Solumassan

Solumassan, or the solar mass, is a standard unit of mass used in astronomy to express the masses of celestial objects relative to the Sun. It is denoted M⊙ and appears widely in papers, simulations, and orbital calculations to compare stars, planets, and galaxies.

Numerically, one solumassan is approximately 1.98847 × 10^30 kilograms. Because the gravitational constant G is uncertain, there is no exact kilogram value tied to the solar mass. In practice, astronomers also rely on the solar gravitational parameter GM⊙, known with high precision and about 1.32712440018 × 10^20 m^3 s^-2, to describe orbital dynamics and gravitational interactions.

Using solar masses simplifies comparisons across vastly different objects. For example, a star with 2 M⊙ has roughly twice the Sun’s mass; supermassive black holes are measured in millions to billions of M⊙; galaxies contain masses spanning billions to trillions of M⊙ when including stars, gas, and dark matter. The solar mass is a convenient unit in stellar evolution models, exoplanet studies, and galactic dynamics, providing a common scale that avoids large numbers in kilograms.

Etymology and usage: the term derives from the Sun and mass, and M⊙ is the conventional symbol for the solar mass. In many languages, the equivalent term is a translation of “solar mass,” and solumassan appears in some linguistic variants. The solar mass is a convention rather than an SI unit, used primarily to facilitate astrophysical calculations and comparisons.