It is part of the cluster, Carlos.
http://en.wikipedia.org/wiki/Messier_15
"M15 also contains Pease 1, the first planetary nebula discovered within a globular cluster[11] in 1928. Just three others have been found in globular clusters since then."
http://messier.seds.org/more/m015_h2.html
"The pinkish object to the upper left of the cluster's core is a gas cloud surrounding a dying star. Known as Kuestner 648, this was the first planetary nebula to be identified in a globular cluster. In 1928, F. G. Pease, working at the 100-inch telescope of California's Mount Wilson Observatory, photographed the spectrum of K 648 and discovered the telltale bright emission of a nebular gas cloud rather than a normal star. In the ensuing 70 years, only three more planetary nebulae have been discovered in globular clusters."
To identify and locate the PN inside mine, I used that photo. The PN is the bluish, lower left of the core of the cluster:
http://upload.wikimedia.org/wikipedi...ier_15_HST.jpg