Charles Messier (Oct 4th & 5th 1780):
'A cluster of three or four small stars wiich looks like a nebula at first sight; it contains a little nebulosity.'
William H. Smyth (1844):
'A trio of 10th magnitude stars in a poor field - this is M-73. I give it out of respect to Messier's memory.'
Quote from Dreyer's New General Catalog(NGC) for NGC 6994:
'Cluster, extremely sparse in stars, very little compressed, no nebula; = M73.'
The four stars that make up M-73 (aka NGC 6994) are probably just a random grouping that happens to lie along the same line of sight (an asterism). The two brightest stars in the group have recorded proper motions in the Tycho Catalog, and they show substantial differences. This would be pretty much impossible if the two were gravitationally bound into a group. However some people continue to hold that this is a real star cluster. Until recently there were several inclusive and conflicting studies. In 2002, M. Odenkirchen and C. Soubiran published an analysis of the high resolution spectra of the six brightest stars within 6 arc minutes of the central position of M73. They demonstrated that the distances from the Earth to the six stars were very different from each other, and the stars were moving in different directions. Therefore, they concluded that the stars were only an asterism.
The group is easy to find with a small telescope, but there is not much to see. We have included this image and page as part of Kopernik Observatory's attempt to image all of the Messier Objects.
George Normandin, KAS
February 16th, 2009