# Detached object

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.
In this way, detached objects differ substantially from most other known TNOs, which form a loosely defined set of populations that have been perturbed to varying degrees onto their current orbit by gravitational encounters with the giant planets, predominantly Neptune. Detached objects have larger perihelia than these other TNO populations, including the objects in orbital resonance with Neptune, such as Pluto, the classical Kuiper belt objects in non-resonant orbits such as Makemake, and the scattered disk objects like Eris.
Detached objects have also been referred to in the scientific literature as extended scattered disc objects (E-SDO), distant detached objects (DDO), or scattered–extended, as in the formal classification by the Deep Ecliptic Survey. This reflects the dynamical gradation that can exist between the orbital parameters of the scattered disk and the detached population.
At least nine such bodies have been securely identified, of which the largest, most distant, and best known is Sedna. Those with large semi-major axes and high perihelion orbits similar to that of Sedna are termed sednoids. As of 2024, there are three known sednoids: Sedna, 2012 VP$_{113}$, and Leleākūhonua. These objects 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; asymmetries such as this one are sometimes attributed to perturbations induced by unseen planets.

## Orbits

Detached objects have perihelia much larger than Neptune's aphelion. They often have highly elliptical, very large orbits with semi-major axes of up to a few hundred astronomical units (AU, the radius of Earth's orbit). Such orbits cannot have been created by gravitational scattering by the giant planets, not even Neptune. Instead, a number of explanations have been put forward, including an encounter with a passing star or a distant planet-sized object, or Neptune migration (which may once have had a much more eccentric orbit, from which it could have tugged the objects to their current orbit) or ejected rogue planets (present in the early Solar System that were ejected).
The classification suggested by the Deep Ecliptic Survey team introduces a formal distinction between scattered-near objects (which could be scattered by Neptune) and scattered-extended objects (e.g. 90377 Sedna) using a Tisserand's parameter value of 3.
The Planet Nine hypothesis suggests that the orbits of several detached objects can be explained by the gravitational influence of a large, unobserved planet between 200 AU and 1200 AU from the Sun and/or the influence of Neptune.

## Classification

Detached objects are one of four distinct dynamical classes of TNO; the other three classes are classical Kuiper-belt objects, resonant objects, and scattered-disc objects (SDO). Sednoids also belong to detached objects. Detached objects generally have a perihelion distance greater than 40 AU, deterring strong interactions with Neptune, which has an approximately circular orbit about 30 AU from the Sun. The boundary between the scattered and detached regions can be defined using an analytical resonance overlap criterion.
The discovery of 90377 Sedna in 2003, together with a few other objects discovered around that time such as (148209) 2000 CR105 and (612911) 2004 XR190, has motivated discussion of a category of distant objects that may also be inner Oort cloud objects or (more likely) transitional objects between the scattered disc and the inner Oort cloud.
Although Sedna is officially considered a scattered-disc object by the MPC, its discoverer Michael E. Brown has suggested that because its perihelion distance of 76 AU is too distant to be affected by the gravitational attraction of the outer planets it should be considered an inner-Oort-cloud object rather than a member of the scattered disc. This classification of Sedna as a detached object is accepted in recent publications.
This line of thinking suggests that the lack of a significant gravitational interaction with the outer planets creates an extended–outer group starting somewhere between Sedna (perihelion 76 AU) and more conventional SDOs like 1996 TL$_{66}$ (perihelion 35 AU), which is listed as a scattered–near object by the Deep Ecliptic Survey.

### Influence of Neptune

One of the problems with defining this extended category is that weak resonances may exist and would be difficult to prove due to chaotic planetary perturbations and the current lack of knowledge of the orbits of these distant objects. They have orbital periods of more than 300 years and most have only been observed over a short observation arc of a couple years. Due to their great distance and slow movement against background stars, it may be decades before most of these distant orbits are determined well enough to confidently confirm or rule out a resonance. Further improvement in the orbit and potential resonance of these objects will help to understand the migration of the giant planets and the formation of the Solar System. For example, simulations by Emel'yanenko and Kiseleva in 2007 show that many distant objects could be in resonance with Neptune. They show a 10% likelihood that 2000 CR$_{105}$ is in a 20:1 resonance, a 38% likelihood that 2003 QK$_{91}$ is in a 10:3 resonance, and an 84% likelihood that (82075) 2000 YW134 is in an 8:3 resonance. The likely dwarf planet (145480) 2005 TB190 appears to have less than a 1% likelihood of being in a 4:1 resonance.

