# Extreme trans-Neptunian object <!-- SOLSIM:BEGIN g31 — Solar System explorer state (hand-built on wt-core, specs/solar/); do not hand-edit inside --> **Microsim — three.js (Wikitube framework):** *Extreme trans-Neptunian objects in the Solar System explorer* <div class="wt-sim" data-src="https://wikitube-3d-microsims.netlify.app/solar/Solar_System.html?obj=etno&embed=1" data-title="Extreme trans-Neptunian objects in the Solar System explorer"></div> *The Solar System explorer locked on this article's state (`?obj=etno`); every object and population of the [[PORTAL_Solar_System|Solar System portal]] has its own state in the same scene.* <!-- SOLSIM:END --> *Try: press l to label the three real sednoid orbits, Sedna, 2012 VP113 and Leleākūhonua, among the sampled points; drag to an edge-on view to see how far the points tilt out of the planets' plane; then drag the year slider from 1800 to 2050 and watch Sedna creep along the inner end of its orbit while Neptune completes more than one circuit.* An **extreme trans-Neptunian object** (**ETNO**) is a [[Trans-Neptunian_object|trans-Neptunian object]] whose orbit has a semi-major axis of at least about 150–250 [[Astronomical_unit|AU]], several times the distance of [[Neptune]] at 30 AU, so that it spends almost all of its time in the outermost [[PORTAL_Solar_System|Solar System]].[^sheppard2019][^dlfm2018caju] The giant planets act on these orbits much more weakly than on those of other known trans-Neptunian objects. Some astronomers argue that an undiscovered [[Planet_Nine]] has herded them into similar orientations, and the known ETNOs show a statistically significant asymmetry in the nodal distances of pairs of orbits, which may point to an outside perturbation.[^sheppard2019][^dlfm2021][^dlfm2022] Sheppard and colleagues split the population by perihelion distance into three groups. Scattered ETNOs, or extreme scattered disc objects, come to perihelion at about 38–45 AU on orbits with eccentricities above 0.85; like ordinary members of the [[Scattered_disc|scattered disc]], they were probably thrown outward by Neptune and still feel the giant planets. Detached ETNOs, or extreme detached disc objects, have perihelia from about 40–45 AU out to 50–60 AU and feel Neptune less. Beyond 50–60 AU lie the [[Sednoid|sednoids]], also called inner [[Oort_cloud|Oort cloud]] objects, which Neptune barely disturbs at all.[^sheppard2019] The explorer at the top of this page draws the population as a cloud of ILLUSTRATIVE points with semi-major axes from 150 to 1,000 AU and perihelia from 40 to 80 AU. Only three orbits in it are real: those of [[Sedna_(dwarf_planet)|Sedna]], 2012 VP113 and Leleākūhonua, taken from the JPL Small-Body Database.[^jpl-sbdb] ## Sednoids The sednoids are the ETNOs whose perihelia sit so far out that Neptune cannot have placed them there. Four are generally recognised: [[Sedna_(dwarf_planet)|Sedna]], 2012 VP113, 541132 Leleākūhonua and 2023 KQ14.[^chen2025] Sedna and 2012 VP113 both reach perihelion more than 70 AU from the [[Sun]], at 76.3 AU and 80.4 AU in barycentric elements, far enough to stay clear of strong kicks from [[Neptune]].[^horizons][^trujillo2014] Leleākūhonua's perihelion lies at about 65 AU, and 2023 KQ14's at about 66 AU.[^horizons][^chen2025] An orbit of that shape is a puzzle. A body scattered outward by Neptune keeps a perihelion near Neptune's distance, because each close pass changes the outer end of the orbit while the inner end stays where the encounter happened. Something else must have raised the sednoids' perihelia. Explanations proposed for Sedna since its discovery in 2003 include an encounter with a planet not yet found on a distant orbit (such as the proposed [[Planet_Nine]]), and a passage of another star, either a random field star or a sibling from the cluster in which the Sun formed.[^brown2004][^wall2011][^brown2010] Each scenario predicts a different spread of orbits among the wider population, which is why every new sednoid is valuable; the [[Sednoid]] article sets out those predictions. The explorer draws Sedna, 2012 VP113 and Leleākūhonua with their real orbits; 2023 KQ14, announced in 2025, is not among them.[^chen2025][^jpl-sbdb] Because the explorer's orbits are heliocentric osculating solutions from the Small-Body Database, their numbers differ somewhat from the barycentric values quoted here: the database solution puts Sedna's aphelion at about 1,010 AU, against roughly 890–940 AU in barycentric elements.