Sahndara was the homeworld of the Platonians.
This inhabited planet orbited the star Sahndara. Before the star went supernova, a mass eugenics program was instituted by the society. The creation of this program was thirty-eight individuals who were bred for their self-reliance, contemplation, and longevity. These individuals escaped their world before its destruction. (TOS: "Plato's Stepchildren")
This planet was only mentioned in dialogue.