Globular Cluster M54
Globular Cluster M54 (also known as Messier Object 54, Messier 54, M54, or NGC 6715) is a globular cluster in the Sagittarius Dwarf Elliptical Galaxy (SagDEG). It was discovered by Charles Messier in 1778. Recently, it was discovered that the globular cluster was not part of the Milky Way, but actually part of SagDEG, making it the first extragalactic globular cluster ever discovered, even if it wasn't recognized as such for nearly two and a quarter centuries. Some speculate that M54 is the core of SagDEG.
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