verhoudingmassaspectrometrie

Mass ratio is a dimensionless quantity describing the relationship between the masses of two objects. It is usually written as m1/m2 or as mA:mB, with m1 and m2 the masses.

A closely related concept is the reduced mass μ = m1 m2/(m1+m2), which appears in the two-body problem and in molecular vibrations.

In astronomy, the mass ratio between a planet and its star, q = m_planet/m_star, is often very small for planets orbiting stars. For example, the Earth–Sun mass ratio is about 3×10^-6 (Earth is about 1/333,000 of the Sun’s mass); the Jupiter–Sun ratio is about 9.5×10^-4.

In planetary systems, the mass ratio influences orbital dynamics and the reflex motion of the star; in chemistry, the reduced mass determines vibrational frequencies of diatomic molecules.

Because it compares two quantities, a mass ratio is dimensionless and independent of unit systems. The term is used across physics, astronomy, and chemistry, with definitions tailored to the specific problem.