<Portal:Solar System

Thetransit of Mercury across the face of the Sun that took place inNovember 2006.Mercury appears as a black speck in the Sun's lower center-right region; the black areas on the left and right edges aresunspots. The transit was first recorded by French astronomerPierre Gassendi on November 7, 1631. Transits of Mercury take place in May or November, at intervals of 7, 13, or 33 years, with the next one scheduled to appear inMay 2016.

A picture of the2012 transit of Venus by theSolar Dynamics Observatory, from 36,000 km (22,000 mi) above the Earth. Atransit of Venus across theSun takes place when theplanetVenus passes directly between the Sun andEarth. 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 in2004, and the next pair of transits will occur in 2117 and 2125.

Asolar flare, a sudden flash of brightness observed over theSun's surface or the solar limb which is interpreted as a large energy release, recorded on August 31, 2012. Such flares are often, but not always, followed by a colossalcoronal mass ejection; in this instance, the ejection traveled at over 900 miles (1,400 km) per second.

TheSun is thestar at the center of theSolar System. It is a nearly perfect sphere ofplasma, heated bynuclear fusion ofhydrogen intohelium in itscore, with internalconvective motion that generates amagnetic field viaa 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, includingoxygen,carbon,neon andiron.Thisfalse-color photograph of the Sun was taken by the Atmospheric Imaging Assembly instrument onNASA'sSolar Dynamics Observatory (SDO) at a wavelength of 304 angstroms, in theextreme ultraviolet region of theelectromagnetic spectrum.

TheSun is thestar at the center of theSolar System. It is a nearly perfect sphere of hotplasma, heated toincandescence bynuclear-fusion reactions in its core, radiating theenergy mainly asvisible light andinfrared 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 ofhydrogen; the rest is mostlyhelium, with much smaller quantities of heavier elements, includingoxygen,carbon,neon, andiron. This diagram illustrates the general structure of the Sun, with all features drawn to scale.

Mercury is the smallest and closest to theSun of the eightplanets in theSolar System. It has no knownnatural satellites. The planet is named after theRoman deityMercury, the messenger to the gods.

Aradar image of thesurface of Venus, centered at 180 degrees east longitude. This composite image was created from mapping by theMagellan probe, supplemented by data gathered by thePioneer orbiter, with simulated hues based on color images recorded byVenera 13 and14. Noprobe has been able to survive more than a few hours onVenus's surface, which is completely obscured by clouds, because theatmospheric pressure is some 90 times that of the Earth's, and its surface temperature is around 450 °C (842 °F).

Pale Blue Dot is the name given to this 1990 photo ofEarth taken fromVoyager 1 when its vantage point reached the edge of theSolar 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 sunlightscattering in the camera'slens, resulting from the small angle between Earth and theSun.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."

Theaurora australis, as seen from theInternational Space Station. Aurorae are natural light displays in the sky caused by the collision of energetic charged particles with atoms in the high altitudethermosphere. The particles originate in themagnetosphere andsolar wind and, on Earth, are directed byEarth's magnetic field into the atmosphere.

TheInternational Space Station (ISS) is aspace station inlow Earth orbit, run as a joint project by the American, Russian, Japanese, European, and Canadian space agencies. Its first component was sent into orbit in 1998, and it has been inhabited continuously since 2000. The ISS consists of pressurised modules, external trusses,solar arrays, and other components, which have been launched by RussianProton andSoyuz rockets, and AmericanSpace Shuttles. It serves as amicrogravity andspace environment research laboratory in which crew members conduct experiments inbiology,human biology,physics,astronomy,meteorology, andother fields.This photograph, taken in 2011 by Italian astronautPaolo Nespoli from a departing Russian Soyuz spacecraft, shows the ISS and the dockedSpace ShuttleEndeavour.

Full moon is alunar phase that occurs when theMoon is on the opposite side of theEarth from theSun, 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 (thenear 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 (thefar side), completely unilluminated.

