[3][4] Although larger and denser than the nearby Quintuplet Cluster, it appears to be slightly younger.

Only stars earlier and more massive than O5 have evolved away from the main sequence while the Quintuplet Cluster includes a number of hot supergiants as well as a red supergiant and three luminous blue variables.

X-ray emission from the cluster suggests that many other members are also in close binary systems with two hot luminous members, but there is little evidence of the evolution of these stars being affected by binary mass exchange.

[4] Work by Donald Figer, an astronomer at the Rochester Institute of Technology suggests that 150 solar masses (M☉) is the upper limit of stellar mass in the current era of the universe.

The limit of 150 solar masses was previously deduced by Carsten Weidner & Pavel Kroupa[7] using observations of the cluster R136.