[^jpl-sbdb][^horizons] ## Most distant objects from the Sun The largest known ETNO orbits reach thousands of astronomical units from the Sun. Of the objects in the barycentric list below, 2014 FE72 has the most extreme orbit: a perihelion of 36.1 AU, just beyond [[Neptune]], and an aphelion of about 4,050 AU.[^horizons][^carnegie2016] Those two numbers fix the rest of the orbit (derived): the semi-major axis is their mean, about 2,040 AU; the eccentricity is (4,050 − 36.1) / (4,050 + 36.1) ≈ 0.98; and [[Kepler's_laws_of_planetary_motion|Kepler's third law]], P = a^1.5 in years and astronomical units, gives a period of about 92,000 years. At such distances the pull of the Sun is weak enough that the [[Tide|tide]] of the [[Milky_Way]] and passing stars start to reshape the orbit.[^carnegie2016][^space2016] Leleākūhonua and 2019 EU5 both have aphelia of roughly 2,300–2,400 AU, and 2021 RR205, 2017 OF201, 2015 KG163 and 2013 SY99 all exceed 1,400 AU.[^horizons] None of these objects is anywhere near its far point today. Discovery depends on reflected sunlight, which fades with the fourth power of distance for a body seen from near the Sun, so almost every known ETNO was found near perihelion; in the list, current distances run from about 33 to 89 AU, while the aphelia run to thousands of AU.[^horizons] At the list's epoch, 2017 OF201, at about 88.5 AU, was the farthest of them from the Sun.[^horizons] Plotted as eccentricity against perihelion, the three groups defined by Sheppard and colleagues separate cleanly: the scattered ETNOs cluster at perihelia of 38–45 AU with the highest eccentricities, the detached ETNOs sit a little farther out, and the [[Sednoid|sednoids]] stand apart beyond 60 AU.[^sheppard2019] The explorer compresses this range with a logarithmic distance scale; an orbit reaching 4,000 AU cannot be drawn at true scale alongside Neptune's orbit at 30 AU in one frame, and the explorer says so if true scale is selected in this state. ## Notable discoveries Most known ETNOs were found in the 2010s by deep surveys looking for faint, slow-moving objects, several of them designed in part to test the [[Planet_Nine]] hypothesis. Their discoveries helped establish the apparent alignment of distant orbits that motivated that hypothesis, and the same surveys also turned up objects that do not fit it.[^batygin2016][^witze2016] ### Trujillo and Sheppard discoveries Chad Trujillo and Scott Sheppard, who announced 2012 VP113 in 2014, went on to report further ETNOs.[^trujillo2014] 2013 FT28 has a longitude of perihelion lined up with that of the proposed Planet Nine but an orbit well inside the planet's hypothetical path, where models suggest it would escape strong gravitational kicks. 2014 SR349 appears anti-aligned with the proposed planet.[^science2016] 2014 FE72, the object with the 4,000 AU aphelion, was announced in August 2016 as an orbit taken so far out that the galaxy shapes it as well as the Sun.[^carnegie2016][^space2016] ### Outer Solar System Origins Survey The Outer Solar System Origins Survey (OSSOS), run on the Canada–France–Hawaii Telescope, added several more ETNOs and quantified how strongly surveys are biased towards finding distant objects at particular orbital orientations.[^shankman2017] 2013 SY99, which lies unusually close to the plane of the planets with an inclination of about 4°,[^horizons] was presented by Michele Bannister in 2016, first in a SETI Institute talk in March and then at the October meeting of the American Astronomical Society's Division for Planetary Sciences.[^seti2016][^bannister2016] The survey's other finds include 2015 KG163, 2015 RX245 and 2015 GT50; the last of these is oriented at roughly a right angle to the proposed Planet Nine rather than aligned or anti-aligned with it.[^shankman2017][^bannister2018] Objects whose perihelia fall below about 36 AU undergo strong encounters with Neptune, so only orbits with more distant perihelia, those of the [[Detached_object|detached objects]] and sednoids, can keep a clean record of any outside perturber.[^batygin2016] ### TESS data search Malena Rice and Gregory Laughlin searched images from NASA's Transiting Exoplanet Survey Satellite (TESS), taken in its sectors 18 and 19, with a shift-stacking method that adds up many frames along trial paths so that a faint moving object builds up signal. The search recovered known objects such as [[Sedna_(dwarf_planet)|Sedna]] and produced 17 new candidates at distances of 80–200 AU from [[Earth]], all needing confirmation from the ground.