Astrophysics & Particle Physics-APPC 2026

Extragalactic Astronomy is concerned with the observation of celestial entities outside the Milky Way galaxy, such as galaxies, clusters of galaxies, quasars, and the intergalactic medium. It seeks to know the origin, evolution, and interactions of these cosmic structures and the universe's large-scale dynamics.Galaxies, the building blocks of the universe, come in a diverse array of shapes, sizes, and compositions, ranging from spiral and elliptical galaxies to irregular and dwarf galaxies. Extragalactic astronomers explore their star populations, gas mass, star formation rate, and central supermassive black holes to follow their evolutionary path and contribution to cosmic structure formation.

Galaxy clusters, the most massive gravitationally bound entities, tell us about dark matter, dark energy, and mass distribution in the universe. Cluster observations and interactions allow scientists to explore cosmic expansion, gravitational lensing, and formation of the large-scale structure. Extreme astrophysical phenomena such as active galactic nuclei (AGNs) and quasars uncover energy-rich events fueled by accretion onto supermassive black holes.Extragalactic astronomy uses multi-wavelength observations over the radio, infrared, optical, ultraviolet, X-ray, and gamma-ray bands to probe galaxies, clusters, and the intergalactic medium. Observational surveys in conjunction with theoretical models and simulations allow astronomers to trace the cosmic web, observe galaxy mergers, and explore how environment affects galaxy evolution.Uniformly studying objects outside the Milky Way provides critical information regarding the universe's origin and evolution, dark matter and dark energy behavior, and how star formation and supermassive black hole activity work.

This area of study connects observational cosmology, high-energy astrophysics, and galaxy formation, providing a well-rounded understanding of the universe on the largest scales.Extragalactic astronomy continues to add to our understanding of cosmic structure and how they interact, assisting scientists in revealing the underlying physics governing the universe outside of our own galaxy.