page_title: Westerlund 1-20
hierarchical_section_title: Westerlund 1-20
caption_attribution_description: English: Comparison of Radii of the 4 known RSGs located in the Westerlund 1 star cluster, in particular Westerlund 1-26, Westerlund 1-237, Westerlund 1-20, Westerlund 1-75
context_page_description: Westerlund 1-20 or Wd 1-20 is a red supergiant located in the Westerlund 1 super star cluster. Its radius was calculated to be around 965 solar radii, making it one of the largest stars discovered so far. This corresponds to a volume 899 million times bigger than the Sun. If placed at the center of the Solar System, the photosphere of Westerlund 1-20 would almost reach the orbit of Jupiter.
  The star is classified as a luminous cool supergiant emitting most of its energy in the infrared spectrum. W20 occupies the upper right corner of the Hertzsprung-Russell diagram. Using the effective temperature of 3,500 K, the bolometric luminosity of 126,000 L☉ and the solar effective temperature of 5,772 K, its 1-20 can be calculated using the Stefan-Boltzmann law.
  Westerlund 1-20 was observed to have an extended, cometary shaped nebula, similar to the other red supergiant Westerlund 1-26. It is therefore likely that its morphology was affected by either the intracluster medium or the cluster wind of Westerlund 1.
context_section_description: Westerlund 1-20 or Wd 1-20 is a red supergiant (RSG) located in the Westerlund 1 super star cluster. Its radius was calculated to be around 965 solar radii (6.72 × 10⁸ km, 4.48 au), making it one of the largest stars discovered so far. This corresponds to a volume 899 million times bigger than the Sun. If placed at the center of the Solar System, the photosphere of Westerlund 1-20 would almost reach the orbit of Jupiter. 
  The star is classified as a luminous cool supergiant emitting most of its energy in the infrared spectrum. W20 occupies the upper right corner of the Hertzsprung-Russell diagram. Using the effective temperature of 3,500 K, the bolometric luminosity of 126,000 L☉ and the solar effective temperature of 5,772 K, its 1-20 can be calculated using the Stefan-Boltzmann law.
  Westerlund 1-20 was observed to have an extended, cometary shaped nebula, similar to the other red supergiant Westerlund 1-26. It is therefore likely that its morphology was affected by either the intracluster medium or the cluster wind of Westerlund 1.
caption: Westerlund 1-20 compared to the other 3 RSGs in the Westerlund 1 star cluster.
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