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Revision as of 09:43, 15 September 2013 by Jhattara(talk | contribs)(distance estimation borrowed from the distance of the cluster the star is located in)
High resolution image of the super star clusterWesterlund 1. Wd 1 BKS AS is seen as the reddish star on the upper left of the dense region of white stars
Westerlund 1 BKS AS (also known as Westerlund 1 W26 and Westerlund 1-26) is a red supergiant or hypergiant star within the outskirts of the Westerlund 1super star cluster. It is widely known as the leading candidate for the largest known star in the universe. It is approximately 1,951-2,544 solar radii. Assuming the higher estimate is correct, this star has the diameter of 3.54 billion kilometers, corresponding to a volume 16.5 billion times bigger than the Sun, and if were placed in the center of the Solar System, its surface can extend to Saturn and 300 million kilometers (2 AU) further.
Physical characteristics
Since its discovery, Westerlund 1 BKS AS has been well known as a strong radio source. It is a very active huge star in the Westerlund 1. Its physical properties are not well understood, due to interstellar extinction within the cluster. Its strong radio emission leads it to have varying estimates, and that, therefore, it may not have the exact diameter as we know it as then. But precise estimates give it the radius within 1,500 solar radii. The debate of its true size is on. Westerlund 1 BKS AS is currently the largest star known in the Milky Way Galaxy, and in the universe.
Radio emission and uncertain variability
As mentioned above, Westerlund 1 BKS AS has been identified as a strong radio source, which led to its uncertain parameters of very different estimates. Also, it has been seen as a star that changes it spectral class during several periods, but it has not been seen to change its luminosity unlike other stars. It was studied extensively in the radio spectrum, because of extinction in visible wavelengths. Its estimate was very uncertain, but it will have a more precise estimate anytime soon.
