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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 objects that orbit it. It formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc. The Sun is a typical star that maintains a balanced equilibrium by the fusion of hydrogen into helium at its core, releasing this energy from its outer photosphere. Astronomers classify it as a G-type main-sequence star.

The largest objects that orbit the Sun are the eight planets. In order from the Sun, they are four terrestrial planets (Mercury, Venus, Earth and Mars); two gas giants (Jupiter and Saturn); and two ice giants (Uranus and Neptune). All terrestrial planets have solid surfaces. Inversely, all giant planets do not have a definite surface, as they are mainly composed of gases and liquids. Over 99.86% of the Solar System's mass is in the Sun and nearly 90% of the remaining mass is in Jupiter and Saturn.

There is a strong consensus among astronomers that the Solar System has at least nine dwarf planets: Ceres, Orcus, Pluto, Haumea, Quaoar, Makemake, Gonggong, Eris, and Sedna. There are a vast number of small Solar System bodies, such as asteroids, comets, centaurs, meteoroids, and interplanetary dust clouds. Some of these bodies are in the asteroid belt (between Mars's and Jupiter's orbit) and the Kuiper belt (just outside Neptune's orbit). Six planets, seven dwarf planets, and other bodies have orbiting natural satellites, which are commonly called 'moons'.

The Solar System is constantly flooded by the Sun's charged particles, the solar wind, forming the heliosphere. Around 75–90 astronomical units from the Sun, the solar wind is halted, resulting in the heliopause. This is the boundary of the Solar System to interstellar space. The outermost region of the Solar System is the theorized Oort cloud, the source for long-period comets, extending to a radius of 2,000–200,000 AU. The closest star to the Solar System, Proxima Centauri, is 4.25 light-years (269,000 AU) away. Both stars belong to the Milky Way galaxy. (Full article...)

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The Earth seen from Apollo 17.
The Earth seen from Apollo 17.
Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust. The remaining 29.2% of Earth's crust is land, most of which is located in the form of continental landmasses within Earth's land hemisphere. Most of Earth's land is at least somewhat humid and covered by vegetation, while large sheets of ice at Earth's polar deserts retain more water than Earth's groundwater, lakes, rivers and atmospheric water combined. Earth's crust consists of slowly moving tectonic plates, which interact to produce mountain ranges, volcanoes, and earthquakes. Earth has a liquid outer core that generates a magnetosphere capable of deflecting most of the destructive solar winds and cosmic radiation.

Earth has a dynamic atmosphere, which sustains Earth's surface conditions and protects it from most meteoroids and UV-light at entry. It has a composition of primarily nitrogen and oxygen. Water vapor is widely present in the atmosphere, forming clouds that cover most of the planet. The water vapor acts as a greenhouse gas and, together with other greenhouse gases in the atmosphere, particularly carbon dioxide (CO2), creates the conditions for both liquid surface water and water vapor to persist via the capturing of energy from the Sun's light. This process maintains the current average surface temperature of 14.76 °C (58.57 °F), at which water is liquid under normal atmospheric pressure. Differences in the amount of captured energy between geographic regions (as with the equatorial region receiving more sunlight than the polar regions) drive atmospheric and ocean currents, producing a global climate system with different climate regions, and a range of weather phenomena such as precipitation, allowing components such as nitrogen to cycle. (Full article...)

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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 · 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

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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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