We present a study of the central parts of the Sagittarius dwarf spheroidal galaxy (Sgr). We found a clear overdensity of Sgrs stars around M~54 (hereafter NS). NS is well represented by a King model and it has the characteristics of a typical dwarf elliptical nucleus. Whether this means that M~54 has spiraled into the potential well of NS or that M~54 is the real nucleus and NS has formed into its potential wells, remains an open question to be addressed.
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