Neptunian object (TNO), also written transneptunian object, [1] 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).


Typically, TNOs are further divided into the classical and resonant objects of the Kuiper belt, the scattered disc and detached objects with the sednoids being the most distant ones. [nb 1] As of October 2020, the catalog of minor planets contains 678 numbered and more than 2,000 unnumbered TNOs. [3] [4] [5] [6] [7]

The first trans-Neptunian object to be discovered was Pluto in 1930. It took until 1992 to discover a second trans-Neptunian object orbiting the Sun directly, 15760 Albion. The most massive TNO known is Eris, followed by Pluto, Haumea, Makemake, and Gonggong. More than 80 satellites have been discovered in orbit of trans-Neptunian objects. TNOs vary in color and are either grey-blue (BB) or very red (RR). They are thought to be composed of mixtures of rock, amorphous carbon and volatile ices such as water and methane, coated with tholins and other organic compounds.

Twelve minor planets with a semi-major axis greater than 150 au and perihelion greater than 30 au are known, which are called extreme trans-Neptunian objects (ETNOs). [8]


Discovery of Pluto

Pluto imaged by New Horizons Pluto in True Color - High-Res.jpg
Pluto imaged by New Horizons

The orbit of each of the planets is slightly affected by the gravitational influences of the other planets. Discrepancies in the early 1900s between the observed and expected orbits of Uranus and Neptune suggested that there were one or more additional planets beyond Neptune. The search for these led to the discovery of Pluto in February 1930, which was too small to explain the discrepancies. Revised estimates of Neptune's mass from the Voyager 2 flyby in 1989 showed that the problem was spurious. [9] Pluto was easiest to find because it has the highest apparent magnitude of all known trans-Neptunian objects. It also has a lower inclination to the ecliptic than most other large TNOs.

Subsequent discoveries

After Pluto's discovery, American astronomer Clyde Tombaugh continued searching for some years for similar objects, but found none. For a long time, no one searched for other TNOs as it was generally believed that Pluto, which up to August 2006 was classified a planet, was the only major object beyond Neptune. Only after the 1992 discovery of a second TNO, 15760 Albion, did systematic searches for further such objects begin. A broad strip of the sky around the ecliptic was photographed and digitally evaluated for slowly moving objects. Hundreds of TNOs were found, with diameters in the range of 50 to 2,500 kilometers. Eris, the most massive TNO, was discovered in 2005, revisiting a long-running dispute within the scientific community over the classification of large TNOs, and whether objects like Pluto can be considered planets. Pluto and Eris were eventually classified as dwarf planets by the International Astronomical Union. In December 2018, the discovery of 2018 VG18 , nicknamed "Farout", was announced. Farout is the most distant Solar System object so-far observed and is about 120 au away from the Sun. It takes 738 years to complete one orbit. [10]


Distribution of trans-Neptunian objects TheTransneptunians 73AU.svg
Distribution of trans-Neptunian objects
Euler diagram showing the types of bodies in the Solar System. Euler-Diagram bodies in the Solar System.jpg
Euler diagram showing the types of bodies in the Solar System.

According to their distance from the Sun and their orbital parameters, TNOs are classified in two large groups: the Kuiper belt objects (KBOs) and the scattered disc objects (SDOs). [nb 1] The diagram to the right illustrates the distribution of known trans-Neptunian objects (up to 70 au) in relation to the orbits of the planets and the centaurs for reference. Different classes are represented in different colours. Resonant objects (including Neptune trojans) are plotted in red, classical Kuiper belt objects in blue. The scattered disc extends to the right, far beyond the diagram, with known objects at mean distances beyond 500 au (Sedna) and aphelia beyond 1,000  ( (87269) 2000 OO67 ).


The Edgeworth-Kuiper belt contains objects with an average distance to the Sun of 30 to about 55 au, usually having close-to-circular orbits with a small inclination from the ecliptic. Edgeworth-Kuiper belt objects are further classified into the resonant trans-Neptunian object, that are locked in an orbital resonance with Neptune, and the classical Kuiper belt objects, also called "cubewanos", that have no such resonance, moving on almost circular orbits, unperturbed by Neptune. There are a large number of resonant subgroups, the largest being the twotinos (1:2 resonance) and the plutinos (2:3 resonance), named after their most prominent member, Pluto. Members of the classical Edgeworth-Kuiper belt include 15760 Albion, 50000 Quaoar and Makemake.

