Missing Matter Caught in the ‘Cosmic Web’

15 May 2008


There seems to be matter missing in the universe, but astronomers at the university of Colorado now say they have definitively found about half of the matter, trapped in a 'cosmic web'.

We can tell that there should be more matter than we can account for, as we can see it's gravitational effect on galaxies

Normal matter, or baryonic matter as it's also known, consists of Baryons - these are the protons, neutrons and subatomic particles that make up the atoms we are familiar with.  The planets, stars and galaxies that we can see make up only a fraction of the matter created in the big bang, and astronomers have been at a loss as to where the rest of it had gone. 

But now scientists have found evidence of baryonic matter in the spaces in between galaxies, what we traditionally think of as being empty space

 To find the matter they used light from distant quasars, likening it to using a flashlight to look through fog.  They used the Space Telescope Imaging Spectrograph (STIS) aboard NASA's Hubble Space Telescope and NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) to observe the spectrum of light from these quasars, and noticed the tell-tale signs of hydrogen and oxygen superimposed on the quasar's light.

But rather than exist in a diffuse cloud, the hot hydrogen and oxygen formed filaments, long trails that make up a 'cosmic web' throughout the universe.

So why didn't we spot this huge reservoir of hot gas before?  It turns out that the filaments are too hot to be seen in visible light, but too cool to show up with x-rays.  Spectrally, the matter had been hiding between the cushions of the sofa!

Now that we have found it, we can start to untangle the cosmic web and make detailed observations which will help us learn how galaxies first form.


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