M73

M73 is one of the most controversial Messier objects — it is a group of just four unrelated stars in Aquarius that form a small Y or triangle pattern. Located about 2,500 light-years from Earth, the four stars (magnitudes 10.5 to 12) are an asterism — an optical alignment with no physical connection. It is not a true cluster.

Located about 1.5 degrees east of M72 in Aquarius. In a telescope it appears as a tiny group of four faint stars in a Y-shaped arrangement. At low power the four stars may blend into a fuzzy patch, which is likely why Messier included it. Higher magnification (80-100x) easily resolves the four individual stars. Like M40, it is primarily of historical interest. Best observed from August through October.

Cataloged by Charles Messier on October 4, 1780, who described it as 'a cluster of three or four small stars, which resembles a nebula at first sight.' For over two centuries, its status as a genuine cluster was debated. Modern proper motion studies confirmed the four stars are unrelated.