### Influence of hypothetical planet(s) beyond Neptune

Mike Brown—who made the Planet Nine hypothesis—makes an observation that "all of the known distant objects which are pulled even a little bit away from the Kuiper seem to be clustered under the influence of this hypothetical planet (specifically, objects with semimajor axis > 100 AU and perihelion > 42 AU)". Carlos de la Fuente Marcos and Ralph de la Fuente Marcos have calculated that some of the statistically significant commensurabilities are compatible with the Planet Nine hypothesis; in particular, a number of objects which are called extreme trans-Neptunian object (ETNOs) may be trapped in the 5:3 and 3:1 mean-motion resonances with a putative Planet Nine with a semimajor axis ~700 AU.

## Possible detached objects

This is a list of known objects by discovery date that could not be easily scattered by Neptune's current orbit and therefore are likely to be detached objects, but that lie inside the perihelion gap of ≈50–75 AU that defines the sednoids.
Objects listed below have a perihelion of more than 40 AU, and a semi-major axis of more than 47.7 AU (the 1:2 resonance with Neptune, and the approximate outer limit of the Kuiper Belt):
| Designation | Diameter (km) | H | q (AU) | a (AU) | Q (AU) | ω (°) | Discovery Year | Discoverer | Notes & Refs |
| 2000 CR$_{105}$ | 243 | 6.3 | 44.252 | 221.2 | 398 | 316.93 | 2000 | M. W. Buie | |
| 2000 YW$_{134}$ | 216 | 4.7 | 41.207 | 57.795 | 74.383 | 316.481 | 2000 | Spacewatch | ≈3:8 Neptune resonance |
| 2001 FL193 | 81 | 8.7 | 40.29 | 50.26 | 60.23 | 108.6 | 2001 | R. L. Allen, G. Bernstein, R. Malhotra | orbit extremely poor, might not be a TNO |
| 2001 KA77 | 634 | 5.0 | 43.41 | 47.74 | 52.07 | 120.3 | 2001 | M. W. Buie | borderline classical KBO |
| 2002 CP154 | 222 | 6.5 | 42 | 52 | 62 | 50 | 2002 | M. W. Buie | orbit fairly poor, but definitely a detached object |
| 2003 UY291 | 147 | 7.4 | 41.19 | 48.95 | 56.72 | 15.6 | 2003 | M. W. Buie | borderline classical KBO |
| Sedna | 995 | 1.5 | 76.072 | 483.3 | 890 | 311.61 | 2003 | M. E. Brown, C. A. Trujillo, D. L. Rabinowitz | Sednoid |
| 2004 PD112 | 267 | 6.1 | 40 | 70 | 90 | 40 | 2004 | M. W. Buie | orbit very poor, might not be a detached object |
| Alicanto | 222 | 6.5 | 47.308 | 315 | 584 | 326.925 | 2004 | Cerro Tololo (unspecified) | |
| 2004 XR190 | 612 | 4.1 | 51.085 | 57.336 | 63.586 | 284.93 | 2004 | R. L. Allen, B. J. Gladman, J. J. Kavelaars J.-M. Petit, J. W. Parker, P. Nicholson | very high inclination; Neptune Mean Motion Resonance (MMR) along with the Kozai Resonance (KR) modified the eccentricity and inclination of 2004 XR$_{190}$ to obtain a very high perihelion |
| 2005 CG81 | 267 | 6.1 | 41.03 | 54.10 | 67.18 | 57.12 | 2005 | CFEPS | — |
