Stephenson 2-18

Stephenson 2-18 (St2-18, also known as Stephenson 2 DFK 1 and RSGC2-18) is a red supergiant (RSG) or red hypergiant (RHG) star. It is close to, and a possible member of, the open cluster Stephenson 2. It is about 6,000 parsecs (20,000 ly) away from Earth in the constellation of Scutum and is one of the largest known stars.

It is also possibly one of the most luminous of its type, if it is a member of the cluster. It is estimated to have a radius of 2,150 times that of the Sun, and a volume 10 billion times that of the Sun, however these parameters are unreliable and it is likely not a member of Stephenson 2.

This star has a spectral type of M6, which is pretty unusual for a supergiant star (below the Hayashi limit) and corresponds to its cool temperature of 3,200 Kelvin.

The clear single image of stephenson 2-18 was first taken in the year 2007 using 2MASS All-Sky Survey camera from Cerro Tololo Inter-American observatory in Chile.

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Category:Supergiants