ESA Space Science | XMM-Newton | 2018 Jun 20
While the mysterious dark matter and dark energy make up about 25 and 70 percent of our cosmos respectively, the ordinary matter that makes up everything we see – from stars and galaxies to planets and people – amounts to only about five percent.
But even this five percent turns out to be quite hard to track down.
The total amount of ordinary matter, which astronomers refer to as baryons, can be estimated from observations of the Cosmic Microwave Background, which is the most ancient light in the history of the Universe, dating back to only about 380 000 years after the Big Bang.
Observations of very distant galaxies allow astronomers to follow the evolution of this matter throughout the Universe’s first couple billions of years. After that, however, more than half of it seemed to have gone missing. ...
Researchers Find Last of the Universe's Missing Ordinary Matter
University of Colorado, Boulder | 2018 Jun 20
Observations of the Missing Baryons in the Warm-Hot Intergalactic Medium - F. Nicastro et al