<p>You can find all kind of objects, like <a href="http://news.vanderbilt.edu/2012/04/rogue-stars-intergalactic-space/">stars</a>, <a href="http://arxiv.org/abs/astro-ph/9609076">planetary nebulæ</a> etc.</p>

<p>But it is mostly a <a href="http://www.google.fr/url?sa=t&amp;rct=j&amp;q=&amp;esrc=s&amp;source=web&amp;cd=6&amp;ved=0CGgQFjAF&amp;url=http%3A%2F%2Fwww.ast.cam.ac.uk%2F~pettini%2FPhysical%2520Cosmology%2Flecture09.pdf&amp;ei=KXtFUqUIpbHQBZa-gfgB&amp;usg=AFQjCNFhJOpTehKEIlaScFmOzOjzAEkQhQ&amp;sig2=Bbt6c1308XUK_NGmOxQ95Q&amp;bvm=bv.53217764,d.d2k">hot, ionized void</a>. How void? The density of the intergalactic medium is about 1 to 100 particles per cubic meter (you can compare it to the mean galactic density, of about a million particles per cubic meter, or that of Earth's atmosphere, of about 10^26 particles cubic meter). How hot? It can go from <a href="http://adsabs.harvard.edu/abs/2010AAS...21631808G">10^5 to 10^7 K</a>.</p>

<p>Fun thing is, even though it is "very empty", is contains however most of the baryons (the "classical matter") of the Universe, if you consider that only <a href="http://www.google.fr/url?sa=t&amp;rct=j&amp;q=&amp;esrc=s&amp;source=web&amp;cd=6&amp;ved=0CGgQFjAF&amp;url=http%3A%2F%2Fwww.ast.cam.ac.uk%2F~pettini%2FPhysical%2520Cosmology%2Flecture09.pdf&amp;ei=KXtFUqUIpbHQBZa-gfgB&amp;usg=AFQjCNFhJOpTehKEIlaScFmOzOjzAEkQhQ&amp;sig2=Bbt6c1308XUK_NGmOxQ95Q&amp;bvm=bv.53217764,d.d2k">5-10% of the total mass of baryons is enclosed in stars and galaxies</a>.</p>

CC BY-SA 3.0
2013-09-27T12:52:02.527Z
2013-09-27T12:52:02.527Z
MBR
<p>There can be stars (and small star systems). Stars need not be found only in galaxies.</p>

<p>There can be gas clouds.</p>

<p>Most nebulae are in intergalactic space. Indeed, for a while, both galaxies and nebulae were termed as "nebulae" until the differing nature of galaxies was discovered.</p>

<p>Almost any (small) structure that can be present in a galaxy can be present in intergalactic space, for that matter. Black holes (neutron stars, white dwarfs, brown dwarfs, ... ), star clusters, star systems, etc can all be present.</p>

<p>Finally, there's a very rare (rare in the density sense) plasma, mainly of hydrogen, that makes up almost all of the intergalactic medium. Zero pressure is an unattainable ideal case.</p>

CC BY-SA 3.0
2014-01-03T14:15:13.097Z
Could you elaborate on this very rare plasma?, sounds interesting
Eduardo Serra
CC BY-SA 3.0
2013-09-27T12:26:45.243Z
2013-09-27T12:26:45.243Z
Manishearth
<p>What bodies can be encountered way outside galaxies - far beyond the farthest edges of galaxies, in the deep space between them? Are there single, galaxy-less stars, giant clouds of gas more dense than that the lower-than-elsewhere content of free hydrogen in space, or any other phenomena that span the void between the galaxies?</p>

<intergalactic-space>
What is there in the intergalactic space?
SF.
# What is there in the intergalactic space?

(Asked by: username_0 on 2013-09-27)

What bodies can be encountered way outside galaxies - far beyond the farthest edges of galaxies, in the deep space between them? Are there single, galaxy-less stars, giant clouds of gas more dense than that the lower-than-elsewhere content of free hydrogen in space, or any other phenomena that span the void between the galaxies?

**Tags:** intergalactic-space

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## 2 answers

### Answer by username_2 on 2013-09-27. Score: 12 | Accepted answer

There can be stars (and small star systems). Stars need not be found only in galaxies.

There can be gas clouds.

Most nebulae are in intergalactic space. Indeed, for a while, both galaxies and nebulae were termed as "nebulae" until the differing nature of galaxies was discovered.

Almost any (small) structure that can be present in a galaxy can be present in intergalactic space, for that matter. Black holes (neutron stars, white dwarfs, brown dwarfs, ... ), star clusters, star systems, etc can all be present.

Finally, there's a very rare (rare in the density sense) plasma, mainly of hydrogen, that makes up almost all of the intergalactic medium. Zero pressure is an unattainable ideal case.

> **Comments:**
> **username_3**: Could you elaborate on this very rare plasma?, sounds interesting  

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### Answer by username_1 on 2013-09-27. Score: 12

You can find all kind of objects, like [stars](http://news.vanderbilt.edu/2012/04/rogue-stars-intergalactic-space/), [planetary nebulæ](http://arxiv.org/abs/astro-ph/9609076) etc.

But it is mostly a [hot, ionized void](http://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&ved=0CGgQFjAF&url=http%3A%2F%2Fwww.ast.cam.ac.uk%2F~pettini%2FPhysical%2520Cosmology%2Flecture09.pdf&ei=KXtFUqUIpbHQBZa-gfgB&usg=AFQjCNFhJOpTehKEIlaScFmOzOjzAEkQhQ&sig2=Bbt6c1308XUK_NGmOxQ95Q&bvm=bv.53217764,d.d2k). How void? The density of the intergalactic medium is about 1 to 100 particles per cubic meter (you can compare it to the mean galactic density, of about a million particles per cubic meter, or that of Earth's atmosphere, of about 10^26 particles cubic meter). How hot? It can go from [10^5 to 10^7 K](http://adsabs.harvard.edu/abs/2010AAS...21631808G).

Fun thing is, even though it is "very empty", is contains however most of the baryons (the "classical matter") of the Universe, if you consider that only [5-10% of the total mass of baryons is enclosed in stars and galaxies](http://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&ved=0CGgQFjAF&url=http%3A%2F%2Fwww.ast.cam.ac.uk%2F~pettini%2FPhysical%2520Cosmology%2Flecture09.pdf&ei=KXtFUqUIpbHQBZa-gfgB&usg=AFQjCNFhJOpTehKEIlaScFmOzOjzAEkQhQ&sig2=Bbt6c1308XUK_NGmOxQ95Q&bvm=bv.53217764,d.d2k).


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