Solar System

Solar System
A representative image of the Solar System with sizes, but not distances, to scale
The Sun and planets of the Solar System
(distances not to scale)
Age4.568 billion years
Location
System mass1.0014 Solar masses
Nearest star
Nearest known planetary systemProxima Centauri system  (4.25 ly)
Planetary system
Semi-major axis of outer known planet (Neptune)30.10 AU  (4.503 billion km)
Distance to Kuiper cliff50 AU
Populations
Stars1  (Sun)
Known planets
Known dwarf planets
Possibly several hundred;[1]
five currently recognized by the IAU
Known natural satellites
525
Known minor planets778,897  (as of 2018-06-21)[4]
Known comets4,017  (as of 2018-06-21)[4]
Identified rounded satellites19
Orbit about Galactic Center
Invariable-to-galactic plane inclination60.19°  (ecliptic)
Distance to Galactic Center27,000 ± 1,000 ly
Orbital speed220 km/s
Orbital period225–250 Myr
Star-related properties
Spectral typeG2V
Frost line≈5 AU[5]
Distance to heliopause≈120 AU
Hill sphere radius≈1–3 ly

The Solar System[a] is the gravitationally bound system of the Sun and the objects that orbit it, either directly or indirectly,[b] including the eight planets and five dwarf planets as defined by the International Astronomical Union (IAU). Of the objects that orbit the Sun directly, the largest eight are the planets,[c] with the remainder being smaller objects, such as dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury.[d]

The Solar System formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The vast majority of the system's mass is in the Sun, with the majority of the remaining mass contained in Jupiter. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being primarily composed of rock and metal. The four outer planets are giant planets, being substantially more massive than the terrestrials. The two largest, Jupiter and Saturn, are gas giants, being composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are ice giants, being composed mostly of substances with relatively high melting points compared with hydrogen and helium, called volatiles, such as water, ammonia and methane. All eight planets have almost circular orbits that lie within a nearly flat disc called the ecliptic.

The Solar System also contains smaller objects.[e] The asteroid belt, which lies between the orbits of Mars and Jupiter, mostly contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptune's orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed mostly of ices, and beyond them a newly discovered population of sednoids. Within these populations are several dozen to possibly tens of thousands of objects large enough that they have been rounded by their own gravity.[10] Such objects are categorized as dwarf planets. Identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto and Eris.[e] In addition to these two regions, various other small-body populations, including comets, centaurs and interplanetary dust clouds, freely travel between regions. Six of the planets, at least four of the dwarf planets, and many of the smaller bodies are orbited by natural satellites,[f] usually termed "moons" after the Moon. Each of the outer planets is encircled by planetary rings of dust and other small objects.

The solar wind, a stream of charged particles flowing outwards from the Sun, creates a bubble-like region in the interstellar medium known as the heliosphere. The heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium; it extends out to the edge of the scattered disc. The Oort cloud, which is thought to be the source for long-period comets, may also exist at a distance roughly a thousand times further than the heliosphere. The Solar System is located in the Orion Arm, 26,000 light-years from the center of the Milky Way.

Discovery and exploration

Andreas Cellarius's illustration of the Copernican system, from the Harmonia Macrocosmica (1660)

For most of history, humanity did not recognize or understand the concept of the Solar System. Most people up to the Late Middle AgesRenaissance believed Earth to be stationary at the centre of the universe and categorically different from the divine or ethereal objects that moved through the sky. Although the Greek philosopher Aristarchus of Samos had speculated on a heliocentric reordering of the cosmos, Nicolaus Copernicus was the first to develop a mathematically predictive heliocentric system.[11][12]

In the 17th century, Galileo discovered that the Sun was marked with sunspots, and that Jupiter had four satellites in orbit around it.[13] Christiaan Huygens followed on from Galileo's discoveries by discovering Saturn's moon Titan and the shape of the rings of Saturn.[14] Edmond Halley realised in 1705 that repeated sightings of a comet were recording the same object, returning regularly once every 75–76 years. This was the first evidence that anything other than the planets orbited the Sun.[15] Around this time (1704), the term "Solar System" first appeared in English.[16] In 1838, Friedrich Bessel successfully measured a stellar parallax, an apparent shift in the position of a star created by Earth's motion around the Sun, providing the first direct, experimental proof of heliocentrism.[17] Improvements in observational astronomy and the use of unmanned spacecraft have since enabled the detailed investigation of other bodies orbiting the Sun.

