Astronomers spent much time analyzing how stars form and how they develop. One problem was to explain what happened to a massive star at the end of its life. In 1967, the term “black hole” was used to describe one type of object that is left when a massive star dies. Four years later, Cygnus X-1 was found, the first candidate for a black hole.
Detecting a Black Hole
The idea of a body so massive that even light could not escape was briefly proposed by the astronomical pioneer, John Michell. Black holes are based on this idea proposed by John Michell and are thus black in color. Astronomers are not able to detect them directly, but can “see” them because of the effect of gravity has on everything around them, such as gas from a nearby star. The boundary of the black hole is called event horizon. Material pulled in towards the hole is swirled around by the gravity, forming a disc, before crossing the horizon.
This is the material that swirls around a black hole forming a rapidly spinning accretion disc. When this material gets pulled closer to the hole, it starts traveling faster and faster and starts getting very hot due to friction. Close to the hole, the material is so hot it emits X-rays before crossing the event horizon and disappearing forever.
Some galaxies have very active centers that give out large amounts of energy. An object of powerful gravity, such as a supermassive black hole, could be the cause of the activity. This type of a hole would be somewhat a hundred million times more massive than the Sun.
Massive stars might end up their lives in an explosion which is called a supernova. This explosion leaves behind a central core. If this central core’s mass gets more than that of three Suns, it becomes a black hole. Gravity forces the core to collapse. As the core shrinks, its gravity increases. At a certain point, it reaches a critical size, that of the event horizon.
Gravity increases at the core of the dying star shrinks.
Anything trying to escape the gravity must travel almost at the speed of light, as the core approaches the size of the event horizon. Once the core is smaller than the event horizon, not even light can escape. The core continues collapsing until it takes up virtually no space. The star is a singularity, a point mass of infinitely high density inside a black hole.
Inside a black hole
Space and time are highly distorted inside a black hole. Anyone ill-fated is likely enough to fall into one would be stretched to look like as a tortellini. This is due to the gravity pulled more on the feet than the head. An observer who is watching the person fall would also see time’s pace being very slow as the person fell towards the event horizon.
The English mathematician theorizes on the nature of space and time. He has shown that a massive collapsing star inevitably becomes a black hole and that all black holes have a singularity – a point, occupying virtually no space that contains the entire mass of a dead star.
“Black holes ain’t as black as they are painted. They are not the eternal prisons they were once thought. Things can get out of a black hole, both to the outside, and possibly, to another universe. So, if you feel you are in a black hole, don’t give up. There’s a way out.” – