M40

M40, A Case of mistaken identity, Winnecke 4 (also known as Messier 40 or WNC 4) is an optical double star consisting of two unrelated stars in a northerly zone of the sky, Ursa Major.

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The pair were discovered by Charles Messier in 1764 while he was searching for a nebula that had been reported in the area by Johannes Hevelius. Not seeing any nebulae, Messier catalogued this apparent pair instead. The pair were rediscovered by Friedrich August Theodor Winnecke in 1863, and included in the Winnecke Catalogue of Double Stars as number 4. Burnham calls M40 “one of the few real mistakes in the Messier catalog,” faulting Messier for including it when all he saw was a double star, not a nebula of any sort.

li-176, I recorded observing this double star on May 4 1991 using the C14 at the Wilson Coulee Observatory
Personal Notes

Keywords:M40, Winnecke 4, Messier, Ursa Major, double star