A black hole is a large quantity of matter constricted into a much smaller area. Due to this, extreme gravitational pull develops. No object, particle or radiation can escape this pull. Every star has a life cycle. When an enormous star completes its life, it dies and leaves behind a core. According to equations, if the mass of the star equals at least three times the mass of the sun, then the force of gravity reaches such extremes that no object in its surrounding environment can hold back. As a result, it pulls in all other matter into it with no point of escape. Due to its massive size and high density, even light cannot pass through it. After formation, a black hole keeps on expanding by pulling in other objects from around it. It is divided into three types - stellar, supermassive and miniature. Stellar are formed when a massive star collapses. Their mass is three solar masses. The second category, supermassive are already present in the galaxy. Since they reside among gases and other stars, they continue to grow steadily. This is known as their diet. Their mass can be equivalent to almost billion and billions of suns. The third type, miniature have not been encountered till date, though they are believed to have formed after Big Bang. Their mass would be less than the sun.
Mass, charge and angular velocity constitute the physical properties. All these properties can be determined. Mass can be measured using Gauss Law. A charged black hole attracts similarly charged objects towards it and repels the oppositely charged ones. Angular momentum can be studied using frame dragging.
When a particle approaches, it nears to a point where to the outside observer, the particle would seem to be frozen. There is deformation of spacetime. The boundary of the area of no return is the event horizon. Inside the event horizon, due to strong gravitational pull, the particle is brought closer to the core. When the particle falls on the black hole, its mass is scattered evenly.
The idea was first brought forward in the year 1783 by John Michell. Later, Pierre Simon Laplace, a mathematician published this idea in two of his books in the year 1796. The general relative theory was founded by Albert Einstein in 1915 which helped in further studying this concept. Over the years, many discoveries and theories have been noted relating to back holes, and even now, researches are being continuously made.