The Quintuplet cluster contains over two dozen post main sequence descendants of massive O-stars, including Wolf-Rayet and OBI stars.
The five Quintuplet-proper members (QPMs) may be dusty late-type Wolf-Rayet carbon stars (DWCLs), and the Pistol star may have a very high luminosity, ≈ 106.7±0.5 L⊙. Coupled with its rather cool temperature, 12–23 kK, the Pistol Star is well in violation of the Humphreys–Davidson limit. We argue that the surrounding “Pistol” nebula was ejected from the star a few thousand years ago.
The cluster stars imply the following approximate cluster properties: tage ∼ 2 to 7 Myrs, M ∼ 104 M⊙, L ∼ 107.3±0.2 L⊙, and NLy,c > 1049.9 s−1. The “Sickle” (G0.18–0.04) radio feature and the mid-IR ring (seen in MSX images) may naturally be explained by the presence of a young cluster and a nearby molecular cloud.