![[solarSystem_sizes.svg|align:center|550]] ## Kuiper Belt The Kuiper Belt is a disk-shaped population of [[Smaller Non-Planetary Bodies#Comet|comet]] nuclei extending from Neptune's orbit $(R \sim 30 \; {\rm AU})$ to several thousand astronomical units from the Sun $(R \in \left[ 30, 1000 \right] \; {\rm AU})$. Though debated, the (highly populated) innermost part of the Kuiper Belt appears to have an outer edge at $R \sim 50 \; {\rm AU}$. > [!key-idea] **Important Characteristics:** > - Neptune and Kuiper Belt have a similar relationship as Jupiter and the [[Asteroid Belt]] > - Through [[Orbital Resonance|orbital resonance (mean-motion resonance)]]... > - the *Astroid:Jupiter* system develops the [[Asteroid Belt#Kirkwood Gaps]] > - the *Neptune:Kuiper Belt* develops the [[#Classical Kuiper Belt]] > - Prevents further planetary (or larger body) formation in the region > - Populated by [[Interstellar Medium#Ice|icy]] remnants ([[Smaller Non-Planetary Bodies#Comet|comet nuclei]]) that did not create larger [[Smaller Non-Planetary Bodies#planetesimals]] or full sized planets during the [[Standard Model of Planetary Formation|formation of the solar system]] due to major perturbations in their orbits caused Neptune. > - Provides the source of short period comets in the solar system ($P<200\,\pu{yr}$) > - First Kuiper Belt object (a [[Smaller Non-Planetary Bodies#Trans-Neptunian Object (TNO)]]) discovered by MIT professor+grad student (Jewitt+Luu?) ## Classical Kuiper Belt Very similar to the dust in the rings of Saturn or the [[Asteroid Belt#Kirkwood Gaps]] in the [[Asteroid Belt]], major gravitational perturbations from Neptune can create [[Orbital Resonance|orbital resonances]] in the Kuiper Belt. Given the size of the Kuiper Belt, many different regions have been categorized based on the properties of the Kuiper Belt Objects (KBOs) found there. ![[kuiperBelt_orbitalResonance.png|align:center|450]] The most notable regions include the *plutinos*, *cubewanos*, and the *twotinos*. The **Classical Kuiper Belt** consist of the *cubewano* region between the 2:3 and 1:2 Neptune resonances at approximately $a \sim 42–48 \; {\rm AU}$. In this region, the objects can remain in their orbits essentially unaltered. This allows $\sim 2/3$ of the KBOs observed to date are found in this region. ![[kuiperBelt_orbitalResonance_popCubwanos.png|align:center]] ## Hot & Cold Population There are two populations of the KBOs that appear in the Kuiper Belt: - Cold Population - make up the majority of the Kuiper Belt population - defined by lower inclinations (lt; 5 \degree$) and near-circular orbits, lying between $a \sim 42 - 47 \; {\rm AU}$. - redder and brighter - smaller KBOs (lower masses) - Formed closer to the current position of the Kuiper Belt - loose binaries would decompose due to encounters with Neptune? - Hot Population - Significantly smaller portion of the Kuiper Belt population - defined by higher inclinations (gt; 5 \degree$) and more eccentric orbits - larger KBOs (higher masses) - Formed near Neptune's original orbit before being scattered out during the [[Planetary Migration|planetary migration]] of the giant planets > [!note] > The terms 'hot' and 'cold' has nothing to do with surface or internal temperatures, but rather refer to the orbits of the objects, by analogy to molecules in a gas, which increase their relative velocity as they heat up.