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M40 is just a double star, one of the three Messier objects that are not nebulous (Nebulae, Galaxies or Star Clusters), being the other two M73 (asterism) and M24 (star patch of the Milky Way). It was discovered by Hevelius in 1660 (he described it as a nebula) and Messier found it and, despite not being nebulous, he included it in his catalogue. The object described by Hevelius should not be mistaken for NGC 4290, on the left hand side of this picture). This galaxy is faint and small enough to be out of Hevelius’s telescope reach. NGC 4290 is even smaller than the smallest Messier object, M57, and can therefore be excluded.
Additional Information
Object
Name(s): M40, Winnecke 4
Type: Double star
RA: 12h 22m 14.4s
Dec: +58º 05’ 10.6”
Constellation: Ursa Major
Size (arcmin): 1.7
Magnitude: +9.6
Distance: 500 ly
Image
Date: 2013-04-20
Location: Corbera de Llobregat, Barcelona, Catalonia
Size (arcmin): 14×10
Telescope: Celestron 11” HD f/10
Camera: FLI ML6303 (3072x2048pix)
Guiding: Orion SSAG/Nikkor 500mm f/8
Total exposure: 10 min (L: 10min)
Processing: PixInsight