Zonnemassa

Zonnemassa, or solar mass, is a standard unit of mass in astronomy used to describe the masses of stars, brown dwarfs, planets, and galaxies. It is defined as the mass of the Sun and is denoted M⨀. In practice, it provides a convenient scale for comparing masses across vastly different objects.

One solar mass is approximately 1.9885 × 10^30 kilograms. It equals about 333,000 Earth masses and about 1,047 Jupiter masses. The precise value in kilograms is not absolutely fixed because the gravitational constant G is poorly known; what is known more accurately is GM⨀, the solar gravitational parameter, which is used in orbital dynamics.

In astrophysics, masses are often expressed in solar masses. Example: a star of 2 M⨀ has about twice the Sun's mass; a supermassive black hole with 10^6 M⨀. The unit is used for stars, exoplanets, and galaxies; for planets, masses are still often given in Earth or Jupiter masses, but for stars and galaxies M⨀ is standard.

Historically, the solar mass emerged as a natural reference unit as astronomical measurements expanded. The International Astronomical Union (IAU) endorses M⨀ as the conventional solar mass in scholarly literature, and researchers commonly use a conventional value in kilograms for practical computations.