AstronautEugene Cernan makes a short test drive of thelunar rover (officially, Lunar Roving Vehicle or LRV) during the early part of the firstApollo 17extravehicular activity. The LRV was only used in the last threeApollo 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.

Ananimation of thephases of the Moon. As the Moon revolves around theEarth, theSun 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'srotation period on its axis to match itsorbital period around the earth. These two periods nearly cancel each other out, except that the Moon's orbit iselliptical. This causes its orbital motion to speed up whencloser to the Earth, and slow down when farther away, causing the Moon'sapparent diameter to change, as well as the wobbling motion observed.

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).

TheMoon is the onlynatural satellite ofEarth and the fifth largest moon in theSolar System. Owing to itssynchronous rotation around Earth, the Moon always shows essentially the same face: itsnear side, which is marked by dark volcanicmaria, as well as the bright ancient crustal highlands and the prominentimpact craters. However, variations in the Moon's orbital speed due to itsorbital eccentricity cause alibration of several degrees of longitude; the alignment of the Moon's orbital plane causes a similar libration in latitude. The Moon was first reached in September 1959 by the Soviet Union's unmannedLuna 2, followed by the first successful soft landing byLuna 9 in 1966. The United StatesApollo program achieved the only manned lunar missions to date, includingApollo 8 in 1968, the first manned orbital mission, as well asApollo 11, the first of six manned landings between 1969 and 1972.This picture shows the near side of the Moon close to its greatest northernecliptic latitude, so the southern craters are especially prominent.Tranquility Base, Apollo 11's landing site, is located near the mid-right in the photograph.

Tranquility Base is the landing site of theApollo 11 mission on theMoon where, on July 20, 1969, humans first landed and walked on a celestial body other than the Earth. This photograph was taken at Tranquility Base byNeil Armstrong, the Apollo 11 commander, and depicts crewmemberBuzz Aldrin with scientific equipment he had just deployed on the lunar surface. In the background on the right of the image is thelunar module,Eagle; the United States flag planted at the site during the mission was blown over the next day by the exhaust of the ascent rocket.

Mars, the fourthplanet from theSun, is named after theRoman god of war because of its bloodred color. Mars has two small, oddly-shaped moons,Phobos andDeimos, named after the sons of theGreek godAres. At some point in the future Phobos will be broken up bygravitational forces.

Victoria Crater, animpact crater atMeridiani Planum, near the equator ofMars. The crater is approximately 800 meters (half a mile) indiameter. It has a distinctive scalloped shape to its rim, caused byerosion and downhill movement of crater wall material. Layeredsedimentary rocks are exposed along the inner wall of the crater, and boulders that have fallen from the crater wall are visible on the crater floor. The floor of the crater is occupied by a striking field of sanddunes. The Mars roverOpportunity can be seen in this image, at roughly the "ten o'clock" position along the rim of the crater.

False-colorMars Reconnaissance Orbiter image of a side of the Chasma Boreale, a canyon in the polarice cap of thePlanum Boreum (north pole ofMars). Light browns are layers of surface dust, greys and blues are layers ofwater andcarbon 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 ofTexas. The Chasma Boreale is up to 100 km (62.5 mi) wide and featuresscarps up to 2 km (1.25 mi) high. For a comparison, theGrand 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 360°panorama taken during the descent from the summit ofHusband Hill, one of theColumbia Hills inGusev crater,Mars. Thisstitched image is composed of 405 individual images taken with five different filters on the panoramic camera over the course of five Martian days.

A composite image ofOlympus Mons onMars, the tallest knownvolcano andmountain in theSolar System. This image was created from black-and-white imagery from theUSGS's Mars Global Digital Image Mosaic and color imagery acquired from the 1978 visit ofViking 1.

