Astrophysics & Particle Physics-APPC 2026

Dark Matter is a type of matter which does not absorb, emit, or reflect light and hence is invisible to regular telescopes. Though not visible, it accounts for nearly 27% of the universe's total mass-energy content and is significant in galaxy formation, cosmic structure, and gravitational dynamics. Indications of dark matter result from a variety of astrophysical observations. Galaxy rotation curves disclose that stars move within galaxies at velocities incompatible with the visible matter, suggesting the presence of unseen mass. Gravitational lensing, when light from distant galaxies is curved by passing through interposing mass, also shows the existence of substantial invisible matter within galaxy clusters.Dark matter is speculated to create a massive halo surrounding galaxies, giving rise to the necessary gravitational scaffolding to keep galaxies bound and enable formation on a large scale of structure within the universe.

Galaxies and clusters would be unable to form or hold their observed forms and dynamics without dark matter. Several candidates for dark matter include Weakly Interacting Massive Particles (WIMPs), axions, sterile neutrinos, and other theoretical particles. Particle physics experiments, underground labs, and space-based detectors are currently searching for signatures of dark matter interactions. In cosmology, dark matter plays a companion role to dark energy in determining the expansion, evolution, and geometry of the universe. Numerical simulations with dark matter accurately reproduce the galaxy distribution, clusters, and the cosmic web, justifying its central part in cosmic evolution.Science learns about fundamental physics, the universe itself, and the physical processes behind galaxy formation and evolution by exploring dark matter. Dark matter is one of the deepest challenges in contemporary astrophysics, connecting observational data, theoretical frameworks, and laboratory particle physics.Dark Matter is a pillar of astrophysics and cosmology that exposes the universe's hidden framework and informs studies on the invisible constituents that shape cosmic evolution.