ប្រព័ន្ធព្រះអាទិត្យ៖ ភាពខុសគ្នារវាងកំណែនានា
ខ្លឹមសារដែលបានលុបចោល ខ្លឹមសារដែលបានសរសេរបន្ថែម
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បន្ទាត់ទី៦៥៖
[[ភព]]ចំនួនប្រាំមួយ និង[[កូនភព]]ពីរទៀត ត្រូវបានវិលជុំវិញដោយ[[តារារណបធម្មជាតិ]] ដែលគេឱ្យឈ្មោះថា [[ព្រះចន្ទ]] (Moons) បន្ទាប់ពី ព្រះចន្ទរបស់ផែនដី ព្រះចន្ទនៃភពខាងក្រៅ ត្រូវបានហ៊ុមព័ន្ធជុំវិញជារង្វង់ ដោយធូលី និងភាគល្អិតផ្សេងទៀត។
The '''Solar System'''<!--
--><ref group="lower-alpha">[[Capitalization]] of the name varies. The [[International Astronomical Union|IAU]], the authoritative body regarding astronomical nomenclature, specifies [http://www.iau.org/public/themes/naming/ capitalizing the names of all individual astronomical objects] ("'''Solar System'''"). However, the name is commonly rendered in lower case ("'''solar system'''"), as, for example, in the ''[[Oxford English Dictionary]]'' and [http://www.m-w.com/dictionary/solar%20system ''Merriam-Webster's 11th Collegiate Dictionary''].</ref> <!--
--> comprises the [[Sun]] and the objects that [[orbit]] it, whether they orbit it directly or by orbiting other objects that orbit it directly.<!--
--><ref group="lower-alpha">The [[Natural satellite|moon]]s orbiting [[List of gravitationally rounded objects of the Solar System#Planets|the Solar System's planets]] are an example of the latter.</ref> <!--
-->Of those objects that orbit the Sun directly, the largest eight are the planets<!--
--><ref group="lower-alpha">Historically, several other bodies were once considered planets, including, from its discovery in 1930 until 2006, [[Pluto]]. See [[Planet#Former planets|Former planets]].</ref> <!--
-->that form the [[planetary system]] around it, while the remainder are significantly smaller objects, such as [[dwarf planet]]s and [[Small Solar System body|small Solar System bodies (SSSBs)]] such as [[comet]]s and [[asteroid]]s.<!--
-->{{#tag:ref
| According to [[IAU definition of planet|current definitions]], objects in orbit around the Sun are classified dynamically and physically into three categories: ''planets'', ''dwarf planets'', and ''small Solar System bodies''.<br/><br/><!--
---Planet:--> A [[planet]] is any body in orbit around the Sun whose [[mass]] is sufficient for [[Gravitation|gravity]] to have pulled it into a (near-)[[Sphere|spherical]] shape and which has [[Clearing the neighbourhood|cleared its immediate neighbourhood]] of all smaller objects. By this definition, the Solar System has eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. As it has not cleared its neighbourhood of other [[Kuiper belt]] objects, Pluto does not fit this definition.<ref name="FinalResolution"/><br/><br/><!--
---Dwarf planet:--> Instead, Pluto is considered to be a [[dwarf planet]], a body orbiting the Sun that is massive enough to be made near-spherical by its own gravity but which has not cleared [[planetesimal]]s from its neighbourhood and is also not a satellite.<ref name="FinalResolution"/> In addition to Pluto, the [[International Astronomical Union|IAU]] has recognized four other dwarf planets in the Solar System: Ceres, Haumea, Makemake, and Eris.<ref name=name>{{cite web |date=2008-11-07 <!--11:42:58--> |title=Dwarf Planets and their Systems |work=Working Group for Planetary System Nomenclature (WGPSN) |url=http://planetarynames.wr.usgs.gov/append7.html#DwarfPlanets |accessdate=2008-07-13 |publisher=U.S. Geological Survey}}</ref> Other objects commonly (but not officially) treated as dwarf planets include {{mpl|2007 OR|10}}, [[90377 Sedna|Sedna]], [[90482 Orcus|Orcus]], and [[50000 Quaoar|Quaoar]].<ref>{{cite web |title=IAU Planet Definition Committee |author=Ron Ekers |publisher=International Astronomical Union |url=http://www.iau.org/public_press/news/release/iau0601/newspaper/ |accessdate=2008-10-13}}</ref> In a reference to Pluto, other dwarf planets orbiting in the [[#Trans-Neptunian region|trans-Neptunian region]] are sometimes called "[[plutoid]]s".<ref name="IAU0804">{{cite news |date=June 11, 2008 |title=Plutoid chosen as name for Solar System objects like Pluto |publisher=[[International Astronomical Union]], Paris |url=http://www.iau.org/news/pressreleases/detail/iau0804/ |accessdate=2008-06-11}}</ref><br/><br/><!--
