Mass relays consist of two fifteen-kilometer (or nine-mile) long curved metal arms surrounding a set of revolving, gyroscopic rings five-kilometers across. These rings contain a massive, blue-glowing core of element zero. The relays are made of an unknown but incredibly resilient material, the same material that the Citadel is built from, and are protected by a quantum shield that renders them nearly impervious to damage by locking their structure in place at the subatomic level. They are even capable of surviving a supernova's wake without being damaged. They are "cold" objects that don't emit heat or radiation, unlike starships, making them difficult to find if their position changes. Some relays, like the Charon Relay, are "gravitationally anchored" to celestial bodies; others appear to