Messier object

One of 110 non-stellar objects catalogued by Charles Messier in the late 18th century.

Messier was a comet hunter; the catalog was his list of fuzzy objects to ignore. It became astronomy's best-known deep-sky checklist: M31 (Andromeda), M42 (Orion Nebula), M45 (Pleiades), M13 (great Hercules cluster), and more.

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