- M 76 The Little Dumbbell Nebula
M 76 is a planetary nebula located along the autumn Milky Way stream in the constellation Perseus. It was discovered in September of 1780 by Pierre Mechain, Messier's colleague. Messier observed it in October of that year, but described it as consisting of "nothing but very small stars". Using a much larger telescope, William Herschel correctly identified it as a nebula. In fact, he thought it consisted of two adjacent nebulas. He was probably seeing the two bright ends of the central bar of the planetary nebula. In any event, he gave it two numbers, NGC 650 and NGC 651.
M 76 is located at a distance of 2550 LY and has a physical diameter of 0.7 LY. The central "bar" of the nebula is actually a torus of nebular material surrounding the faint (visual magnitude 17.5) central star— we are seeing it edge-on, so it is like seeing the Ring Nebula (M 57) from the side. The two fainter lobes of nebula stretching out on either side of the central bar are parts of a shell resulting from an earlier expansion of stellar material.
Of the four planetary nebulas in Messier's list, M 76 is the faintest. With a visual magnitude of 10.1, it is an object primarily for larger telescopes, although it can be perceived as a small faintly glowing patch in a 3-inch scope under good conditions.
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