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.
The particles in this gas are baryons; particles made up of three quarks, like protons and neutrons. 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 effect is essentially light left over from the Big Bang scattering off the particles in the gas. When this happens, it leaves a trace in the cosmic microwave background (CMB), the relic radiation from the earliest universe seen from across space.
“This result establishes the presence of ionised gas in large-scale filaments, and suggests that the missing baryons problem may be resolved via observations of the cosmic web,” said the authors of the second study.
“The missing baryon problem is solved,” claims Hideki Tanimura at the Institute of Space Astrophysics in Orsay, France, leader of one of the groups