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{{Infobox planetary system
| title = Yggdrasil system
| image = 
| caption = Yggdrasil and the planets of the solar system. Not to scale.
| age = 4.568 billion years
| location = 
| ascension = 
| declination = 
| system_mass = 
| neareststar = [[Avalon]]
| nearestplanetary = 
| semimajoraxis = 25.01 AU<br>{{small|(3.74 billion km)}}
| proto-planetarydisc = 
| Kuiper_cliff = 
| stars = 1 {{small|([[Yggdrasil]])}}
| planets = {{hlist|6 ([[Muspellheim]]|[[Jotunnheim]]|[[Svartalfheim]]|[[Vanaheim]]|[[Niflheim]]|[[Helheim]])}}
| dwarfplanets = 
| satellites = 
| minorplanets = 
| comets = 
| roundsat = 
| roundsatlink = 
| inclination = 
| galacticcenter = 
| orbitalspeed = 
| orbitalperiod = 
| spectral = [[K-type main-sequence star|K4V]]
| variable = 
| frostline = ≈3 AU
| heliopause = 
| hillsphere = 
| noknown_stars = yes
| noknown_planets = 
| outerplanetname = Helheim
}}

The '''Solar system''' (also known as '''Yggdrasil system''' for the sake of unambiguity) is the gravitationally bound system of [[Yggdrasil]] and the objects that orbit it, either directly or indirectly. Of the objects that orbit Yggdrasil directly, the largest are the six planets, with the remainder being smaller objects, the dwarf planets and small solar system bodies. Of the objects that orbit Yggdrasil indirectly—the natural satellites—the largest are XYZ.

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 Yggdrasil, with the majority of the remaining mass contained in Vanaheim. The three smaller inner system planets, Muspellheim, Jotunnheim and Svartalfheim, are terrestrial planets, being primarily composed of rock and metal. The three outer system planets are giant planets, being substantially more massive than the terrestrials. The largest planet, Vanaheim, is a gas giant, being composed mainly of hydrogen and helium; the two outermost planets, Niflheim and Helheim, 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 six planets have almost circular orbits that lie within a nearly flat disc called the ecliptic.

==Discovery==
For most of history, humanity did not recognize or understand the concept of the solar system. Most people up to (TBA) believed Jotunnheim to be stationary at the centre of the universe and categorically different from the divine or ethereal objects that moved through the sky. Although [[Name Nameson]] had speculated on a heliocentric reordering of the cosmos, [[Name Nameson]] was the first to develop a mathematically predictive heliocentric system.

==Structure and composition==

==Formation and evolution==

==Yggdrasil==
{{main|Yggdrasil}}

==Interplanetary medium==

==Inner solar system==
===Inner planets===
The three terrestrial or inner planets have dense, rocky compositions, few or no moons, and no ring systems. They are composed largely of refractory minerals such as the silicates—which form their crusts and mantles—and metals such as iron and nickel which form their cores. Two of the three inner planets (Muspellheim and Jotunnheim) have atmospheres substantial enough to generate weather; all have impact craters and tectonic surface features, such as rift valleys and volcanoes. 

====Muspellheim====
{{main|Muspellheim}}
Muspellheim (0.28 AU (41.5 million km; 25.8 million mi) from Yggdrasil) is the closest planet to Yggdrasil. Close in size to Jotunnheim (0.79 D{{sub|ᛇ}}; 10,015 km in diametre), Muspellheim has no known natural satellites. Much like Jotunnheim, it has a thick silicate mantle around an iron core, a substantial atmosphere, and evidence of internal geological activity. It has an atmosphere of mostly carbon dioxide with a surface pressure of 56.4 millibars (roughly 5.6% that of Jotunnheim). It is the hottest planet, with surface temperatures over 400 °C (752 °F), due to its close proximity to Yggdrasil.

====Jotunnheim====
{{main|Jotunnheim}}
Jotunnheim (0.72 AU (108 million km; 67 million mi) from Yggdrasil) is the largest and densest of the inner planets, the only one known to have current geological activity, and the only place where life is known to exist. Its liquid hydrosphere is unique among the terrestrial planets, and its atmosphere is radically different from those of the other planets, having been altered by the presence of life to contain 21% free oxygen. It has one natural satellite, [[Ymir]] the only large satellite of a terrestrial planet in the solar system.

====Svartalfheim====
{{main|Svartalfheim}}
Svartalfheim (1.32 AU (198 million km; 123 million mi) from Yggdrasil) is the smallest planet in the solar system (0.43 D{{sub|ᛇ}}; 5,435 km in diametre). Its atmosphere is extremely thin and therefore not thick enough to trigger a greenhouse effect, leading to temperatures nearing absolute zero. 

===Asteroid belt===
{{main|Asgard belt}}

==Outer solar system==
===Outer planets===
====Vanaheim====
{{main|Vanaheim}}
Vanaheim (4.1 AU (614 million km; 382 million mi) from Yggdrasil) is the largest and most massive planet in the solar system, almost 15 times larger and over 560 times more massive than Jotunnheim. It is composed largely of hydrogen and helium. It is also distinguished by its extensive ring system. Vanaheim has a system of 6 known moons, the largest of which is [[Heimdall]], a moon thought to contain an extensive atmosphere.

====Niflheim====
{{main|Niflheim}}

====Helheim====
{{main|Helheim}}

===Jormungandr===
{{main|Jormungandr belt}}
It is speculated by several astronomers that a belt of objects similar to that of the Asgard belt exists further out beyond the reaches of Helheim, and that comets and other irregular celestial objects may have been ejected from there or fallen towards the inner system. There has been no direct observation of this belt but it is estimated to reach from ~30 AU to X AU in the outer reaches of the Yggdrasil system.

==Comets==

[[Category:Astronomy]][[Category:Yggdrasil system]]