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Parallax
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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. Change of parallactic angle with altitude. Measurement of parallax by observations from a northern and a southern observatory. Diagram illustrating stellar parallax, showing Earth at two points in its orbit around the Sun, with lines connecting each position to a distant star and forming an angle labeled p to represent the parallax shift. Diagram showing binocular and instantaneous parallax, with two eyes labeled NL and NR, and lines from each eye converging on two points, A and B, to illustrate depth perception.
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Nicolaus Copernicus. Nicolas Copernicus (1473-1543) Polish astronomer. In 1543 he published, forward proof of a Heliocentric (sun centered) universe. Coloured stipple engraving published London 1802. De revolutionibus orbium coelestium libri vi.
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Parallax: References & Edit History

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  • Kaj Aa. Strand
  • The Editors of Encyclopaedia Britannica
    Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors.

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Article History

Type Description Contributor Date
Article title updated for style. Nov 10, 2026
Invalidated site: Princeton University - Department of Astrophysical Sciences - Parallax Background. Oct 27, 2026
Add new Web site: Physics LibreTexts - Bias in Parallax Measurements. Nov 03, 2025
Add new Web site: National Center for Biotechnology Information - PubMed Central - Parallax: High Accuracy Three-Dimensional Single Molecule Tracking Using Split Images. Jun 02, 2025
Add new Web site: IOPscience - Techniques for Measuring Parallax and Proper Motion with VLBI (PDF). Feb 28, 2025
Add new Web site: Khan Academy - Intro to parallax. Dec 06, 2024
Add new Web site: Boston University - Parallax and Triangulation. Oct 08, 2024
Add new Web site: The Royal Society Publishing - Philosophical Transactions B - The neural basis of depth perception from motion parallax. Aug 31, 2024
Add new Web site: Open Library Publishing Platform - Fanshawe College Astronomy - Parallax and the Parsec. Mar 01, 2024
Add new Web site: The Nebraska Astronomy Applet Project - Parallax. Nov 24, 2023
Add new Web site: University of Sheffield - Departmrnt of Physics and Astronomy - Parallax. Sep 28, 2023
Add new Web site: Coe College - Parallax. Jun 09, 2023
Add new Web site: Princeton University - Department of Astrophysical Sciences - Parallax Background. Jan 19, 2023
Add new Web site: Space.com - What Is Parallax? Oct 14, 2022
Add new Web site: HyperPhysics - Parallax. Dec 19, 2019
Added diagram depicting the calculation of star distances. Jan 27, 2011
Article revised and updated. Jul 14, 2010
Updated information on direct and indirect measurement. Sep 09, 2009
Added new Web site: Hyperphysics - Parallax. Mar 18, 2008
Added new Web site: HyperPhysics - Parallax. Mar 10, 2008
Article added to new online database. Jul 20, 1998
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