The Solar System Portal
The Solar System is the gravitationally bound system of the Sun and the objects that orbit it. It was 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...)
Selected article –
Formation and evolution of the Solar System.
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Jupiter Credit: Cassini probeJupiter is the fifth planet from the Sun and by far the largest within the Solar System. It is 318 times more massive than Earth, with a diameter 11 times that of Earth, and with a volume 1300 times that of Earth. Its best known feature is the Great Red Spot, a storm larger than Earth, which was first observed by Galileo four centuries ago. This picture, taken by the Cassini orbiter was one of 26 thousand images taken of Jupiter during the course of its flyby and is the most detailed global color portrait of the planet ever produced. -
Image: Tom RuenAn animation of the phases of the Moon. As the Moon revolves around the Earth, the Sun lights the Moon from a different side, creating the different phases. In the image, the Moon appears to get bigger as well as "wobble" slightly. Tidal locking synchronizes the Moon's rotation period on its axis to match its orbital period around the earth. These two periods nearly cancel each other out, except that the Moon's orbit is elliptical. This causes its orbital motion to speed up when closer to the Earth, and slow down when farther away, causing the Moon's apparent diameter to change, as well as the wobbling motion observed. -
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Comet Hale-Bopp 29-03-1997 Credit: Philipp SalzgeberComet 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 inspired a mass suicide among followers of the Heaven's Gate cult. -
Image credit: Cassini orbiterThe most detailed full-disc view of Titan, the largest moon of Saturn and second-largest in the Solar System. The brighter region on the right side and equatorial region is named Xanadu, and the large, dark region at the center is Shangri-la. This image has been processed to reduce the effects of the atmosphere and to sharpen surface features. It has been trimmed to show only the illuminated surface and not the atmosphere above the edge of the moon. -
Photo credit: Mars Reconnaissance OrbiterPhobos, the larger and closer of the two moons of Mars, as seen from about 6,000 kilometres (3,700 mi) away. A small, irregularly shaped object, Phobos orbits about 9,377 km (5,827 mi) from the center of Mars, closer to its primary than any other planetary moon. The illuminated part of Phobos seen in the images is about 21 km (13 mi) across. The most prominent feature in the images is the large crater Stickney in the lower right. With a diameter of 9 km (5.6 mi), it is the largest feature on Phobos. -
Photo credit: The Apollo 17 crewThe Blue Marble is a famous photograph of Earth. NASA officially credits the image to the entire Apollo 17 crew — Eugene Cernan, Ronald Evans and Jack Schmitt — all of whom took photographic images during the mission. Apollo 17 passed over Africa during daylight hours and Antarctica is also illuminated. The photograph was taken approximately five hours after the spacecraft's launch, while en route to the Moon. Apollo 17, notably, was the last manned lunar mission; no humans since have been at a range where taking a "whole-Earth" photograph such as "The Blue Marble" would be possible. -
Photograph: NASA/Dan BurbankComet Lovejoy is a long-period comet and Kreutz Sungrazer which was discovered in 2011. Named after its discoverer, Terry Lovejoy, the comet was nicknamed "The Great Christmas Comet" owing to it becoming visible near Christmas. -
Photo credit: Joaquim Alves GasparIllustration of the Ptolemaic geocentric model of the Universe (the theory that the Earth is the center of the universe) by Portuguese cosmographer and cartographer Bartolomeu Velho. Taken from his treatise Cosmographia, made in Paris, 1568. Notice the distances of the bodies to the centre of the Earth (left) and the times of revolution, in years (right). -
The Day the Earth Smiled refers to the date July 19, 2013, on which the Cassini spacecraft turned to image Saturn, its entire ring system, and the Earth from a position where Saturn eclipsed the Sun. Cassini imaging team leader and planetary scientist Carolyn Porco called for all the world's people to reflect on humanity's place in the cosmos, to marvel at life on Earth, and to look up and smile in celebration. The final mosaic, shown here, was released four months later and includes planets Earth, Mars, and Venus, and a host of Saturnian moons. -
These images are composites of the complete radar image collection obtained by the Magellan mission. The Magellan spacecraft was launched aboard Space Shuttle Atlantis in May 1989 and began mapping the surface of Venus in September 1990. The spacecraft continued to orbit Venus for four years, returning high-resolution images, altimetry, thermal emissions and gravity maps of 98 percent of the surface. Magellan spacecraft operations ended on October 12, 1994, when the radio contact was lost with the spacecraft during its controlled descent into the deeper portions of the Venusian atmosphere.