| 2005 EO$_{297}$ | 161 | 7.2 | 41.215 | 62.98 | 84.75 | 349.86 | 2005 | M. W. Buie | — |
| 2005 TB$_{190}$ | 372 | 4.5 | 46.197 | 75.546 | 104.896 | 171.023 | 2005 | A. C. Becker, A. W. Puckett, J. M. Kubica | Neptune Mean Motion Resonance (MMR) along with the Kozai Resonance (KR) modified the eccentricity and inclination to obtain a high perihelion |
| 2006 AO101 | 168 | 7.1 | — | — | — | — | 2006 | Mauna Kea (unspecified) | orbit extremely poor, might not be a TNO |
| 2007 JJ$_{43}$ | 558 | 4.5 | 40.383 | 48.390 | 56.397 | 6.536 | 2007 | Palomar (unspecified) | borderline classical KBO |
| 2007 LE38 | 176 | 7.0 | 41.798 | 54.56 | 67.32 | 53.96 | 2007 | Mauna Kea (unspecified) | — |
| 2008 ST291 | 640 | 4.2 | 42.27 | 99.3 | 156.4 | 324.37 | 2008 | M. E. Schwamb, M. E. Brown, D. L. Rabinowitz | ≈1:6 Neptune resonance |
| 2009 KX36 | 111 | 8.0 | — | 100 | 100 | — | 2009 | Mauna Kea (unspecified) | orbit extremely poor, might not be a TNO |
| 2010 DN$_{93}$ | 486 | 4.7 | 45.102 | 55.501 | 65.90 | 33.01 | 2010 | Pan-STARRS | ≈2:5 Neptune resonance; Neptune Mean Motion Resonance (MMR) along with the Kozai Resonance (KR) modified the eccentricity and inclination to obtain a high perihelion |
| 2010 ER65 | 404 | 5.0 | 40.035 | 99.71 | 159.39 | 324.19 | 2010 | D. L. Rabinowitz, S. W. Tourtellotte | — |
| 2010 GB174 | 222 | 6.5 | 48.8 | 360 | 670 | 347.7 | 2010 | Mauna Kea (unspecified) | — |
| 2012 FH84 | 161 | 7.2 | 42 | 56 | 70 | 10 | 2012 | Las Campanas (unspecified) | — |
| 2012 VP113 | 702 | 4.0 | 80.47 | 256 | 431 | 293.8 | 2012 | S. S. Sheppard, C. A. Trujillo | Sednoid |
| 2013 FQ28 | 280 | 6.0 | 45.9 | 63.1 | 80.3 | 230 | 2013 | S. S. Sheppard, C. A. Trujillo | ≈1:3 Neptune resonance; Neptune Mean Motion Resonance (MMR) along with the Kozai Resonance (KR) modified the eccentricity and inclination to obtain a high perihelion |
| 2013 FT28 | 202 | 6.7 | 43.5 | 310 | 580 | 40.3 | 2013 | S. S. Sheppard | — |
| 2013 GP$_{136}$ | 212 | 6.6 | 41.061 | 155.1 | 269.1 | 42.38 | 2013 | OSSOS | — |
| 2013 GQ136 | 222 | 6.5 | 40.79 | 49.06 | 57.33 | 155.3 | 2013 | OSSOS | borderline classical KBO |
| 2013 GG138 | 212 | 6.6 | 46.64 | 47.792 | 48.946 | 128 | 2013 | OSSOS | borderline classical KBO |
| 2013 JD$_{64}$ | 111 | 8.0 | 42.603 | 73.12 | 103.63 | 178.0 | 2013 | OSSOS | — |
| 2013 JJ$_{64}$ | 147 | 7.4 | 44.04 | 48.158 | 52.272 | 179.8 | 2013 | OSSOS | borderline classical KBO |
| 2013 SY99 | 202 | 6.7 | 50.02 | 694 | 1338 | 32.1 | 2013 | OSSOS | — |
| 2013 SK100 | 134 | 7.6 | 45.468 | 61.61 | 77.76 | 11.5 | 2013 | OSSOS | — |
| 2013 UT$_{15}$ | 255 | 6.3 | 43.89 | 195.7 | 348 | 252.33 | 2013 | OSSOS | — |
| 2013 UB17 | 176 | 7.0 | 44.49 | 62.31 | 80.13 | 308.93 | 2013 | OSSOS | — |
