Editing Kuiper belt (section)

=== Classical belt ===
{{Main|Classical Kuiper belt object}}
Between the 2:3 and 1:2 resonances with Neptune, at approximately 42–48&nbsp;AU, the gravitational interactions with Neptune occur over an extended timescale, and objects can exist with their orbits essentially unaltered. This region is known as the [[Classical Kuiper belt object|classical Kuiper belt]], and its members comprise roughly two thirds of KBOs observed to date.<ref>{{cite web |last1=Lunine |first1=Jonathan I. |date=2003 |title=The Kuiper Belt |url=http://www.gsmt.noao.edu/gsmt_swg/SWG_Apr03/The_Kuiper_Belt.pdf |access-date=23 June 2007 |archive-date=9 August 2007 |archive-url=https://web.archive.org/web/20070809103013/http://www.gsmt.noao.edu/gsmt_swg/SWG_Apr03/The_Kuiper_Belt.pdf |url-status=dead }}</ref><ref>
{{cite web |last1=Jewitt |first1=D. |date=February 2000 |title=Classical Kuiper Belt Objects (CKBOs) |url=http://www2.ess.ucla.edu/~jewitt/kb/kb-classical.html |access-date=23 June 2007 |archive-url=https://web.archive.org/web/20070609094740/http://www.ifa.hawaii.edu/~jewitt/kb/kb-classical.html |archive-date=9 June 2007}}</ref> Because the first modern KBO discovered ([[15760 Albion|Albion]], but long called (15760) 1992 QB<sub>1</sub>), is considered the prototype of this group, classical KBOs are often referred to as [[cubewanos]] ("Q-B-1-os").<ref>{{cite book |last1=Murdin |first1=P. |title=The Encyclopedia of Astronomy and Astrophysics |date=2000 |isbn=978-0-333-75088-9 |doi=10.1888/0333750888/5403 |bibcode=2000eaa..bookE5403. |article=Cubewano}}</ref><ref>{{cite journal |last1=Elliot |first1=J. L. |display-authors=etal |date=2005 |title=The Deep Ecliptic Survey: A Search for Kuiper Belt Objects and Centaurs. II. Dynamical Classification, the Kuiper Belt Plane, and the Core Population |url=http://occult.mit.edu/_assets/documents/publications/Elliot2005AJ129.1117.pdf |journal=[[The Astronomical Journal]] |volume=129 |issue=2 |pages=1117–1162 |bibcode=2005AJ....129.1117E |doi=10.1086/427395 |doi-access=free |access-date=18 August 2012 |archive-date=21 July 2013 |archive-url=https://web.archive.org/web/20130721180750/http://occult.mit.edu/_assets/documents/publications/Elliot2005AJ129.1117.pdf |url-status=live }}</ref> The [[Committee on Small Body Nomenclature|guidelines]] established by the [[IAU]] demand that classical KBOs be given names of mythological beings associated with creation.<ref name="clas">{{cite web |title=Naming of Astronomical Objects: Minor Planets |url=http://www.iau.org/public_press/themes/naming/#minorplanets |publisher=[[International Astronomical Union]] |access-date=17 November 2008 |archive-date=16 December 2008 |archive-url=https://web.archive.org/web/20081216024716/http://www.iau.org/public_press/themes/naming/#minorplanets |url-status=live }}</ref>

The classical Kuiper belt appears to be a composite of two separate populations. The first, known as the "dynamically cold" population, has orbits much like the planets; nearly circular, with an [[orbital eccentricity]] of less than 0.1, and with relatively low inclinations up to about 10° (they lie close to the plane of the Solar System rather than at an angle). The cold population also contains a concentration of objects, referred to as the kernel, with semi-major axes at 44–44.5 AU.<ref name="Petit 2011">{{cite journal |last1=Petit |first1=J.-M. |last2=Gladman |first2=B. |last3=Kavelaars |first3=J.J. |last4=Jones |first4=R.L. |last5=Parker |first5=J. |title=Reality and origin of the Kernel of the classical Kuiper Belt |journal=EPSC-DPS Joint Meeting |date=2011 |issue=2–7 October 2011 |url=http://meetingorganizer.copernicus.org/EPSC-DPS2011/EPSC-DPS2011-722.pdf |access-date=4 May 2016 |archive-date=4 March 2016 |archive-url=https://web.archive.org/web/20160304194450/http://meetingorganizer.copernicus.org/EPSC-DPS2011/EPSC-DPS2011-722.pdf |url-status=live }}</ref> The second, the "dynamically hot" population, has orbits much more inclined to the ecliptic, by up to 30°. The two populations have been named this way not because of any major difference in temperature, but from analogy to particles in a gas, which increase their relative velocity as they become heated up.<ref name="Levison2003">{{cite journal |last1=Levison |first1=Harold F. |last2=Morbidelli |first2=Alessandro |date=2003 |title=The formation of the Kuiper belt by the outward transport of bodies during Neptune's migration |journal=[[Nature (journal)|Nature]] |volume=426 |issue=6965 |pages=419–421 |doi=10.1038/nature02120 |pmid=14647375 |bibcode=2003Natur.426..419L|s2cid=4395099 }}</ref> Not only are the two populations in different orbits, the cold population also differs in color and [[albedo]], being redder and brighter, has a larger fraction of binary objects,<ref name="Stephen_Noll_2006">{{cite journal |last1=Stephens |first1=Denise C. |last2=Noll |first2=Keith S. |title=Detection of Six Trans-Neptunian Binaries with NICMOS: A High Fraction of Binaries in the Cold Classical Disk |journal=The Astronomical Journal |date=2006 |volume=130 |issue=2 |pages=1142–1148 |doi=10.1086/498715 |arxiv=astro-ph/0510130 |bibcode=2006AJ....131.1142S|s2cid=204935715 }}</ref> has a different size distribution,<ref name="Fraser_etal_2014"/> and lacks very large objects.<ref name="Levison_Stern_2001">{{cite journal |last1=Levison |first1=Harold F. |last2=Stern |first2=S. Alan |title=On the Size Dependence of the Inclination Distribution of the Main Kuiper Belt |journal=The Astronomical Journal |date=2001 |volume=121 |issue=3 |pages=1730–1735 |doi=10.1086/319420 |arxiv=astro-ph/0011325 |bibcode=2001AJ....121.1730L|s2cid=14671420 }}</ref> The mass of the dynamically cold population is roughly 30 times less than the mass of the hot.<ref name="Fraser_etal_2014"/> The difference in colors may be a reflection of different compositions, which suggests they formed in different regions. The hot population is proposed to have formed near Neptune's original orbit and to have been scattered out during the [[planetary migration|migration]] of the giant planets.<ref name=beyond/><ref name="Morbidelli2005">{{cite arXiv
 |last1=Morbidelli |first1=Alessandro
 |date=2005
 |title=Origin and Dynamical Evolution of Comets and their Reservoirs
 |eprint=astro-ph/0512256
}}</ref> The cold population, on the other hand, has been proposed to have formed more or less in its current position because the loose binaries would be unlikely to survive encounters with Neptune.<ref name="Parker_etal_2011a"/> Although the Nice model appears to be able to at least partially explain a compositional difference, it has also been suggested the color difference may reflect differences in surface evolution.<ref name="Levison2008"/>