Mass–luminosity relation

The empirical relationship between a star’s mass and luminosity. Among main-sequence stars, luminosity rises steeply with mass, though the relation varies across stellar masses.

Hydrostatic equilibrium: The balance between inward gravity and outward pressure in a star or other self-gravitating object. Greater mass raises the pressure needed to support a star against gravity.
Binary star: A system of two stars bound to each other by gravity and orbiting a common center of mass. Binary orbits provide direct masses for testing the relation against observed luminosities.
Sun: The star at the center of the Solar System, a G-type main-sequence star about 4.6 billion years old. It provides the reference mass and luminosity used in solar-unit comparisons.
Stellar evolution: The sequence of physical changes a star undergoes from formation through its final state. A star’s luminosity can change substantially as it leaves the main sequence.
Stellar structure: The physical organization and internal properties of stars, governed by gravity, energy transport, and matter. Models of stellar interiors derive how mass shapes luminosity.
Stellar mass: The amount of matter contained in a star, commonly expressed relative to the Sun’s mass. The relation estimates masses when luminosity is known and direct orbital measurements are unavailable.
Sirius: The brightest star in Earth’s night sky, a nearby binary whose primary is an A-type main-sequence star. Its main-sequence primary offers a bright example with a dynamically measured mass.
Red giant: A luminous, expanded star that has exhausted hydrogen in its core and is burning fuel in surrounding layers. Red giants do not follow the main-sequence mass–luminosity relation.
Stellar nucleosynthesis: The formation of chemical elements through nuclear reactions inside stars and stellar explosions. Fusion in a star’s core supplies the energy that becomes its luminosity.
Massive star: A star substantially more massive than the Sun, with a short lifetime and high luminosity. Massive main-sequence stars illustrate the steep rise of luminosity with mass.

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