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| + | The Solar System is the gravitationally bound system of the planets and the Sun plus other objects that orbit it, either directly or indirectly. It is approximately 4.571 billion years ago and it is located in the [[Milky Way]] |
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| − | __NOWYSIWYG__{{SeeAlso|articledesc = planetary system|otherarticletype = film|otherlinkpage = Solar System (educational film)}} |
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| + | [[File:Solar System.png|thumb|220x220px|The Sun and the eight planets.]] |
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| − | {{SolarSystemInfo}} |
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| − | The '''Solar System''' comprises the [[Sun]] and the many objects that orbit around it{{mdash}}eight [[planet]]s, known [[dwarf planet]]s, their 172 known [[natural satellite|moons]], and countless [[asteroid]]s and [[comet]]s. The system occupies a disk-shaped volume of space more than 7.45 billion miles (12 billion kilometers) across. At the center is the Sun which contains more than 99 percent of the solar system's mass.<ref>{{cite book |
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| − | |author = Carole Stott, Clint Twist |
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| − | |origyear = 2003 |
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| − | |origmonth = June |
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| − | |title = Space Facts - DK Pockets |
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| − | |publisher = DK Publishing |
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| − | |id = ISBN 9780789495938}}</ref> |
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| − | The charted regions of the Solar System consists of the Sun, four relatively small inner planets surrounded by a belt of rocky asteroids, and four gas giants surrounded by the Kuiper belt of icy objects. |
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| − | The hypothetical [[Oort cloud]] may also exist at a distance roughly a thousand times beyond these regions. The [[solar wind]], a flow of plasma from the Sun, permeates the Solar System, creating a bubble in the interstellar medium known as the heliosphere, which extends out to the middle of the scattered disc. |
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| − | ==Orbit== |
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| − | [[File:Oort_cloud_Sedna_orbit.svg|thumb|left|300px|The [[orbits]] of the bodies in the Solar System to scale (clockwise from top left).]] |
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| − | An orbital period is the time it takes one object to travel around another in a complete circuit. The orbital period of a planet around the Sun is also the length of its year. The rotational period of a planet is how long it takes to make a complete turn on its axis. |
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| − | Most of the planets, moons, and asteroids travel in almost circular orbits in the same direction (west to east) around the Sun. Most orbits also lie close to the plane of Earth's [[orbit]], called the ''ecliptic''. So if you looked at the solar system side-on, you would see most of the orbits are roughly on the same level. [[Mercury]]'s and [[Pluto]]'s orbits are not—they orbit at an angle.<ref name=DKEncyclopediaSpace>{{cite book |
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| − | |author = Peter Bond |
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| − | |origyear = 2010 |
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| − | |title = Space: A Visual Encyclopedia |
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| − | |publisher = DK Publishing |
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| − | |id = ISBN 9780756662776}}</ref> |
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| − | ==Formation== |
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| − | [[File:FormationOfTheSolarSystem.png|thumb|350px|A diagram shows the formation of the Solar System.]] |
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| − | The solar system is the name given to the planetary system of which the [[Earth]] is a part. It comprises planets,{{nbsp}}moons, comets, meteors and asteroids which are all held{{nbsp}}together by the gravitational pull of a star, named either{{nbsp}}the Sun or Sol. The solar system is believed to have{{nbsp}}formed from one [[nebula]], the solar nebula. |
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| − | As gravity{{nbsp}}forced the nebula to condense it became more dense and{{nbsp}}pressure inside it increased, resulting in the creation of a{{nbsp}}protostar, which began heating up to form the sun we{{nbsp}}see today. The proto-star would have been surrounded by interstellar dust and gases which began clumping together as a result of gravity. This process continued until, about 4.6 billion years ago, the clumps of rock and gas became much larger, and eventually gravity forced these irregular-shaped objects into the globular-shaped planets we see today. Many of the rocks did not become large enough to form planets and either remain today as asteroids, or they collided with the planets earlier in their history causing the large impact craters still visible throughout the solar system.<ref name=PocketGuideStarsAndPlanets>{{cite book |
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| − | |author = Duncan John |
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| − | |origyear = 2009 |
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| − | |title = A Pocket Guide to the Stars & Planets |
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| − | |id = ISBN 9781407579009}}</ref> |
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| − | ==The Sun== |
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| − | {{main|Sun}} |
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| − | [[File:Sunrise_over_the_Moon.jpg|thumb|left|Sunlight on the [[Moon]] is much brighter than that on [[Earth]], due to the Moon's lack of an atmosphere. The seven [[Apollo program|Apollo]] landings all occurred during the early lunar morning. This allowed the astronauts to spot [[crater]]s and boulders more easily, without the harsh sunlight during the day.<br><small>[[NASA]]/Science Photo Library</small>]] |
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| − | [[File:Planets_and_sun_size_comparison.jpg|thumb|left|300px|The Sun compared to the planets]] |
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| − | The Sun is our nearest star, located about 93 million miles (150 million km) from Earth. Even though it's made entirely of gas, its mass is 333,000 times greater than that of Earth and 750 times greater than that of all the planets in the solar system put together.<ref name=DKEncyclopediaSpace /> |
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| − | ===Fate=== |
