A Weyr /ˈwɪər/ is a collection of dragons, their riders and support staff in Anne McCaffrey's fictional world of Pern. The function of a Weyr is to fight Thread, a spore that originates in the Oort cloud of the Rukbat solar system, carried by a planetoid referred to as the Red Star with a loose elliptical orbit. The time during which Thread falls is called a Pass. These Passes last about 50 years, usually with a break of 200 years between, although extended periods have been known to occur due to orbital mechanics.