[^rice2020] A follow-up campaign on the William Herschel Telescope failed to recover two of the candidates, which were either fainter than predicted or not real.[^dlfm2022tess][^ing2022] ## List The table gives selected ETNOs with perihelia beyond 30 AU and semi-major axes above 250 AU, the criteria used in the Planet Nine literature. Elements are barycentric (referred to the centre of mass of the Solar System, not the Sun) from JPL Horizons at epoch JD 2459600.5; the stability class is the one assigned by Batygin and colleagues in simulations that include a hypothetical [[Planet_Nine]].[^horizons][^mpc][^batygin2019] Semi-major axis and eccentricity follow from the perihelion and aphelion (derived) as described above. | Object | Perihelion (AU) | Semi-major axis (AU) | Aphelion (AU) | Inclination (°) | Stability with Planet Nine | |---|---|---|---|---|---| | Sedna | 76.3 | 485 | 893 | 11.9 | stable | | 2012 VP113 | 80.4 | 261 | 443 | 24.1 | stable | | Leleākūhonua | 64.8 | 1,193 | 2,322 | 11.7 | stable | | 474640 Alicanto | 47.3 | 327 | 608 | 25.6 | stable | | 2010 GB174 | 48.6 | 342 | 636 | 21.6 | stable | | 2007 TG422 | 35.6 | 502 | 969 | 18.6 | unstable | | 2013 SY99 | 50.0 | 733 | 1,420 | 4.2 | metastable | | 2014 FE72 | 36.1 | 2,040 | 4,050 | 20.6 | unstable | | 2015 BP519 | 35.2 | 433 | 831 | 54.1 | not assessed | | 2017 OF201 | 44.9 | 837 | 1,629 | 16.2 | not assessed | Trujillo and Sheppard's 2014 study, which first pointed out the clustering, used [[Sedna_(dwarf_planet)|Sedna]], 2012 VP113, Alicanto, 2007 TG422 and 2010 GB174 among its objects; Brown and Batygin added 2013 RF98 in 2016, and the others were announced later.[^trujillo2014][^batygin2016] The most unusual member is 2015 BP519, nicknamed Caju, which has the highest inclination in the list and the most distant nodes; de la Fuente Marcos and de la Fuente Marcos treat it as a probable outlier.[^becker2018][^dlfm2018caju] ## Notes Derived values are marked "(derived)" in the text: they follow from the listed perihelion q and aphelion Q through a = (q + Q)/2 and e = (Q − q)/(Q + q), and from Kepler's third law, P = a^1.5 with P in years and a in AU. The explorer's ETNO points are an ILLUSTRATIVE sample, not individual catalogued orbits. ## References [^sheppard2019]: Sheppard, S. S.; Trujillo, C. A.; Tholen, D. J.; Kaib, N. (2019). "A new high perihelion trans-Plutonian inner Oort cloud object: 2015 TG387". *The Astronomical Journal* 157: 139. https://doi.org/10.3847/1538-3881/ab0895 [^dlfm2018caju]: de la Fuente Marcos, C.; de la Fuente Marcos, R. (2018). "A fruit of a different kind: 2015 BP519 as an outlier among the extreme trans-Neptunian objects". *Research Notes of the AAS* 2: 167. https://doi.org/10.3847/2515-5172/aadfec [^dlfm2021]: de la Fuente Marcos, C.; de la Fuente Marcos, R. (2021). "Peculiar orbits and asymmetries in extreme trans-Neptunian space". *Monthly Notices of the Royal Astronomical Society* 506: 633–649. https://doi.org/10.1093/mnras/stab1756 [^dlfm2022]: de la Fuente Marcos, C.; de la Fuente Marcos, R. (2022). "Twisted extreme trans-Neptunian orbital parameter space: statistically significant asymmetries confirmed". *Monthly Notices of the Royal Astronomical Society: Letters* 512: L6–L10. https://doi.org/10.1093/mnrasl/slac012 [^jpl-sbdb]: JPL Small-Body Database (elements for 90377 Sedna, (2012 VP113), 541132 Leleākūhonua, fetched 2026-09-18). NASA Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html [^chen2025]: Chen, Y.-T.; Lykawka, P. S.; Huang, Y.; Kavelaars, J. J.; Fraser, W. C.; Bannister, M. T.; et al. (2025). "Discovery and dynamics of a Sedna-like object with a perihelion of 66 au". *Nature Astronomy* 9: 1309–1316. https://doi.org/10.1038/s41550-025-02595-7 [^horizons]: JPL Horizons On-Line Ephemeris System, barycentric osculating orbital elements at epoch JD 2459600.5. NASA Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/horizons/ [^trujillo2014]: Trujillo, C. A.; Sheppard, S. S. (2014). "A Sedna-like body with a perihelion of 80 astronomical units". *Nature* 507: 471–474. https://doi.org/10.1038/nature13156 [^brown2004]: Brown, M. E.; Trujillo, C.; Rabinowitz, D. (2004). "Discovery of a candidate inner Oort cloud planetoid". *The Astrophysical Journal* 617: 645–649. https://doi.org/10.1086/422095 [^wall2011]: Wall, M. (24 August 2011). "A conversation