Ananimated image showing theapparent retrograde motion of Mars in 2003 as seen fromEarth. All the true planets appear to periodically switch direction as they cross the sky. Because Earth completes itsorbit 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 is the fourth planet from the Sun and is known as the "Red Planet" due to its reddish appearance as seen from Earth. The planet is named afterMars, the Roman god of war. Aterrestrial planet, Mars hasa thin atmosphere and surface features reminiscent both of theimpact craters of the Moon and the volcanoes, valleys, deserts andpolar ice caps of the Earth. The planet has the highest mountain in theSolar System,Olympus Mons, as well as the largest canyon,Valles Marineris. Mars'srotation period and seasonal cycles are also similar to those of the Earth. Of all the planets in the Solar System other than Earth, Mars is the most likely to harbour liquid water and perhaps life. There are ongoing investigations assessing Mars's past potential forhabitability, as well asthe possibility of extant life. Future astrobiology missions are planned, includingNASA'sMars 2020 rover and theEuropean Space Agency (ESA)'sRosalind Franklin rover. In November 2016, NASA reported finding a large amount ofunderground ice in theUtopia Planitia region of the planet. The volume of water detected has been estimated to be equivalent to the volume of water inLake Superior. Mars has two moons,Phobos andDeimos, which are small and irregularly shaped. This picture is atrue-colour image of Mars, taken from a distance of about 240,000 kilometres (150,000 mi) by theOSIRIS instrument on ESA'sRosetta spacecraft, during its February 2007 flyby of the planet. The image was generated using OSIRIS's orange (red), green and blue filters.

AlthoughMars is smaller than the Earth and 50 percent farther from the Sun,its climate has important similarities with the Earth, such as the presence ofpolar ice caps, seasonal changes and observable weather patterns. This image shows layered deposits inPlanum 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 theHiRISE camera on boardNASA'sMars Reconnaissance Orbiter.

Phobos, the larger and closer of the twomoons ofMars, 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 largecraterStickney in the lower right. With a diameter of 9 km (5.6 mi), it is the largest feature on Phobos.

101955 Bennu is acarbonaceous asteroid discovered by theLincoln Near-Earth Asteroid Research project in 1999. Bennu has a roughly spheroidal shape, an effective diameter of about 484 m (1,588 ft), and a rough, boulder-strewn surface. It is apotentially hazardous object, with a cumulative 1-in-2,700 chance of impacting Earth between 2175 and 2199. It is named after theBennu, an ancient Egyptian bird deity associated with the Sun, creation, and rebirth. This mosaic image of Bennu consists of twelve PolyCam images taken by NASA'sOSIRIS-REx spacecraft from a range of 24 km (15 mi). The primary goal of the mission is to collect a sample from the asteroid's surface, which is scheduled to take place on October 20, 2020, andreturn the sample to Earth for analysis.

False-color detail ofJupiter'satmosphere, imaged byVoyager 1, showing theGreat 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 variablewave motion. To give a sense of Jupiter's scale, the white oval storm directly below the Great Red Spot is approximately the same diameter asEarth.

Thispolar map ofJupiter, taken by theCassini orbiter as itneared Jupiter during a flyby on its way toSaturn, is the most detailed global color map of the planet ever produced. The south pole is in the center of the map and theequator is at the edge. The map shows a variety of colorful cloud features, including parallel reddish-brown and white bands, theGreat 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.

Ananimated view ofVoyager I's approach toJupiter. Oneframe of this image was taken each Jupiter day (approximately 10 hours) between January 6 and February 9, 1979, as thespace probe flew from 58 million to 31 million kilometers from Jupiter during that time. The small, round, dark spots appearing in some frames are the shadows cast by themoons passing between Jupiter and theSun, while the small, white flashes around the planet, are the moons themselves.

