The zones and quadrants ("quadrants" like there's not up to 26 of them now). Zones are the spiral arms of the galaxy and are lettered A to Q. Quadrants radiate out along each zone and are labelled B-Z as required. Stars are then numbered to identify solar system, planets and other objects of interest are numbered from the closest to the star outwards (for overlapping orbits, the orbit which reaches closest to the star takes precedence), and a category is then applied (eg M for moon, A for asteroid). The standard numbering system is Zone-Planet-Quadrant-Star-Category.