Solar system

Introduction & Top Questions
Composition of the solar system
- Orbits
- Planets and their moons
- Asteroids and comets
- The interplanetary medium
Origin of the solar system
- Early scientific theories
  - The Kant-Laplace nebular hypothesis
  - Twentieth-century developments
- Modern ideas
  - Formation of the solar nebula
  - Differentiation into inner and outer planets
  - Later stages of planetary accretion
  - Formation of the outer planets and their moons
  - The small bodies
  - Formation of ring systems
  - Solution to the angular momentum puzzle
- Studies of other solar systems

References & Edit History Related Topics

Images, Videos & Interactives

Illustration showing the eight planets of the solar system in order from the Sun-Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune-depicted to scale by size, with labeled diameters in miles and kilometers. The Sun is partially visible on the left for comparison.

Diagram of the solar system showing orbital paths of all eight planets around the Sun, labeled from Mercury to Neptune.

Illustration of the solar system showing the orbits of the Sun, eight planets, Moon, asteroid belt, Kuiper belt, Oort cloud, Pluto, and a comet, with distances labeled in astronomical units for scale.

Interactive comparing planet sizes in the solar system from left to right: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Understand the relative size of the Sun, the Moon, and other solar system objects

Hear about the band of dust and debris left by comets, which are visible as meteors (shooting stars)

At a Glance

solar system summary

Quizzes

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

Astronomy and Space Quiz

The orbits of the planets and other elements of the solar system, including asteroids, Kuiper belt, Oort cloud, comet

Space Odyssey

Ursa major constellation illustration art. (Big Dipper) stars, space, night sky)

Stars: Explosions in Space

Saturn. Saturn and its rings. Second largest planet of the solar system. Space Art

Planets and the Earth’s Moon

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 are Centaur objects linked to the Kuiper belt and short-period comets?
How are meteoroids, meteors, and meteorites different?
How are moons in the solar system different from one another?
How are sunspots connected to the Sun’s magnetic field?
How are the inner terrestrial planets different from the outer giant planets?
How can an object in the asteroid belt show cometlike activity?
How can craters reveal the history of a planet or moon’s surface?
How did Isaac Newton explain why planets orbit the Sun?
How did Johannes Kepler use Tycho Brahe’s observations to develop the laws of planetary motion?
How did planetesimals combine to form planets?
How did the Oort cloud get its population of icy objects?
How did the discovery of Kuiper belt objects change scientists’ understanding of Pluto?
How did the solar system form from a cloud of gas and dust?
How do Jupiter and Saturn change the paths of some comets?
How do asteroid orbits differ from comet orbits?
How do convection currents transport energy through the outer part of the Sun?
How do meteorites help scientists study the early solar system?
How do near-Earth asteroids create an impact hazard for Earth?
How do passing stars send some Oort cloud comets toward the inner solar system?
How do solar neutrinos provide evidence about nuclear reactions in the Sun?
How does Newton’s law of gravity relate to Kepler’s laws of planetary motion?
How does nuclear fusion power the Sun?
How does the Oort cloud differ from the Kuiper belt?
How far is Earth from the Sun in astronomical units and kilometres?
How is an astronomical unit used to measure distances in the solar system?
How is the Eta Aquarid meteor shower connected to Halley’s Comet?
How large is the Sun compared with Earth?
How long does sunlight take to travel from the Sun to Earth?
How old is the solar system?
How was the solar neutrino problem solved?
How were Uranus and Neptune discovered?
What are Kepler’s three laws of planetary motion?
What causes the Sun’s 11-year sunspot cycle?
Where do most meteorites found on Earth come from?
Where is the asteroid belt located?
Which objects are recognized as dwarf planets in the solar system?
Which planets are classified as terrestrial planets?
Which planets in the solar system have ring systems?
Which planets orbit the Sun in order from closest to farthest?
Which requirements must an object meet to be classified as a planet by the International Astronomical Union?
Why are Jupiter, Saturn, Uranus, and Neptune much less dense than Earth?
Why are Mercury, Venus, Earth, and Mars rocky planets?
Why are many meteorites found on Antarctic ice flows?
Why did Pluto fail the International Astronomical Union’s definition of a planet?
Why did a planet not form in the asteroid belt between Mars and Jupiter?
Why did icy materials condense farther from the young Sun than rocky materials?
Why do Jupiter and Saturn contain mostly hydrogen and helium?
Why does a small amount of mass become energy during fusion in the Sun?
Why does the Sun contain more than 99 percent of the solar system’s mass?
Why is Halley’s Comet called a periodic comet?
Why is Io one of the most volcanically active bodies in the solar system?
Why is the Sun’s corona much hotter than its visible surface?
Why was Pluto reclassified as a dwarf planet in 2006?
How many planets are in the solar system?
How did the solar system form?

Science Astronomy

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External Websites

Open Library Publishing Platform - Fanshawe College Astronomy - An Overview of the Solar System
The Nine Planets - Solar System Facts
Live Science - The solar system: Facts about our cosmic neighborhood
Physics LibreTexts - Our Solar System
Space.com - Solar system planets, order and formation: A guide

Britannica Websites

Articles from Britannica Encyclopedias for elementary and high school students.

solar system - Children's Encyclopedia (Ages 8-11)
solar system - Student Encyclopedia (Ages 11 and up)

Solar system

astronomy

Written by

Tobias Chant Owen

Professor of Astronomy, University of Hawaii at Manoa, Honolulu. Coauthor of The Planetary System; The Search for Life in the Universe; and numerous research articles.

Tobias Chant Owen

Fact-checked by

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....

Britannica Editors

Last updated

Nov. 11, 2026 •History

Solar system, assemblage consisting of the Sun—an average star in the Milky Way Galaxy—and those bodies orbiting around it: 8 (formerly 9) planets with more than 400 known planetary satellites (moons); many asteroids, some with their own satellites; comets and other icy bodies; and vast reaches of highly tenuous gas and dust known as the interplanetary medium. The solar system is part of the "observable universe," the region of space that humans can actually or...

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