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Mars, the fourth planet from the Sun, is named after the Roman god of war because of its blood red color. Mars has two small, oddly-shaped moons, Phobos and Deimos, named after the sons of the Greek god Ares. At some point in the future Phobos will be broken up by gravitational forces. The atmosphere on Mars is 95% carbon dioxide. In 2003 methane was also discovered in the atmosphere. Since methane is an unstable gas, this indicates that there must be (or have been within the last few hundred years) a source of the gas on the planet.
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Solar eclipse of 11 August 1999 The solar eclipse of 1999 August 11, as seen from France. This was the most viewed total eclipse in human history, although some areas offered impaired visibility due to adverse weather conditions. The path of the Moon's shadow began in the Atlantic Ocean, before traversing Cornwall, northern France, southern Germany, Austria, Hungary and northern Serbia. Its maximum was in Romania, and it continued across the Black Sea, Turkey, Iran, southern Pakistan and India. -
Earthrise, as seen by Apollo 8 Credit: William AndersEarthrise, the first occasion in which humans saw the Earth seemingly rising above the surface of the Moon, taken during the Apollo 8 mission on December 24, 1968. This view was seen by the crew at the beginning of its fourth orbit around the Moon, although the first photograph taken was in black-and-white. Note that the Earth is in shadow here. A photo of a fully lit Earth would not be taken until the Apollo 17 mission. -
Realistic-color mosaic of images of Jupiter's moon Europa taken by NASA's Jupiter orbiter Galileo in 1995 and 1998. This view of the moon's anti-Jovian hemisphere shows numerous lineae, linear features created via a tectonic process in which crustal plates of water ice floating on a subsurface ocean (kept warm by tidal flexing) shift in relative position. Reddish regions are areas where the ice has a higher mineral content. The north polar region is at right. (Geologic features are annotated in Commons.) -
A TRACE image of sunspots on the surface, or photosphere, of the Sun from September 2002, is taken in the far ultraviolet on a relatively quiet day for solar activity. However, the image still shows a large sunspot group visible as a bright area near the horizon. Although sunspots are relatively cool regions on the surface of the Sun, the bright glowing gas flowing around the sunspots have a temperature of over one million °C (1.8 million °F). The high temperatures are thought to be related to the rapidly changing magnetic field loops that channel solar plasma.
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Photo credit: Mars Reconnaissance OrbiterFalse-color Mars Reconnaissance Orbiter image of a side of the Chasma Boreale, a canyon in the polar ice cap of the Planum Boreum (north pole of Mars). Light browns are layers of surface dust, greys and blues are layers of water and carbon dioxide ice. Regular geometric cracking is indicative of higher concentrations of water ice.