Another subclass of Kuiper belt objects is the so-called scattering objects (SO). These are non-resonant objects that come near enough to Neptune to have their orbits changed from time to time (such as causing changes in semi-major axis of at least 1.5 AU in 10 million years), and are thus undergoing gravitational scattering. Scattering objects are easier to detect than other trans-Neptunian objects of the same size because they come nearer to Earth, some having perihelia around 20 AU. Several are known with g-band absolute magnitude below 9, meaning that the estimated diameter is more than 100 km. It is estimated that there are between 240,000 and 830,000 scattering objects bigger than r-band absolute magnitude 12, corresponding to diameters greater than about 18 km. Scattering objects are hypothesized to be the source of the so-called Jupiter-family comets (JFCs), which have periods of less than 20 years. [11] [12] [13]


The scattered disc contains objects farther from the Sun, with very eccentric and inclined orbits. These orbits are non-resonant and non-planetary-orbit-crossing. A typical example is the most-massive-known TNO, Eris. Based on the Tisserand parameter relative to Neptune (TN), the objects in the scattered disc can be further divided into the "typical" scattered disc objects (SDOs, Scattered-near) with a TN of less than 3, and into the detached objects (ESDOs, Scattered-extended) with a TN greater than 3. In addition, detached objects have a time-averaged eccentricity greater than 0.2 [14] The Sednoids are a further extreme sub-grouping of the detached objects with perihelia so distant that it is confirmed that their orbits cannot be explained by perturbations from the giant planets, [15] nor by interaction with the galactic tides. [16]

Physical characteristics

Looking back at Pluto, the largest visited KBO so far Pluto crescent.jpg
Looking back at Pluto, the largest visited KBO so far

Given the apparent magnitude (>20) of all but the biggest trans-Neptunian objects, the physical studies are limited to the following:

Studying colours and spectra provides insight into the objects' origin and a potential correlation with other classes of objects, namely centaurs and some satellites of giant planets (Triton, Phoebe), suspected to originate in the Kuiper belt. However, the interpretations are typically ambiguous as the spectra can fit more than one model of the surface composition and depend on the unknown particle size. More significantly, the optical surfaces of small bodies are subject to modification by intense radiation, solar wind and micrometeorites. Consequently, the thin optical surface layer could be quite different from the regolith underneath, and not representative of the bulk composition of the body.

Small TNOs are thought to be low-density mixtures of rock and ice with some organic (carbon-containing) surface material such as tholin, detected in their spectra. On the other hand, the high density of Haumea, 2.6–3.3 g/cm3, suggests a very high non-ice content (compare with Pluto's density: 1.86 g/cm3). The composition of some small TNOs could be similar to that of comets. Indeed, some centaurs undergo seasonal changes when they approach the Sun, making the boundary blurred (see 2060 Chiron and 7968 Elst–Pizarro). However, population comparisons between centaurs and TNOs are still controversial. [17]

Color indices

Colors of trans-Neptunian objects. Yellow names in brackets are non trans-Neptunian objects added for reference. Mars and Triton are also not to scale. TheTransneptunians Color Distribution.svg
Colors of trans-Neptunian objects. Yellow names in brackets are non trans-Neptunian objects added for reference. Mars and Triton are also not to scale.
Illustration of the relative sizes, albedos and colours of some large TNOs TheTransneptunians Size Albedo Color.svg
Illustration of the relative sizes, albedos and colours of some large TNOs

Colour indices are simple measures of the differences in the apparent magnitude of an object seen through blue (B), visible (V), i.e. green-yellow, and red (R) filters. The diagram illustrates known colour indices for all but the biggest objects (in slightly enhanced colour). [18] For reference, two moons, Triton and Phoebe, the centaur Pholus and the planet Mars are plotted (yellow labels, size not to scale). Correlations between the colours and the orbital characteristics have been studied, to confirm theories of different origin of the different dynamic classes:

