Sigma Octanus system

Sigma Octanus is a system of planets in FLEETCOM Sector Three with over 3 million people on Sigma Octanus IV. The Keyes Loop and The Battle of Sigma Octanus IV occurred here in 2552. Master Chief also found a strange Forerunner artifact in Côte d'Azur's museum on Sigma Octanus IV while the Covenant tried to retrieve it.

There is in fact no star with the designation Sigma Octanus. However, there is an actual star named Sigma Octantis, a slight spelling change, located 270 lightyears from Sol, which is the most southern of all visible stars in the sky.