Portal:Solar system

☆ Save On Wikipedia ↗

The Solar System Portal

The Sun and planets of the Solar System (distances not to scale)

The Solar System is the gravitationally bound system of the Sun and the masses that orbit it, most prominently its eight planets, of which Earth is one. The Solar System is an isolated single-star planetary system (not part of a larger star system) within the Milky Way Galaxy. The system formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, creating the Sun and a protoplanetary disc from which the orbiting bodies assembled.

The Sun accounts for 99.86% of the Solar System's total mass. Inside the Sun's core, hydrogen is fused into helium, releasing energy that is emitted through the Sun's photosphere. This creates the heliosphere and a decreasing temperature gradient across the Solar System.

The next most massive objects of the system are the eight planets, which by definition dominate the orbits they occupy. Closest to the Sun in order of increasing distance are the terrestrial planetsMercury, Venus, Earth and Mars. These four planets are part of the inner Solar System. Earth and Mars are the only planets that orbit within the Sun's habitable zone, in which sunlight can keep surface water liquid under atmospheric pressure. Beyond the frost line at about five astronomical units (AU), are the planets of the outer Solar System: two gas giants (Jupiter and Saturn) and two ice giants (Uranus and Neptune). Jupiter and Saturn possess nearly 90% of the non-stellar mass of the Solar System.

Objects of planetary mass that do not dominate their orbit but directly orbit the Sun are called dwarf planets. The International Astronomical Union's Minor Planet Center lists Ceres, Pluto, Eris, Makemake, and Haumea as dwarf planets. Four other Solar System objects are generally identified as such: Orcus, Quaoar, Gonggong, and Sedna. Less massive than the dwarf planets are the vast number of small Solar System bodies, such as asteroids, comets, centaurs, meteoroids, and interplanetary dust clouds. The dwarf planet Ceres and many of these smaller bodies are located in the asteroid belt (between Mars's and Jupiter's orbit), while all other dwarf planets are members of populations of trans-Neptunian objects, which may be found in the Kuiper belt just outside Neptune or in the further scattered disc. (Full article...)

Selected article –

Io (moon).
Io (moon).
Io (pronounced /ˈaɪoʊ/ eye'-oe, or as Greek Ῑώ) is the innermost of the four Galilean moons of Jupiter and, with a diameter of 3,642 kilometers, the fourth largest moon in the Solar System. It was discovered in 1610 by Galileo Galilei, along with the other Galilean satellites. This discovery furthered the adoption of the Copernican model of the Solar System and the development of Kepler's laws of motion. Unlike most satellites in the outer Solar System (which have a thick coating of ice), Io is primarily composed of silicate rock surrounding a molten iron or iron sulfide core. Io has one of the most geologically active surfaces in the solar system, with over 400 active volcanoes. This extreme geologic activity is the result of tidal heating from friction generated within Io's interior by Jupiter's varying pull. Several volcanoes produce plumes of sulfur and sulfur dioxide that climb as high as 500 km (310 mi). Io's surface is also dotted with more than 100 mountains that have been uplifted by extensive compression at the base of the moon's silicate crust. Some of these peaks are taller than Earth's Mount Everest. Most of Io's surface is characterized by extensive plains coated with sulfur and sulfur dioxide frost. (Full article...)

Selected picture

Did you know –

Categories

Solar System news

16 June 2026 – Discoveries of exoplanets
The NASA's James Webb Space Telescope discovers that the Hot Jupiter exoplanet HD 80606 b is being roasted by its home star. The research findings were presented at the 248th American Astronomical Society in Pasedena, California, U.S. (Space.com)
9 June 2026 – Artemis program
NASA announces that its astronauts Randy Bresnik, Frank Rubio, and Andre Douglas, and ESA astronaut Luca Parmitano will crew the Artemis III mission in late 2027. The mission's goal is to evaluate rendezvous and docking operations with SpaceX's Starship HLS and Blue Origin's Blue Moon spacecraft. (NBC News)
21 April 2026 – Mars Exploration Program
NASA announces that the Curiosity rover has detected more than 20 organic molecules on Mars using a chemical analysis method involving tetramethylammonium hydroxide, conducted for the first time on another planet, indicating the long-term preservation of compounds associated with prebiotic chemistry. (AFP via The Manila Times)
10 April 2026 – Artemis program
NASA's Artemis II spacecraft completes its mission and splashes down in the northern Pacific Ocean near San Diego, California, U.S. (The Guardian) (Space.com)
6 April 2026 – Artemis program
NASA's Artemis II spacecraft carrying four astronauts breaks the record for furthest distance humans have ever travelled from Earth surpassing the previous 248,655 miles (400,171 kilometers) record set by Apollo 13 in April 1970. (AP)

Major topics

Solar System: Planets (Definition · Planetary habitability · Terrestrial planets · Gas giants · Rings) · Dwarf planets (Plutoid) · Colonization · Discovery timelineˑ Exploration · Moons · Planetariums

Sun: Sunspot · Solar wind · Solar flare · Solar eclipse
Mercury: Geology · Exploration (Mariner 10 · MESSENGER · BepiColombo) · Transit
Venus: Geology · Atmosphere · Exploration (Venera · Mariner program 2/5/10 · Pioneer · Vega 1/2ˑ Magellan · Venus Express) · Transit
Earth: History · Geology · Geography · Atmosphere · Rotation
Moon: Geology · Selenography · Atmosphere · Exploration (Luna · Apollo 8/11) · Orbit · Lunar eclipse
Mars: Moons (Phobos · Deimos) · Geology · Geography · Atmosphere · Exploration (Mariner · Mars · Viking 1/2 · Pathfinder · MER)
Ceres: Exploration (Dawn)
Jupiter: Moons (Amalthea, Io · Europa · Ganymede · Callisto) · Rings · Atmosphere · Magnetosphere · Exploration (Pioneer 10/11 · Voyager 1/2 · Ulysses · Cassini · Galileo · New Horizons)
Saturn: Moons (Mimas · Enceladus · Tethys · Dione · Rhea · Titan · Iapetus) · Rings · Exploration (Pioneer 11 · Voyager 1/2 · CassiniHuygens)
Uranus: Moons (Miranda · Ariel · Umbriel · Titania · Oberon) · Rings · Exploration (Voyager 2)
Neptune: Moons (Triton) · Rings · Exploration (Voyager 2)
Planets beyond Neptune
Pluto: Moons (Charon, Nix, Hydra, Kerberos, Styx) · Geology · Atmosphere · Exploration (New Horizons)
Haumea: Moons (Hi'iaka, Namaka) · Ring
Quaoar: Weywot · Rings
Makemake: S/2015 (136472) 1
Gonggong: Xiangliu
Eris: Dysnomia
Sedna
Small bodies: Meteoroids · Asteroids (Asteroid belt) · Centaurs · TNOs (Kuiper belt · Scattered disc · Oort cloud) · Comets (Hale–Bopp · Halley's · Hyakutake · Shoemaker–Levy 9)
Formation and evolution of the Solar System: History of Solar System formation and evolution hypotheses · Nebular hypothesis
See also: Featured content · Featured topic · Good articles · List of objects

Bold articles are featured.
Italicized articles are on dwarf planets or major moons.

Things you can do

The planet Saturn, see here eclipsing the sun
The planet Saturn, see here eclipsing the sun

Associated Wikimedia

The following Wikimedia Foundation sister projects provide more on this subject:

Discover Wikipedia using portals