Britannica Sources used in this answer

How did Gaia extend the distance range of parallax measurements?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

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.

The Gaia satellite significantly extended the range and precision of parallax measurements by utilizing advanced space-based telescopes to overcome the limitations of Earth-based observations, which are hindered by atmospheric interference.12

While previous missions like Hipparcos achieved measurements for stars up to 650 parsecs away with an accuracy of about a thousandth of an arc second, Gaia improved upon this by providing measurements for the brightest stars with an accuracy of 0.000007 arc second—approximately 140 times more precise than its predecessor. By operating from the second Lagrangian point (L2) and scanning the entire sky, Gaia was able to extend the reach of trigonometric parallax to stars as far away as 10 kiloparsecs with an accuracy of 20 percent. This leap in precision allowed astronomers to create a highly accurate three-dimensional map of a vast portion of the Milky Way Galaxy.12