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Portal:Solar System

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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 planets – Mercury, 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...)

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Io, with two plumes erupting from its surface.
Io, with two plumes erupting from its surface.
Volcanism on Io, a moon of Jupiter, produces lava flows, volcanic pits, and plumes of sulfur and sulfur dioxide hundreds of kilometres high. This volcanic activity was discovered in 1979 by Voyager 1 imaging scientists. Observations of Io by passing spacecraft and Earth-based astronomers have revealed more than 150 active volcanoes. Io's volcanism makes the satellite one of only four known volcanically active worlds in the solar system. First predicted shortly before the Voyager 1 flyby, the heat source for Io's volcanism comes from tidal heating produced by Io's forced orbital eccentricity. Io's volcanism has led to the formation of hundreds of volcanic centres and extensive lava formations, making the moon the most volcanically active body in the solar system. Three different types of volcanic eruptions have been identified, differing in duration, intensity, lava effusion rate, and whether the eruption occurs within a volcanic pit. Lava flows on Io, tens or hundreds of kilometres long, have primarily basaltic composition, similar to lavas seen on Earth at shield volcanoes such as Kīlauea in Hawaii. As a result of the presence of significant quantities of sulfurous materials in Io's crust and on its surface, during some eruptions, sulfur, sulfur dioxide gas, and pyroclastic material are blown up to 500 kilometres (310 mi) into space, producing large, umbrella-shaped volcanic plumes. (Full article...)

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Major categories
Solar System
Celestial mechanics Comets ...in fiction
Minor planets Moons Planetary missions
Planets... Sun Surface feature nomenclature...


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Solar System news

1 October 2026 – SpaceX Crew-13
The SpaceX Crew-13 mission to the International Space Station launches, carrying two NASA astronauts, one Roscosmos cosmonaut, and one Canadian Space Agency astronaut, from Cape Canaveral Space Force Station in Florida, United States. (AFP via France 24)
16 September 2026 – Discoveries of exoplanets
Astronomers confirm the existence of Elias 2-24 b, the youngest known exoplanet, which is less than one million years old and located approximately 450 light-years from Earth. The discovery was observed through the W.M. Keck Observatory in Mauna Kea, Hawaii, U.S., using a coronagraph. (Space.com)
16 September 2026 –
NASA's Lunar Reconnaissance Orbiter discovers a recently formed crater on the moon larger than the Colosseum in Rome, Italy. (Phys.org)
3 September 2026 –
The BepiColombo begins its final mission to Mercury, eight years after its launch by the European Space Agency and the Japan Aerospace Exploration Agency. (Space.com)
NASA discovers a 10–sided pattern on the south pole of Saturn using its Hubble Space Telescope from the Goddard Space Flight Center in Maryland, United States. (The Peninsula) (ScienceDaily)

Major topics

The SunMercuryVenusThe MoonEarthMarsPhobos and DeimosCeresThe main asteroid beltJupiterMoons of JupiterSaturnMoons of SaturnUranusMoons of UranusNeptuneMoons of NeptunePlutoMoons of PlutoHaumeaMoons of HaumeaMakemakeThe Kuiper BeltErisDysnomiaThe Scattered DiscThe Hills CloudThe Oort Cloud

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 · Cassini–Huygens)
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.

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

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