Messier 55

Messier 55 (also known as M55 or NGC 6809 or "The Summer Rose Star") is a globular cluster in the constellation Sagittarius. It was discovered by Nicolas Louis de Lacaille in June 16, 1752 while observing from South Africa. M55 is at a distance of about 17,600 light-years away from Earth. It has a mass of about 269,000 times that of the Sun. As with other Milky Way globular clusters, it has a low abundance of elements other than hydrogen and helium compared to the Sun—what astronomers term the metallicity of the cluster. Only about 55 variable stars have been discovered in the central part of M55.