Difference Between Kuiper Belt and Oort Cloud

Kuiper Belt vs Oort Cloud

The outer regions of the solar system are littered with thousands of small icy bodies. They were hidden from the human vision until powerful enough telescopes were developed in the mid and late 20th century. The planet Pluto was the only body belonging to these clouds (specifically to Kuiper belt) that was discovered before 20th century.

Kuiper belt and the Oort cloud are two regions in space where these planetesimals can be found.

What is Kuiper Belt?

Kuiper belt is a region of the solar system extending beyond the orbit of Neptune, at 30AU to 50AU from the sun containing large chunks of ice. It mainly consists of frozen bodies containing water, methane, and ammonia. Those are similar to asteroid, but differ in composition where asteroid are made of rocky and metallic substances.

Since its discovery in 1992, over 1000 Kuiper belt objects (KBO) have been discovered. Largest three of these objects are Pluto, Haumea, and Makemake, which are known as dwarf planets. (Pluto was demoted from the planet state to dwarf planet by the IAU in 2006).

Three major regions of Kuiper belt exist. The region between 42AU -48AU from the sun is called the classic belt and the objects in this region are dynamically stable because the Neptune`s gravity affects them at a minimal level.

At the regions where there`s (Mean motion resonance) MMR of 3:2 and 1:2, there are a significant increase in the number of KBOs present. Pluto lies in the region with 3:2 resonance.

Comets, which had short periods (less than 200 years), seem to have come from this cloud.

What is Oort Cloud?

Oort cloud is a spherical shaped cloud surrounding the solar system, lying 50,000 AU from the center of the sun. The outer regions of the cloud reach the boundary of the solar system. It is considered to contain a large number of planetesimals, made of frozen water, methane and ammonia.

It is believed that there is also a disc shaped inner Oort cloud, which is termed as the Hills cloud. It is believed to be the remnants of the proto-planetary disc of the solar system pushed away by the gravitational effects of the larger plants like Jupiter and Saturn in the early stage of the solar system evolution. It also contains giant molecular clouds.

The long period comets are generated from this region in space, where icy bodies in the cloud is influenced by the gravity of the other stars. These comets have very large eccentric orbits and take thousands of years to complete one cycle.

What is the difference between Kuiper Belt and Oort Cloud?

• Kuiper belt is located around the solar system approximately in disc shape from 30AU to 50AU from the center of the sun.

• Oort cloud starts from 50,000 AU and extends all the way to the edge of the solar system. It is believed to have a spherical shell type of region and a disk type region with planetesimals.

• Comets with short periods originated from the Kuiper belt. (< 200yrs)

• Comets with long periods originated from the Oort cloud (periods vary from hundreds to thousands of years).

• The objects in the Kuiper belt are strongly affected by the large gravitational bodies in the solar system, specially the sun and the giant planets. Effect of the gravity of the giant planets on the Oort cloud is almost nonexistent, though they are affected by the gravity of the objects in the disc of the milky way because of the gravity of the sun reaches its effective limits at these regions.