What is Intergalactic Space?

The space between stars is known as interstellar space, and so the space between galaxies is called intergalactic space. These are the vast empty spaces that sit between galaxies. For example, if you wanted to travel from the Milky Way to the Andromeda galaxy, you would need to cross 2.5 million light-years of intergalactic space.

Intergalactic space is as close as you can get to an absolute vacuum. There’s very little dust and debris, and scientists have calculated that there’s probably only one hydrogen atom per cubic meter. The density of material is higher near galaxies, and lower in the midpoint between galaxies.

Galaxies are connected by a rarefied plasma that is thought to posses a cosmic filamentary structure, which is slightly denser than the average density of the Universe. This material is known as the intergalactic medium, and it’s mostly made up of ionized hydrogen. Astronomers think that the intergalactic medium is about 10 to 100 times denser than the average density of the Universe.

This intergalactic medium can actually be seen by our telescopes here on Earth because it’s heated up to tens of thousands, or even millions of degrees. This is hot enough for electrons to escape from hydrogen nuclei during collisions. We can detect the energy released from these collisions in the X-ray spectrum. NASA’s Chandra X-Ray Observatory – a space telescope designed to search for X-rays – has detected vast clouds of hot intergalactic medium in regions where galaxies are colliding together in clusters.

We have written many articles about galaxies for Universe Today. Here’s an article about how intergalactic dust might be messing up observations, and here’s an article about a cosmic hurricane in a starburst galaxy.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

Fraser Cain

Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay. Here's a link to my Mastodon account.

Recent Posts

How Could Astronauts Call for Help from the Moon?

Exploring the Moon poses significant risks, with its extreme environment and hazardous terrain presenting numerous…

12 hours ago

There Was a 15 Minute Warning Before Tonga Volcano Exploded

Volcanoes are not restricted to the land, there are many undersea versions. One such undersea…

12 hours ago

Main Sequence and White Dwarf Binaries are Hiding in Plain Sight

Some binary stars are unusual. They contain a main sequence star like our Sun, while…

14 hours ago

What a Misplaced Meteorite Told Us About Mars

11 million years ago, Mars was a frigid, dry, dead world, just like it is…

16 hours ago

Uranus is Getting Colder and Now We Know Why

Uranus is an oddball among the Solar System's planets. While most planets' axis of rotation…

19 hours ago

How Scientists Repurposed a Camera on ESA’s Mars Express Mission

A camera aboard the Mars Express orbiter finds a new lease on life. Sometimes, limitations…

21 hours ago