Johannes Kepler

Introduction & Top Questions
Kepler’s social world
Astronomical work

References & Edit History Quick Facts & Related Topics

Images & Videos

Kepler's revolutionary laws of planetary motion

planetary orbits: Kepler, Newton, and gravity

A diagram illustrating Kepler's first law of planetary motion, showing Earth traveling in an elliptical orbit around the Sun, which is positioned at one focus of the ellipse.

A diagram illustrating Kepler's second law of planetary motion, showing an elliptical orbit around the Sun with two shaded sectors representing equal areas swept by a planet in equal time intervals, labeled as one month each.

A chart explains Kepler's third law of planetary motion, showing a table of planets with their orbital periods, mean distances from the Sun, and calculations demonstrating that the ratio of the period squared to the mean distance cubed is nearly constant. Mathematical formulas and a summary of the law are included.

frontispiece from Tabulae Rudolphinae (1627; “Rudolphine Tables”) by Johannes Kepler

At a Glance

Johannes Kepler summary

Quizzes

View of the Andromeda Galaxy (Messier 31, M31).

Astronomy and Space Quiz

Michael Faraday (L) English physicist and chemist (electromagnetism) and John Frederic Daniell (R) British chemist and meteorologist who invented the Daniell cell.

Faces of Science

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.

All About Astronomy

Related Questions

How accurate were Tycho Brahe's planetary observations compared with earlier observations?
How did Isaac Newton explain why Kepler's laws work?
How did Johannes Kepler respond to Galileo's telescopic discoveries?
How did Johannes Kepler support Nicolaus Copernicus's Sun-centered model?
How did Johannes Kepler use the five regular polyhedrons in his early model of the solar system?
How did Johannes Kepler's work challenge the belief in uniform circular motion?
How did Kepler's laws improve on Copernicus's model of planetary motion?
How did Michael Maestlin influence Johannes Kepler's interest in astronomy?
How did Tycho Brahe's observations help Johannes Kepler make discoveries?
How did the Rudolphine Tables use Tycho Brahe's astronomical observations?
How do Kepler's laws apply to moons and artificial satellites?
How do the gravitational pulls of planets affect Keplerian orbits?
How does Kepler's first law describe the paths of planets around the Sun?
How does Kepler's second law explain changes in a planet's speed?
How does Kepler's third law connect a planet's distance from the Sun with its orbital period?
How does eccentricity describe the shape of a planet's orbit?
What are Johannes Kepler's three laws of planetary motion?
What are perihelion and aphelion in a planet's orbit around the Sun?
What did Johannes Kepler contribute to the study of light and vision?
What does it mean for a planet to sweep out equal areas in equal times?
What idea did Johannes Kepler explore in Mysterium cosmographicum?
What kind of telescope did Johannes Kepler describe in Dioptrice?
What observations of Jupiter did Johannes Kepler publish in 1611?
What paths can a comet follow under Newton's law of gravitation?
What position did Johannes Kepler receive after Tycho Brahe died in 1601?
What role did Johannes Kepler have in Graz, Austria?
What were the Rudolphine Tables, and why were they important?
When and where was Johannes Kepler born?
When did Johannes Kepler announce his third law of planetary motion?
When did Johannes Kepler publish his first two laws of planetary motion?
Where did Johannes Kepler study before becoming an astronomer?
Which book contained Johannes Kepler's third law of planetary motion?
Which book presented Johannes Kepler's first two laws of planetary motion?
Why are Kepler's laws approximate rather than perfectly exact for the solar system?
Why did Johannes Kepler originally plan to become a theologian?
Why did Johannes Kepler reject circular orbits for Mars?
Why did Mars help Johannes Kepler discover that planetary orbits are elliptical?
Why did Tycho Brahe invite Johannes Kepler to Prague?
Why does a planet move faster when it is closer to the Sun?
Why was Kepler's second law important to Isaac Newton's study of gravity?
Why were Tycho Brahe's measurements of Mars especially useful to Johannes Kepler?
What was Johannes Kepler’s profession? When and how did it begin?
What was Johannes Kepler known for?
Who did Johannes Kepler influence?
How and where did Johannes Kepler die?
What is Robert Hooke famous for?
Why is Nicolaus Copernicus famous?
What did Nicolaus Copernicus do for a living?
How did Nicolaus Copernicus influence others?
What is Isaac Newton most famous for?
How was Isaac Newton educated?

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External Websites

NASA - Jet Propulsion Laboratory - The History of Johannes Kepler
NASA - Chandra X-ray Observatory - The Astronomers Tycho Brahe and Johannes Kepler
MacTutor History of Mathematics - Biography of Johannes Kepler
Physics LibreTexts - Johannes Kepler (1571-1630) and his Laws of Planetary Motion
German Patent and Trade Mark Office - Johannes Kepler
High Altitude Observatory - Johannes Kepler (1571ï¿½1630)
Stanford Encyclopedia of Philosophy - Biography of Johannes Kepler
BBC - In Our Time - Johannes Kepler
Linda Hall Library - Johannes Kepler
World History Encyclopedia - Biography of Johannes Kepler
Famous Scientists - Biography of Johannes Kepler
New Mexico Museum of Space History - Johannes Kepler

Britannica Websites

Articles from Britannica Encyclopedias for elementary and high school students.

Johannes Kepler - Children's Encyclopedia (Ages 8-11)
Johannes Kepler - Student Encyclopedia (Ages 11 and up)

Johannes Kepler

German astronomer

Written by

Robert S. Westman

Professor of History and Science Studies, University of California, San Diego, at La Jolla. Author of Johannes Kepler's Adoption of the Copernican Hypothesis and others.

Robert S. Westman

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Britannica Editors

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....

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Last updated

Nov. 11, 2026 •History

Johannes Kepler (born December 27, 1571, Weil der Stadt, Württemberg [Germany]—died November 15, 1630, Regensburg) German astronomer who discovered three major laws of planetary motion, conventionally designated as follows: (1) the planets move in elliptical orbits with the Sun at one focus; (2) the time necessary to traverse any arc of a planetary orbit is proportional to the area of the sector between the central body and that arc (the “area law”); and (3) there...

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