| 2013 VD24 | 128 | 7.8 | 40 | 50 | 70 | 197 | 2013 | Dark Energy Survey | orbit very poor, might not be a detached object |
| 2013 YJ151 | 336 | 5.4 | 40.866 | 72.35 | 103.83 | 141.83 | 2013 | Pan-STARRS | — |
| 2014 EZ51 | 770 | 3.7 | 40.70 | 52.49 | 64.28 | 329.84 | 2014 | Pan-STARRS | — |
| 2014 FC69 | 533 | 4.6 | 40.28 | 73.06 | 105.8 | 190.57 | 2014 | S. S. Sheppard, C. A. Trujillo | |
| 2014 FZ71 | 185 | 6.9 | 55.9 | 76.2 | 96.5 | 245 | 2014 | S. S. Sheppard, C. A. Trujillo | ≈1:4 Neptune resonance; Neptune Mean Motion Resonance (MMR) along with the Kozai Resonance (KR) modified the eccentricity and inclination to obtain a very high perihelion |
| 2014 FC72 | 509 | 4.5 | 51.670 | 76.329 | 100.99 | 32.85 | 2014 | Pan-STARRS | ≈1:4 Neptune resonance; Neptune Mean Motion Resonance (MMR) along with the Kozai Resonance (KR) modified the eccentricity and inclination to obtain a very high perihelion |
| 2014 JM80 | 352 | 5.5 | 46.00 | 63.00 | 80.01 | 96.1 | 2014 | Pan-STARRS | ≈1:3 Neptune resonance; Neptune Mean Motion Resonance (MMR) along with the Kozai Resonance (KR) modified the eccentricity and inclination to obtain a high perihelion |
| 2014 JS80 | 306 | 5.5 | 40.013 | 48.291 | 56.569 | 174.5 | 2014 | Pan-STARRS | borderline classical KBO |
| 2014 OJ394 | 423 | 5.0 | 40.80 | 52.97 | 65.14 | 271.60 | 2014 | Pan-STARRS | in 3:7 Neptune resonance |
| 2014 QR441 | 193 | 6.8 | 42.6 | 67.8 | 93.0 | 283 | 2014 | Dark Energy Survey | — |
| 2014 SR349 | 202 | 6.6 | 47.6 | 300 | 540 | 341.1 | 2014 | S. S. Sheppard, C. A. Trujillo | — |
| 2014 SS349 | 134 | 7.6 | 45 | 140 | 240 | 148 | 2014 | S. S. Sheppard, C. A. Trujillo | ≈2:10 Neptune resonance; Neptune Mean Motion Resonance (MMR) along with the Kozai Resonance (KR) modified the eccentricity and inclination to obtain a high perihelion |
| 2014 ST373 | 330 | 5.5 | 50.13 | 104.0 | 157.8 | 297.52 | 2014 | Dark Energy Survey | — |
| 2014 UT228 | 154 | 7.3 | 43.97 | 48.593 | 53.216 | 49.9 | 2014 | OSSOS | borderline classical KBO |
| 2014 UA230 | 222 | 6.5 | 42.27 | 55.05 | 67.84 | 132.8 | 2014 | OSSOS | — |
| 2014 UO231 | 97 | 8.3 | 42.25 | 55.11 | 67.98 | 234.56 | 2014 | OSSOS | — |
| 2014 WK509 | 584 | 4.0 | 40.08 | 50.79 | 61.50 | 135.4 | 2014 | Pan-STARRS | — |
| 2014 WB556 | 147 | 7.4 | 42.6 | 280 | 520 | 234 | 2014 | Dark Energy Survey | — |
| 2015 AL281 | 293 | 6.1 | 42 | 48 | 54 | 120 | 2015 | Pan-STARRS | borderline classical KBO orbit very poor, might not be a detached object |
| 2015 AM$_{281}$ | 486 | 4.8 | 41.380 | 55.372 | 69.364 | 157.72 | 2015 | Pan-STARRS | — |
| 2015 BE$_{519}$ | 352 | 5.5 | 44.82 | 47.866 | 50.909 | 293.2 | 2015 | Pan-STARRS | borderline classical KBO |
| 2015 FJ345 | 117 | 7.9 | 51 | 63.0 | 75.2 | 78 | 2015 | S. S. Sheppard, C. A. Trujillo | ≈1:3 Neptune resonance; Neptune Mean Motion Resonance (MMR) along with the Kozai Resonance (KR) modified the eccentricity and inclination to obtain a very high perihelion |
