Sector 9 was a region of space in the Alpha Quadrant. This sector was within the Federation sphere of influence. The Altair system was located in this sector.
In 2267, Admiral Komack was the Starfleet Command flag officer in charge of Sector 9. (TOS: "Amok Time")
"The Explored Galaxy" was a map of charted space in the Alpha Quadrant. Altair was located between the Tholian Assembly and Romulus. Both locations were identified in DS9: "The Search, Part II", "Call to Arms" as being located in this quadrant. The chart, first seen chronologically in Star Trek VI: The Undiscovered Country, was also seen in several Star Trek: The Next Generation and Star Trek: Deep Space Nine episodes set in the 24th century, from the year 2364 to 2370. These were TNG: "Conspiracy", "The Measure Of A Man", "The Emissary", "The Mind's Eye", "The Game", and DS9: "In the Hands of the Prophets", "Cardassians".