Astrophysics & Particle Physics-APPC 2026

Black Holes are areas of space where the gravity is so strong that nothing, including light, can escape. They are created by the collapse of massive stars or as supermassive black holes at galaxy centers. Black holes are characterized by their event horizon, the point beyond which escape is not possible, and the singularity, an infinitely dense point at their center where our current laws of physics fail.

Approximately three solar masses in mass, stellar-mass black holes are formed from the collapse of massive stars, whereas supermassive black holes, with masses millions or even billion times that of the Sun, are found at galactic centers and play a role in galaxy evolution and galaxy dynamics. Intermediate-mass black holes can be present, filling the gap between stellar and supermassive types.Black holes tend to be accompanied by accretion disks, made up of matter that spirals inwards. Gravitational forces and friction warm this material, producing a tremendous radiation, which tends to be seen in X-rays. High-energy particle jets that are powerful can also arise from black holes, affecting surrounding space. Observations of such phenomena give essential information about extreme gravity physics and the effects of relativity.Theoretical expectations, such as Hawking radiation, imply that black holes lose mass slowly over a period of time due to quantum processes.

A new window has been opened for black-hole science using gravitational-wave astronomy, in that stellar-mass black holes have been detected merging and directly demonstrated their presence and character.Black holes are at the heart of Einstein's theory of general relativity to test, as they provide a probes of space-time behavior that cannot be achieved anywhere else. They also contribute in a fundamental way to cosmology, galaxy evolution, and high-energy astrophysics, shaping the distribution of matter and energy throughout the universe.Study of black holes integrates theoretical modeling, computer simulations, and multi-wavelength observations, from radio through X-rays, enabling scientists to probe these mysterious objects in finer detail than ever before. Understanding black holes not only reveals the most extreme environments in the universe but also provides fundamental insights into the nature of gravity, space, and time.