Cygnia Minor was an inhabited planet. This planet was near Planet Q and Benecia.
In 2266, an Earth colony on Cygnia Minor was facing famine. Doctor Thomas Leighton, a scientist living on a colony on the nearby Planet Q, sent a signal to the starship Enterprise, claiming to have discovered an extraordinary new synthetic food which would end the crisis on Cygnia Minor. It was soon discovered, however, that Leighton had lied about the discovery in order to lure the Enterprise to Planet Q to convince Captain Kirk that he had found Kodos the Executioner. (TOS: "The Conscience of the King")
The location of Benecia on "The Explored Galaxy" wall chart
"The Explored Galaxy" was a map of charted space in the Alpha Quadrant. Benecia 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".
According to the Star Trek: Star Charts ("United Federation of Planets I"), in 2378, Cygnia Minor was a Federation member. Humans founded colonies on M-class planets. Conjecturally, Cygnia Minor might be M-class. (TNG: "Justice")