Editing Solar System (section)

=== Extreme trans-Neptunian objects<span class="anchor" id="Detached objects"></span>===
{{Main|Extreme trans-Neptunian object}}
[[File:Distant object orbits + Planet Nine.png|thumb|upright=1.3|The current orbits of [[90377 Sedna|Sedna]], [[2012 VP113]], [[541132 Leleākūhonua|Leleākūhonua]] (pink), and other very [[ETNO|distant objects]] (red, brown and cyan) along with the predicted orbit of the hypothetical [[Planet Nine]] (dark blue)]]

Some objects in the Solar System have a very large orbit, and therefore are much less affected by the known giant planets than other minor planet populations. These bodies are called extreme trans-Neptunian objects, or ETNOs for short.<ref name="Sheppard-2018">{{cite journal |last1=Sheppard |first1=Scott S. |last2=Trujillo |first2=Chadwick A. |last3=Tholen |first3=David J. |last4=Kaib |first4=Nathan |year=2019 |title=A New High Perihelion Trans-Plutonian Inner Oort Cloud Object: 2015 TG387 |journal=The Astronomical Journal |volume=157 |issue=4 |page=139 |arxiv=1810.00013 |bibcode=2019AJ....157..139S |doi=10.3847/1538-3881/ab0895 |s2cid=119071596 |doi-access=free}}</ref> Generally, ETNOs' [[semi-major axis|semi-major axes]] are at least 150–250&nbsp;AU wide.<ref name="Sheppard-2018" /><ref name="Caju_outlier">{{cite journal |last1=de la Fuente Marcos |first1=Carlos |last2=de la Fuente Marcos |first2=Raúl |date=12 September 2018 |title=A Fruit of a Different Kind: 2015 BP<sub>519</sub> as an Outlier among the Extreme Trans-Neptunian Objects |journal=[[Research Notes of the AAS]] |volume=2 |issue=3 |pages=167 |arxiv=1809.02571 |bibcode=2018RNAAS...2..167D |doi=10.3847/2515-5172/aadfec |s2cid=119433944 |doi-access=free}}</ref> For example, [[541132 Leleākūhonua]] orbits the Sun once every ~32,000&nbsp;years, with a distance of 65–2000&nbsp;AU from the Sun.<ref name="jpldata2" group="D">{{cite web |title=JPL Small-Body Database Browser: (2015 TG387) |url=https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=3830896 |access-date=13 December 2018 |publisher=[[Jet Propulsion Laboratory]] |type=2018-10-17 last obs. |archive-date=14 April 2020 |archive-url=https://web.archive.org/web/20200414180200/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=3830896 |url-status=live }}</ref>

This population is divided into three subgroups by astronomers. The [[Scattered disc object|scattered]] ETNOs have [[perihelia]] around 38–45&nbsp;AU and an exceptionally high [[Orbital eccentricity|eccentricity]] of more than 0.85. As with the regular scattered disc objects, they were likely formed as result of [[Planetary migration#Gravitational scattering|gravitational scattering]] by Neptune and still interact with the giant planets. The [[Detached object|detached]] ETNOs, with perihelia approximately between 40–45 and 50–60&nbsp;AU, are less affected by Neptune than the scattered ETNOs, but are still relatively close to Neptune. The [[sednoid]]s or [[Hills Cloud|inner Oort cloud]] objects, with perihelia beyond 50–60&nbsp;AU, are too far from Neptune to be strongly influenced by it.<ref name="Sheppard-2018" />

Currently, there is one ETNO that is classified as a dwarf planet:
* {{Dp|Sedna}} (76.2–937&nbsp;AU) was the first extreme trans-Neptunian object to be discovered. It is a large, reddish object, and takes ~11,400&nbsp;years to complete one orbit. [[Michael E. Brown|Mike Brown]], who discovered the object in 2003, asserts that it cannot be part of the scattered disc or the Kuiper belt because its perihelion is too distant to have been affected by Neptune's migration.<ref>{{Cite web |last=Jewitt |first=David |date=2004 |title=Sedna – 2003 VB<sub>12</sub> |url=http://www2.ess.ucla.edu/~jewitt/kb/sedna.html |url-status=live |archive-url=https://web.archive.org/web/20110716032018/http://www2.ess.ucla.edu/~jewitt/kb/sedna.html |archive-date=16 July 2011 |access-date=23 June 2006 |website=University of Hawaii}}</ref> The [[Sednoid|sednoid population]] is named after Sedna.<ref name="Sheppard-2018" />