| 2015 GP50 | 222 | 6.5 | 40.4 | 55.2 | 70.0 | 130 | 2015 | S. S. Sheppard, C. A. Trujillo | — |
| 2015 KH162 | 671 | 3.9 | 41.63 | 62.29 | 82.95 | 296.805 | 2015 | S. S. Sheppard, D. J. Tholen, C. A. Trujillo | — |
| 2015 KG163 | 101 | 8.3 | 40.502 | 826 | 1610 | 32.06 | 2015 | OSSOS | — |
| 2015 KH163 | 117 | 7.9 | 40.06 | 157.2 | 274 | 230.29 | 2015 | OSSOS | ≈1:12 Neptune resonance |
| 2015 KE172 | 106 | 8.1 | 44.137 | 133.12 | 222.1 | 15.43 | 2015 | OSSOS | 1:9 Neptune resonance |
| 2015 KG172 | 280 | 6.0 | 42 | 55 | 69 | 35 | 2015 | R. L. Allen D. James D. Herrera | orbit fairly poor, might not be a detached object |
| 2015 KQ174 | 154 | 7.3 | 49.31 | 55.40 | 61.48 | 294.0 | 2015 | Mauna Kea (unspecified) | ≈2:5 Neptune resonance; Neptune Mean Motion Resonance (MMR) along with the Kozai Resonance (KR) modified the eccentricity and inclination to obtain a very high perihelion |
| 2015 RX245 | 255 | 6.2 | 45.5 | 410 | 780 | 65.3 | 2015 | OSSOS | — |
| Leleākūhonua | 300 | 5.5 | 65.02 | 1042 | 2019 | 118.0 | 2015 | S. S. Sheppard, C. A. Trujillo, D. J. Tholen | Sednoid |
| 2017 DP121 | 161 | 7.2 | 40.52 | 50.48 | 60.45 | 217.9 | 2017 | | — |
| 2017 FP161 | 168 | 7.1 | 40.88 | 47.99 | 55.1 | 218 | 2017 | | borderline classical KBO |
| 2017 SN132 | 97 | 5.8 | 40.949 | 79.868 | 118.786 | 148.769 | 2017 | S. S. Sheppard, C. A. Trujillo, D. J. Tholen | |
| 2018 VM35 | 134 | 7.6 | 45.289 | 240.575 | 435.861 | 302.008 | 2018 | Mauna Kea (unspecified) | |
The following objects can also be generally thought to be detached objects, although with slightly lower perihelion distances of 38–40 AU.
| Designation | Diameter (km) | H | q (AU) | a (AU) | Q (AU) | ω (°) | Discovery Year | Discoverer | Notes & Refs |
| 2003 HB$_{57}$ | 147 | 7.4 | 38.116 | 166.2 | 294 | 11.082 | 2003 | Mauna Kea (unspecified) | — |
| 2003 SS422 | 168 | 7.04 | 39.574 | 198.181 | 356.788 | 206.824 | 2003 | Cerro Tololo (unspecified) | — |
| 2005 RH52 | 128 | 7.8 | 38.957 | 152.6 | 266.3 | 32.285 | 2005 | CFEPS | — |
| 2007 TC434 | 168 | 7.0 | 39.577 | 128.41 | 217.23 | 351.010 | 2007 | Las Campanas (unspecified) | 1:9 Neptune resonance |
| 2012 FL84 | 212 | 6.6 | 38.607 | 106.25 | 173.89 | 141.866 | 2012 | Pan-STARRS | — |
| 2014 FL72 | 193 | 6.8 | 38.1 | 104 | 170 | 259.49 | 2014 | Cerro Tololo (unspecified) | — |
| 2014 JW80 | 352 | 5.5 | 38.161 | 142.62 | 247.1 | 131.61 | 2014 | Pan-STARRS | — |
| 2014 YK$_{50}$ | 293 | 5.6 | 38.972 | 120.52 | 202.1 | 169.31 | 2014 | Pan-STARRS | — |
| 2015 DM319 | | 8.78 | 39.491 | 272.302 | 505.113 | 43.227 | 2015 | OSSOS | |
| 2015 GT50 | 88 | 8.6 | 38.46 | 333 | 627 | 129.3 | 2015 | OSSOS | — |