Editing Classical Kuiper belt object (section)

== Toward a formal definition ==
There is no official definition of 'cubewano' or 'classical KBO'. However, the terms are normally used to refer to objects free from significant perturbation from Neptune, thereby excluding KBOs in orbital resonance with Neptune ([[resonant trans-Neptunian object]]s). The [[Minor Planet Center]] (MPC) and the [[Deep Ecliptic Survey]] (DES) do not list cubewanos (classical objects) using the same criteria. Many TNOs classified as cubewanos by the MPC, such as dwarf planet [[Makemake]], are classified as ScatNear (possibly [[Perturbation (astronomy)|scattered]] by Neptune) by the DES. {{mpl|(119951) 2002 KX|14}} may be an inner cubewano near the [[plutino]]s. Furthermore, there is evidence that the Kuiper belt has an 'edge', in that an apparent lack of low-inclination objects beyond 47–49&nbsp;AU was suspected as early as 1998 and shown with more data in 2001.<ref name="Trujillo 2001">
{{cite journal |last1=Trujillo |first1=Chadwick A. |last2=Brown |first2=Michael E. |year=2001 |title=The Radial Distribution of the Kuiper Belt |url=http://www.gps.caltech.edu/~chad/publications/2001-trujillo-brown.pdf |journal=The Astrophysical Journal |volume=554 |issue=1 |pages=L95–L98 |bibcode=2001ApJ...554L..95T |doi=10.1086/320917 |s2cid=7982844 |url-status=dead |archive-url=https://web.archive.org/web/20060919003142/http://www.gps.caltech.edu/~chad/publications/2001-trujillo-brown.pdf |archive-date=2006-09-19 |df=dmy-all}}</ref> Consequently, the traditional usage of the terms is based on the orbit's semi-major axis, and includes objects situated between the 2:3 and 1:2 resonances, that is between 39.4 and 47.8 AU (with exclusion of these resonances and the minor ones in-between).<ref name="JewittDelsanti2006"/>

These definitions lack precision: in particular the boundary between the classical objects and the [[scattered disk]] remains blurred. {{Asof|2023}}, there are 870 objects with perihelion (q) > 40 AU and aphelion (Q) < 48 AU.<ref name="MPC_list"/>

=== DES classification ===
Introduced by the report from the [[Deep Ecliptic Survey]] by J. L. Elliott et al. in 2005 uses formal criteria based on the mean orbital parameters.<ref name="DES_Elliot2006" /> Put informally, the definition includes the objects that have never crossed the orbit of Neptune. According to this definition, an object qualifies as a classical KBO if:
* it is not [[Resonant trans-Neptunian object|resonant]]
* its average [[Tisserand's parameter]] with respect to Neptune exceeds 3
* its average eccentricity is less than 0.2.

=== SSBN07 classification ===
An alternative classification, introduced by [[Brett J. Gladman|B. Gladman]], [[Brian G. Marsden|B. Marsden]] and C. van Laerhoven in 2007, uses a 10-million-year orbit integration instead of the Tisserand's parameter. Classical objects are defined as not resonant and not being currently scattered by Neptune.<ref name="ArizonaBook_Gladman2007">
{{cite book |last1=Gladman |first1=B. J. |last2=Marsden |first2=B. |last3=van Laerhoven |first3=C. |year=2008 |chapter=Nomenclature in the Outer Solar System |title=The Solar System Beyond Neptune |chapter-url=http://www.lpi.usra.edu/books/ssbn2008/7002.pdf |archive-url=https://web.archive.org/web/20121102205338/http://www.lpi.usra.edu/books/ssbn2008/7002.pdf |archive-date=2012-11-02 |url-status=live |editor-last=Barucci |editor-first=M. A. |publisher=University of Arizona Press |location=Tucson |isbn=978-0-8165-2755-7 |display-editors=etal}}</ref>

Formally, this definition includes as ''classical'' all objects with their ''current'' orbits that
*are non-resonant (see the [[Resonant trans-Neptunian object#Classification methods|definition of the method]])
*have a semi-major axis greater than that of Neptune (30.1 AU; i.e. excluding centaurs) but less than 2000 AU (to exclude inner-Oort-cloud objects)
*are not being scattered by Neptune
*have their eccentricity <math>e < 0.240</math> (to exclude detached objects)
Unlike other schemes, this definition includes the objects with major semi-axis less than 39.4 AU (2:3 resonance)—termed '''''inner classical belt''''', or more than 48.7 (1:2 resonance) – termed '''''outer classical belt''''', and reserves the term '''''main classical belt''''' for the orbits between these two resonances.<ref name="ArizonaBook_Gladman2007" />