Messier 72 & Messier 73 in Aquarius

Messier 72 (M72 or NGC 6981 in the New General Catalogue) is a globular star cluster in the western part of constellation Aquarius. It has an apparent magnitude of 9.35 and lies at a distance of 54,570 light years from Earth. Messier 72 was discovered by Charles Messier’s colleague Pierre Méchain on August 29, 1780. Messier found the object on October 4 together with Messier 73, which lies about 1.5 degrees to the east. He added them both to his catalogue. In small telescopes, M72 appears as a faint nebula. Medium-sized instrument can resolve the stars in the surrounding field. Larger telescopes will reveal a cluster with an apparent diameter of 2.5 arc minutes. The full angular diameter of M72 is 6.6 arc minutes, which is corresponding to 106 light years of a spatial extension.
Messier 73 (M73, also known as NGC 6994) is an asterism of four stars. It was once treated as a potential sparsely populated open cluster, which consists of stars that are physically associated in space as well as on the sky. The question of whether the stars were an asterism or an open cluster was a matter of debate in the early 2000s.