M73

Messier 73, abbreviated M73, is the 73rd item in the Messier catalog and lies in the constellation Aquarius. Unlike many objects in the catalog, M73 is not considered a true star cluster.

M73 is widely described as an asterism rather than a physically related group of stars. It consists of a small number of stars that, through a telescope, can appear to form a loose pattern, but the stars are at different distances from Earth and are not gravitationally bound to one another. Consequently, M73 does not represent a genuine cluster or a single stellar population.

Historically, M73 was cataloged by Charles Messier in the late 18th century as part of his effort to distinguish star clusters and nebulae from comets. In modern catalogs and star-spotting guides, it is classified as an asterism rather than an open cluster or globular cluster. Because its constituent stars are relatively faint and not physically associated, M73 is of interest mainly as a curiosity in the study of the Messier catalog and historical observing practices.

Observation and viewing notes are modest: the quartet of stars that forms the asterism is not a prominent naked-eye feature, and observing it typically requires a small telescope or good binoculars under dark skies. The object serves as a reminder that not all Messier entries correspond to physically meaningful stellar groups.