While the relatively dimmer bodies, as well as the population as the whole, are reddish (V−I = 0.3–0.6), the bigger objects are often more neutral in colour (infrared index V−I < 0.2). This distinction leads to suggestion that the surface of the largest bodies is covered with ices, hiding the redder, darker areas underneath. [21]

Mean-color indices of dynamical groups in the outer Solar System [22] :35
Color Plutinos Cubewanos Centaurs SDOs Comets Jupiter trojans

Spectral type

Among TNOs, as among centaurs, there is a wide range of colors from blue-grey (neutral) to very red, but unlike the centaurs, bimodally grouped into grey and red centaurs, the distribution for TNOs appears to be uniform. [17] The wide range of spectra differ in reflectivity in visible red and near infrared. Neutral objects present a flat spectrum, reflecting as much red and infrared as visible spectrum. [23] Very red objects present a steep slope, reflecting much more in red and infrared. A recent attempt at classification (common with centaurs) uses the total of four classes from BB (blue, or neutral color, average B−V = 0.70, V−R = 0.39, e.g. Orcus) to RR (very red, B−V = 1.08, V−R = 0.71, e.g. Sedna) with BR and IR as intermediate classes. BR (intermediate blue-red) and IR (moderately red) differ mostly in the infrared bands I, J and H.

Typical models of the surface include water ice, amorphous carbon, silicates and organic macromolecules, named tholins, created by intense radiation. Four major tholins are used to fit the reddening slope:

As an illustration of the two extreme classes BB and RR, the following compositions have been suggested

Size determination and distribution

Size comparison between the Moon, Neptune's moon Triton, Pluto, several large TNOs, and the asteroid Ceres. Their respective shapes are not represented. Selected Planemos.svg
Size comparison between the Moon, Neptune's moon Triton, Pluto, several large TNOs, and the asteroid Ceres. Their respective shapes are not represented.

Characteristically, big (bright) objects are typically on inclined orbits, whereas the invariable plane regroups mostly small and dim objects. [21]

It is difficult to estimate the diameter of TNOs. For very large objects, with very well known orbital elements (like Pluto), diameters can be precisely measured by occultation of stars. For other large TNOs, diameters can be estimated by thermal measurements. The intensity of light illuminating the object is known (from its distance to the Sun), and one assumes that most of its surface is in thermal equilibrium (usually not a bad assumption for an airless body). For a known albedo, it is possible to estimate the surface temperature, and correspondingly the intensity of heat radiation. Further, if the size of the object is known, it is possible to predict both the amount of visible light and emitted heat radiation reaching Earth. A simplifying factor is that the Sun emits almost all of its energy in visible light and at nearby frequencies, while at the cold temperatures of TNOs, the heat radiation is emitted at completely different wavelengths (the far infrared).

Thus there are two unknowns (albedo and size), which can be determined by two independent measurements (of the amount of reflected light and emitted infrared heat radiation). TNOs are so far from the Sun that they are very cold, hence producing black-body radiation around 60 micrometres in wavelength. This wavelength of light is impossible to observe on the Earth's surface, but only from space using, e.g. the Spitzer Space Telescope. For ground-based observations, astronomers observe the tail of the black-body radiation in the far infrared. This far infrared radiation is so dim that the thermal method is only applicable to the largest KBOs. For the majority of (small) objects, the diameter is estimated by assuming an albedo. However, the albedos found range from 0.50 down to 0.05, resulting in a size range of 1,200–3,700 km for an object of magnitude of 1.0. [24]

