How do astronomers measure the mass of a distant star?
Quick Answer
They often use binary star systems, where the stars orbit each other and their orbital motions reveal their masses through gravity. In special cases, the mass can also be estimated from a star’s spectrum and evolution stage.
The Full Story
The most reliable stellar masses come from binary systems. By measuring the orbit of two stars around their shared center of mass, astronomers can apply Kepler’s laws and Newton’s gravity to infer the masses. Eclipsing binaries are especially valuable because the stars pass in front of each other, revealing orbital size and inclination more precisely. For single stars, astronomers estimate mass by comparing temperature, brightness, and spectral type to stellar evolution models. This is how the Sun’s mass becomes the reference point for much of stellar astronomy.
Key Facts
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