Object Analysis

Stephenson 2-18 is currently considered one of the largest stars ever discovered, if not the largest. It is a red supergiant located in the constellation Scutum, approximately 19,000 light-years from Earth. It is part of the massive open cluster Stephenson 2.

The scale of this star is almost impossible to comprehend. It has a radius estimated at 2,150 times that of the Sun. If placed at the center of our Solar System, its surface would extend past the orbit of Saturn. It is roughly 440,000 times more luminous than the Sun.

Because it is so bloated, the star is extremely unstable and is losing mass at a prodigious rate. It is in the very final stages of its life cycle and will eventually explode as a Type II supernova. Stephenson 2-18 represents the absolute upper limit of how large a star can grow before its own radiation pressure begins to tear it apart.