Notable objects

134340 Pluto a dwarf planet and the first TNO discovered
15760 Albion the prototype cubewano, the first Kuiper belt object discovered after Pluto
(385185) 1993 RO the next plutino discovered after Pluto
(15874) 1996 TL66 the first object to be identified as a scattered disc object
1998 WW31 the first binary Kuiper belt object discovered after Pluto
47171 Lempo a plutino and triple system consisting of a central binary pair of similar size, and a third outer circumbinary satellite
20000 Varuna a large cubewano, known for its rapid rotation (6.3 h) and elongated shape
28978 Ixion large plutino, was considered to be among the largest Kuiper belt objects upon discovery
50000 Quaoar large cubewano with a satellite; sixth-largest-known Kuiper belt object and was considered to be among the largest Kuiper belt objects upon discovery
90377 Sedna a distant object, proposed for a new category named extended scattered disc (E-SDO), [25] detached objects, [26] distant detached objects (DDO) [27] or scattered-extended in the formal classification by DES. [14]
90482 Orcus The largest known plutino, after Pluto. Has a relatively large satellite.
136108 Haumea a dwarf planet, the third-largest-known trans-Neptunian object. Notable for its two known satellites, rings, and unusually short rotation period (3.9 h). It is the most massive known member of the Haumea collisional family. [28] [29]
136472 Makemake a dwarf planet, a cubewano, and the fourth-largest known trans-Neptunian object [30]
136199 Eris a dwarf planet, a scattered disc object, and currently the most massive known trans-Neptunian object. It has one known satellite, Dysnomia
(612911) 2004 XR190 a scattered disc object following a highly inclined but nearly circular orbit
225088 Gonggong second-largest scattered-disc object with a satellite
(528219) 2008 KV42 "Drac"the first retrograde TNO, having an orbital inclination of i = 104°
(471325) 2011 KT19 "Niku"a TNO having an unusually high orbital inclination of 110° [31]
2012 VP113 a sednoid with a large perihelion of 80 au from the Sun (50 au beyond Neptune)
486958 Arrokoth contact binary cubewano encountered by the New Horizons spacecraft in 2019
2018 VG18 "Farout"the first trans-Neptunian object discovered while beyond 100 au (15 billion km) from the Sun
2018 AG37 "FarFarOut"most distant observable trans-Neptunian object at 132 au (19.7 billion km) from the Sun


Kuiper belt object 486958 Arrokoth, in images taken by the New Horizons spacecraft UltimaThule CA06 color 20190516.png
Kuiper belt object 486958 Arrokoth, in images taken by the New Horizons spacecraft

The only mission to date that primarily targeted a trans-Neptunian object was NASA's New Horizons , which was launched in January 2006 and flew by the Pluto system in July 2015 [32] and 486958 Arrokoth in January 2019. [33]

In 2011, a design study explored a spacecraft survey of Quaoar, Sedna, Makemake, Haumea, and Eris. [34]

In 2019 one mission to TNOs included designs for orbital capture and multi-target scenarios. [35] [36]

Some TNOs that were studied in a design study paper were 2002 UX25 , 1998 WW31 , and Lempo. [36]

The existence of planets beyond Neptune, ranging from less than an Earth mass (Sub-Earth) up to a brown dwarf has been often postulated [37] [38] for different theoretical reasons to explain several observed or speculated features of the Kuiper belt and the Oort cloud. It was recently proposed to use ranging data from the New Horizons spacecraft to constrain the position of such a hypothesized body. [39]

NASA has been working towards a dedicated Interstellar Precursor in the 21st century, one intentionally designed to reach the interstellar medium, and as part of this the flyby of objects like Sedna are also considered. [40] Overall this type of spacecraft studies have proposed a launch in the 2020s, and would try to go a little faster than the Voyagers using existing technology. [40] One 2018 design study for an Interstellar Precursor, included a visit of minor planet 50000 Quaoar, in the 2030s. [41]

Extreme trans-Neptunian objects

Overview of trans-Neptunian objects with extreme TNOs grouped into three categories at the top. Extreme transneptunian object eccentricity vs perihelion.png
Overview of trans-Neptunian objects with extreme TNOs grouped into three categories at the top.
Sedna's orbit takes it far beyond even the Kuiper belt (30-50 au), out to nearly 1,000 au (Sun-Earth distance) Sedna orbit.svg
Sedna's orbit takes it far beyond even the Kuiper belt (30–50 au), out to nearly 1,000 au (Sun–Earth distance)

Among the extreme trans-Neptunian objects are three high-perihelion objects classified as sednoids: 90377 Sedna, 2012 VP113 , and 541132 Leleākūhonua. They are distant detached objects with perihelia greater than 70 au. Their high perihelia keep them at a sufficient distance to avoid significant gravitational perturbations from Neptune. Previous explanations for the high perihelion of Sedna include a close encounter with an unknown planet on a distant orbit and a distant encounter with a random star or a member of the Sun's birth cluster that passed near the Solar System. [42] [43] [44]

