Astrophysics & Particle Physics-APPC 2026

Radio Astronomy is the observational astronomy discipline that examines celestial bodies by observing radio frequency radiation. In contrast to optical astronomy, which detects visible light, radio astronomy discovers aspects of the universe invisible to the human eye, uncovering aspects of the universe on huge scales.Radio telescopes, ranging from single-dish instruments to interferometric arrays such as the Very Large Array (VLA), detect and map radio emissions from stars, galaxies, quasars, pulsars, and nebulae.

Radio interferometry enables astronomers to obtain high-resolution images by co-adding signals from several telescopes, essentially forming a telescope with dimensions equal to the distance between the instruments.Main objects of radio astronomy are pulsars, rapidly rotating neutron stars that radiate periodic radio pulses; active galactic nuclei and quasars, which emit powerful radio jets; and the cosmic microwave background, residual radiation from the early universe containing essential information on cosmology and the Big Bang.Radio astronomy also investigates the interstellar medium, tracing gas and dust clouds, molecular areas, and magnetic fields in galaxies.

Watching out for neutral hydrogen via the 21-cm line, astronomers map the structure, spin, and evolution of galaxies. Astrophysical jets, magnetospheres, and cosmic masers are other events that can only be detected uniquely in the radio spectrum.Space-based radio observatories, together with networks on the ground, push observations outside Earth's ionospheric interference, making it possible to investigate low-frequency radio waves and far-away cosmic signals. Radio surveys yield statistical information regarding galaxy populations, star-forming sites, and transient phenomena like fast radio bursts (FRBs).Through radio astronomy, hidden patterns and dynamic processes in the universe are unveiled, supplementing optical, infrared, X-ray, and gamma-ray observations. It is crucial for the study of stellar evolution, galaxy evolution, high-energy astrophysics, and cosmology and is therefore a foundation for multi-wavelength astrophysical studies.