Messier 102
Galaxy
Messier 102 (also known as M102) is a galaxy listed in the Messier Catalogue that cannot be unambiguously identified. Its original discoverer Pierre Méchain retracted his discovery two years after publication and said that it was a duplicate observation of Messier 101. Later historical evidence favors that M102 is actually the galaxy NGC 5866, although other galaxies have been suggested as possible identities. The National Aeronautics and Space Administration (NASA) considers it to be the same as NGC 5866.
History
The Messier Catalogue was a list of astronomical objects compiled by Charles Messier between 1771 and 1781, in which he briefly described each object and provided their coordinates on the sky. Because Messier was only interested in finding comets, he created this list of non-comet objects that frustrated his hunt for them. Astronomer Pierre Méchain collaborated with Messier on the compilation of his list.
M102 was observed by Méchain in late March or early April 1781 and was added by Messier to the final version of his catalogue published in 1781. However, Messier did not include the coordinates of M102 on his catalogue, leading to confusion about the exact object they observed. His description of the object was the following:
Nébuleuse entre les étoiles Omicron du Bouvier & Iota du Dragon: elle est très-foible; près d'elle est une étoile de la sixième grandeur.
Begin with the source’s own compact description: “Messier 102” is galaxy. The dossier treats that line as a proposition to test through Messier and Galaxy, not as a finished interpretation.
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The phrase “galaxy” supplies a clear boundary for inquiry. It also exposes the unanswered questions: who defined that boundary, when it became stable and which sources sit outside it.
Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated May 15, 2026. The linked authority identifier is Q14374. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1771 and 1781.
Overview language is designed for orientation and should not be treated as a substitute for the evidence cited beneath it. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “Messier 102” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.