Portal:Solar System

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 was formed 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc. The Sun is an ordinary main sequence star that maintains a balanced equilibrium by the fusion of hydrogen into helium at its core, releasing this energy from its outer photosphere.

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 eight dwarf planets: Ceres, 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, six 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, 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 2,000–200,000 astronomical units (0.032–3.2 light-years). The closest star to the Solar System, Proxima Centauri, is 4.25 light-years away. Both stars belong to the Local Group and the Milky Way galaxy. (Full article...)

Selected article –

The dwarf planet Ceres from the Dawn spacecraft

A dwarf planet is a celestial body orbiting the Sun that is massive enough to be spherical as a result of its own gravity but has not cleared its neighbouring region of planetesimals and is not a satellite. They are smaller than planets, but more massive than small solar system bodies. The term was adopted in 2006 by the International Astronomical Union (IAU) as a result of the increase in discoveries of trans-Neptunian objects that rivaled Pluto in size, and finally precipitated by the discovery of an even more massive object, Eris. The IAU currently recognizes five dwarf planets—Ceres (pictured), Pluto, Haumea, Makemake, and Eris. It is suspected that at least another 40 known objects in the Solar System are dwarf planets, but the number might be as high as 2,000. The 2006 definition has been both praised and criticized, and has been disputed by some scientists. (Full article...)

More selected articles

Selected picture

• 
  Jupiter

  Diagram: Kelvin Song

  A diagram of Jupiter showing a model of the planet's interior, with a rocky core overlaid by a deep layer of liquid metallic hydrogen and an outer layer predominantly of molecular hydrogen. Jupiter's true interior composition is uncertain. For instance, the core may have shrunk as convection currents of hot liquid metallic hydrogen mixed with the molten core and carried its contents to higher levels in the planetary interior. Furthermore, there is no clear physical boundary between the hydrogen layers—with increasing depth the gas increases smoothly in temperature and density, ultimately becoming liquid.
• 

  

  Five global views of Venus by Magellan.

  Magellan (spacecraft)

  Credit: NASA/Jet Propulsion Laboratory

  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.
• 

  

  Mars

  Mars

  Credit: NASA

  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.
• 

  

  Solar eclipse of 11 August 1999

  Solar eclipse of 1999 August 11

  Credit: Luc Viatour

  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.
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  Europa (moon)

  Photo credit: NASA/JPL

  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.)
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  Iapetus

  Photo credit: Cassini orbiter

  A close-up of 10 km (6.2 mi) high mountains within the equatorial ridge on Saturn's moon Iapetus, photographed by the Cassini orbiter. Above the middle of the image can be seen a place where an impact has exposed the bright ice beneath the dark overlying material. The image was taken on September 10, 2007, with the Cassini spacecraft narrow-angle camera at a distance of approximately 3,870 km (2,400 mi) from Iapetus.
• 
  Moons of the Solar System

  Image credit: NASA, Deuar, TotoBaggins, KFP

  A natural satellite is an object that orbits a planet or other body larger than itself and which is not man-made. Such objects are often called moons. Shown here are 28 of the 240 moons of the Solar System, including those of the dwarf planets Pluto and Eris as well as that of asteroid 243 Ida. The Earth is included for scale.
• 
  Lunar phase

  Image: Tom Ruen

  An 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.
• 
  Planet Mars

  Photo credit: NASA

  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.
• 

  

  Sunspot TRACE image

  Sunspot

  Credit: NASA/TRACE

  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.
• 
  Lunar rover

  Photo credit: Harrison Schmitt

  Astronaut Eugene Cernan makes a short test drive of the lunar rover (officially, Lunar Roving Vehicle or LRV) during the early part of the first Apollo 17 extravehicular activity. The LRV was only used in the last three Apollo missions, but it performed without any major problems and allowed the astronauts to cover far more ground than in previous missions. All three LRVs were abandoned on the Moon.
• 
  Lakes of methane on Titan

  Image credit: Cassini orbiter

  This 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."
• 

  

  Comet Hale-Bopp 29-03-1997

  Comet Hale–Bopp

  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 inspired a mass suicide among followers of the Heaven's Gate cult.
• 
  C/2014 Q2 (Lovejoy)

  Photograph: John Vermette

  C/2014 Q2 (Lovejoy) is a long-period comet discovered in 2014 by Australian astronomer Terry Lovejoy using a 0.2-meter (8 in) Schmidt–Cassegrain telescope. It was discovered at apparent magnitude 15 in the southern constellation of Puppis, and is the fifth comet discovered by Lovejoy. Its blue-green glow is the result of organic molecules and water released by the comet fluorescing under the harsh UV and optical light of the sun as it passes through space.
• 
  Uranus

  Photo: NASA/JPL/Voyager 2 mission

  Uranus is the seventh planet from the Sun and the fourth most massive in the Solar System. In this photograph from 1986 the planet appears almost featureless, but recent terrestrial observations have found seasonal changes to be occurring.
• 
  The Blue Marble

  Photo credit: The Apollo 17 crew

  The 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.
• 
  Lunar distance

  Model: Nickshanks

  Lunar distance is a measurement of the distance from the Earth to the Moon. This diagram shows the distance, averaging 384,400 km (238,900 mi), to scale, as well as the Earth and the Moon (scroll to see the entire image).
• 
  Neptune

  Photograph credit: NASA / JPL

  Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet and the densest giant planet. Neptune is 17 times the mass of Earth, slightly more massive than its near-twin Uranus. Neptune is denser and physically smaller than Uranus because its greater mass causes more gravitational compression of its atmosphere. Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 au (4.5 billion km; 2.8 billion mi). It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune's trident.
  