---SSSBs:--> The remaining objects in orbit around the Sun are known as [[Small Solar System body|small Solar System bodies]].<ref name="FinalResolution">{{cite news |title=The Final IAU Resolution on the definition of "planet" ready for voting |publisher=IAU |date=2006-08-24 |url=http://www.iau.org/iau0602.423.0.html |accessdate=2007-03-02}}</ref><!--
--->|name=footnoteB |group=lower-alpha<!--
-->}}
The Solar System [[Formation and evolution of the Solar System|formed 4.6 billion years ago]] from the gravitational collapse of a giant [[molecular cloud]]. The vast majority of the system's [[mass]] is in the Sun, with most of the remaining mass contained in [[Jupiter]]. The four smaller inner planets, [[Mercury (planet)|Mercury]], [[Venus]], [[Earth]] and [[Mars]], also called the [[terrestrial planets]], are primarily composed of rock and metal. The four outer planets, called the [[gas giant]]s, are substantially more massive than the terrestrials. The two largest, Jupiter and [[Saturn]], are composed mainly of [[hydrogen]] and [[helium]]; the two outermost planets, [[Uranus]] and [[Neptune]], are composed largely of substances with relatively high melting points (compared with hydrogen and helium), called [[Volatiles|ices]], such as water, ammonia and [[methane]], and are often referred to separately as "ice giants". All planets have almost circular orbits that lie within a nearly flat disc called the [[plane of the ecliptic|ecliptic plane]].
The Solar System also contains regions populated by [[Small Solar System body|smaller objects]].<ref group=lower-alpha name=footnoteB /> The [[asteroid belt]], which lies between 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]], linked populations of [[trans-Neptunian object]]s composed mostly of ices. Within these populations are several dozen to more than ten thousand objects that may be large enough to have been rounded by their own gravity.<ref name=Stern2012>"Today we know of more than a dozen dwarf planets in the solar system".[http://pluto.jhuapl.edu/overview/piPerspective.php?page=piPerspective_08_24_2012 The PI's Perspective]</ref> Such objects are referred to as [[dwarf planet]]s. Identified dwarf planets include the asteroid [[Ceres (dwarf planet)|Ceres]] and the trans-Neptunian objects [[Pluto]] and [[Eris (dwarf planet)|Eris]].<ref group=lower-alpha name=footnoteB /> In addition to these two regions, various other small-body populations, including [[comet]]s, [[Centaur (minor planet)|centaurs]] and [[interplanetary dust]], freely travel between regions. Six of the planets, at least three of the dwarf planets, and many of the smaller bodies are orbited by [[natural satellite]]s,<ref group=lower-alpha>See [[List of natural satellites of the Solar System]] for the full list of natural satellites of the eight planets and first five dwarf planets.</ref> usually termed "moons" after Earth's [[Moon]]. Each of the outer planets is encircled by [[planetary ring]]s of dust and other small objects.
The [[solar wind]], a flow of [[plasma (physics)|plasma]] from the Sun, creates a [[stellar wind bubble|bubble]] in the [[interstellar medium]] known as the [[heliosphere]], which extends out to the edge of the [[scattered disc]]. The [[Oort cloud]], which is believed to be the source for [[long-period comet]]s, may also exist at a distance roughly a thousand times further than the heliosphere. The [[Heliopause (astronomy)|heliopause]] is the point at which pressure from the solar wind is equal to the opposing pressure of [[interstellar wind]]. The Solar System is located in the [[Orion Arm]], 26,000 light years from the center of the [[Milky Way]].
== យត្តស័ព្ទ ==
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