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| − | {{main|Sun#Fate}} |
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| − | [[File:White_Dwarf_Sun.jpg|thumb|Artwork{{nbsp}}of the [[sun]] forming a planetary{{nbsp}}nebula 5 billion years from now.{{nbsp}}Ejected gas (purple) is expanding{{nbsp}}towards the lifeless [[Earth]] (lower{{nbsp}}right) and moon (lower left) from{{nbsp}}the dying sun (upper center). This{{nbsp}}stage in the life of the sun follows its expansion during its red{{nbsp}}giant stage. When its nuclear fuel{{nbsp}}has been used up, its outer layers{{nbsp}}are ejected in this way. The remnant cools to form a white{{nbsp}}dwarf star.<br><small>[[Joe Tucciarone]]/Science Photo Library</small>]] |
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| − | In about 5 billion years, the hydrogen in the center of the Sun will start to run out. The helium will get squeezed. This will speed up the hydrogen burning. Our star will slowly puff into a red giant. It will eat all of the inner planets, even the Earth. |
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| − | As the helium gets squeezed, it will soon get hot enough to burn into carbon. At the same time, the carbon can also join helium to form oxygen. The Sun is not very big compared to some stars. It will never get hot enough in the center to burn carbon and oxygen. These elements will collect in the center of the star. Later it will shed most of its outer layers, creating a planetary nebula, and reveal a hot white dwarf star. |
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| − | Nearly 99 percent of all stars in the galaxy will end their lives as white dwarfs. By studying the stars that have already changed, we can learn about the fate of our own Sun. |
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| − | ==Planets== |
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| − | {{main|Planet}} |
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| − | [[File:Size_planets_comparison.jpg|thumb|350px|Planets of the Solar System to scale. Jupiter and Saturn (top row), Uranus and Neptune (top middle), Earth and Venus (bottom middle), Mars and Mercury.]] |
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| − | The known planets in the solar system can be divided{{nbsp}}into two groups. The four planets closest to the sun,{{nbsp}}[[Mercury]], [[Venus]], [[Earth]] and [[Mars]], are called the{{nbsp}}"terrestrial planets" after the Latin word for "land"{{nbsp}}because they all share similar surfaces comprising solid{{nbsp}}rock surrounding dense, metallic cores. The four outer{{nbsp}}planets, [[Jupiter]], [[Saturn]], [[Uranus]] and [[Neptune]] are known{{nbsp}}as the "Jovian planets," implying their similarities to the{{nbsp}}planet Jupiter{{mdash}}they are all much larger than the{{nbsp}}terrestrial planets, and do not share their rocky surfaces{{nbsp}}and metallic core. Instead they are giant balls of{{nbsp}}atmosphere, mainly comprising gases surrounding{{nbsp}}relatively small rocky cores. The terrestrial and the{{nbsp}}jovian planets are helpfully divided by a belt of asteroids,{{nbsp}}orbiting the sun between Mars and Jupiter. More recently{{nbsp}}Uranus and Neptune have been called Uranian rather{{nbsp}}than Jovian planets to highlight their differences to{{nbsp}}Jupiter and Saturn; mainly that they are appreciably{{nbsp}}smaller, are both bluish-greenish in color, comprise a{{nbsp}}significant amount of methane and have a thick coating of{{nbsp}}ice around their cores.<ref name=PocketGuideStarsAndPlanets /> |
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| − | ==Inner planets== |
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| − | [[File:Telluric_planets_size_comparison.jpg|thumb|The inner planets. From left to right: Earth, Mars, Venus, and Mercury (sizes to scale, interplanetary distances not)]] |
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| − | ===Mercury=== |
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| − | {{Main|Mercury}} |
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| − | Mercury is the closest planet |
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| − | to the Sun has changed little in |
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| − | billions of years. It is a small, |
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| − | heavily cratered world with |
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| − | no atmosphere and no moons. |
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| − | Its year lasts 88 Earth days.<ref name=DKEncyclopediaSpace /> |
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| − | ===Venus=== |
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| − | {{Main|Venus}} |
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| − | Venus is the second planet |
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| − | from the Sun is similar in size |
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| − | to Earth, but the air pressure |
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| − | is 90 times greater than on |
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| − | Earth. It has no moon. Its year |
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| − | lasts 224 Earth days.<ref name=DKEncyclopediaSpace /> |
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| − | ===Earth=== |
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| − | {{Main|Earth}} |
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| − | Earth is the third planet |
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| − | from the Sun is the largest of |
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| − | the four rocky planets and the |
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| − | only planet with liquid water. |
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| − | Its year lasts 365 days.<ref name=DKEncyclopediaSpace /> |
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| − | ===Mars=== |
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| − | {{Main|Mars}} |
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| − | Mars is the fourth planet |
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| − | from the Sun has many |
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| − | craters as well as volcanoes, |
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| − | rift valleys, and winding |
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| − | canyons. It also has two moons. |
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| − | Its year lasts 687 Earth days.<ref name=DKEncyclopediaSpace /> |
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| − | ==Asteroid belt== |
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| − | {{Main|Asteroid|Asteroid belt}} |
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| − | [[File:InnerSolarSystem-en.png|thumb|Image of the [[asteroid belt]] (white), the [[Jupiter trojan]]s (green), the [[Hilda]]s (orange), and [[near-Earth asteroid]]s.]] |
