Oort cloud

An Oort cloud is a spherical cloud primarily composed of icy objects left over from the creation of planets, typically found surrounding nearby stars. Oort clouds often contain methane, water, and ammonia. Many planetary systems have Oort clouds surrounding their edges, such as the Sol system. An Oort cloud was located in the same system as Thales.

Sol system
The Sol system is home to a large Oort cloud, located approximately 0.79 light-years away from the star. There are numerous asteroids, comets, and small planetoids located in the cloud. The Oort cloud was used by the Office of Naval Intelligence for covert operations and constructions. The was constructed within the Oort cloud, with construction beginning circa 2537. Only high-ranking officers were informed of Infinity ' s existence. Construction workers remained stationed in the Oort cloud for years to ensure project secrecy. Despite these precautions, in January 2553, the New Colonial Alliance discovered Infinity ' s location. The rebels, led by Ilsa Zane, reached the Oort cloud with a Darter dropship and infiltrated the ship disguised as construction workers. Eventually the rebels were eliminated and Zane was knocked into space. A prowler discovered her somewhere in the Oort cloud and took her aboard. Infinity first left the Oort cloud in March 2553, after a number of further upgrades to the ship from the Huragok, to aid Arbiter Thel 'Vadam at Sanghelios.

Epsilon Eridani system
The Epsilon Eridani system was the location of a massive Oort cloud. Located on the very outer edges of the system, the cloud largely consisted of ice. This Oort cloud was noted as being too large to search in even a hundred years. Within the Oort cloud, ONI discovered a planetoid with a Forerunner installation—designated "Site 17"—beneath its surface. Establishing Teller Station above the planetoid, ONI scientists spent years attempting to enter the Forerunner site. In the summer of 2552, with the beginning of the Fall of Reach, the facility's defences prepared to abandon the station to combat the invading Covenant after one final attempt at entering the submerged installation. However, the effort led to the activation of Forerunner systems within the site, exposing the site's location to the Covenant Fleet of Valiant Prudence. The scientists managed to recover an object from within Site 17 and prepared to leave the Oort cloud. While Supreme Commander Rho 'Barutamee ordered for parts of his fleet to recover the object and destroy the human researchers, Vice Admiral Michael Stanforth attempted to lure the Covenant forces into a trap at Reach. Following the Raid on Reach, the human-captured Ascendant Justice exited slipspace in the Oort cloud to hide from the Covenant and to plot their next moves. Cortana had chosen to enter the system at the Oort cloud because she knew the Covenant would not be able to find them inside of it.

Tau Ceti system
The Tau Ceti system has an Oort cloud surrounding its outer edges. During Operation: FIRST STRIKE, Vice Admiral Danforth Whitcomb and Lieutenant Elias Haverson exited slipspace within the system to the Oort cloud near Tau Ceti to gather intelligence from a distance and observe the battle.

23 Librae system
The Oort cloud at 23 Librae is located on the very edge of the planetary system. The Exodus Project was a plan formulated by the Rubble Security Council to transport the one million civilians of the Rubble into the Oort cloud within the system, in the event of the return of the Covenant. The Oort cloud had never been explored.

San'Shyuum home system
The home system of the San'Shyuum was once the location of a dense Oort cloud, found beyond the system's four gas giants. It consisted of icy dust, the remnants of ancient cometary material. Ancient San'Shyuum had used the Oort cloud as a way to fuel their early starships. Eventually, the Oort cloud became depleted and only a thick mist remained. Some time prior to his capture by Master Builder Faber during the Battle of Janjur Qom, the Didact used the remains of the Oort cloud to observe the system's inner planets without being detected.

List of appearances

 * Halo: First Strike
 * Halo: The Cole Protocol
 * Halo: Cryptum
 * Halo: Glasslands
 * Halo: The Thursday War
 * Halo: Initiation
 * Halo: Hunters in the Dark
 * Halo: Fleet Battles