"A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it."
Objects with such strong gravitational fields that nothing, not even light, can escape them.
General Relativity: The mathematical theory that describes the behavior of space, time, and gravity.
Space-time: The fabric of the universe that describes how objects move and interact with each other.
Singularity: A point of infinite density at the center of a black hole.
Event horizon: The boundary around a black hole beyond which no energy or matter can escape.
Schwarzschild radius: The distance from the center of a black hole where the escape velocity is equal to the speed of light.
Accretion disk: A rotating disk of gas and dust that surrounds a black hole and feeds its growth.
Hawking radiation: The theoretical prediction that black holes emit radiation and gradually evaporate over time.
Gravitational waves: Ripples in the fabric of space-time caused by the acceleration of massive objects, such as black holes.
Kerr black hole: A rotating black hole that has a ring-shaped singularity.
Supermassive black hole: A black hole with a mass of millions or billions of times that of the Sun, often found at the center of galaxies.
Galactic center: The region at the center of a galaxy where a supermassive black hole is located.
Quasars: Extremely bright and distant sources of radiation, thought to be powered by accretion onto supermassive black holes.
Black hole mergers: The collision and merging of two black holes, which produces a burst of gravitational waves.
Wormholes: Theoretical tunnels in space-time that could allow for faster-than-light travel or time travel.
Singularities in cosmology: The possibility that the universe as a whole began from a singularity, similar to the center of a black hole.
Stellar Black Holes: These black holes are the most common and are formed from the remnants of massive stars after they have undergone a supernova explosion. Stellar black holes have a mass between 3 and 20 times that of the sun, with a radius of about 10 kilometers.
Intermediate Black Holes: These black holes have a mass between 100 and 100,000 times that of the sun and are thought to be formed by the merging of several smaller black holes. Intermediate black holes are relatively rare and are difficult to detect.
Supermassive Black Holes: These black holes have a mass greater than 100,000 times that of the sun and are found at the centers of most galaxies, including our own Milky Way. It is still not clear how supermassive black holes are formed, but they are thought to grow by consuming surrounding matter and merging with other black holes over time.
Primordial Black Holes: These black holes are hypothesized to have formed in the early Universe. They would be tiny, with a mass just a few times that of the moon, and would be extremely difficult to detect.
Micro Black Holes: These black holes are also tiny, with a mass less than that of a person. They are thought to be created in particle collisions and may exist in the upper atmosphere.
Naked Singularity Black Holes: These black holes violate Einstein's theory of general relativity and are not thought to actually exist in nature. They are hypothetical black holes that do not have an event horizon, meaning that their singularity (the point of infinite density at the center of the black hole) is exposed, rather than hidden behind an event horizon.
"The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole."
"The boundary of no escape is called the event horizon."
"It has no locally detectable features according to general relativity."
"A black hole acts like an ideal black body, as it reflects no light."
"Quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass."
"This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly."
"Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace."
"Karl Schwarzschild found the first modern solution of general relativity that would characterize a black hole."
"David Finkelstein, in 1958, first published the interpretation of 'black hole' as a region of space from which nothing can escape."
"The discovery of neutron stars by Jocelyn Bell Burnell in 1967 sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality."
"The first black hole known was Cygnus X-1, identified by several researchers independently in 1971."
"Black holes of stellar mass form when massive stars collapse at the end of their life cycle."
"Supermassive black holes of millions of solar masses may form by absorbing other stars and merging with other black holes."
"There is consensus that supermassive black holes exist in the centres of most galaxies."
"The presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as visible light."
"Any matter that falls onto a black hole can form an external accretion disk heated by friction, forming quasars, some of the brightest objects in the universe."
"If other stars are orbiting a black hole, their orbits can be used to determine the black hole's mass and location."
"Such observations can be used to exclude possible alternatives such as neutron stars. In this way, astronomers have identified numerous stellar black hole candidates in binary systems."
"The radio source known as Sagittarius A*, at the core of the Milky Way galaxy, contains a supermassive black hole of about 4.3 million solar masses."