Oort Cloud Facts

Another name for the Oort Cloud is the Öpik–Oort cloud, named after Dutch astronomer Jan Oort who, in 1950, proposed the existence of an outside area for the origination of comets and Estonian astronomer, Ernst Öpik, who theorized its existence.

What is the Oort cloud

The Oort cloud is a spherical cloud filled with icy objects that are 50,000 AU (Astronomical Units) or 7.5 km from the Sun.

To put this in perspective, this is almost ¼ of the distance to the nearest star, Proxima Centari.

The Oort cloud contains objects that are believed to be the remains of the early development of the sun and planets.

How did the Oort Cloud form

It was thought that these objects were originally part of the Kuiper belt but became scattered due to the gravitational pull of the gas giants.

The Oort cloud is so far out that it defines the cosmographical solar system boundary at the very edge of the Sun’s gravitational influence.

Objects in the Oort cloud are considered to be loosely bound to our solar system and are effected by the passing stars’ gravitational pull.

It must be noted that since there has been no close-up research on the Oort cloud, there are a lot of unsettled debates among astronomers.

One of the observations that they have had is that they have seen the orbits of such long-period comets as Halley’s Comet as a baseline for the idea that these may originate in the Oort cloud.

Other long-period objects such as Jupiter-family comets and “centaurs” are also thought to have Oort cloud origins.

The short-period comets are theorized as originating in areas outside of the Oort cloud called the scattered disc, although it is possible that some may have once been part of the Oort cloud.

Astronomers haven’t had the ability to observe the Oort cloud directly, so some of the ideas are theoretical. It is believed that the Oort cloud looks like a spherical ball with thick walls that are from 2,000-5,000 AU (0.03-0.08 light years).

How big is the Oort cloud

To say that the Oort cloud is “big” is an understatement. Using computer models, scientists estimate that there are several trillion objects larger than 1 km in diameter and another several billion that are of various sizes.

While we can see very distant galaxies with our telescopes, the closer and smaller objects in the Oort cloud still can’t be viewed.

The James Webb Space Telescope setting are still not enough because the objects in the Oort cloud are just too faint.

To have Oort cloud direct imaging we would have to have 100 billion times better telescopes.

Facts about the Oort Cloud

  • All objects that are outside of the Neptune orbit, including the Kuiper belt and Oort cloud objects are known as trans-Neptunian objects (TNO)
  • Scientists theorize that at one time, our Sun captured the material that is Oort cloud cometary from the outer discs of other stars that were forming in the Sun’s nebula.
  • There are two regions to the Oort cloud: the outer spherical Oort cloud and the inner disc-shaped cloud called the Hills cloud.
  • Water ice, methane, and ammonia are the elements that make up most of the Oort cloud objects.
  • Long-period comets are those with orbit paths that are over 200 years and are believed to have originated in the Oort cloud.
  • In 2003, the planetoid Sedna, also known as 90377, was discovered. It is thought to have originated in the inner Oort cloud. As of 2012, astronomers believe that Sedna is nearing three times the distance of the Neptune from the Sun.
  • Scientists can confirm the theory, but it’s thought that the Oort Clous contains around 2 trillion objects.


  • How many parts does the Oort Cloud have?
  • How many objects do scientists think are in the Oort Cloud?
    2 trillion
  • What are the three elements that make up most of the objects in the Oort Cloud?
    Water ice, methane, and ammonia
  • What type of comets do they believe originated in the Oort Cloud?
    long period
  • What is the theory of how scientists believe the Oort Cloud originated?
    remains of the early development of the sun and planets
  • What boundary does the Oort Clout define?
    cosmographical solar system boundary