Astrophysics & Particle Physics-APPC 2026

Dark Energy is an enigmatic energy that fills all of space and is deemed to be the cause of the accelerating expansion of the universe. Discovered in the late 1990s from observations of type Ia supernovae, dark energy is believed to contribute approximately 68% of the total energy density of the universe.The nature of dark energy is still one of the most pressing unsolved challenges in cosmology. The most straightforward solution is the cosmological constant (Λ) in Einstein's field equations, a constant energy density of unoccupied space. Other theories suggest dynamic fields like quintessence, or changes to gravity on cosmological scales.Dark energy impacts the universe's large-scale structure, reducing the rate of growth of cosmic structures as a result of its repulsive gravitational influence. Knowledge of dark energy is crucial in order to foretell the future destiny of the universe, whether it will expand indefinitely, experience a "Big Freeze," or develop differently in other models.Cosmologists investigate dark energy by making precise observations of the Hubble parameter, galaxy surveys, gravitational lensing, and future space missions. These measurements are designed to limit models of dark energy and see if it is indeed constant or time and space variable. With the study of dark energy, researchers seek to discover underlying physics beyond the Standard Model, learn about the forces causing cosmic acceleration, and learn about the universe's composition and evolution. Dark energy is a leading subject of current astrophysics and theoretical cosmology, shaping investigation into the ultimate destiny and large-scale evolution of the universe.