Other Languages
Afrikaans: Sonnestelsel
Alemannisch: Sonnensystem
aragonés: Sistema Solar
armãneashti: Sistemlu solaru
অসমীয়া: সৌৰজগত
asturianu: Sistema Solar
azərbaycanca: Günəş sistemi
تۆرکجه: گونش سیستمی
বাংলা: সৌরজগৎ
Bahasa Banjar: Tata Surya
Bân-lâm-gú: Thài-iông-hē
Basa Banyumasan: Tata Surya
башҡортса: Ҡояш системаһы
беларуская: Сонечная сістэма
беларуская (тарашкевіца)‎: Сонечная сыстэма
भोजपुरी: सौर मंडल
Boarisch: Sunsystem
bosanski: Sunčev sistem
català: Sistema solar
davvisámegiella: Beaivvášgoddi
Deutsch: Sonnensystem
ދިވެހިބަސް: އިރަވީ ނިޒާމު
Ελληνικά: Ηλιακό σύστημα
español: Sistema solar
Esperanto: Sunsistemo
estremeñu: Sistema Solal
Fiji Hindi: Saur mandal
føroyskt: Sólskipanin
français: Système solaire
Gàidhlig: An Crios-Grèine
贛語: 太陽系
ગુજરાતી: સૂર્યમંડળ
客家語/Hak-kâ-ngî: Thai-yòng-hi
한국어: 태양계
हिन्दी: सौर मण्डल
hrvatski: Sunčev sustav
বিষ্ণুপ্রিয়া মণিপুরী: সৌরজগত
Bahasa Indonesia: Tata Surya
interlingua: Systema solar
Interlingue: Solari sistema
íslenska: Sólkerfið
italiano: Sistema solare
Basa Jawa: Tata Surya
ಕನ್ನಡ: ಸೌರಮಂಡಲ
Kapampangan: Solar System
къарачай-малкъар: Кюн система
ქართული: მზის სისტემა
kaszëbsczi: Słuńcowi Ùstôw
қазақша: Күн жүйесі
kernowek: System howlek
Kiswahili: Mfumo wa jua
Kreyòl ayisyen: Sistèm solè
Кыргызча: Күн системасы
latviešu: Saules sistēma
Lëtzebuergesch: Sonnesystem
lietuvių: Saulės sistema
Limburgs: Zonnestèlsel
Livvinkarjala: Päiväzensistiemu
la .lojban.: solri ciste
lumbaart: Sistema Solar
magyar: Naprendszer
македонски: Сончев систем
Malagasy: Rafi-masoandro
മലയാളം: സൗരയൂഥം
მარგალური: ბჟაშ სისტემა
مازِرونی: خورشیدی منظومه
Bahasa Melayu: Sistem Suria
Mìng-dĕ̤ng-ngṳ̄: Tái-iòng-hiê
Mirandés: Sistema Solar
монгол: Нарны аймаг
မြန်မာဘာသာ: နေအဖွဲ့အစည်း
Nāhuatl: Tonatiuh ichan
Nederlands: Zonnestelsel
Nedersaksies: Zunnesysteem
नेपाली: सौर्यमण्डल
नेपाल भाषा: सौर्यमण्डल
日本語: 太陽系
Napulitano: Sistema solare
Nordfriisk: Sansüsteem
norsk nynorsk: Solsystemet
ଓଡ଼ିଆ: ସୌର ଜଗତ
oʻzbekcha/ўзбекча: Quyosh tizimi
ਪੰਜਾਬੀ: ਸੂਰਜ ਮੰਡਲ
Patois: Suola Sistim
Piemontèis: Sistema solar
Plattdüütsch: Sünnsystem
português: Sistema Solar
Ripoarisch: Sunnesystem
română: Sistemul solar
Romani: Kham-Sestemi
rumantsch: Sistem solar
Runa Simi: Inti Llika
русиньскый: Сонячна сістема
саха тыла: Күн систиэмэтэ
संस्कृतम्: सूर्यमण्डलम्
Seeltersk: Sunnensystem
sicilianu: Sistema sulari
Simple English: Solar System
slovenčina: Slnečná sústava
slovenščina: Osončje
српски / srpski: Сунчев систем
srpskohrvatski / српскохрватски: Sunčev sistem
Basa Sunda: Surya Mandala
svenska: Solsystemet
Taqbaylit: Anagraw Afukan
татарча/tatarça: Кояш системасы
తెలుగు: సౌరమండలము
Türkçe: Güneş Sistemi
Türkmençe: Gün ulgamy
тыва дыл: Хүн системазы
українська: Сонячна система
ئۇيغۇرچە / Uyghurche: قۇياش سىستېمىسى
vepsän kel’: Päiväižen sistem
Tiếng Việt: Hệ Mặt Trời
Volapük: Solasit
文言: 太陽系
West-Vlams: Zunnestelsel
Winaray: Sistema solar
吴语: 太阳系
ייִדיש: זון סיסטעם
粵語: 太陽系
žemaitėška: Saulės sėstema
中文: 太阳系
डोटेली: सौर्यमण्डल
ГӀалгӀай: Маьлха ков
Kabɩyɛ: Wɩsɩ cejewiye
Lingua Franca Nova: Sistem solal