Sirius Sector

In the Galactic Atlas edition 817 (which does not include Gallian systems), the Sirius Sector - a Galaxy not too far away from the Milky Way - counts 124 systems, of which 56 are property of the various House governments (not counting Outcasts and Corsairs) and 67 which are not.

Human settlement

Shortly before losing the Great War (and the destruction of the Sol system),the Alliance launched five Sleeper Ships in a desperate attempt to escape a future under a communist Coalition regime. All of them bare the Hispania (which was sabotaged by the Coalition spies which should later form the Sirius Coalition Revolutionary Army) arrived intact in the Sirius system, granting humanity a new beginning in a foreign galaxy.

Geography

There are four main nebulas in the Sirius Sector: the Crow Nebula, Walker Nebula, The Barrier, and the Edge Nebula.