Editing Outer space (section)

=== Intergalactic space ===
{{Main|Warm–hot intergalactic medium|Intracluster medium|Intergalactic dust}}
[[File:Structure of the Universe.jpg|thumb|alt=Structure of the Universe|Large-scale matter distribution in a cubic section of the universe. The blue fiber-like structures represent the matter, and the empty regions in between represent the [[cosmic void]]s of the intergalactic medium]]

Intergalactic space is the physical space between galaxies. Studies of the large-scale distribution of galaxies show that the universe has a foam-like structure, with [[Galaxy groups and clusters|groups and clusters of galaxies]] lying along filaments that occupy about a tenth of the total space. The remainder forms [[cosmic void]]s that are mostly empty of galaxies. Typically, a void spans a distance of 7–30 megaparsecs.{{sfn|Wszolek|2013|p=67}}

Surrounding and stretching between galaxies is the [[intergalactic medium]] (IGM). This [[rarefaction|rarefied]] plasma<ref name=jafelice_opher1992/> is organized in a [[galaxy filament|galactic filamentary]] structure.<ref name=wadsley2002/> The diffuse photoionized gas contains filaments of higher density, about one atom per cubic meter,<ref name="Harvard & Smithsonian 2022 k265"/> which is 5–200 times the average density of the universe.<ref name="apj_714_1715"/> The IGM is inferred to be mostly primordial in composition, with 76% hydrogen by mass, and enriched with higher mass elements from high-velocity galactic outflows.<ref name="Oppenheimer_Davé_2006"/>

As gas falls into the intergalactic medium from the voids, it heats up to temperatures of 10<sup>5</sup>&nbsp;K to 10<sup>7</sup>&nbsp;K.<ref name=baas41_908/> At these temperatures, it is called the [[warm–hot intergalactic medium]] (WHIM). Although the plasma is very hot by terrestrial standards, 10<sup>5</sup> K is often called "warm" in astrophysics. Computer simulations and observations indicate that up to half of the atomic matter in the universe might exist in this warm–hot, rarefied state.<ref name="apj_714_1715" /><ref name=ssr134_1_141/><ref name="apjs_182_378"/> When gas falls from the filamentary structures of the WHIM into the galaxy clusters at the intersections of the cosmic filaments, it can heat up even more, reaching temperatures of 10<sup>8</sup>&nbsp;K and above in the so-called [[intracluster medium]] (ICM).<ref name="apj546_100"/>

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| header            = Overview of different scales of space as [[Location of Earth|regions around Earth]]
| image1            = L2 rendering.jpg
| width1            = 93
| caption1          = [[Earth#Earth–Moon system|Earth-Moon System]]
| image2            = Inner solar system objects top view for wiki.png
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| caption2          = [[Inner Solar System]] with [[Near-Earth object]]s
| image3            = Oort cloud Sedna orbit.svg
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| caption3          = [[Solar&nbsp;System]] and [[Oort cloud]]
| image4            = Angular map of fusors around Sol within 9ly (large).png
| width4            = 93
| caption4          = [[List of nearest stars and brown dwarfs|Nearest stars]]
| image5            = Local Interstellar Clouds with motion arrows.jpg
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| caption5          = [[Local Interstellar Cloud]] and neighbouring [[interstellar medium]]
| image6            = Galaxymap.com, map 100 parsecs (2022).png
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| caption6          = [[List of nearby stellar associations and moving groups|Star association]]s and interstellar medium map of the [[Local Bubble]]
| image7            = Galaxymap.com, map 1000 parsecs (2022).png
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| caption7          = Molecular clouds around the Sun inside the [[Orion-Cygnus Arm]]
| image8            = OrionSpur.png
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| caption8          = Orion-Cygnus Arm and neighbouring arms
| image9            = Milky Way Arms ssc2008-10.svg
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| caption9          = Orion-Cygnus Arm inside the [[Milky&nbsp;Way]]
| image10            = Milky Way side view.png
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| caption10          = The Sun within the structure of the Milky&nbsp;Way
| image11           = 06-Local Group (LofE06240).png
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| caption11         = [[Satellite galaxies of the Milky Way]] in [[Local Group]]
| image12           = 07-Laniakea (LofE07240).png
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| caption12         = [[Virgo Supercluster|Virgo SCl]] in [[Laniakea Supercluster|Laniakea SCl]]
| image13           = Laniakea.gif
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| caption13         = Laniakea SCl in [[Pisces–Cetus Supercluster Complex]]
| image14           = Observable Universe with Measurements 01.png
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| caption14         = [[Observable Universe]] of the [[Universe]]
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