  This picture of Neptune was taken by NASA's Voyager 2 spacecraft in 1989, at a range of 4.4 million miles (7.1 million kilometres) from the planet, approximately four days before closest approach. The photograph shows the Great Dark Spot, a storm about the size of Earth, in the centre, while the fast-moving bright feature nicknamed the "Scooter" and the Small Dark Spot can be seen on the western limb. These clouds were seen to persist for as long as the spacecraft's cameras could resolve them.
• 

  

  Earthrise, as seen by Apollo 8

  Apollo 8

  Credit: William Anders

  Earthrise, 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.
• 

  

  Jupiter

  Jupiter

  Credit: Cassini probe

  Jupiter 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.
• 
  Pale Blue Dot

  Photo credit: NASA/JPL

  Pale Blue Dot is the name given to this 1990 photo of Earth taken from Voyager 1 when its vantage point reached the edge of the Solar System, a distance of roughly 3.7 billion miles (6 billion kilometres). Earth can be seen as a blueish-white speck approximately halfway down the brown band to the right. The light band over Earth is an artifact of sunlight scattering in the camera's lens, resulting from the small angle between Earth and the Sun. Carl Sagan came up with the idea of turning the spacecraft around to take a composite image of the Solar System. Six years later, he reflected, "All of human history has happened on that tiny pixel, which is our only home."
• 
  Mercury (planet)

  Photograph: NASA/APL/CIS; edit: Jjron

  Mercury is the smallest and closest to the Sun of the eight planets in the Solar System. It has no known natural satellites. The planet is named after the Roman deity Mercury, the messenger to the gods.
• 
  Polar map of Jupiter

  Photo credit: Cassini orbiter

  This 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.

General images

The following are images from various Solar System-related articles on Wikipedia.

• 
  The Ring nebula, a planetary nebula similar to what the Sun will become (from Formation and evolution of the Solar System)
• 
  Comparison between the habitable zones of the Solar System and Gliese 581 (planet d was later found to not exist). The habitable zone is highly dependent on parent star's luminosity. (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)
• 
  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)
• 
  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 Jupiter
  

    Orbit of Jupiter

    Orbit of Saturn

    Orbit of Uranus

    Orbit of Neptune

  (from Formation and evolution of the Solar System)
• 
  Linear map of the inner Solar System, showing many asteroid populations (from Solar System)
• 
  The Solar System to scale, labelled. Distance of objects is not to scale. The asteroid belt lies between the orbits of Mars and Jupiter, the Kuiper belt lies beyond Neptune's orbit.
• 
  Location of the Solar System within the Milky Way (from Formation and evolution of the Solar System)
• 
  Orbit classification of Kuiper belt objects. Some clusters that is subjected to orbital resonance are also marked. (from Solar System)
• 
  Apparent size of the Sun as seen from the Solar System's planets (from Solar System)
• 
  Diagram of the Milky Way, with galactic features and the relative position of the Solar System labelled. (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)
• 
  True-scale Solar System poster made by Emanuel Bowen in 1747. At that time, Uranus, Neptune, nor the asteroid belts have been discovered yet. (from 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 Solar System within the interstellar medium, with the different regions and their distances on a steped horizontal distance scale (object's size not to scale). (from Solar System)
• 
  Overview of the evolution of the Sun, a G-type main-sequence star. Around 11 billion years after being formed by the Solar System's protoplanetary disk, the Sun will expand to become a red giant; Mercury, Venus and possibly the Earth will be swallowed. (from Solar System)
• 
  Comet Hale–Bopp seen in 1997 (from Solar System)
• 
  Artist's conception of a protoplanetary disk (from Formation and evolution of the 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)
• 
  Coronal mass ejections play a dominant role in the Solar System's environment and space weather in general. (from Solar System)
• 
  Pierre-Simon Laplace, one of the originators of the nebular hypothesis (from Formation and evolution of the Solar System)
• 
  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)
• 
  Animations of the Solar System's outer planets orbiting. This animation is 100 times faster than the inner planet animation. (from Solar System)
• 
  The detached object Sedna and its orbit within the Solar System (from 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)
• 
  The motion of 'lights' moving across the sky is the basis of the classical definition of planets: wandering stars. (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)
• 
  Artist's conception of the giant impact thought to have formed the Moon (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)
• 
  Diagram of the Sun's magnetosphere and helioshealth (from Solar System)
• 
  The Sun in true white color (from Solar System)

Did you know –

• ...that Yogi Rock (pictured) is a rock found on Mars by the Mars Pathfinder mission that looks surprisingly like Yogi Bear's head?

• ...that the Kuiper crater in the Kuiper quadrangle, named after Dutch American astronomer Gerard Kuiper, has the highest albedo recorded on Mercury?

• ...that 6Q0B44E, a recently discovered satellite of Earth, is thought to be a large piece of space debris?

• ...that 17th century philosopher Cesare Cremonini refused to look at the Moon's mountains through Galileo's telescope, because Aristotle had proved the Moon was a perfect sphere?

• ...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?

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In the news

Wikinews Space portal

• 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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The planet Saturn, see here eclipsing the sun

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