Messier 9

Messier 9 is a globular cluster in the constellation of Ophiuchus, discovered by Charles Messier in 1764 – he described it as a nebulous cloud with no stars in it. In 1783, William Herschel was able to resolve individual stars in the cluster. M 9 is 25.800 light-years away and has an apparent magnitude of +7,7.

Messier 9 is one of the closest globular clusters to the galactic core, being only 5.500 light-years away from it. Here we cannot find blue stragglers, but 24 variable stars have been identified, most of them RR Lyrae type. The cluster’s diameter is 90 light-years away.

Located between the Sun and the cluster, the dust cloud Barnards 64 partially obscures the stars at the cluster’s edge. The average spectral class of the stars in Messier 9 is F2, meaning that the stars are much older and metal-poor than the Sun.