List of most massive stars

This is a list of the most massive stars that have been discovered, in solar mass units (M☉).

Uncertainties and caveats

Most of the masses listed below are contested and, being the subject of current research, remain under review and subject to constant revision of their masses and other characteristics. Indeed, many of the masses listed in the table below are inferred from theory, using difficult measurements of the stars' temperatures, composition, and absolute magnitude. All the masses listed below are uncertain: Both the theory and the measurements are pushing the limits of current knowledge and technology. Both theories and measurements could be incorrect.

Complications with distance and obscuring clouds

Since massive stars are rare, astronomers must look very far from Earth to find them. All the listed stars are many thousands of light years away making their light especially faint, which makes measurements difficult. In addition to being far away, many stars of such extreme mass are surrounded by clouds of outflowing gas created by extremely powerful stellar winds. This outflow obscures the stars, making it difficult to determine the physical properties of the star needed to calculate its mass: The surrounding gas interferes with the already difficult-to-obtain measurements of stellar temperatures and brightness, which greatly complicates the issue of estimating internal chemical compositions and structures.

Both the obscuring clouds and the great distances also make it difficult to judge whether the star is just a single supermassive object or, instead, a multiple star system.