Stephenson 2-18

Every one might have heard that the largest star is UY Scuti star

                                 UY Scuti

But, what is largest than UY Scuti?

Stephenson 2-18, yes Stephenson 2-18 is largest than UY Scuti and also the largest star ever discovered.

About Stephenson 2-18

Stephenson 2-18 also known as RSGC2-18, has now replaced UY-Scuti as the biggest star that we know of till now. Its estimated radius is about 2150 times that of our Sun and a volume of about 10 billion times our sun. Whereas, the radius of UY-Scuti is about 1700 Solar radii.

Radius: 1.4958 billion km

Surface temperature: 3,200 K

Distance to Earth: 19,570 light years

Magnitude: 15.263

Luminosity: 437,000 L

Spectral type: M6

Constellation: Scutum

It is also known as Stephenson 2 DFK 1 or RSGC2-18

 It belongs to the constellation the constellation Scutum.

Scutum constellation is one of the smallest constellations and 84th constellations in size. It stretches about 109° in the southern sky. Constellation Sagittarius, Aquila, Serpens Cauda are the neighboring constellations of Scutum constellation. 

More info...

       When the cluster was originally discovered in 1990, Stephenson 2, and therefore Stephenson 2-18, was originally estimated to have a distance of around 30 kiloparsecs (98,000 light-years), much further than the cluster is thought to reside today. This greater distance was calculated by the assumption that the cluster stars were all M-type supergiants, then calculating the distance modulus based on their typical absolute magnitudes.

Properties:

Stephenson 2-18 is usually classified as a red supergiant, partly due to its broad line profile. However, its significant infrared excess has led the authors of Davies (2007) to state that the star might be a red hypergiant, like VY Canis Majoris. It is also stated that Stephenson 2-18 is on the brink of ejecting its outer layers and evolving into a luminous blue variable (LBV) or Wolf–Rayet star (WR star).

Temperature:

An effective temperature of 3,200 K was calculated in a 2012 study by SED integration using the DUSTY model, which would make it much cooler than the coolest red supergiants predicted by stellar evolutionary theory (typically around 3,500 K).

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