See also


  1. 1 2 The literature is inconsistent in the use of the phrases "scattered disc" and "Kuiper belt". For some, they are distinct populations; for others, the scattered disk is part of the Kuiper belt, in which case the low-eccentricity population is called the "classical Kuiper belt". Authors may even switch between these two uses in a single publication. [2]

Related Research Articles

<span class="mw-page-title-main">Classical Kuiper belt object</span> Kuiper belt object, not controlled by an orbital resonance with Neptune

A classical Kuiper belt object, also called a cubewano ( "QB1-o"), is a low-eccentricity Kuiper belt object (KBO) that orbits beyond Neptune and is not controlled by an orbital resonance with Neptune. Cubewanos have orbits with semi-major axes in the 40–50 AU range and, unlike Pluto, do not cross Neptune's orbit. That is, they have low-eccentricity and sometimes low-inclination orbits like the classical planets.

<span class="mw-page-title-main">Kuiper belt</span> Area of the Solar System beyond the planets, comprising small bodies

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.

<span class="mw-page-title-main">Planets beyond Neptune</span> Hypothetical planets further than Neptune

Following the discovery of the planet Neptune in 1846, there was considerable speculation that another planet might exist beyond its orbit. The search began in the mid-19th century and continued at the start of the 20th with Percival Lowell's quest for Planet X. Lowell proposed the Planet X hypothesis to explain apparent discrepancies in the orbits of the giant planets, particularly Uranus and Neptune, speculating that the gravity of a large unseen ninth planet could have perturbed Uranus enough to account for the irregularities.

In astronomy, the plutinos are a dynamical group of trans-Neptunian objects that orbit in 2:3 mean-motion resonance with Neptune. This means that for every two orbits a plutino makes, Neptune orbits three times. The dwarf planet Pluto is the largest member as well as the namesake of this group. The next largest members are Orcus, (208996) 2003 AZ84, and Ixion. Plutinos are named after mythological creatures associated with the underworld.

<span class="mw-page-title-main">Centaur (small Solar System body)</span> Type of Solar System object

In planetary astronomy, a centaur is a small Solar System body that orbits the Sun between Jupiter and Neptune and crosses the orbits of one or more of the giant planets. Centaurs generally have unstable orbits because they cross or have crossed the orbits of the giant planets; almost all their orbits have dynamic lifetimes of only a few million years, but there is one known centaur, 514107 Kaʻepaokaʻawela, which may be in a stable orbit. Centaurs typically exhibit the characteristics of both asteroids and comets. They are named after the mythological centaurs that were a mixture of horse and human. Observational bias toward large objects makes determination of the total centaur population difficult. Estimates for the number of centaurs in the Solar System more than 1 km in diameter range from as low as 44,000 to more than 10,000,000.

<span class="mw-page-title-main">28978 Ixion</span> Plutino

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.

<span class="mw-page-title-main">90482 Orcus</span> Trans-Neptunian planetoid

Orcus is a large trans-Neptunian object and likely dwarf planet located in the Kuiper belt, with one large moon, Vanth. It has an estimated diameter of 870 to 960 km, comparable to the Inner Solar System dwarf planet Ceres. Orcus had been accepted by many astronomers as a dwarf planet, though as of 2024 that classification remains somewhat controversial. The surface of Orcus is relatively bright with albedo reaching 23 percent, neutral in color, and rich in water ice. The ice is predominantly in crystalline form, which may be related to past cryovolcanic activity. Other compounds like methane or ammonia may also be present on its surface. Orcus was discovered by American astronomers Michael Brown, Chad Trujillo, and David Rabinowitz on 17 February 2004.

