Portal:Solar System
The Solar System Portal
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...)
Selected article –
Mars imaged by the Hubble Space Telescope in 2003.
The relatively flat plains in northern parts of Mars strongly contrast with the cratered terrain in southern highlands – this terrain observation is known as the Martian dichotomy. Mars hosts many enormous extinct volcanoes (the tallest is Olympus Mons, 21.9 km or 13.6 mi tall) and one of the largest canyons in the Solar System (Valles Marineris, 4,000 km or 2,500 mi long). Geologically, the planet is fairly active with marsquakes trembling underneath the ground, dust devils sweeping across the landscape, and cirrus clouds. Carbon dioxide is substantially present in Mars's polar ice caps and thin atmosphere. During a year, there are large surface temperature swings on the surface between −78.5 °C (−109.3 °F) to 5.7 °C (42.3 °F) similar to Earth's seasons, as both planets have significant axial tilt. (Full article...)
Selected picture
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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. -
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. -
Photograph: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research InstitutePluto is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. Discovered by Clyde Tombaugh in 1930, Pluto was originally considered to be the ninth planet from the Sun. Following the discovery of several objects of similar size in the Kuiper belt, its status as a planet was questioned, and in 2006 the International Astronomical Union (IAU) gave a definition of the term "planet" that excluded Pluto. The largest and second-most-massive known dwarf planet in the Solar System, Pluto is primarily made of ice and rock. It is relatively small, with a moderately eccentric and inclined orbit.
This photograph of Pluto is a composite of four near-true color images taken by the New Horizons spacecraft in 2015. The most prominent feature in the image, the bright, youthful, nitrogen ice plains of Sputnik Planitia, the left lobe of heart-shaped Tombaugh Regio, is at right center. This contrasts with the darker, more cratered terrain of Cthulhu Macula at lower left. -
The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, heated to incandescence by nuclear-fusion reactions in its core, radiating the energy mainly as visible light and infrared radiation. It is by far the most important source of energy for life on Earth. Its diameter is about 1.39 million kilometres (860,000 mi), or 109 times that of Earth. Its mass is about 330,000 times that of Earth, and accounts for about 99.86 percent of the total mass of the Solar System. Roughly three-quarters of the Sun's mass consists of hydrogen; the rest is mostly helium, with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron. This diagram illustrates the general structure of the Sun, with all features drawn to scale. -
Photo: NASA/ISS Expedition 23 crewThe aurora australis, as seen from the International Space Station. Aurorae are natural light displays in the sky caused by the collision of energetic charged particles with atoms in the high altitude thermosphere. The particles originate in the magnetosphere and solar wind and, on Earth, are directed by Earth's magnetic field into the atmosphere. -
Photo credit: Luc ViatourFull moon is a lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun, and when the three celestial bodies are aligned as closely as possible to a straight line. At this time, as seen by viewers on Earth, the hemisphere of the Moon that is facing the Earth (the near side) is fully illuminated by sunlight and appears round. Only during a full moon is the opposite hemisphere of the Moon, which is not visible from Earth (the far side), completely unilluminated. -
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. -
Image credit: SeavAn animated image showing the apparent retrograde motion of Mars in 2003 as seen from Earth. All the true planets appear to periodically switch direction as they cross the sky. Because Earth completes its orbit in a shorter period of time than the planets outside its orbit, we periodically overtake them, like a faster car on a multi-lane highway. When this occurs, the planet will first appear to stop its eastward drift, and then drift back toward the west. Then, as Earth swings past the planet in its orbit, it appears to resume its normal motion west to east. -
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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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. -
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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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. -
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.) -
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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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. -
Photograph credit: NASA / JPL–Caltech / University of ArizonaAlthough Mars is smaller than the Earth and 50 percent farther from the Sun, its climate has important similarities with the Earth, such as the presence of polar ice caps, seasonal changes and observable weather patterns. This image shows layered deposits in Planum Boreum, in the north polar region of Mars, which formed from a 3-kilometre-thick (2 mi) stack of dusty water-ice layers about 1,000 km (600 mi) across. The layers record information about the climate of the planet stretching back several million years. Erosion has created scarps and troughs that expose the layering. The tan-colored layers are the dusty water ice of the polar layered deposits, however a section of bluish layers is visible below them. These bluish layers contain sand-sized rock fragments that likely formed a large polar dunefield before the overlying dusty ice was deposited. This photograph, depicting an area approximately 1.3 km (0.8 mi) across, was captured by the HiRISE camera on board NASA's Mars Reconnaissance Orbiter. -
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. -
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. -
The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of plasma, heated by nuclear fusion of hydrogen into helium in its core, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 1.39 million kilometres (860,000 miles) or 109 times that of Earth, while its mass is about 330,000 times that of Earth. It accounts for about 99.86% of the total mass of the Solar System. Roughly three-quarters of the Sun's mass consists of hydrogen; the rest is mostly helium, with much smaller quantities of heavier elements, including oxygen, carbon, neon and iron.
