Beta Niobe was a star and system, until it went supernova in 2269.
In the antimatter universe, its counterpart is a sun called Amphion. (TAS episode: "The Counter-Clock Incident")
The star was orbited by several planets, including Sarpeidon, which were destroyed when the star went nova. (TOS episode: "All Our Yesterdays", TOS novel: Yesterday's Son)
Radiation emitted by Beta Niobe, as well as the Minara supernova, threatened many nearby systems for years to follow, including Verzhik, which was particularly badly damaged in 2279. (TOS - Mere Anarchy eBook: The Darkness Drops Again)
One of the planets contained a Federation colony in the mid-23rd century. In 2259, Dmitri Valtane, the son of Larisa and Nikolai Valtane, was born there. (ST video game: Starship Creator)