How Do We Know How Far Away the Stars Are?

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Diagram illustrating how astronomers calculate the distance to a star using parallax: Earth is shown in two positions on opposite sides of its orbit around the Sun, with lines extending to a nearby star X and further to distant background stars. The apparent shift in star X's position, measured as angle A, is used to determine its distance, with the baseline labeled as 186,000,000 miles.

How Do We Know How Far Away the Stars Are?: Media

“Star light, star bright, first star I see tonight”…is trillions of miles away.

Images

M17

M17

M17, the Swan Nebula, is a star-making cloud in the constellation Sagittarius.

University of Wisconsin—JPL/Caltech/NASA

Diagram illustrating how astronomers calculate the distance to a star using parallax: Earth is shown in two positions on opposite sides of its orbit around the Sun, with lines extending to a nearby star X and further to distant background stars. The apparent shift in star X's position, measured as angle A, is used to determine its distance, with the baseline labeled as 186,000,000 miles.

stellar distances

Calculating stellar distances.

Encyclopædia Britannica, Inc.