# Detached 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: under show, choose small bodies to leave the sampled distant orbits on their own, and drag to look down on the plane of the planets to see that none of them comes inside Neptune's orbit; then press l and find Sedna, the best-known detached object, and scroll out to follow its orbit towards 1,000 AU.* **Detached objects** are a dynamical class of [[Trans-Neptunian_object|trans-Neptunian objects]] whose perihelia lie far enough beyond [[Neptune]] that the known planets affect them only weakly; apart from the pull of the [[Sun]], they are in effect cut off from the rest of the planetary system.[^lykawka2008][^jewitt2006] Other trans-Neptunian populations, including the resonant objects such as [[Pluto]], the classical [[Kuiper_belt|Kuiper belt]] objects such as [[Makemake]] and the [[Scattered_disc|scattered disc]] objects such as [[Eris_(dwarf_planet)|Eris]], owe their present orbits in varying degrees to encounters with the giant planets, above all Neptune. Detached objects have larger perihelia than all of them.[^gladman2008] The same bodies appear in the literature as extended scattered disc objects, distant detached objects, and, in the Deep Ecliptic Survey's formal scheme, "scattered-extended" objects, names that reflect a gradual transition from the scattered disc rather than a sharp edge.[^gladman2002][^gomes2006][^elliot2005] At least nine had been securely identified by 2007, and many more candidates are now known; the largest and best known is [[Sedna_(dwarf_planet)|Sedna]].[^lykawka2007] Detached objects with very distant perihelia and large semi-major axes, like Sedna, are called [[Sednoid|sednoids]]; four were known in 2025.[^huang2024][^chen2025] The most distant detached orbits show a statistically significant asymmetry in their nodal distances, which some authors read as the signature of an unseen planet.[^dlfm2021][^dlfm2022] The explorer at the top of this page shows the far end of the class, the [[Extreme_trans-Neptunian_object|extreme trans-Neptunian objects]]: ILLUSTRATIVE points with semi-major axes of 150 to 1,000 AU and perihelia of 40 to 80 AU, plus the real orbits of three sednoids.[^jpl-sbdb] ## Orbits A detached object's perihelion lies well beyond Neptune's aphelion, about 30.3 [[Astronomical_unit|AU]], and its orbit is usually a long ellipse with a semi-major axis of up to several hundred AU.[^jpl-t1][^jewitt2006] Such orbits are hard to make. A body scattered by Neptune comes back, orbit after orbit, to the distance at which the encounter happened, so scattering alone produces perihelia near Neptune's orbit, not 10 or 40 AU beyond it. Proposed ways to lift the perihelia include a close passage of another star, a distant planet-sized body, an early phase in which Neptune's own orbit was more eccentric and reached farther out, and rogue planets that passed through the young Solar System before being ejected.[^morbidelli2004][^gomes2006][^gladman2002][^gladman2006][^huang2022] In the [[Planet_Nine]] hypothesis, several detached orbits are shaped by a large unseen planet between about 200 and 1,200 AU from the Sun, together with Neptune.[^batygin2016] The Deep Ecliptic Survey separates "scattered-near" objects, which Neptune can still scatter, from "scattered-extended" ones such as Sedna, using the Tisserand parameter with respect to Neptune, T = a_N/a + 2 cos i √((a/a_N)(1 − e²)), with the dividing line at T = 3.[^elliot2005] T is nearly conserved during encounters with Neptune, so it measures how strongly an orbit is coupled to the planet. For Sedna, with a = 506 AU, e = 0.85 and i = 11.9°, T ≈ 4.3; for 1996 TL66, a conventional scattered disc object with a = 84.7 AU, e = 0.59 and i = 24°, T ≈ 2.8 (both derived, with a_N = 30.07 AU).