This false-color photograph of the Sun was taken by the Atmospheric Imaging Assembly instrument on NASA's Solar Dynamics Observatory (SDO) at a wavelength of 304 angstroms, in the extreme ultraviolet region of the electromagnetic spectrum. -
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. -
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. -
Photo credit: Voyager 1False-color detail of Jupiter's atmosphere, imaged by Voyager 1, showing the Great Red Spot and a passing white oval. The wavy cloud pattern to the left of the Red Spot is a region of extraordinarily complex and variable wave motion. To give a sense of Jupiter's scale, the white oval storm directly below the Great Red Spot is approximately the same diameter as Earth. -
Photo credit: Cassini orbiterRhea, at 1,528 kilometres (949 mi) across, is the second-largest moon of Saturn and the ninth largest moon in the Solar System. It was discovered in 1672 by Giovanni Domenico Cassini, who named it after the Titan Rhea of Greek mythology, "mother of the gods".
The giant Tirawa impact basin is seen above and to the right of center. Tirawa, and another basin to its southwest, are both covered in impact craters, indicating they are quite ancient.
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General images
The following are images from various Solar System-related articles on Wikipedia.
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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 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 outer planets Jupiter, Saturn, Uranus and Neptune, compared to the inner planets Earth, Venus, Mars, and Mercury at the bottom right (from Solar System) -
Solar System diagram made by Emanuel Bowen in 1747. At that time, Uranus, Neptune, nor the asteroid belts have been discovered yet. Orbits of planets are drawn to scale, but the orbits of moons and the size of bodies are not. (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) -
Artist's conception of a protoplanetary disk (from Formation and evolution of the Solar System) -
An artist's impression of the Oort cloud, a region still well within the sphere of influence of the Solar System, including a depiction of the much further inside Kuiper belt (inset); the sizes of objects are over-scaled for visibility. (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) -
Overview of the inner Solar System up to Jupiter's orbit (from Solar System) -
The planets, zodiacal light and meteor shower (top left of image) (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 orbits of Sedna, 2012 VP113, Leleākūhonua (pink), and other very distant objects (red, brown and cyan) along with the predicted orbit of the hypothetical Planet Nine (dark blue) (from Solar System) -
Artist's conception of the giant impact thought to have formed the Moon (from Formation and evolution of the Solar System) -
The orbital eccentricities and inclinations of the scattered disc population compared to the classical and resonant Kuiper belt objects (from Solar System) -
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The current Sun compared to its peak size in the red-giant phase (from Solar System)
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Diagram of the Sun's magnetosphere and helioshealth (from 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) -
Animations of the Solar System's inner planets orbiting. Each frame represents 2 days of motion. (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) -
Comet Hale–Bopp seen in 1997 (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) -
Pierre-Simon Laplace, one of the originators of the nebular hypothesis (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)
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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) -
Diagram of the early Solar System's protoplanetary disk, out of which Earth and other Solar System bodies formed (from Solar System) -
Diagram of the Milky Way, with galactic features and the relative position of the Solar System labeled. (from Solar System) -
Orbit classification of Kuiper belt objects. Some clusters that is subjected to orbital resonance are marked. (from 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 JupiterOrbit of JupiterOrbit of SaturnOrbit of UranusOrbit of Neptune(from Formation and evolution of the Solar System) -
The Sun in true white color (from Solar System) -
Location of the Solar System within the Milky Way (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) -
The Ring nebula, a planetary nebula similar to what the Sun will become (from Formation and evolution of the Solar System)
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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 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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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
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- 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) · 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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