Westerlund 1 is a red supergiant cluster in the constellation Ara. As its name suggests, it was discovered by Bengt Westerlund in 1961. Westerlund also discovered the largest known star, WOH G64. Westerlund 1 is notable for containing four extreme red supergiant stars. Westerlund 1 also contains six yellow hypergiants, 24 Wolf Rayets, and a Luminous blue variable among many other star types. The cluster is located 3.78 Kiloparsecs from Earth.
Red Supergiant Stars within the cluster
Westerlund 1 contains four red supergiant stars, which all are contenders for the title of largest known star. Westerlund 1-237 is currently the largest of the four. Below is the astronomical data for the four:
Westerlund 1-237
Radius (in Solar Radii): 1,245 R☉
Diameter (in Kilometers): 1,733,040,000 km
Spectral type: M3Ia (Red)
Westerlund 1-26
Radius (in Solar Radii): 1,145 R☉
Diameter (in Kilometers): 1,593,840,000 km
Spectral type: M0.5 (Red)
Westerlund 1-20
Radius (in Solar Radii): 858 R☉
Diameter (in Kilometers): 1,194,336,000 km
Spectral type: M6I (Red)
Westerlund 1-75
Radius (in Solar Radii): 722 R☉
Diameter (in Kilometers): 1,005,024,000 km
Spectral type: M4Ia (Red)
