Messier 73 (M73, also known as NGC 6994) is an asterism of four stars in the constellation Aquarius which was long thought to be a small open cluster.

[5] M73 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.

[6] However, G. Carraro, published results in 2000 based on a similar analysis and concluded that the stars did not follow any color-luminosity relation.

[8] The controversy was resolved in 2002, when M. Odenkirchen and C. Soubiran published an analysis of the high resolution spectra of the six brightest stars within 6 ′ of the centre point.

[9] Although M73 was determined to be only a chance alignment of stars, further analysis of asterisms is still important for the identification of sparsely populated open clusters.