The Eirhess System is located in the Teneebia Sector. The Teneebia Sector is a sector in the Beta Quadrant that can be found in the Alpha Centauri Sector Block.
A sector block is a grouping of three or four sectors. To navigate to a sector block, the player may choose from several neighboring blocks on the map screen, under "Systems List". Sector blocks appear as solid white dots.
A sector is a unit of spatial measurement, and is a subdivision of a quadrant in the galaxy. Each sector contains several systems and is navigable via sector space, which is like an overview map. Once the player approaches a star system, he or she may enter that system.
The Milky Way Galaxy in Star Trek Online is divided into quadrants, which consist of sector blocks, containing several sectors, and usually numerous star systems.
Local space consists of the sector blocks in the Alpha and Beta Quadrants near the Sol System. In general, four quadrants (Alpha, Beta, Gamma and Delta) make up the Galaxy but not yet in STO.