The Takarian homeworld was the second planet of its star system with a M-class atmosphere. This planet was the home to a humanoid, pre-industrial civilization at a Bronze Age level of technology, among them the inhabitants of Takar and the Ga'nah Province. (VOY: "False Profits")
While dialogue would seem to suggest that Takar was a city or region, StarTrek.com names the M-class world Takar II. 
The Star Trek Encyclopedia (4th ed., vol. 1, p. 290), in the entry for "Ga'nah", classified the planet as M-class.