We used to think of our universe as being comprised of isolated galaxies surrounded by the vast darkness of intergalactic space. Now, that picture has been shown to be much more complicated.
In 2008, researchers at the University of Colorado at Boulder think they have identified some of the material of the cosmic web that extends between galaxies.
This discovery has also shed light on one of the universe's greatest mysteries: where was all the missing normal, or baryonic matter?
To see the spectral web, scientists observed the light coming from 18 quasars. Quasars are thought to be massive galaxies with large black holes at their center.
What emerged was a spiderweb-like structure that permeates the space between galaxies, with the galaxies being nodes on that web.
Using the Space Telescope Imaging Spectrograph onboard NASA's Hubble Space Telescope, and NASA's Far Ultraviolet Spectroscopic Explorer, the astronomers identified the web's filaments as being comprised of hot gases — mostly hydrogen.
The largest filament is named the Hercules–Corona Borealis Great Wall, and it is a staggering 10 billion light-years long, and contains several billion galaxies. The largest void between filaments is the Keenan, Barger, and Cowie (KBC) void, and it has a diameter of 2 billion light-years.
Within the spherical KBC, void lies our home galaxy, the Milky Way, and our planet, Earth.
Why This Structure?
The question is: how did this structure come to be? The answer can be found in the nature of space itself — pairs of particles and anti-particles are constantly coming into existence then annihilating one another.
Normally, these pairs of particles destroy each other, but the rapid expansion of space, called inflation, prevented that from happening. The inflationary period occurred roughly, 10-32 seconds after the Big Bang. This caused discrepancies in the density of the universe.
Under the effect of gravity, these discrepancies caused differences in the way matter grouped together, clumping in some spots, but not in others. However, that doesn't entirely explain the cosmic web.
The Cosmic Web website used data from 24,000 galaxies to construct three possible models for how the cosmic web came to be.
The first model, the Fixed Length Model, is based on the distance between galaxies, where all galaxies within a set distance of l are connected by an undirected link.
The second model, the Varying Length Model, is based on galaxies' sizes, with the length of each link being proportional to the size of the galaxy, where l = a Ri1/2.
The third model, the Nearest Neighbor Model, is based on galaxies' closest neighbors, where the length of each link depends on the distance to the nearest galaxy.
Of the three models, the third, the Nearest Neighbor Model, correlated the best with what was observed, thus revealing a clearer picture of the blueprint for our universe.