The Planum Boreum's permanent ice cap has a maximum depth of 3 km (1.9 mi). It is roughly 1200 km (750 mi) in diameter, an area equivalent to about 1½ times the size of Texas. The Chasma Boreale is up to 100 km (62.5 mi) wide and features scarps up to 2 km (1.25 mi) high. For a comparison, the Grand Canyon is approximately 1.6 km (1 mi) deep in some places and 446 km (279 mi) long but only up to 24 km (15 mi) wide. -
A true-color image of Io, one of the moons of Jupiter, taken by the Galileo spacecraft. The dark spot just left of the center is the erupting volcano Prometheus. The whitish plains on either side of it are coated with volcanically deposited sulfur dioxide frost, whereas the yellower regions contain a higher proportion of sulfur. -
Photo credit: Cassini orbiterThis polar map of Jupiter, taken by the Cassini orbiter as it neared Jupiter during a flyby on its way to Saturn, is the most detailed global color map of the planet ever produced. The south pole is in the center of the map and the equator is at the edge. The map shows a variety of colorful cloud features, including parallel reddish-brown and white bands, the Great Red Spot, multi-lobed chaotic regions, white ovals, and many small vortexes. Many clouds appear in streaks and waves due to continual stretching and folding by Jupiter's winds and turbulence. -
Lakes of methane on TitanImage credit: Cassini orbiterThis false-color radar image taken by the Cassini orbiter provides convincing evidence for large bodies of liquid methane on Titan. Images taken during a fly-by of the moon on July 22, 2006 show more than 75 large bodies of liquid ranging in diameter from three to 70km (1.9 to 43.6 mi) in the moon's northern hemisphere. Intensity in this colorized image is proportional to how much radar brightness is returned. The lakes, darker than the surrounding terrain, are emphasized here by tinting regions of low backscatter in blue. Radar-brighter regions are shown in tan. Smallest details in this image are about 500 m (1,640 ft) across. On January 3, 2007, NASA announced that scientists have "definitive evidence of lakes filled with methane on Saturn's moon Titan." -
Photo credit: Cassini orbiterHyperion, a moon of Saturn, is one of the largest highly irregular (non-spherical) bodies in the Solar System. Enhanced image processing was used to bring out details and color differences in this photo taken by the Cassini orbiter. Hyperion is entirely saturated with deep, sharp-edged craters that give it the appearance of a giant sponge. Dark material fills the bottom of each crater. -
The Milky Way is the galaxy that contains the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term Milky Way is a translation of the Latin via lactea, from the Greek γαλαξίας κύκλος (galaxías kýklos, 'milky circle'). From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies.
This picture shows a portion of the Milky Way as seen from Cerro Paranal in Chile, home to the European Southern Observatory (ESO)'s Very Large Telescope, depicting the region spanning the constellations from Sagittarius to Scorpius. The colourful nebulae surrounding Rho Ophiuchi and Antares can be seen to the right, while the dusty lane of the galaxy runs obliquely through the image, dotted with reddish objects such as the Lagoon and Trifid Nebulae. This region of the Milky Way also includes the Galactic Center, likely containing a supermassive black hole, Sagittarius A*. -
Saturn's moon Mimas, as imaged by the Cassini spacecraft. It was discovered on 17 September 1789 by English astronomer William Herschel, and was named after Mimas, a son of Gaia in Greek mythology, by Herschel's son John. The large Herschel Crater is the dominating feature of the moon. With a diameter of 396 km (246 mi), it is the smallest astronomical body that is known to be rounded due to self-gravitation.
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General images
The following are images from various Solar System-related articles on Wikipedia.