A 14-frame clip showing theatmosphere of Jupiter as viewed from theNASA probeCassini. Taken over a span of 24 Jupiter rotations between October 31 and November 9, 2000, this clip shows various patterns of motion across the planet. TheGreat Red Spot rotates counterclockwise, and the uneven distribution of its high haze is obvious. To the east (right) of the Red Spot, oval storms, like ball bearings, roll over and pass each other. East-west bands adjacent to each other move at different rates. Strings of small storms rotate around northern-hemisphere ovals. The large grayish-blue "hot spots" at the northern edge of the white Equatorial Zone change over time as they proceed eastward across the planet. Ovals in the north rotate counter to those in the south. Small, very bright features appear quickly and randomly in turbulent regions, possibly lightning storms. The smallest visible features at the equator are about 600 km (370 miles) across.

A diagram ofJupiter showing a model of the planet's interior, with a rockycore overlaid by a deep layer of liquidmetallic hydrogen and an outer layer predominantly ofmolecular 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.

An animation of an eruption by theTvashtar Paterae volcanic region on the innermost ofJupiter'sGalilean moons,Io. Theejecta plume is 330 km (205 mi) high, though only its uppermost half is visible in this image, as its source lies over the moon's limb on its far side. This animation consists of a sequence of five images taken byNASA'sNew Horizons probe on March 1, 2007, over the course of eight minutes from 23:50UTC.

A true-color image ofIo, one of the moons ofJupiter, taken by theGalileo spacecraft. The dark spot just left of the center is the erupting volcanoPrometheus. The whitish plains on either side of it are coated with volcanically depositedsulfur dioxide frost, whereas the yellower regions contain a higher proportion ofsulfur.

Realistic-color mosaic of images ofJupiter's moonEuropa taken by NASA's Jupiter orbiterGalileo in 1995 and 1998. This view of the moon'santi-Jovian hemisphere shows numerouslineae, linear features created via atectonic process in which crustal plates of water ice floating on asubsurface ocean (kept warm bytidal 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 inCommons.)

Saturneclipsing theSun, as seen by theCassini orbiter. Individualrings seen in this image include (in order, starting from most distant): E ring, Pallene ring (visible very faintly in an arc just below Saturn), G ring, Janus/Epimetheus ring (faint), F ring (narrow brightest feature), Main rings (A,B,C), and D ring (bluish, nearest Saturn). Interior to the G ring and above the brighter main rings is the pale dot of Earth.

The Day the Earth Smiled refers to the date July 19, 2013, on which theCassini spacecraft turned to imageSaturn, its entirering system, and the Earth from a position where Saturn eclipsed the Sun.Cassini imaging team leader and planetary scientistCarolyn 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 ofSaturnian moons.

TheCassini–Huygensspace-research project involved a collaboration betweenNASA, theEuropean Space Agency, and theItalian Space Agency to send aprobe to study the planetSaturn and its system, includingits rings andits natural satellites.This natural-color mosaic image, combining thirty photographs, was taken by theCassini orbiter over the course of approximately two hours on 23 July 2008 as it panned its wide-angle camera across Saturn and its ring system as the planet approachedequinox. Six moons are pictured in the panorama, with the largest,Titan, visible at the bottom left.

Thisfalse-colorradar image taken by theCassini orbiter provides convincing evidence for large bodies of liquidmethane onTitan. 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 lowbackscatter 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 onSaturn's moon Titan."

Hyperion, a moon ofSaturn, is one of the largest highly irregular (non-spherical) bodies in theSolar System. Enhanced image processing was used to bring out details and color differences in this photo taken by theCassini orbiter. Hyperion is entirely saturated with deep, sharp-edgedcraters that give it the appearance of a giant sponge. Dark material fills the bottom of each crater.

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

False-color mosaic shows the entire hemisphere ofIapetus (1,468 km or 912 mi across) visible from theCassini orbiter on the outbound leg of its encounter with the two-tonedmoon of Saturn in September 2007. The centrallongitude of the trailing hemisphere is 24 degrees to the left of the image's center. It is hypothesized that the moon'stwo-toned nature is due to thesublimation of various icesevaporated from the warmer parts of the surface.

