Oort

Definition

The Oort Cloud is a hypothetical spherical shell of icy objects believed to surround the Sun at distances ranging from 2,000 to 100,000 astronomical units (AU). It is thought to be the source of long-period comets entering the inner solar system.

5 Must Know Facts For Your Next Test

1. The Oort Cloud was first proposed by Dutch astronomer Jan Oort in 1950.
2. It is divided into two regions: the inner Hills cloud and the outer Oort cloud.
3. The objects within the Oort Cloud are composed primarily of water ice, methane, and ammonia.
4. Long-period comets originating from the Oort Cloud have orbits that take them thousands of years to complete around the Sun.
5. The existence of the Oort Cloud has not been directly observed but is supported by mathematical models and observations of comet behavior.

Review Questions

• What is the primary composition of objects in the Oort Cloud?
• Who proposed the existence of the Oort Cloud?
• How does the distance range of the Oort Cloud compare to that of other parts of our solar system?

Related terms

Kuiper Belt: A region beyond Neptune's orbit containing many small icy bodies and dwarf planets.

Long-Period Comet: A comet with an orbital period greater than 200 years, often originating from the Oort Cloud.

Astronomical Unit (AU): A unit of measurement equal to approximately 93 million miles, or the average distance between Earth and the Sun.