Phi Puma was a star. Sometime before 2165, Phi Puma had supernovaed. This event created a concussion ring that eventually reached Bayard's Planet.

On several occasions in 2364, viewscreen readouts aboard the USS Enterprise-D showed the location of Phi Puma's nova, in the form of star charts from the Enterprise library computer. (TNG: "The Naked Now", "The Last Outpost", "Datalore", "Conspiracy")

Star Chart 1