Vega IX is the ninth planet orbiting the star Vega.
Vega IX was once home to the Vegan species, who ruled a large area of local space until at least the 20th century. (ST reference: The Worlds of the Federation) The planet was later colonized the Federation, as the site of the Vega colony, as well as by Delta III. TOS - Star Trek 2 novelization: Tomorrow is Yesterday)
Montgomery Scott visited the planet sometime during his long career, and disliked many things about it, including the food. Unfortunately for him, the food was very popular with the Kropaslin. (SCE eBook: The Future Begins)