A celestial array is a type of protoss navigation tool used for starships (or at least the Spear of Adun). It facilitates travel between different planets and star systems. When activated, it displays an image that covers the entire area its in, that also encompasses those accessing it. It is able to cover the entire Milky Way.
A celestial array is found on the bridge of the Spear of Adun in the campaign of Legacy of the Void. It functions similarly to the starmap of Wings of Liberty, acting as a hub through which a player can select planets to visit.