Westerlund 1-237

largest known stars and one of the most luminous of its type.^[7]

supergiant emitting most of its energy in the infrared spectrum.^[11] It is surrounded by a radio nebula which is similar in mass to those of Westerlund 1-20 and Westerlund 1 W26, and moreover directly comparable to that of VY Canis Majoris. The elliptical structure of this nebula however indicates that it has been less affected by the cluster wind of Westerlund 1 (W20 and W26 have pronounced cometary shaped nebulae). The outflow velocity for the RSG wind is assumed to be around 30 km/s. The nebula itself seems to have a mass of 0.07 M_☉ and a radius of about 0.11 parsecs. This results in a kinematic age around 3,600 years and a time averaged mass loss rate of 2×10⁻⁵ M_☉ per year.^[12]

parsecs^[13] based on it being commonly thought of as a member of the Westerlund 1 star cluster (the elliptical shape of its nebula indicates that it might not be near the center of W1, while other RSGs like W20 and W26 are).^[12] Another but older source suggests a similar distance of 3,000±500 parsecs.^[7]

mas for W1-237, implying a distance of 623+139
−96 pc and a luminosity of 7,178–7,379 L_☉ with a corresponding radius of 216 R_☉.^[14][8] In 2020, the parallax was revised to the much smaller value of 0.3370±0.1235 mas.^[5]