[^jpl-t1][^jpl-sbdb][^horizons] ## Classification Detached objects form one of four main dynamical classes of trans-Neptunian object, alongside the classical Kuiper belt objects, the resonant objects and the scattered disc objects; the [[Sednoid|sednoids]] are a subset of the detached class.[^gladman2008] A detached object generally has a perihelion beyond about 40 AU, which keeps it out of strong encounters with Neptune on its nearly circular orbit at 30 AU. Where exactly the scattered disc ends and the detached region begins can be computed from the point at which Neptune's resonances stop overlapping, since overlapping resonances are what let an orbit wander chaotically.[^batygin2021][^hadden2023] The category grew out of the discovery of Sedna in 2003 and of objects found around the same time, such as 2000 CR105 and 2004 XR190, which may be inner [[Oort_cloud|Oort cloud]] objects or, more likely, transitional bodies between the scattered disc and the inner cloud.[^jewitt2006] The Minor Planet Center lists Sedna as a scattered disc object, but its discoverer Michael Brown has argued that a perihelion of 76 AU puts it out of the outer planets' reach and makes it an inner Oort cloud object; more recent work treats it as detached.[^brown-sedna][^jewitt2009] On that view the extended, outer group begins somewhere between Sedna and ordinary scattered disc objects such as 1996 TL66, with its perihelion of 35 AU.[^buie2007] ### Influence of Neptune Neptune may still hold some detached objects in weak mean-motion resonances, but proving it is difficult. The orbits take more than 300 years, most have been followed for only a small fraction of that, and the objects move slowly against the stars, so it may take decades before their orbits are known well enough to confirm or rule out a resonance.[^emelyanenko2008] Emelʹyanenko and Kiseleva's simulations gave a 10% chance that 2000 CR105 is in the 20:1 resonance, 38% that 2003 QK91 is in the 10:3, and 84% that 2000 YW134 is in the 8:3, but under 1% that 2005 TB190 is in the 4:1.[^emelyanenko2008] [[Kepler's_laws_of_planetary_motion|Kepler's third law]] places each resonance: an object that completes p orbits while Neptune completes k lies at a = a_N (k/p)^(2/3), so the 8:3 resonance lies at 30.07 × (8/3)^(2/3) ≈ 57.8 AU, close to 2000 YW134's 58.3 AU, and the 4:1 at about 75.8 AU (derived).[^jpl-t1][^jpl-sbdb] ### Influence of hypothetical planet(s) beyond Neptune Michael Brown has noted that the known distant objects pulled even slightly away from the Kuiper belt, those with semi-major axes above 100 AU and perihelia above 42 AU, all appear clustered in the way a distant planet would produce.[^brown2016] Carlos and Raúl de la Fuente Marcos found statistically significant commensurabilities among the [[Extreme_trans-Neptunian_object|extreme trans-Neptunian objects]] consistent with Planet Nine, with several objects possibly trapped in 5:3 and 3:1 mean-motion resonances with a planet whose semi-major axis is about 700 AU.[^dlfm2014][^dlfm2016] ## Possible detached objects Catalogues of candidate detached objects usually take bodies with perihelia above 40 AU and semi-major axes above 47.7 AU, the location of Neptune's 1:2 resonance and the approximate outer edge of the classical Kuiper belt, and set aside the sednoids beyond the perihelion gap of about 50–75 AU.[^mpc-q40][^brown-dps] Many such bodies have poorly known orbits, and some listed as borderline may prove to be classical Kuiper belt objects or resonant objects.[^mpc-q40] | Object | Perihelion (AU) | Semi-major axis (AU) | Inclination (°) | Discovered | Note | |---|---|---|---|---|---| | 2000 CR105 | 44.2 | 229 | 22.7 | 2000 | possibly in 20:1 resonance | | 2000 YW134 | 41.2 | 58.3 | 19.8 | 2000 | probably in 8:3 resonance | | 2004 XR190 | 51.5 | 57.8 | 46.5 | 2004 | near-circular, highly inclined | | 474640 Alicanto | 47.4 | 342 | 25.5 | 2004 | extreme TNO | | 2010 GB174 | 48.5 | 360 | 21.5 | 2010 | extreme TNO | | 2013 SY99 | 49.9 | 813 | 4.2 | 2013 | extreme TNO, low inclination | | 2014 FZ71 | 55.9 | 75.9 | 25.4 | 2014 | near 1:4 resonance | | 2015 FJ345 | 50.5 | 62.8 | 35.1 | 2015 | near 1:3 resonance | Values are heliocentric osculating elements from the JPL Small-Body Database, rounded.