Nova Atar III was a planet, a class M planet located somewhere in the space of the galaxy's Alpha or Beta Quadrants, the third planet in orbit of the Nova Atar star system.
History and specifics
By the 2260s decade, Accellus IX was a holding of the Federation, and was home to the Smithsonian Annex, a museum complex which presented artifacts from all over the Alpha and Beta Quadrants. (TOS video game: Judgment Rites)