Inside History on Instagram: "Stephenson 2-18 (also known as St2-18 or Stephenson 218) ranks among the largest known stars in the universe. This colossal red supergiant is situated in the constellation Scutum, roughly 19,000 light-years away from Earth. Its estimated radius is about 2,150 times that of the Sun—so immense that if placed at the center of our solar system, its surface would stretch past the orbit of Saturn. Despite its size, Stephenson 2-18 is relatively cool, with a surface temper