[^jpl-sbdb] 2004 XR190 illustrates one route to detachment: its orbit is nearly circular yet steeply inclined, and models attribute its high perihelion to a Neptune mean-motion resonance acting with the Kozai effect, which trades eccentricity for inclination.[^allen2006][^sheppard2016] Sheppard and colleagues found the same mechanism likely for several of the moderate-eccentricity objects they discovered, among them 2014 FZ71 and 2015 FJ345.[^sheppard2016] ## See also - [[Classical_Kuiper_belt_object]] - [[Scattered_disc]] · [[Resonant_trans-Neptunian_object]] - [[Extreme_trans-Neptunian_object]] · [[Sednoid]] - [[Planet_Nine]] ## Notes Derived values are marked "(derived)". The Tisserand parameter uses Neptune's semi-major axis, 30.07 AU, from JPL Table 1. Resonance locations follow from Kepler's third law: for an object completing p orbits while Neptune completes k, a = a_N (k/p)^(2/3). ## References [^lykawka2008]: Lykawka, P. S.; Mukai, T. (2008). "An outer planet beyond Pluto and the origin of the trans-Neptunian belt architecture". *The Astronomical Journal* 135: 1161–1200. https://doi.org/10.1088/0004-6256/135/4/1161 [^jewitt2006]: Jewitt, D.; Delsanti, A. (2006). "The Solar System beyond the planets". In Blondel, P.; Mason, J. (eds.), *Solar System Update: Topical and Timely Reviews in Solar System Sciences*. Springer-Praxis. ISBN 3-540-26056-0. http://www.ifa.hawaii.edu/faculty/jewitt/papers/2006/DJ06.pdf [^gladman2008]: Gladman, B.; Marsden, B. G.; Vanlaerhoven, C. (2008). "Nomenclature in the outer Solar System". In Barucci, M. A.; et al. (eds.), *The Solar System Beyond Neptune*. University of Arizona Press, pp. 43–57. https://ui.adsabs.harvard.edu/abs/2008ssbn.book...43G [^gladman2002]: Gladman, B.; Holman, M.; Grav, T.; Kavelaars, J.; Nicholson, P.; Aksnes, K.; et al. (2002). "Evidence for an extended scattered disk". *Icarus* 157: 269–279. https://doi.org/10.1006/icar.2002.6860 [^gomes2006]: Gomes, R. S.; Matese, J. J.; Lissauer, J. J. (2006). "A distant planetary-mass solar companion may have produced distant detached objects". *Icarus* 184: 589–601. https://doi.org/10.1016/j.icarus.2006.05.026 [^elliot2005]: Elliot, J. L.; Kern, S. D.; Clancy, K. B.; Gulbis, A. A. S.; Millis, R. L.; Buie, M. W.; et al. (2005). "The Deep Ecliptic Survey: a search for Kuiper belt objects and Centaurs. II. Dynamical classification, the Kuiper belt plane, and the core population". *The Astronomical Journal* 129: 1117–1162. https://doi.org/10.1086/427395 [^lykawka2007]: Lykawka, P. S.; Mukai, T. (2007). "Dynamical classification of trans-Neptunian objects: probing their origin, evolution, and interrelation". *Icarus* 189: 213–232. https://doi.org/10.1016/j.icarus.2007.01.001 [^huang2024]: Huang, Y.; Gladman, B. (2024). "Primordial orbital alignment of sednoids". *The Astrophysical Journal Letters* 962: L33. https://doi.org/10.3847/2041-8213/ad2686 [^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 [^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 (osculating elements fetched 2026-09-18). NASA Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html [^jpl-t1]: JPL Solar System Dynamics. "Approximate positions of the planets", Table 1. https://ssd.jpl.nasa.gov/planets/approx_pos.html [^morbidelli2004]: Morbidelli, A.; Levison, H. F. (2004). "Scenarios for the origin of the orbits of the trans-Neptunian objects 2000 CR105 and 2003 VB12 (Sedna)". *The Astronomical Journal* 128: 2564–2576. https://doi.org/10.1086/424617 [^gladman2006]: Gladman, B.; Chan, C. (2006). "Production