Portal:Solar System
The Solar System Portal

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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Fine dust is prevalent across the surface and the atmosphere, being picked up and spread at the low Martian gravity even by the weak wind of the tenuous atmosphere. The terrain of Mars roughly follows a north–south divide, the Martian dichotomy, with the northern hemisphere mainly consisting of relatively flat, low lying plains, and the southern hemisphere of cratered highlands. Geologically, the planet is fairly active with marsquakes trembling underneath the ground, but also hosts many enormous volcanoes that are extinct (the tallest is Olympus Mons, 21.9 km or 13.6 mi tall), as well as one of the largest canyons in the Solar System (Valles Marineris, 4,000 km or 2,500 mi long). Mars has two natural satellites that are small and irregular in shape: Phobos and Deimos. With a significant axial tilt of 25 degrees, Mars experiences seasons, like Earth (which has an axial tilt of 23.5 degrees). A Martian solar year is equal to 1.88 Earth years (687 Earth days), a Martian solar day (sol) is equal to 24.6 hours. (Full article...)
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General images
The following are images from various Solar System-related articles on Wikipedia.
Did you know –
- ...that New York's Panther Mountain (pictured) was the site of a prehistoric meteor crash?
- ...that the Beethoven crater in the Beethoven quadrangle on Mercury is the eleventh largest named impact crater in the Solar System?
- ...that the planet Mars appears red primarily because of a ubiquitous layer of dust containing nanophase ferric oxides?
- ...that the 1997 volcanic eruption of Pillan Patera on Jupiter's moon Io was the largest effusive eruption ever witnessed?
- ...that scarps, ridges, and troughs, such as the 650 km long and 2 km high Discovery Rupes cutting through the Rameau crater, are common features in the Discovery quadrangle on the planet Mercury?
- ...that the Kármán line dividing the Earth's atmosphere and outer space is defined by the Fédération Aéronautique Internationale as 100 km above mean sea level?
- ...that Mars' south polar ice cap may be melting due to global warming?
- ...that Lowell Observatory staff resisted building the telescope used to discover the dwarf planet Pluto until trustee Roger Putnam ordered them to do so?
Categories
| Solar System | ||
|---|---|---|
| Celestial mechanics | Comets | ...in fiction |
| Minor planets | Moons | Planetary missions |
| Planets... | Sun | Surface feature nomenclature... |

Solar System news
- 26 July 2026 – International Space Station expeditions
- Expedition 74, the joint NASA–Roscosmos–ESA expedition aboard the International Space Station, ends after the Soyuz MS-28 undocks and lands on Earth in Kazakhstan. (CNN)
- 16 July 2026 –
- Astronomers report the first observationally confirmed atmosphere around a rocky exoplanet within its star's habitable zone, after detecting helium escaping from the upper atmosphere of LHS 1140 b, a super-Earth approximately 49 light-years from Earth. (Space.com)
- 15 July 2026 – Discoveries of exoplanets
- Astronomers directly image the exoplanet Beta Pictoris d next to its star, located 63 light-years away, using NASA's James Webb Space Telescope and European Southern Observatory's Very Large Telescope. It is also reported to be fainter than its sibling Beta Pictoris b. The discovery is published in the The Astrophysical Journal. (ABC News) (Space.com)
- 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)
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 · 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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