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Planet
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solar system to scale
A white man in glasses holds a microphone under the text. Ask an Editor, and. What is planetary alignment?, against a starry space background.
The Sun and planets in its orbit.
Learn about the dwarf planets within our solar system
Explore exoplanets and the techniques used to detect them
Which of these planets is made up mostly of gases? Diagram showing the Moon orbiting Earth, with arrows illustrating gravitational forces between them and how gravity alters the Moon's natural path, resulting in its curved orbit around the planet.
Know the ten interesting facts that prove the earth is round
At a Glance
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planet summary
Quizzes
Model of a molecule. Atom, Biology, Molecular Structure, Science, Science and Technology. Homepage 2010 arts and entertainment, history and society
Science Quiz
The orbits of the planets and other elements of the solar system, including asteroids, Kuiper belt, Oort cloud, comet
Space Odyssey
Saturn. Saturn and its rings. Second largest planet of the solar system. Space Art
Planets and the Earth’s Moon
1 July 2002: The Solar and Heliospheric Observatory (SOHO) satellite reveals a massive solar eruption more than 30 times the Earth's diameter. The eruption formed when a loop of a magnetic field over the surface of the Sun trapped hot gas.
Brightest Star in the Solar System
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
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Planet: References & Edit History

Article Contributors

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  • 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 09, 2026
Modified link of Web site: IOPScience - The Astronomical Journal - What is a Planet? Sep 18, 2026
Media added. Jul 23, 2026
Add new Web site: The Open University - OpenLearn - What is a planet? Dec 29, 2025
Media added. Sep 09, 2025
Add new Web site: Journal of Emerging Technologies and Innovative Research - Formation of Planets in Solar System. Nov 18, 2024
Added material about extrasolar planets. Sep 27, 2024
Add new Web site: American Geosciences Institute - What is a Planet? Sep 20, 2024
Add new Web site: IOPScience - The Astronomical Journal - What is a Planet? Apr 19, 2024
Add new Web site: Space.com - Solar system planets, order and formation: A guide. Mar 07, 2024
Add new Web site: The Planets - Planet Facts – The Planets In Order. Sep 07, 2023
Add new Web site: OpenStax - Astronomy 2e - Composition and Structure of Planets. Oct 26, 2022
Add new Web site: The Planetary Society - What is a Planet? Aug 20, 2022
Media added. Nov 14, 2019
Revised title etymology. Oct 01, 2019
Corrected display issue. May 30, 2019
Media added. Dec 07, 2017
Added video. Jan 08, 2016
Add new Web site: Rader's Cosmos4Kids.com - What Makes a Planet? Jun 03, 2014
Add new Web site: National Geographic Kids - Space - What is a Planet? Jun 02, 2014
Add new Web site: Quatr.us - Planet. Mar 10, 2013
Add new Web site: How Stuff Works - Science - Planet. Feb 05, 2013
Add new Web site: National Geographic Society - Encyclopedic Entry - Planet. Feb 05, 2013
Add new Web site: Buzzle.com - Planet. Feb 05, 2013
Add new Web site: NASA Hubblesite - Discovering Planet Beyond. Feb 05, 2013
Add new Web site: Smithsonian National Air and Space Museum - Exploring the Planets. Feb 05, 2013
Add new Web site: Enchanted Learning - Planet. Feb 05, 2013
Add new Web site: Planets of the Solar System. Feb 01, 2013
Add new Web site: Planets of the Solar System. Feb 01, 2013
Add new Web site: Planets of the Solar System. Feb 01, 2013
Add new Web site: Planets of the Solar System. Feb 01, 2013
Add new Web site: How Stuff Works - Science - Planet. Oct 18, 2011
Added new Web site: Royal Museums Greenwich - Eclipse. May 10, 2009
Added new Web site: Sea and Sky - Planets. Apr 16, 2009
Added new Web site: National Geographic - Science and Space - Planets. Apr 16, 2009
Article revised and updated. Jun 12, 2008
Added new Web site: Office of Naval Research - Observing the Sky: Observing the Planets - Introduction. May 19, 2008
Added new Web site: NASA - The Terrestrial Planet Finder. Apr 26, 2007
Added new Web site: Michael E. Brown - California Institute of Technology - Discovery of Eris. Mar 28, 2007
Added new Web site: Michael E. Brown - California Institute of Technology - Discovery of Eris. Mar 28, 2007
Added new Web site: NASA - Solar System Exploration. Dec 14, 2006
Added new Web site: NASA Science - About the Planets. Nov 07, 2006
Added new Web site: NASA's Planetary Photojournal. Nov 07, 2006
Article revised and updated. Sep 29, 2006
Added new Web site: University of Tennessee - Astronomy 161: The Solar System. Jun 30, 2006
Added new Web site: The Nine Planets - Phobos. Jun 08, 2006
Added new Web site: The Nine Planets - Phobos. Jun 08, 2006
Added new Web site: Sun, Planet and Satellite Data. May 11, 2006
Added new Web site: Sun, Planet and Satellite Data. May 11, 2006
Article revised and updated. Apr 06, 2006
Article revised. Oct 23, 1998
Article added to new online database. Jul 20, 1998
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