In the late 1990s, cosmologists made a prediction about how much ordinary matter there should be in the universe. About 5%, they estimated, should be regular stuff with the rest a mixture of dark matter and dark energy. But when cosmologists counted up everything they could see or measure at the time, they came up short. By a lot.
The sum of all the ordinary matter that cosmologists measured only added up to about half of the 5% what was supposed to be in the universe.
It took the discovery of a new celestial phenomenon and entirely new telescope technology, but earlier this year, our team finally found the missing matter.
Baryon is a classification for types of particles — sort of an umbrella term — that encompasses protons and neutrons, the building blocks of all the ordinary matter in the universe. Everything on the periodic table and pretty much anything that you think of as “stuff” is made of baryons.
Read more: Space