Most dark matter is thought to be non-baryonic; it may be composed of some as-yet-undiscovered subatomic particles. The primary candidate for dark matter is some new kind of elementary particle that has not yet been discovered, particularly weakly interacting massive particles (WIMPs).
Dark matter does not interact electromagnetically, therefore charged leptons and photons could not be dark matter particles. Neutrinos have been considered, but simulations seem to rule out this possibility. And quarks and gluons don’t exist outside hadrons, of which the longer living one’s proton and neutron, and their anti-particles, interact electromagnetically.
Dark matter is not made of any particles from the standard model.
Dark matter makes galaxies spin faster. There is a large-scale distribution of galaxies, with too many small galaxies than gravity alone can produce. Galaxies are not distributed randomly throughout the universe but are grouped in gravitationally bound clusters. The Milky Way is part of a poor cluster called the Local Group which contains about 50 galaxies including dwarf galaxies. Clusters are then grouped together in superclusters which contain dozens of clusters.
A galaxy that was governed by normal matter alone (L) would display much lower rotational speeds in the outskirts than towards the center, similar to how planets in the Solar System move. However, observations indicate that rotational speeds are largely independent of radius (R) from the galactic center, leading to the inference that a large amount of invisible, or dark, matter must be present. Gravity binds everything together; it keeps galaxy clusters intact. Gravity also forms galaxies into different shapes: spiral, elliptical, and irregular. … Spiral galaxies are constantly making new stars, whereas elliptical galaxies do not make new stars.
Modified Newtonian dynamics (MOND) is a hypothesis that proposes a modification of Newton’s laws to account for observed properties of galaxies. It is an alternative to the hypothesis of dark matter in terms of explaining why galaxies do not appear to obey the currently understood laws of physics. It is an alternative to the hypothesis that the dynamics of galaxies are determined by massive, invisible dark matter halos. Both MOND and dark matter halos stabilize disk galaxies, helping them retain their rotation-supported structure and preventing their transformation into elliptical galaxies.
The even distribution means that dark energy does not have any local gravitational effects, but rather a global effect on the universe as a whole. This leads to a repulsive force, which tends to accelerate the expansion of the universe.
