This stunning new image of Messier 107 -one of 150 globular clusters that orbit the Milky Way-was captured by the Wide Field Imager on the 2.2-metre telescope at ESO’s La Silla Observatory in Chile. Messier 107, also known as NGC 6171, a compact and ancient family of stars that lies about 21 000 light-years away, is a bustling metropolis: thousands of stars in globular clusters like this one are concentrated into a space that is only about twenty times the distance between our Sun and its nearest stellar neighbour, Alpha Centauri. A significant number of these stars have already evolved into red giants, one of the last stages of a star’s life, and have a yellowish colour in the image.
Messier 107 has undergone intensive observations, being one of the 160 stellar fields that was selected for the Pre-FLAMES Survey — a preliminary survey conducted between 1999 and 2002 using the 2.2-metre telescope at ESO’s La Silla Observatory in Chile, to find suitable stars for follow-up observations with the VLT’s spectroscopic instrument FLAMES . Using FLAMES, it is possible to observe up to 130 targets at the same time, making it particularly well suited to the spectroscopic study of densely populated stellar fields, such as globular clusters.
M107 is not visible to the naked eye, but, with an apparent magnitude of about eight, it can easily be observed from a dark site with binoculars or a small telescope. The globular cluster is about 13 arcminutes across, which corresponds to about 80 light-years at its distance, and it is found in the constellation of Ophiuchus, north of the pincers of Scorpius. Roughly half of the Milky Way’s known globular clusters are actually found in the constellations of Sagittarius, Scorpius and Ophiuchus, in the general direction of the centre of the Milky Way. This is because they are all in elongated orbits around the central region and are on average most likely to be seen in this direction.