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Intergalactic space is more than just an empty void.
Credit: Shutterstock
▼ The vast voids between galaxies can stretch millions of light-years across and may appear empty. But these spaces actually contain more matter than the galaxies themselves.
"If you took a cubic meter, there would be less than one atom in it," Michael Shull, an astronomer at the University of Colorado Boulder, told Live Science. "But when you add it all up, it's somewhere between 50 and 80% of all the ordinary matter out there."undefined
So, where did all this matter come from? And what's it up to?
The matter between galaxies — often called the intergalactic medium, or IGM for short — is mostly hot, ionized hydrogen (hydrogen that has lost its electron) with bits of heavier elements such as carbon, oxygen and silicon thrown in. While these elements typically don't glow bright enough to be seen directly, scientists know they're there because of the signature they leave on light that passes by.
In the 1960s, astronomers first discovered quasars— incredibly bright and active galaxies in the distant universe — and shortly thereafter, they noticed that the light from the quasars had missing pieces. These pieces had been absorbed by something in between the quasar and the astronomers' telescopes — this was the gas of the IGM. In the decades since, astronomers have discovered vast webs and filaments of gas and heavy elements that collectively contain more matter than all the galaxies combined. Some of this gas was likely left over from the Big Bang, but the heavier elementshint that some of it comes from old stardust, spewed out by galaxies.
While the most-remote regions of the IGM will be eternally isolated from neighboring galaxies as the universe expands, more "suburban" regions play an important role in galaxy life. (▪ ▪ ▪)
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