However, our observations of normal matter (protons, neutrons and electrons) only account for about 2.5 percent of the universe-the rest of it is nowhere to be found.
Now, two papers have come out suggesting we may have found half of this missing chunk, in huge stretches of hot, diffuse gas that hold galaxies together.
Researchers from Institute of Space Astrophysics in France and University of Edinburgh in the United Kingdom found the missing matter made of particles called baryons, linking galaxies together through filaments of hot, diffuse gas.
Instead, under the action of gravity, matter is concentrated into so-called filamentary structures, forming a network of knots and links called the "cosmic web". Both teams found definitive evidence of gas filaments between the galaxies. Two teams, who both separately uploaded papers to the arXiv preprint server in September, found these baryons using an effect called Sunyaev-Zel'dovich (tSZ). This interaction leaves behind markers of the gas that can be captured and studied.
These baryons make up half of the universe's "missing matter", which has eluded scientists for decades. As the light travels, some of it scatters off the electrons in the gas, leaving a dim patch in the cosmic microwave background - our snapshot of the remnants from the birth of the cosmos.
The arguments of scientists based on the analysis of data obtained from the orbiting Planck Observatory, which is created to study the cosmic microwave background. This phenomenon allowed the researchers to see strands of matter that are normally far too dim to observe. This effect is essentially light left over from the Big Bang scattering off the particles in the gas.
The teams looked at galaxies mapped in the Sloan Digital Sky Survey predicted to be connected by baryons.
The Edinburgh team put together images of over a million pairs of galaxies for their study, while the French team stacked data on 260,000 pairs. This mismatch is known as the "missing baryon problem".
The Scottish team found the strands to be six times denser - confirmation they are dense enough to form filaments between galaxies.
Hideki Tanimura, leader of one of the groups in France, told the New Scientist that the missing baryon problem had been solved. "If this factor is included, our findings are very consistent with the other group".
"Everybody sort of knows that it has to be there, but this is the first time that somebody - two different groups, no less - has come up with a definitive detection", professor Ralph Kraft, from the Harvard-Smithsonian Center for Astrophysics in MA, who wasn't involved in the studies, told New Scientist.