<span class="mw-page-title-main">90377 Sedna</span> Dwarf planet

Sedna is a dwarf planet in the outermost reaches of the inner Solar System, orbiting the Sun beyond the orbit of Neptune. Discovered in 2003, the planetoid's surface is one of the reddest known among Solar System bodies. Spectroscopy has revealed Sedna's surface to be mostly a mixture of the solid ices of water, methane, and nitrogen, along with widespread deposits of reddish-colored tholins, a chemical makeup similar to those of some other trans-Neptunian objects. Within the range of uncertainties, it is tied with the dwarf planet Ceres in the asteroid belt as the largest dwarf planet not known to have a moon. Its diameter is roughly 1,000 km. Owing to its lack of known moons, the Keplerian laws of planetary motion cannot be employed for determining its mass, and the precise figure as yet remains unknown.

<span class="mw-page-title-main">38628 Huya</span> Trans-Neptunian object

38628 Huya ( hoo-YAH; provisional designation 2000 EB173) is a binary trans-Neptunian object located in the Kuiper belt, a region of icy objects orbiting beyond Neptune in the outer Solar System. Huya is classified as a plutino, a dynamical class of trans-Neptunian objects with orbits in a 3:2 orbital resonance with Neptune. It was discovered by the Quasar Equatorial Survey Team and was identified by Venezuelan astronomer Ignacio Ferrín in March 2000. It is named after Juyá, the mythological rain god of the Wayuu people native to South America.

<span class="nowrap">(55565) 2002 AW<sub>197</sub></span> Classical Kuiper belt object

(55565) 2002 AW197 (provisional designation 2002 AW197) is a classical, non-resonant trans-Neptunian object from the Kuiper belt in the outermost region of the Solar System, also known as a cubewano. With a likely diameter of at least 700 kilometers (430 miles), it is approximately tied with 2002 MS4 and 2013 FY27 (to within measurement uncertainties) as the largest unnamed object in the Solar System. It was discovered at Palomar Observatory in 2002.

<span class="mw-page-title-main">Scattered disc</span> Collection of bodies in the extreme Solar System

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.

<span class="nowrap">(84922) 2003 VS<sub>2</sub></span> Trans-Neptunian object

(84922) 2003 VS2 is a trans-Neptunian object discovered by the Near Earth Asteroid Tracking program on 14 November 2003. Like Pluto, it is in a 2:3 orbital resonance with Neptune and is thus a plutino. Analysis of light-curve suggests that it is not a dwarf planet.

<span class="mw-page-title-main">Detached object</span> Dynamical class of minor planets

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.

<span class="mw-page-title-main">225088 Gonggong</span> Dwarf planet in the scattered-disc

Gonggong 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 from the Sun. As of 2019, its distance from the Sun is 88 AU, and it is the sixth-farthest known Solar System object. According to the Deep Ecliptic Survey, 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.

(55638) 2002 VE95 (provisional designation 2002 VE95) is a trans-Neptunian object from the outermost region of the Solar System. It was discovered on 14 November 2002, by astronomers with the Near-Earth Asteroid Tracking program at the Palomar Observatory in California, United States. This resonant trans-Neptunian object is a member of the plutino population, locked in a 2:3 resonance with Neptune. The object is likely of primordial origin with a heterogeneous surface and a notably reddish color (RR) attributed to the presence of methanol and tholins. It has a poorly defined rotation period of 6.8 hours and measures approximately 250 kilometers (160 miles) in diameter, too small to be a dwarf planet candidate. As of 2021, it has not yet been named.

<span class="mw-page-title-main">Sednoid</span> Group of Trans-Neptunian objects

A sednoid is a trans-Neptunian object with a perihelion well beyond the Kuiper cliff at 47.8 AU. The consensus among astronomers is that there are only three objects that are known from this population: 90377 Sedna, 2012 VP113, and 541132 Leleākūhonua (2015 TG387). All three have perihelia greater than 60 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 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.

<span class="nowrap">(82158) 2001 FP<sub>185</sub></span>

(82158) 2001 FP185 (provisional designation 2001 FP185) is a highly eccentric trans-Neptunian object from the scattered disc in the outermost part of the Solar System, approximately 330 kilometers in diameter. It was discovered on 26 March 2001, by American astronomer Marc Buie at Kitt Peak National Observatory in Arizona, United States.

<span class="mw-page-title-main">Extreme trans-Neptunian object</span> Solar system objects beyond the other known trans-Neptunian objects

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. The orbits of ETNOs are 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.

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.


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