Phi Puma was a star. Prior to 2165, this star went supernova which formed a concussion ring with a diameter of least ninety light years. In 2165, this ring reached Bayard's Planet.
In 2364, the location of Phi Puma was labeled in a star chart depicting the concusssion ring expansion. This chart was stored in the USS Enterprise-D library computer. Later that year, the chart was scanned by Outpost 63. (TNG: "The Naked Now", production art; TNG: "The Last Outpost")
This star was only mentioned in writing.