AI overview
Messier 54 is a dense, spherical collection of hundreds of thousands of old stars held together by gravity. It's notable as one of the few globular clusters that orbits outside our Milky Way galaxy, making it valuable for studying how galaxies interact and how stars form in different cosmic environments.
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Messier 54 (also known as M54 or NGC 6715) is a globular cluster in the constellation Sagittarius. It was discovered by Charles Messier in 1778 and then included in his catalog of objects that could be mistaken for comets.
It is easily found in the sky, being close to the star ζ Sagittarii. It is, however, not resolvable into individual stars even with larger amateur telescopes.