So far as telescopes in space go, the European Space Agency and NASA’s Hubble Space Telescope is among the most prolific in sending back stunning images of distant stars and galaxies to Earth. And the latest image it sent back is of a nearby super star cluster which is home to one of the largest stars ever discovered.
Called Westerlund 1, the relatively young star cluster is called “super” for the fact that it has more mass and is more luminous than other young star clusters. A rarity in the Milky Way, the cluster lies about 15,000 light-years from Earth and on its outer fringes lives a star named Westerlund 1-26. With a radius of over 1,500 times that of the sun, according to a NASA statement, it is among the biggest stars ever observed in the known universe.
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For a perspective of size, if it was placed where the sun is in our solar system, it would engulf all the inner planets, as well as Jupiter. Classified as a red supergiant or hypergiant, it is over 300,000 times brighter than sun when seen in radio wavelengths, making it actually close to 380,000 times the sun’s luminosity.
However, despite its size, Westerlund 1-26 is quite a ways from being the largest star discovered so far. At least three stars are considered to be larger —UY Scuti, about 9,500 light-years away; WHO G64, about 168,000 light-years away in the Large Magellanic Cloud; and RW Cephei, thought to be about 11,500 light-years away. UY Scuti is the top contender for being the largest known star so far.
It must also be kept in mind the radii of the largest stars are not well-defined and there are large uncertainties in the determining their exact sizes.
Westerlund 1 was discovered in 1961. Most of its stars are thought to have originated in the same burst of activity about three million years ago, making them all much younger than the sun, which is over 4.5 billion years old. It also means all the stars in the cluster have roughly the same compositions.