Kuiper Belt: A Disk Of Dwarf Planets in Solar System

A Kuiper belt is a ring-shaped disk outside the orbit of Neptune at a distance of 30 to 50 AU from the Sun of the Milky Way.


Kuiper Belt Overview


It is one of the Solar System’s dwarf spheroidal disc and it’s 20 times more massive than the Asteroid belt between the orbits of Mars and Jupiter.

The belt is believed to be composed mainly of dwarf planets orbiting in resonance. The “regular” dwarf planet Pluto is part of the Kuiper belt.




The Kuiper belt is believed to be composed mainly of dwarf planets, though the exact composition is uncertain.

Though some speculation exists, there are no direct or indirect observations that can be used to verify or refute this.


Still, it is probable, based on the mass distribution and orbits of the objects, that the belt contains thousands of smaller objects.


The planet Neptune may also be a member of the Kuiper belt. The mass of the “regular” Kuiper belt is estimated to be on the order of and to be completely made up of dwarf planets.

These are all very far from the Sun and travel in almost the same plane as the Solar System.

They are relatively dark due to the low illumination from the Sun and most have strong orbits that are inclined about 20° with respect to the plane of the Solar System.

The object with the largest known orbit is Pluto, which takes 1.3 Earth years to complete one trip around the Sun.

Kuiper belts were first proposed by American astronomer Gerard Kuiper in the 1930s.


Objects in The Kuiper Belt


The population of objects that could have given rise to the formation of the Kuiper belt is called the “Kuiper–Schwassmann–Robertson–Walker (KSWR) population” after the astronomers who developed the theory in the early 1980s.


Since then, the existence of the disc has been confirmed many times, most notably in 2006 with the finding of the Oort Cloud within it.


About 150 objects have been found in the Kuiper belt that is at least, about one-sixth of the way out from the Sun.

All of these have aphelion distances greater than the Solar System’s orbit.

Since the mass of the objects in the Kuiper belt is so small, their average distance from the Sun is enormous.


Even if these objects were, on average, more massive than Earth, they would still travel much more slowly than the Solar System’s planets due to their low gravitational attraction.


If an object travels faster than the Solar System’s escape velocity, then its orbit will reach out to much greater distances than the Solar System.


Therefore, one very common sight in the Kuiper belt is an object so distant that it appears as a tiny point of light to an observer on Earth.


These objects have masses same or close to the mass of the dwarf p[lanet Pluto.

These objects have eccentric orbits that are very far from being circular.


The average distance from the Sun to a typical Kuiper belt object is estimated to be 50 to 60 AU, although this figure is disputed.


The density of objects in the Kuiper belt is very low because their low mass makes them rapidly disperse in the relatively dense and compact Kuiper belt region.

A typical object takes only 10 years to traverse the entire disc.

Most Kuiper belt objects have orbits that are almost identical to that of the Earth, which would make it one of the densest regions of the Solar System.

However, there is evidence that the Kuiper belt is actually quite dynamically variable. Some Kuiper belt objects have objects in the Kuiper belt at aphelion, and others in the Oort cloud at perihelion.


Studies of the longitude coordinates of bodies in the Oort cloud showed that most Oort cloud objects have eccentric orbits and orbital eccentricities that are different from those of the main belt.


Measurement of the orbital inclinations and inclinations of objects has been done for a few hundred objects in the belt, which gave rise to two classes of objects.


Asteroids with inclinations ranging from about 30° to 70° to 90° to 120° were classified as Very Long-Range Belt Objects (VLBOs).


Larger objects have a much larger range of inclinations, ranging from 70° to 90° to 180° to 225° to 300°. The orbits of these objects are highly inclined, sometimes as much as 90°. Most objects have very low inclinations of less than 20°.


These are termed Kuiper Belt Objects (KBOs). Together they are called the Neptune system. An object’s position in the Kuiper belt depends strongly on its longitude.


For example, a small body with a semi-major axis of 1,207 AU is still moving in a low inclination orbit on a nearly circular orbit about the Sun and has a declination of −67.0°.


Besides small bodies moving in near-circular orbits, an extreme case is an extreme outlier with a perihelion about, which is about 2,600 AU, 1,100 AU distant from the Sun.


Another example is a small object with a semi-major axis of 5,300 AU which has an inclination of, about the same as Mercury’s and which had an eccentricity of about 0.0284.


The first objects were discovered in the mid-1980s and the discovery of thousands of smaller objects has continued ever since, more than 10,000 known objects at the end of 2017.


Out of this number, 1061 had had perihelia between 30 and 70 AU, indicating that they were made of similar material as the small Kuiper belt objects and were migrated out from this belt.


As of December 2013, a dozen of these are among the 10,000 known. A fraction of these has very short orbital periods, less than a year.


In 2015, scientists discovered a large (two-kilometer or greater) object out to 700 AU, although the object was not declared a “planet” by the IAU

Updated: April 5, 2021 — 10:39 pm

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