The Solar System Portal

The Solar System consists of the Sun and the other celestial objects gravitationally bound to it: the eight planets, their 165 known moons, five currently identified dwarf planets and their four known moons, and billions of small bodies. This last category includes asteroids, Kuiper belt objects, comets, meteoroids and interplanetary dust. In broad terms, the charted regions of the Solar System consist of the Sun, four terrestrial inner planets, an asteroid belt composed of small rocky bodies, four gas giant outer planets, and a second belt, called the Kuiper belt, composed of icy objects. Beyond the Kuiper belt lies the scattered disc, the heliopause, and ultimately the hypothetical Oort cloud. In order of their distances from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Six of the eight planets are in turn orbited by natural satellites, usually termed "moons" after Earth's Moon, and each of the outer planets is encircled by planetary rings of dust and other particles. All the planets except Earth are named after gods and goddesses from Greco-Roman mythology. The five dwarf planets are Pluto, Makemake, and Haumea, the three largest known Kuiper belt objects; Ceres, the largest object in the asteroid belt; and Eris, the largest known object in the scattered disc.

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Jupiter is the fifth planet from the Sun and the largest planet within the solar system. It is two and a half times as massive as all of the other planets in our solar system combined. Jupiter, along with Saturn, Uranus, and Neptune, is classified as a gas giant. When viewed from Earth, Jupiter can reach an apparent magnitude of -2.8, making it the fourth brightest object in the night sky. The planet was known by astronomers of ancient times and was associated with the mythology and religious beliefs of many cultures. Jupiter is primarily composed of hydrogen with only a small proportion of helium; it may also have a rocky core of heavier elements. The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the seventeenth century. Surrounding the planet is a faint planetary ring system and a powerful magnetosphere. There are also at least 63 moons, including the four large moons called the Galilean moons that were first discovered by Galileo Galilei in 1610. Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager fly-by missions and later by the Galileo orbiter.

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Selected picture

Credit: Philipp Salzgeber

Comet Hale-Bopp sails across the sky in the vicinity of Pazin in Istria, Croatia. To the lower right of the comet the Andromeda Galaxy is also faintly visible. The comet was visible to the naked eye for a record 18 months, twice as long as the Great Comet of 1811. At perihelion, it shone brighter than any star in the sky except Sirius, and its two tails stretched 30-40 degrees across the sky. The passage of Hale-Bopp was notable also for inciting a degree of panic about comets not seen for decades. Rumours that the comet was being followed by an alien spacecraft gained remarkable currency, and inspired a mass suicide among followers of the Heaven's Gate cult.

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Did you know...

• ...that the passing of the Great Comet of 1577 (pictured) caused almost century-long debate, during which Galileo argued that comets were merely optical illusions?
• ...that systematic mapping of the Michelangelo quadrangle on Mercury has revealed the presence of four nearly obliterated multi-ring impact basins, possibly the oldest features in the mapped areas of the planet?
• ...that there have been several proposals for space advertising projects, including a giant, 1km² billboard visible from Earth?
• ...that some astrologers claim Earth has a second moon they call Lilith?
• ...that the Caloris Basin on Mercury, one of the largest impact basins in the Solar System, is surrounded by a series of geological formations believed to have been produced by the basin's ejecta?
• ...that Kordylewski clouds are large concentrations of dust that orbit Earth at the distance of the Moon?
• ...that no viable solution has yet been found to counteract radiation from space, which is a serious threat to astronauts on any future mission to Mars?
• ...that Claudia Alexander was the last project manager of NASA's Galileo mission to Jupiter?
• ...that the Tolstoj crater, a 400-km (240 mile) wide impact crater on the planet Mercury has an extensive, and remarkably well-preserved, radially-lineated ejecta blanket?
• ...that Malin Space Science Systems operates the camera on the Mars Global Surveyor?
• ...that Abbott Lawrence Rotch established the Blue Hill Meteorological Observatory in 1885, which maintains the longest-running meteorological record of any observation site in the United States?
• ...that the asteroid 7796 Járacimrman, discovered in 1996 on Kleť Observatory and named after the famous fictitious Czech genius Jára Cimrman, proved to be the lost asteroid that had already been observed in 1973 on Brera-Merate Observatory in northern Italy?

