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How far away is a star with a parallax of 0.1 arcsecond?

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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. — Parallax Calculating stellar distances.

A star with a parallax of 0.1 arcsecond is 10 parsecs away.

This is determined by the relationship between distance and parallax, where the distance in parsecs is the reciprocal of the parallax measured in arcseconds. Since 1 parsec is equivalent to approximately 3.26 light-years, a star at a distance of 10 parsecs is approximately 32.6 light-years away.12