with Pluto's killer: Q & A with astronomer Mike Brown". *Space.com*. http://www.space.com/12711-pluto-killer-mike-brown-dwarf-planets-interview.html [^brown2010]: Brown, M. E. (28 October 2010). "There's something out there – part 2". *Mike Brown's Planets*. http://www.mikebrownsplanets.com/2010/10/theres-something-out-there-part-2.html [^carnegie2016]: Carnegie Institution for Science (29 August 2016). "Hunt for ninth planet reveals new extremely distant Solar System objects". https://carnegiescience.edu/news/hunt-ninth-planet-reveals-new-extremely-distant-solar-system-objects [^space2016]: *Space.com* (29 August 2016). "The search for Planet Nine: new finds boost case for distant world". http://www.space.com/33890-planet-nine-existence-evidence-grows.html [^batygin2016]: Batygin, K.; Brown, M. E. (2016). "Evidence for a distant giant planet in the Solar System". *The Astronomical Journal* 151: 22. https://doi.org/10.3847/0004-6256/151/2/22 [^witze2016]: Witze, A. (2016). "Evidence grows for giant planet on fringes of Solar System". *Nature* 529: 266–267. https://doi.org/10.1038/529266a [^science2016]: *Science* news (25 October 2016). "Objects beyond Neptune provide fresh evidence for Planet Nine". https://www.science.org/content/article/objects-beyond-neptune-provide-fresh-evidence-planet-nine [^shankman2017]: Shankman, C.; Kavelaars, J. J.; Bannister, M. T.; et al. (2017). "OSSOS. VI. Striking biases in the detection of large semimajor axis trans-Neptunian objects". *The Astronomical Journal* 154: 50. https://doi.org/10.3847/1538-3881/aa7aed [^seti2016]: SETI Institute (18 March 2016). "Exploring the outer Solar System: now in vivid colour – Michele Bannister (SETI Talks)". https://www.youtube.com/watch?v=_w9N6yABAW4 [^bannister2016]: Bannister, M. T.; et al. (2016). "A new high-perihelion a ~700 AU object in the distant Solar System". *AAS Division for Planetary Sciences Meeting* 48, id. 113.08. Bibcode 2016DPS....4811308B. [^bannister2018]: Bannister, M. T.; et al. (2018). "OSSOS. VII. 800+ trans-Neptunian objects — the complete data release". *The Astrophysical Journal Supplement Series* 236: 18. https://doi.org/10.3847/1538-4365/aab77a [^rice2020]: Rice, M.; Laughlin, G. (2020). "Exploring trans-Neptunian space with TESS: a targeted shift-stacking search for Planet Nine and distant TNOs in the galactic plane". *The Planetary Science Journal* 1: 81. https://doi.org/10.3847/PSJ/abc42c [^dlfm2022tess]: de la Fuente Marcos, C.; de la Fuente Marcos, R.; Vaduvescu, O.; Stanescu, M. (2022). "Distant trans-Neptunian object candidates from NASA's TESS mission scrutinized: fainter than predicted or false positives?". *Monthly Notices of the Royal Astronomical Society: Letters* 513: L78–L82. https://doi.org/10.1093/mnrasl/slac036 [^ing2022]: Isaac Newton Group of Telescopes (20 May 2022). "Distant trans-Neptunian object candidates: fainter than predicted or false positives?". https://www.ing.iac.es/PR/press/tess.html [^mpc]: Minor Planet Center. "List of objects with q > 30 AU and a > 250 AU". https://minorplanetcenter.net/db_search/show_by_properties?perihelion_distance_min=30&semimajor_axis_min=250 [^batygin2019]: Batygin, K.; Adams, F. C.; Brown, M. E.; Becker, J. C. (2019). "The planet nine hypothesis". *Physics Reports* 805: 1–53. https://doi.org/10.1016/j.physrep.2019.01.009 [^becker2018]: Becker, J. C.; et al. (2018). "Discovery and dynamical analysis of an extreme trans-Neptunian object with a high orbital inclination". *The Astronomical Journal* 156: 81. https://doi.org/10.3847/1538-3881/aad042 ## External links - Sheppard, S. S. "Known extreme outer Solar System objects". Carnegie Science, Earth and Planets Laboratory. https://sites.google.com/carnegiescience.edu/sheppard/home/discoveries - JPL Small-Body Database lookup. https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html - Minor Planet Center, orbit search by properties. https://minorplanetcenter.net/db_search ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Extreme_trans-Neptunian_object) : [Wikitube](https://en.wikitube.io/wiki/Extreme_trans-Neptunian_object) · pinned revision [1368577624](https://en.wikipedia.org/w/index.php?oldid=1368577624) · 2026-09-18 ## Previous hub tags Hubs: `Life_Physics`. Portals: [[PORTAL_Solar_System]]. --- *Solar System portal child articles, wave 1 · 2026-09-18 · drafted · row SOL-023 · explorer state `?obj=etno`.* <!-- hub_tags: Life_Physics · PORTAL_Solar_System -->