Since Messier's time, there has been controversy over the status of this formation, and specifically about whether or not it represents a cluster of related stars. It is now generally considered that they do not. The stars' distances from Earth, and their respective proper motions, are quite different from one another. Messier's 'cluster', then, actually appears to be no more than an asterism, a group of stars on the same line of sight from Earth. The 'BWM' designations shown on this map relate to the Bassino Waldhausen Martinez catalogue of 144 stars in this small region of the sky.
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