The most detailed full-disc view ofTitan, the largest moon ofSaturn andsecond-largest in theSolar System. The brighter region on the right side and equatorial region is namedXanadu, and the large, dark region at the center isShangri-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.

Rhea, at 1,528 kilometres (949 mi) across, is the second-largestmoon ofSaturn and theninth largest moon in theSolar System. It was discovered in 1672 byGiovanni Domenico Cassini, who named it after theTitanRhea ofGreek 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 inimpact craters, indicating they are quite ancient.

Saturn's moonMimas, as imaged by theCassini spacecraft. It was discovered on17 September 1789 by English astronomerWilliam Herschel, and was named afterMimas, a son ofGaia inGreek mythology, by Herschel's sonJohn. The largeHerschel Crater is the dominating feature of the moon. With a diameter of 396 km (246 mi), it is the smallestastronomical body that is known to be rounded due to self-gravitation.

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

Neptune is the eighth and farthest knownplanet from theSun in theSolar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet and the densestgiant planet. Neptune is 17 times the mass ofEarth, slightly more massive than its near-twinUranus. 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 theRoman god of the sea and has theastronomical symbol ♆, a stylised version of the god Neptune'strident.This picture of Neptune was taken byNASA'sVoyager 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 theGreat Dark Spot, a storm about the size of Earth, in the centre, while the fast-moving bright feature nicknamed the "Scooter" and theSmall 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.

Pluto is adwarf planet in theKuiper belt, a ring ofbodies beyond Neptune. Discovered byClyde Tombaugh in 1930, Pluto was originally considered to be theninth planet from the Sun. Following the discovery of several objects of similar size in the Kuiper belt, its status as aplanet was questioned, and in 2006 theInternational Astronomical Union (IAU) gavea definition of the term "planet" that excluded Pluto. The largest and second-most-massive known dwarf planet in theSolar System, Pluto is primarily made of ice and rock. It is relatively small, with a moderatelyeccentric and inclined orbit.This photograph of Pluto is acomposite of four near-true color images taken by theNew Horizons spacecraft in 2015. The most prominent feature in the image, the bright, youthful, nitrogen ice plains ofSputnik Planitia, the left lobe of heart-shapedTombaugh Regio, is at right center. This contrasts with the darker, more cratered terrain ofCthulhu Macula at lower left.

CometC/2006 P1 (McNaught), as seen fromSwifts Creek, Victoria,Australia. Thisnon-periodiccomet, the brightest in over 40 years, was discovered on August 7, 2006 by British-AustralianastronomerRobert H. McNaught. It was first visible in the northern hemisphere, reachingperihelion on January 12, 2007 at a distance of 0.17 AU.

Comet Lovejoy is along-period comet andKreutz 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 black-and-white photographic mosaic depicting thecomet67P/Churyumov–Gerasimenko, as photographed by the probeRosetta. ThisJupiter-family comet, which was originally from theKuiper belt, is about 4.3 km (2.7 mi) across, has a currentorbital 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 onphotographic plates in 1969 by Soviet astronomersKlim Churyumov andSvetlana Gerasimenko,after whom it is named.

C/2014 Q2 (Lovejoy) is a long-periodcomet discovered in 2014 by Australian astronomerTerry Lovejoy using a 0.2-meter (8 in)Schmidt–Cassegrain telescope. It was discovered atapparent magnitude 15 in the southern constellation ofPuppis, 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.

Anatural satellite is an object thatorbits aplanet or other body larger than itself and which is not man-made. Such objects are often calledmoons. Shown here are 28 of the 240 moons of theSolar System, including those of thedwarf planetsPluto andEris as well as that ofasteroid243 Ida. TheEarth is included for scale.

Illustration of thePtolemaicgeocentric model of the Universe (the theory that theEarth is the center of theuniverse) byPortuguese cosmographer and cartographerBartolomeu Velho. Taken from his treatiseCosmographia, 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).

