Around 80% of the universe is missing in the form of dark matter and dark energy.
Roughly 80% of the mass of the universe is made up of material that scientists cannot directly observe. Known as dark matter, this bizarre ingredient does not emit light or energy. So why do scientists think it dominates?
Since at least the 1920s, astronomers have hypothesized that the universe contains more matter than seen by the naked eye. Support for dark matter has grown since then, and although no solid direct evidence of dark matter has been detected, there have been strong possibilities in recent years.
"Motions of the stars tell you how much matter there is," Pieter van Dokkum, a researcher at Yale University, said in a statement. "They don't care what form the matter is, they just tell you that it's there." Van Dokkum led a team that identified the galaxy Dragonfly 44, which is composed almost entirely of dark matter.
The familiar material of the universe, known as baryonic matter, is composed of protons, neutrons, and electrons. Dark matter may be made of baryonic or non-baryonic matter. To hold the elements of the universe together, dark matter must make up approximately 80% percent of the universe. The missing matter could simply be more challenging to detect, made up of regular, baryonic matter.