Stephenson 2-18, also known as RSGC2-18 and Stephenson 2 DFK 1, is a red supergiant stars in the Stephenson 2 supercluster, in the Scutum constellation, about 20.000 light years or 6,000 parsecs away and it is located near the Supermassive black hole, Sagittarius A. The star is extremely large, having a gigantic diameter of nearly 2150 times the diameter of the Sun, and it is probably approaching the potential largest size of Red Supergiant stars and probably is one of the largest stars in the Universe.
Stephenson 2-18 is now known as being one of the largest, if not the current largest star ever discovered, surpassing other stars like VY Canis Majoris and UY Scuti. Stephenson 2-18 has a radius of 2,150 solar radii, being larger than almost the entire orbit of Saturn (1,940 - 2,169 solar radii). Currently, this Star is estimated to have a volume of at least 10 billion times that of the Sun. By comparison to this star, the Sun is pretty much the size size of a grain of dust, in comparison to a very big basketball. The star is probably approaching the potential largest size of Red Supergiant stars, as mentioned above, therefore, it is very possible that Stephenson 2-18 is undoubtly one of the largest stars that currently exist in the entire observable/known Universe.
Stephenson 2-18's mass is estimated to be about 12 to 16 times the mass of the Sun. Currently, Stephenson 2-18 fuses helium into heavier elements like lithium and carbon, burning through more and more mass. The star is even larger than the previously known as the largest star, UY Scuti, but actually, it is quite less massive. UY Scuti's mass is estimated to be about 30 times the mass of the Sun. Stephenson 2-18 likely lost large amounts of it's mass of it's massive size as a Red Supergiant star. As Stephenson 2-18 continues to burn elements in it's core, it will die eventually, giving it's mass back to the Galaxy. This mass will create new stars and planets.
Stephenson 2-18, alongside with size, is also one of the most luminous stars, at 440,000 units of solar luminosity. ( Solar luminosity means luminosity of the Sun). Stephenson 2-18 is much less massive than UY Scuti, as mentioned above, but larger in size and brighter in luminosity. Stephenson 2-18 has big luminosity, as Red Supergiant stars are some of the most luminous and largest stars in the Universe. The average temperature of Stephenson 2-18 is 3,200 kelvin.
- Wikipedia article: https://en.wikipedia.org/wiki/Stephenson_2-18
- Kurzgesagt - In a Nutshell: https://youtu.be/3mnSDifDSxQ
- Kids learning tube: https://youtu.be/E7in_nJuN88
- UY Scuti: UY Scuti