The Denobula Triaxa system was a planetary system. This system consisted of at least one star and at least one planet. This planet, known as Denobula, was inhabited by a warp capable species, the Denobulans. (ENT: "Breaking the Ice")
According to the Star Trek: Star Charts (pg. 36, "United Federation of Planets"), the Denobula Triaxa system, also known by its Bayer designation as Iota Boötis, was located in or near Federation space, in the Alpha Quadrant. Denobula Triaxa A was a Class G star with a magnitude of +7, which was 1/10 the brightness of Sol. Denobula Triaxa B and C were Class G stars. In 2378, Denobula was a Federation member.
According to Startrek.com, this system had only one planet. [1]