TheMilky Way is thegalaxy that contains theSolar 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 Latinvia lactea, from the Greekγαλαξίας 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 theUniverse. Following the 1920Great Debate between the astronomersHarlow Shapley andHeber Curtis, observations byEdwin Hubble showed that the Milky Way is just one of many galaxies.This picture shows a portion of the Milky Way as seen fromCerro Paranal in Chile, home to theEuropean Southern Observatory (ESO)'sVery Large Telescope, depicting the region spanning the constellations fromSagittarius toScorpius. The colourfulnebulae surroundingRho Ophiuchi andAntares can be seen to the right, while the dusty lane of the galaxy runs obliquely through the image, dotted with reddish objects such as theLagoon andTrifid Nebulae. This region of the Milky Way also includes theGalactic Center, likely containing asupermassive black hole,Sagittarius A*.

The Blue Marble is a famous photograph ofEarth.NASA officially credits the image to the entireApollo 17 crew —Eugene Cernan,Ronald Evans andJack Schmitt — all of whom took photographic images during the mission.Apollo 17 passed overAfrica during daylight hours andAntarctica is also illuminated. The photograph was taken approximately five hours after the spacecraft's launch, whileen route to theMoon.Apollo 17, notably, was the last manned lunar mission; nohumans since have been at a range where taking a "whole-Earth" photograph such as "The Blue Marble" would be possible.

These images are composites of the complete radar image collection obtained by theMagellan mission. TheMagellan spacecraft was launched aboardSpace ShuttleAtlantis in May 1989 and began mapping the surface ofVenus in September 1990. The spacecraft continued to orbitVenus 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 theVenusian atmosphere.

Thesolar eclipse of 1999 August 11, as seen from France. This was the most viewedtotal eclipse in human history, although some areas offered impaired visibility due to adverse weather conditions. The path of theMoon's shadow began in theAtlantic Ocean, before traversingCornwall, northernFrance, southernGermany,Austria,Hungary and northernSerbia. Its maximum was inRomania, and it continued across theBlack Sea,Turkey,Iran, southernPakistan andIndia.

Mars, the fourthplanet from theSun, is named after theRoman god of war because of its bloodred color. Mars has two small, oddly-shaped moons,Phobos andDeimos, named after the sons of theGreek godAres. At some point in the future Phobos will be broken up bygravitational forces. The atmosphere on Mars is 95%carbon dioxide. In 2003methane 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 thegas on the planet.

ATRACE image ofsunspots on the surface, orphotosphere, of theSun from September2002, is taken in the farultraviolet 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 hightemperatures are thought to be related to the rapidly changingmagnetic field loops that channel solarplasma.

Comet Hale–Bopp sails across the sky in the vicinity ofPazin inIstria,Croatia. To the lower right of the comet theAndromeda Galaxy is also faintly visible. Thecomet was visible to the naked eye for a record 18 months, twice as long as theGreat Comet of 1811. Atperihelion, it shone brighter than any star in the sky exceptSirius, 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 analienspacecraft inspired a mass suicide among followers of theHeaven's Gatecult.

Earthrise, the first occasion in which humans saw theEarth seemingly rising above the surface of theMoon, taken during theApollo 8 mission on December 24, 1968. This view was seen by the crew at the beginning of its fourthorbit around the Moon, although thefirst photograph taken was in black-and-white. Note that the Earth is in shadow here. A photo of afully lit Earth would not be taken until theApollo 17 mission.

Jupiter is the fifthplanet from the Sun and by far thelargest within theSolar System. It is 318 times more massive than Earth, with adiameter 11 times that of Earth, and with avolume 1300 times that of Earth. Its best known feature is theGreat Red Spot, astorm larger than Earth, which was first observed byGalileo four centuries ago. This picture, taken by theCassini 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.