Westerlund 1-75 Explained

Westerlund 1 W75 or Wd 1-75 is a red supergiant (RSG) located in the Westerlund 1 super star cluster. Its radius is calculated to be around 668 solar radii[1] (4.65 × 108 km, 3.10 au). This corresponds to a volume 298 million times bigger than the Sun. If placed at the center of the Solar System, Westerlund 1-75 would engulf the inner limits of the asteroid belt.

The star is classified as a luminous cool supergiant emitting most of its energy in the infrared spectrum.[2] It occupies the upper right corner of the Hertzsprung-Russell diagram. Using the effective temperature of 3,600 K, the bolometric luminosity of 68,000 L☉ and the solar effective temperature of 5,772 K,[3] the radius of Westerlund 1-75 can be calculated using the Stefan-Boltzmann law at .

Like Westerlund 1-20, Westerlund 1 W26 and Westerlund 1-237, Westerlund 1-75 was observed to be a radio source, however it is weakest along the RSGs in its cluster and remains unresolved at any wavelength.[4]

Westerlund 1-75 is surrounded by extended nebula, although it appears less massive than nebulae around typical red supergiant stars.[5]

See also

Notes and References

  1. Fok. Thomas K. T.. Nakashima. Jun-Ichi. Yung. Bosco H. K.. Hsia. Chih-Hao. Deguchi. Shuji. 2012. Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters. The Astrophysical Journal. 760. 1. 65. 1209.6427. 2012ApJ...760...65F. 10.1088/0004-637X/760/1/65. 53393926.
  2. Web site: Cl* Westerlund 1 W 75. Simbad.
  3. Web site: Sun Fact Sheet. Williams. D. R.. 2013.
  4. Dougherty. S. M.. Clark. J. S.. Negueruela. I.. Johnson. T.. Chapman. J. M.. 2010-02-01. Radio emission from the massive stars in the galactic super star cluster Westerlund 1. Astronomy & Astrophysics. en. 511. A58. 10.1051/0004-6361/200913505. 0912.4165. 2010A&A...511A..58D. 0004-6361. free.
  5. 10.1093/mnrasl/sly046 . Asymmetric ejecta of cool supergiants and hypergiants in the massive cluster Westerlund 1 . 2018 . Andrews . H. . Fenech . D. . Prinja . R. K. . Clark . J. S. . Hindson . L. . Monthly Notices of the Royal Astronomical Society: Letters . 477 . 1 . L55–L59 . free . 1803.07008 . 2018MNRAS.477L..55A . 53640431 .

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