Editing Classical Kuiper belt object (section)

== Cold and hot populations: physical characteristics ==
In addition to the distinct orbital characteristics, the two populations display different physical characteristics.

The difference in colour between the red cold population, such as [[486958 Arrokoth]], and more heterogeneous hot population was observed as early as in 2002.<ref name="Doressoundiram2002">
{{cite journal |author1=A. Doressoundiram |author2=N. Peixinho |author3=C. de Bergh |author4=S. Fornasier |author5=P. Thebault |author6=M. A. Barucci |author7=C. Veillet |title=The Color Distribution in the Edgeworth-Kuiper Belt |journal=The Astronomical Journal |date=October 2002 |arxiv=astro-ph/0206468 |bibcode=2002AJ....124.2279D |doi=10.1086/342447 |volume=124 |issue=4 |page=2279|s2cid=30565926 }}</ref>
Recent studies, based on a larger data set, indicate the cut-off inclination of 12° (instead of 5°) between the cold and hot populations and confirm the distinction between the homogenous red cold population and the bluish hot population.<ref name="LacerdaJewitt2008">
{{cite journal |first1=Nuno |last1=Peixinho |first2=Pedro |last2=Lacerda |first3=David |last3=Jewitt |author3-link=David Jewitt |title=Color-inclination relation of the classical Kuiper belt objects |journal=The Astronomical Journal |date=August 2008 |arxiv=0808.3025 |bibcode=2008AJ....136.1837P |doi=10.1088/0004-6256/136/5/1837 |volume=136 |issue=5 |pages=1837|s2cid=16473299 }}</ref>

Another difference between the low-inclination (cold) and high-inclination (hot) classical objects is the observed number of [[binary asteroid|binary objects]]. Binaries are quite common on low-inclination orbits and are typically similar-brightness systems. Binaries are less common on high-inclination orbits and their components typically differ in brightness. This correlation, together with the differences in colour, support further the suggestion that the currently observed classical objects belong to at least two different overlapping populations, with different physical properties and orbital history.<ref name="NollGrundy-binaries2008">
{{cite journal |author1=K. Noll |author2=W. Grundy |author3=D. Stephens |author4=H. Levison |author5=S. Kern |title=Evidence for two populations of classical transneptunian objects: The strong inclination dependence of classical binaries |journal=Icarus |date=April 2008 |arxiv=0711.1545 |bibcode=2008Icar..194..758N |doi=10.1016/j.icarus.2007.10.022 |volume=194 |issue=2 |pages=758|s2cid=336950 }}</ref>