There are two types of Line Officers in the United States Navy. Unrestricted Line Officers serve in the Navy’s warfare communities, such as Surface Warfare Special Operations, Special Warfare, and so forth, and are eligible for command at sea. Restricted Line Officers, on the other hand, are able to assume command of operations in their specialty at shore installation, but are not eligible to take command at sea. A few examples of the fields in which Restricted Line Officers serve are Aircraft Maintenance, Information Dominance, and Aeronautical Engineering.
All Line Officers wear a single star on the outer face of each sleeve, one-quarter of an inch above the uppermost stripe indicating their rank and centered between the front and rear creases of the sleeve. The star is five-pointed, and it is sewn onto the sleeve with a single ray pointing down. These rules are spelled out in Part 2, Section 1 of the fourth chapter of the United States Navy Uniform Regulations (NAVPERS 15665I).
Stars were not approved for wear on officers’ uniforms until January, 1864. Nine years later, the regulations were modified to specify that the star should be inverted, with a single ray pointing downward—a rule that has generated considerable curiosity ever since, especially since no explanation is given for the mandate. While many fringe theories abound ranging from bizarre occult symbolism to the supposed bankruptcy of the United States in 1873, the most commonly posited reason is the simplest and most likely the most accurate: It is inverted to make it easily distinguishable from the “upright” stars found on the sleeve devices worn by General and Flag officers.