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Simulation showing outer planets and Kuiper belt:
a) Before Jupiter/Saturn 2:1 resonance
b) Scattering of Kuiper belt objects into the Solar System after the orbital shift of Neptune
c) After ejection of Kuiper belt bodies by JupiterOrbit of JupiterOrbit of SaturnOrbit of UranusOrbit of Neptune(from Formation and evolution of the Solar System) -
Relative size of the Sun as it is now (inset) compared to its estimated future size as a red giant (from Formation and evolution of the Solar System) -
Orbit classification of Kuiper belt objects. Some clusters that is subjected to orbital resonance are marked. (from Solar System) -
Overview of the inner Solar System up to Jupiter's orbit (from Solar System) -
True-scale Solar System diagram made by Emanuel Bowen in 1747. At that time, Uranus, Neptune, nor the asteroid belts have been discovered yet. (from Solar System) -
Diagram of the Local Interstellar Cloud, the G-Cloud and surrounding stars. As of 2022, the precise location of the Solar System in the clouds is an open question in astronomy. (from Solar System) -
The Sun in true white color (from Solar System) -
The motion of 'lights' moving across the sky is the basis of the classical definition of planets: wandering stars. (from Solar System) -
Comet Hale–Bopp seen in 1997 (from Solar System) -
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To-scale diagram of distance between planets, with the white bar showing orbital variations. The size of the planets is not to scale. (from Solar System) -
Comparison of the habitable zones for different stellar temperatures, with a sample of known exoplanets plus the Earth, Mars, and Venus (from Solar System) -
Hubble image of protoplanetary discs in the Orion Nebula, a light-years-wide stellar nursery probably very similar to the primordial nebula from which the Sun formed (from Formation and evolution of the Solar System) -
The current Sun compared to its peak size in the red-giant phase (from Solar System)
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The planets, zodiacal light and meteor shower (top left of image) (from Solar System) -
Diagram of the Sun's magnetosphere and helioshealth (from Solar System) -
Pierre-Simon Laplace, one of the originators of the nebular hypothesis (from Formation and evolution of the Solar System) -
Meteor Crater in Arizona. Created 50,000 years ago by an impactor about 50 metres (160 ft) across, it shows that the accretion of the Solar System is not over. (from Formation and evolution of the Solar System) -
The orbits of Sedna, 2012 VP113, Leleākūhonua, and other very distant objects along with the predicted orbit of the hypothetical Planet Nine (from Solar System) -
The Solar System (left) within the interstellar medium, with the different regions and their distances on a logarithmic scale (from Solar System) -
The outer planets Jupiter, Saturn, Uranus and Neptune, compared to the inner planets Earth, Venus, Mars, and Mercury at the bottom right (from Solar System) -
Diagram of the Milky Way, with galactic features and the relative position of the Solar System labelled. (from Solar System) -
The four largest asteroids: Ceres, Vesta, Pallas, Hygiea. Only Ceres and Vesta have been visited by a spacecraft and thus have a detailed picture. (from Solar System) -
The orbital eccentricities and inclinations of the scattered disc population compared to the classical and resonant Kuiper belt objects (from Solar System) -
Neptune and its moon Triton, taken by Voyager 2. Triton's orbit will eventually take it within Neptune's Roche limit, tearing it apart and possibly forming a new ring system. (from Formation and evolution of the Solar System) -
Plot of objects around the Kuiper belt and other asteroid populations. J, S, U and N denotes Jupiter, Saturn, Uranus and Neptune. (from Solar System) -
Diagram of the early Solar System's protoplanetary disk, out of which Earth and other Solar System bodies formed (from Solar System) -
Animations of the Solar System's outer planets orbiting. This animation is 100 times faster than the inner planet animation. (from Solar System) -
The Ring nebula, a planetary nebula similar to what the Sun will become (from Formation and evolution of the Solar System) -
Artist's conception of a protoplanetary disk (from Formation and evolution of the Solar System) -
Artist's conception of the giant impact thought to have formed the Moon (from Formation and evolution of the Solar System) -
Location of the Solar System within the Milky Way (from Formation and evolution of the Solar System) -
Animations of the Solar System's inner planets orbiting. Each frame represents 2 days of motion. (from Solar System)
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Did you know –
- ...that although NASA originally thought that there was only one scalloped margin dome on the planet Venus (pictured), they have since discovered hundreds of them?
- ...that the Battle of Szkłów in 1654 occurred during a solar eclipse?
- ...that NASA engineer Harvey Allen's "Blunt Body Theory" made possible the design of heat shields that protected the Mercury, Gemini and Apollo astronauts?
- ...that the Explorer 32 satellite was able to determine the density of the upper atmosphere through ground-based observations of the effect of drag on the satellite?
- ...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?
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- April 7: NASA's helicopter Ingenuity survives its first night at Mars
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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
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Italicized articles are on dwarf planets or major moons.
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