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In the news

Wikinews Space portal

• March 7: Paleontologists reaffirm the cause of dino extinction
• March 2: NASA scientist: Chile earthquake may have shifted Earth's axis, shortened day
• January 14: Cocaine found at Kennedy Space Center
• December 19: NASA flyby of Saturn moon Titan produces first image of liquid on another world
• December 10: Hubble telescope spots oldest galaxies ever seen
• November 22: Ex-cosmonaut Konstantin Feoktistov dies; Soviet space pioneer was 83
• November 22: Astronaut's baby born 200 miles below him
• November 18: Russia may delay launch of "Angara" rocket due to funding cuts
• November 14: NASA mission finds water on the Moon
• November 10: Prospects for a space elevator rise
• October 18: IBEX satellite releases first all sky map
• October 7: New ring discovered around Saturn, could explain dark side of its moon

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	Solar System
Celestial mechanics	Comets	...in fiction
Minor planets	Moons	Planetary missions
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Space	Astronomical objects	Space exploration

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Major topics

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

Sun: Sunspot ˑ Solar wind ˑ Solar flare ˑ Solar eclipse

Mercury: Geology ˑ Exploration (Mariner 10 ˑ MESSENGER ˑ BepiColombo) ˑ Transit

Venus: Geology ˑ Atmosphere ˑ Exploration (Venera ˑ Mariner program 2/5/10 ˑ Pioneer ˑ Vega 1/2ˑ Magellan ˑ Venus Express) ˑ Transit

Earth: History ˑ Geology ˑ Geography ˑ Atmosphere ˑ Rotation

Moon: Geology ˑ Selenography ˑ Atmosphere ˑ Exploration (Luna ˑ Apollo 8/11) ˑ Orbit ˑ Lunar eclipse

Mars: Moons (Phobos ˑ Deimos) ˑ Geology ˑ Geography ˑ Atmosphere ˑ Exploration (Mariner ˑ Mars ˑ Viking 1/2 ˑ Pathfinder ˑ MER)

Ceres: Exploration (Dawn)

Jupiter: Moons (Amalthea, Io ˑ Europa ˑ Ganymede ˑ Callisto) ˑ Rings ˑ Atmosphere ˑ Magnetosphere ˑ Exploration (Pioneer 10/11 ˑ Voyager 1/2 ˑ Ulysses ˑ Cassini ˑ Galileo ˑ New Horizons)

Saturn: Moons (Mimas ˑ Enceladus ˑ Tethys ˑ Dione ˑ Rhea ˑ Titan ˑ Iapetus) ˑ Rings ˑ Exploration (Pioneer 11 ˑ Voyager 1/2 ˑ Cassini–Huygens)

Uranus: Moons (Miranda ˑ Ariel ˑ Umbriel ˑ Titania ˑ Oberon) ˑ Rings ˑ Exploration (Voyager 2)

Neptune: Moons (Triton) ˑ Rings ˑ Exploration (Voyager 2)

Planets beyond Neptune

Pluto: Moons (Charon, Nix, Hydra) ˑ Exploration (New Horizons)

Haumea: Moons (Hi'iaka, Namaka)

Makemake

Eris: Dysnomia

Small bodies: Meteoroids ˑ Asteroids (Asteroid belt) ˑ Centaurs ˑ TNOs (Kuiper belt ˑ Scattered disc ˑ Oort cloud) ˑ Comets (Hale-Bopp ˑ Halley's ˑ Hyakutake ˑ Shoemaker-Levy 9)

Formation and evolution of the Solar System: History of Solar System formation and evolution hypotheses ˑ Nebular hypothesis

See Also: Featured content ˑ Featured topic ˑ Good articles ˑ List of objects

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Here are some tasks you can do: Requests: To help us assess the quality and importance of Solar System articles, please see: Category:Unassessed Solar System articles and Category:Unknown-importance Solar System articles. Stubs: Beagle (crater), Early bombardment phase, Kordylewski cloud, List of Solar System bodies formerly regarded as planets, Small Solar System body, Solar conjunction