The Sagittarius Arm (also known as the Carina-Sagittarius Arm) is a minor spiral arm of the Milky Way galaxy. It varies from approximately 2,000 to 4,000 light-years across. The Saggital Gulf divides the nearer part of the arm in two - the gulf is an area of low stellar density that occupies the majority of the Sagittal Gulf, Coreward Gulf and Tulaki Spur Sectors. The Sagittarius Arm in the Trailing Coreward Quadrant is primarily controlled by the Dominion, and contains Origin, the homeworld of the Tulaki species.
The Milky Way is a barred spiral galaxy, consisting of a central crossbar from which two major and several minor spiral arms radiate outwards. The Sagittarius Arm lies between two major spiral arms — the Centaurus Arm inside and the Perseus Arm outside. More locally, the Orion Arm lies between the Sagittarius Arm and the Perseus Arm. The Sagittarius Arm is one of the most pronounced arms in the galaxy as a large number of young stars, ionized gases and giant molecular clouds are concentrated in it.
The Sagittarius Arm was named by the pre-Fall Terrans for its proximity to the Sagittarius and Carina constellations as seen from Terra. The Sagittarius Arm is divided into two parts. Curving outward from the galaxy's central bar is the Sagittarius Arm (Sagittarius bar), which further outward becomes the Carina Arm.