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Non-baryonic matter, as implied by the name, is any sort of matter that is not composed primarily of baryons. This might include neutrinos and free electrons, dark matter, supersymmetric particles, axions, and black holes.
There are two main candidates for non-baryonic dark matter: new hypothetical particles and primordial black holes. Unlike baryonic matter, nonbaryonic particles do not contribute to the formation of the elements in the early universe (Big Bang nucleosynthesis) [78] and so its presence is revealed only via its gravitational effects, or weak lensing.
The commonly accepted view is that most of the dark matter is non-baryonic in nature. [63] As such, it is composed of particles as yet unobserved in the laboratory. Perhaps they are supersymmetric particles, [65] which are not Standard Model particles but relics formed at very high energies in the early phase of the universe and still floating ...
As "dark matter", baryonic dark matter is undetectable by its emitted radiation, but its presence can be inferred from gravitational effects on visible matter. This form of dark matter is composed of "baryons", heavy subatomic particles such as protons and neutrons and combinations of these, including non-emitting ordinary atoms.
The missing baryon problem is claimed to be resolved. Using observations of the kinematic Sunyaev–Zel'dovich effect spanning more than 90 % of the lifetime of the Universe, in 2021 astrophysicists found that approximately 50 % of all baryonic matter is outside dark matter haloes, filling the space between galaxies. [108]
In physical cosmology, the baryon asymmetry problem, also known as the matter asymmetry problem or the matter–antimatter asymmetry problem, [1] [2] is the observed imbalance in baryonic matter (the type of matter experienced in everyday life) and antibaryonic matter in the observable universe.
A MAssive Compact Halo Object (MACHO) is a kind of astronomical body that might explain the apparent presence of dark matter in galactic halos. A MACHO is a body that emits little or no radiation and drifts through interstellar space unassociated with any planetary system (and may or may not be composed of normal baryonic matter). Since MACHOs ...
The density of baryonic matter can be obtained directly by summing up all the known baryonic matter. This is highly nontrivial, since although luminous matter such as stars and galaxies are easily summed, baryonic matter can also exist in highly non-luminous form, such as black holes, planets, and highly diffuse interstellar gas.