Alpha Majoris was the primary of the Alpha Majoris system. The system included the planet Alpha Majoris I. (TOS: "Wolf in the Fold") This star was located in the Alpha Quadrant. Its location in the Milky Way Galaxy was depicted on a Federation star chart in 2293. (Star Trek VI: The Undiscovered Country)
The first planet of the system was home to an animal known as the Mellitus, a "cloud creature". In its normal state, it existed as a gas held together by a highly cohesive electromagnetic field. When the mellitus stopped, it became solid. These abilities were considered similar to those possessed by the Redjac entity. (TOS: "Wolf in the Fold")
"The Explored Galaxy"
"The Explored Galaxy" was a map of charted space in the Alpha Quadrant. Alpha Majoris 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 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".
Alpha Majoris (Dubbe, Alpha Ursae Majoris) was located in or near Federation space, in the Alpha Quadrant. This was a quadrinary star system. Alpha Majoris A was a K class star with a magnitude of +3, which was ten times brighter than Sol. Alpha Majoris B was a K class star. Alpha Majoris c was a F class star. Alpha Majoris D was an A class star. (page 47)