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The Solar System Portal
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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 – show another
![Eris (centre) and Dysnomia (left of centre), taken by the Hubble Space Telescope.](https://upload.wikimedia.org/wikipedia/commons/thumb/5/5b/Eris_and_dysnomia2.jpg/140px-Eris_and_dysnomia2.jpg)
Eris has one large known moon, Dysnomia. In February 2016, Eris's distance from the Sun was 96.3 AU (14.41 billion km; 8.95 billion mi), more than three times that of Neptune or Pluto. With the exception of long-period comets, Eris and Dysnomia were the most distant known natural objects in the Solar System until the discovery of 2018 AG37 and 2018 VG18 in 2018. (Full article...)
Selected picture
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Image 1Photograph 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.
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Image 2Uranus 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.
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Image 3Photo credit: Cassini orbiterFalse-color mosaic shows the entire hemisphere of Iapetus (1,468 km or 912 mi across) visible from the Cassini orbiter on the outbound leg of its encounter with the two-toned moon of Saturn in September 2007. The central longitude of the trailing hemisphere is 24 degrees to the left of the image's center. It is hypothesized that the moon's two-toned nature is due to the sublimation of various ices evaporated from the warmer parts of the surface.
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Image 4Photo 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.
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Image 5Image: 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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Image 6These 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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Image 7Photo 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.
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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 9A 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.
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Image 10Saturn'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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Image 11Comet 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.
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Image 12Photograph: John VermetteC/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.
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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. -
Image 14Photo credit: Harrison SchmittAstronaut 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.
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Image 15A 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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Image 16The 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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Image 17The 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*. -
Image 18A picture of the 2012 transit of Venus by the Solar Dynamics Observatory, from 36,000 km (22,000 mi) above the Earth. A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth. It is one of the rarest predictable astronomical phenomena and happens in pairs eight years apart that are separated from each other by 105 or 121 years. The last transit before 2012 was in 2004, and the next pair of transits will occur in 2117 and 2125.
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Image 19Photo: 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.
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Image 20Mars, 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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Image 21Photograph: 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. -
Image 22A black-and-white photographic mosaic depicting the comet 67P/Churyumov–Gerasimenko, as photographed by the probe Rosetta. This Jupiter-family comet, which was originally from the Kuiper belt, is about 4.3 km (2.7 mi) across, has a current orbital period of 6.45 years, a rotation period of approximately 12.4 hours, and a maximum velocity of 135,000 km/h (38 km/s; 84,000 mph). It was first observed on photographic plates in 1969 by Soviet astronomers Klim Churyumov and Svetlana Gerasimenko, after whom it is named.
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Image 23Image 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.
General images
The following are images from various Solar System-related articles on XIV.
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Image 1The 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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Image 2The Sun in true white color (from Solar System)
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Image 3Hubble 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)
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Image 4Diagram of the early Solar System's protoplanetary disk, out of which Earth and other Solar System bodies formed (from Solar System)
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Image 5Diagram of the Milky Way, with galactic features and the relative position of the Solar System labelled. (from Solar System)
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Image 6The orbits of Sedna, 2012 VP113, Leleākūhonua, and other very distant objects along with the predicted orbit of the hypothetical Planet Nine (from Solar System)
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Image 7True-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)
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Image 8Location of the Solar System within the Milky Way (from Formation and evolution of the Solar System)
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Image 9The 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)
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Image 10The outer planets Jupiter, Saturn, Uranus and Neptune, compared to the inner planets Earth, Venus, Mars, and Mercury at the bottom right (from Solar System)
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Image 11Orbit classification of Kuiper belt objects. Some clusters that is subjected to orbital resonance are marked. (from Solar System)
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Image 12Artist's conception of a protoplanetary disk (from Formation and evolution of the Solar System)
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Image 13Comparison of the habitable zones for different stellar temperatures, with a sample of known exoplanets plus the Earth, Mars, and Venus (from Solar System)
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Image 14Neptune 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)
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Image 15The Ring nebula, a planetary nebula similar to what the Sun will become (from Formation and evolution of the Solar System)
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Image 16Diagram of the Sun's magnetosphere and helioshealth (from Solar System)
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Image 17Overview of the inner Solar System up to Jupiter's orbit (from Solar System)
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Image 18Diagram 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)
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Image 19Simulation 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) -
Image 20Animations of the Solar System's inner planets orbiting. Each frame represents 2 days of motion. (from Solar System)
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Image 22Artist's conception of the giant impact thought to have formed the Moon (from Formation and evolution of the Solar System)
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Image 24Plot of objects around the Kuiper belt and other asteroid populations. J, S, U and N denotes Jupiter, Saturn, Uranus and Neptune. (from Solar System)
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Image 25Relative 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)
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Image 26To-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)
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Image 27Meteor 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)
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Image 28The Solar System (left) within the interstellar medium, with the different regions and their distances on a logarithmic scale (from Solar System)
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Image 29Animations of the Solar System's outer planets orbiting. This animation is 100 times faster than the inner planet animation. (from Solar System)
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Image 30Pierre-Simon Laplace, one of the originators of the nebular hypothesis (from Formation and evolution of the Solar System)
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Image 31The current Sun compared to its peak size in the red-giant phase (from Solar System)
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Image 32The 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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Image 33The planets, zodiacal light and meteor shower (top left of image) (from Solar System)
Did you know – show different entries
- ...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 ridges and escarpments in the Victoria quadrangle of the planet Mercury have been associated with the stresses caused by the Sun slowing Mercury's rotation through tidal forces?
- ...that J002E3 was at first thought to be a new moon of Earth when discovered in 2002. But was later found to be the third stage of the Apollo 12 Saturn V?
- ...that the Tooting impact crater on Mars was named after the London suburb of the same name because the discoverer "thought ※ mum and brother would get a kick out of having their home town paired with a land form on Mars"?
- ...that 99% of the mass of the Carme group, a group of retrograde irregular satellites of Jupiter, is located in Carme?
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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
![](https://upload.wikimedia.org/wikipedia/commons/4/43/Solar_System_Template_2.png)
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
Bold articles are featured.
Italicized articles are on dwarf planets or major moons.
Things you can do
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