The open cluster Westerlund 2 lies in a giant HII complex known as RCW 49. The cluster stars are between 1 and 2 million years old and their stellar winds and radiation have evacuated the dust within the central region of RCW 49. Westerlund 2 is remarkable for the presence of one of the most massive stellar systems known. The star system known as WR20a (seen in the lower right in the chart below) is actually two massive stars in an eclipsing binary system. The two massive suns are both Wolf Rayet stars each with over 80 solar masses.

"Early-type stars in the core of the young open cluster
Westerlund 2" , G. Rauw et al.,

RCW-49 (Spitzer Space Telescope and Chandra X-Ray Observatory)

Credit: X-ray; Y.Nazé, G.Rauw, J.Manfroid (Université de Liège), CXC, NASA
Infrared; E.Churchwell (University of Wisconsin), JPL, Caltech, NASA