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| − | Lying |
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| − | between Mars and Jupiter, |
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| − | the belt is around 112 |
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| − | million miles (180 million |
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| − | km) wide and contains |
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| − | thousands of asteroids.<ref name=DKEncyclopediaSpace /> |
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| − | ==Outer planets== |
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| − | [[File:Gas_giants_in_the_solar_system.jpg|thumb|From top to bottom: Neptune, Uranus, Saturn, and Jupiter (Montage with approximate colour and size)]] |
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| − | ===Jupiter=== |
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| − | {{Main|Jupiter}} |
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| − | Jupiter is the fifth planet |
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| − | from the Sun is also the largest. |
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| − | It has thin rings, 63 moons, |
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| − | and a cloud feature called the |
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| − | Great Red Spot. Its year lasts |
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| − | almost 12 Earth years.<ref name=DKEncyclopediaSpace /> |
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| − | ===Saturn=== |
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| − | {{Main|Saturn}} |
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| − | Saturn is the sixth |
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| − | planet from the Sun is the |
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| − | second largest, after Jupiter, |
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| − | but is light enough to float. |
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| − | It has 62 moons. Its year |
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| − | lasts 29.5 Earth years.<ref name=DKEncyclopediaSpace /> |
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| − | ===Uranus ö=== |
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| − | {{Main|Uranus}} |
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| − | Uranus is the seventh planet from the |
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| − | Sun has a dark ring system |
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| − | and 27 moons. Its year |
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| − | lasts 84 Earth years.<ref name=DKEncyclopediaSpace /> |
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| − | ===Neptune=== |
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| − | {{Main|Neptune}} |
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| − | Neptune is the |
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| − | eighth planet from the Sun |
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| − | has a thin ring system and |
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| − | 13 moons. Its year lasts |
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| − | almost 165 Earth years.<ref name=DKEncyclopediaSpace /> |
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| − | ==Centaurs== |
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| − | {{main|Centaur}} |
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| − | The centaurs are icy comet-like bodies whose orbits have semi-major axes greater than Jupiter's (5.5 AU) and less than Neptune's (30 AU). The largest known centaur, [[10199 Chariklo]], has a diameter of about 250 km. The first centaur discovered, [[2060 Chiron]], has also been classified as comet (95P) because it develops a coma just as comets do when they approach the Sun. |
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| − | ==Pluto== |
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| − | {{Main|Pluto}} |
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| − | Pluto was once known as |
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| − | the ninth planet from the |
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| − | Sun, but it is now classified |
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| − | as a dwarf planet.<ref name=DKEncyclopediaSpace /> |
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| − | ==Comets== |
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| − | {{main|Comet}} |
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| − | [[File:Comet_c1995o1.jpg|thumb|[[Comet Hale–Bopp]]]] |
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| − | A comet is a celestial object consisting of a nucleus of ice and dust and, when near the sun, a "tail" of gas and dust particles pointing away from the sun. |
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| − | ==Kuiper belt== |
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| − | {{main|Kuiper belt}} |
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| − | [[File:Outersolarsystem_objectpositions_labels_comp.png|thumb|left|Plot of all Kuiper belt objects known in 2007, set against the four outer planets]] |
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| − | The Kuiper belt, sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets, extending from the orbit of Neptune to approximately 50 AU from the Sun. |
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| − | ==Oort cloud== |
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| − | {{main|Oort cloud}} |
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| − | [[File:Kuiper_oort-en.svg|thumb|290px|An artist's rendering of the Oort cloud, the Hills cloud, and the Kuiper belt (inset)]] |
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| − | The Oort cloud is a spherical 'cloud' of frozen objects at the very edge of our solar system. You can imagine it a bit like a fishbowl, with the Solar System at the centre, and the spherical cloud of icy bodies on the edge. |
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| − | ==References== |
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| − | {{Reflist}} |
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| − | ==External links== |
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| − | *[http://www.solarviews.com/ Views of the Solar System] |
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| − | *[http://www.nineplanets.org/ Nine Planets] |
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| − | *[http://www.windows2universe.org/our_solar_system/solar_system.html The Solar System - Windows to the Universe] |
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[[Category:Solar System]] |
[[Category:Solar System]] |
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