Britannica
Sources used in this answer
How did the giant planets help create the Oort cloud?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Small body
Asteroid Ida and its satellite, Dactyl, photographed by the Galileo spacecraft on August 28, 1993, from a distance of about 10,870 km (6,750 miles). Ida is about 56 km (35 miles) long and shows the irregular shape and impact craters characteristic of many asteroids. The Galileo image revealed that Ida is accompanied by a tiny companion about 1.5 km (1 mile) wide, the first proof that some asteroids have natural satellites.
The Oort cloud is believed to have been formed from icy planetesimals that originally accreted in the outer regions of the protoplanetary disk during the early history of the solar system.1
As the giant planets—Jupiter, Saturn, Uranus, and Neptune—formed, their immense gravitational influence played a critical role in shaping the distribution of these icy bodies. Specifically, billions of these icy planetesimals were gravitationally scattered by the formation of the giant planets, particularly Uranus and Neptune, and expelled from their original vicinity. These objects were flung to the outermost reaches of the solar system, where they settled into the vast, roughly spherical shell now known as the Oort cloud.123