Westerlund 1 (sometimes Wd1) is the most massive compact young star cluster in the local group and is about 5kpc away. It has gone undetected as such until recently due to high extinction in its direction. The only stars that have been identified in it are the brightest, including 6　yellow hypergiants, 3 red supergiants, 13 or more Wolf-Rayet stars, Luminous Blue Variables, and 25 or more OB supergiants. Besides hosting some of the most massive and least understood stars in the galaxy, it is an analog to extragalactic super star clusters that may help astronomers determine what occurs in SSCs.

See also

• CXO J164710.2-455216, (aka. Westerlund 1 magnetar) a slow X-ray pulsar (magnetar)

References

• On the massive stellar population of the super star cluster Westerlund 1, Clark et al 2005
• Westerlund 1: Neutron Star Discovered Where a Black Hole Was Expected
• A Neutron Star with a Massive Progenitor in Westerlund 1
• A census of the Wolf-Rayet content in Westerlund 1 from near-infrared imaging and spectroscopy
• Artist’s impression of a magnetar X-ray satellites catch magnetar in gigantic stellar ‘hiccup’, ESA website, 2007
• Simbad
• Image Westerlund 1