of the extended scattered disk by rogue planets". *The Astrophysical Journal* 643: L135–L138. https://doi.org/10.1086/505214 [^huang2022]: Huang, Y.; Gladman, B.; Beaudoin, M.; Zhang, K. (2022). "A rogue planet helps to populate the distant Kuiper belt". *The Astrophysical Journal Letters* 938: L23. https://doi.org/10.3847/2041-8213/ac9480 [^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 [^horizons]: JPL Horizons On-Line Ephemeris System, barycentric osculating orbital elements for 90377 Sedna at epoch 2026-09-18 (retrieved 2026-09-18). NASA Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/horizons/ [^batygin2021]: Batygin, K.; Mardling, R. A.; Nesvorný, D. (2021). "The stability boundary of the distant scattered disk". *The Astrophysical Journal* 920: 148. https://doi.org/10.3847/1538-4357/ac19a4 [^hadden2023]: Hadden, S.; Tremaine, S. (2023). "Scattered disc dynamics: the mapping approach". *Monthly Notices of the Royal Astronomical Society* 527: 3054–3075. https://doi.org/10.1093/mnras/stad3478 [^brown-sedna]: Brown, M. E. "Sedna (the coldest most distant place known in the Solar System; possibly the first object in the long-hypothesized Oort cloud)". California Institute of Technology. http://www.gps.caltech.edu/~mbrown/sedna/ [^jewitt2009]: Jewitt, D.; Moro-Martín, A.; Lacerda, P. (2009). "The Kuiper belt and other debris disks". In Thronson, H. A.; et al. (eds.), *Astrophysics in the Next Decade*. Springer. http://www.ifa.hawaii.edu/faculty/jewitt/papers/2008/JML08.pdf [^buie2007]: Buie, M. W. (28 December 2007). "Orbit fit and astrometric record for 15874". Southwest Research Institute. http://www.boulder.swri.edu/~buie/kbo/astrom/15874.html [^emelyanenko2008]: Emelʹyanenko, V. V.; Kiseleva, E. L. (2008). "Resonant motion of trans-Neptunian objects in high-eccentricity orbits". *Astronomy Letters* 34: 271–279. https://doi.org/10.1134/S1063773708040075 [^brown2016]: Brown, M. E. (February 2016). "Why I believe in Planet Nine". *The Search for Planet Nine*. http://www.findplanetnine.com/2016/02/why-i-believe-in-planet-nine.html [^dlfm2014]: de la Fuente Marcos, C.; de la Fuente Marcos, R. (2014). "Extreme trans-Neptunian objects and the Kozai mechanism: signalling the presence of trans-Plutonian planets". *Monthly Notices of the Royal Astronomical Society: Letters* 443: L59–L63. https://doi.org/10.1093/mnrasl/slu084 [^dlfm2016]: de la Fuente Marcos, C.; de la Fuente Marcos, R. (2016). "Commensurabilities between ETNOs: a Monte Carlo survey". *Monthly Notices of the Royal Astronomical Society: Letters* 460: L64–L68. https://doi.org/10.1093/mnrasl/slw077 [^mpc-q40]: Minor Planet Center. "List of objects with q > 40 AU and a > 47.7 AU". http://minorplanetcenter.net/db_search/show_by_properties?perihelion_distance_min=40&semimajor_axis_min=47.7 [^brown-dps]: Brown, M. E. "How many dwarf planets are there in the outer Solar System?". California Institute of Technology. http://www.gps.caltech.edu/~mbrown/dps.html [^allen2006]: Allen, R. L.; Gladman, B.; Kavelaars, J. J.; Petit, J.-M.; Parker, J. W.; Nicholson, P. (2006). "Discovery of a low-eccentricity, high-inclination Kuiper belt object at 58 AU". *The Astrophysical Journal* 640: L83–L86. https://doi.org/10.1086/503098 [^sheppard2016]: Sheppard, S. S.; Trujillo, C.; Tholen, D. J. (2016). "Beyond the Kuiper belt edge: new high perihelion trans-Neptunian objects with moderate semimajor axes and eccentricities". *The Astrophysical Journal Letters* 825: L13. https://doi.org/10.3847/2041-8205/825/1/L13 ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Detached_object) : [Wikitube](https://en.wikitube.io/wiki/Detached_object) · pinned revision [1362623012](https://en.wikipedia.org/w/index.php?oldid=1362623012) · 2026-09-18 ## Previous hub tags Hubs: `Life_Physics`. 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