Portal:Solar System
The Solar System Portal
The Solar System is the gravitationally bound system of the Sun and the objects that orbit it. The largest of these objects are the eight planets, which in order from the Sun are four terrestrial planets (Mercury, Venus, Earth and Mars); two gas giants (Jupiter and Saturn); and two ice giants (Uranus and Neptune). The Solar System developed 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc.
All four terrestrial planets belong to the inner Solar System and have solid surfaces. Inversely, all four giant planets belong to the outer Solar System and do not have a definite surface, as they are mainly composed of gases and liquids. 99.86% of the Solar System's mass is in the Sun and nearly 90% of the remaining mass are in Jupiter and Saturn. There is a strong consensus among astronomers that the Solar System has eight dwarf planets, which consist of one asteroid-belt object – Ceres; four Kuiper-belt objects – Pluto, Haumea, Quaoar, and Makemake; and three scattered-disc objects – Gonggong, Eris, and Sedna.
There are a vast number of smaller objects orbiting the Sun, called small Solar System bodies. This category includes asteroids, comets, centaurs, meteoroids and interplanetary dust clouds. Many of these objects are in the asteroid belt between the orbits of Mars and Jupiter (1.5–4.5 AU), and the Kuiper belt just outside Neptune's orbit (30–50 AU). Six of the major planets, the six largest possible dwarf planets, and many of the smaller bodies are orbited by natural satellites, commonly called "moons" after Earth's Moon. Two natural satellites, Jupiter's moon Ganymede and Saturn's moon Titan, are larger than Mercury, the smallest terrestrial planet, though they are less massive.
The Solar System is constantly flooded by the Sun's charged particles, the Solar wind, forming the heliosphere. Pushed against by the surrounding interstellar medium of the Local Cloud, the Solar wind starts slowing at 75 to 90 AU (the termination shock), before being halted, resulting in the heliopause, the boundary of the Solar System to interstellar space. The outermost region of the Solar System is the Oort cloud, the source for long-period comets, extending from 2,000 AU to the edge of the Solar System's sphere of gravitational influence at up to 200,000 AU (3.2 ly). The closest star to the Solar System, Proxima Centauri, is 4.25 ly away. The Solar System orbits the Galactic Center of the Milky Way galaxy, as part of its Orion Spur, at a distance of 26,000 ly. (Full article...)
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Jupiter was the first planet to form, and its inward migration during the primordial Solar System impacted much of the formation history of the other planets. Jupiter is primarily composed of hydrogen (90% by volume), followed by helium, which makes up a quarter of its mass and a tenth of its volume. The ongoing contraction of Jupiter's interior generates more heat than the planet receives from the Sun. Its internal structure is believed to consist of an outer mantle of fluid metallic hydrogen, and a diffuse inner core of denser material. Because of its rapid rotation rate of 1 rotation per 10 hours, Jupiter's shape is an oblate spheroid: it has a slight but noticeable bulge around the equator. The outer atmosphere is divided into a series of latitudinal bands, with turbulence and storms along their interacting boundaries. The most obvious result of this is the Great Red Spot, a giant storm which has been observed since 1831 and possibly earlier. (Full article...)
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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 the south pole of the planet Mercury is located in the Bach quadrangle?
- ...that the Sweden Solar System is currently the world's largest scale model of the Solar System?
- ...that the dominant feature in the Shakespeare quadrangle is the 1300 km wide Caloris Planitia, the largest and best preserved impact basin on Mercury observed by the spacecraft Mariner 10?
- ...that the nearly circular shape of Lukanga Swamp, a wetland covering 2,600 km² in Central Province, Zambia, has led to speculation that it may be a crater formed by the impact of a meteorite?
Categories
Solar System | ||
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Celestial mechanics | Comets | ...in fiction |
Minor planets | Moons | Planetary missions |
Planets... | Sun | Surface feature nomenclature... |
In the news
- April 7: NASA's helicopter Ingenuity survives its first night at Mars
- December 25: 'Earth-based life can survive in hydrogen-rich atmospheres': MIT professor Dr Seager tells Wikinews about her research on organisms thriving in oxygen-less environment
- July 7: Astronomer Anthony Boccaletti discusses observation of birth of potential exoplanet with Wikinews
- May 31: SpaceX successfully launches its first crewed spaceflight
- May 22: Astronomer tells Wikinews about discovery of closest black hole known so far
- October 12: Cosmonaut Alexei Leonov dies at age 85
- October 10: Swedish academy announces 2019 Nobel Prize winners in physics
- September 14: Astronomers find water vapour in atmosphere of exoplanet K2-18b
- March 5: SpaceX Crew Dragon capsule docks with International Space Station
- January 9: Simple animals could live in Martian brines: Wikinews interviews planetary scientist Vlada Stamenković
- November 29: NASA's InSight Lander makes it to Mars
- October 12: Manned Soyuz space mission aborts during launch
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) · Exploration (New Horizons)
- Haumea: Moons (Hi'iaka, Namaka)
- Makemake
- Eris: Dysnomia
- 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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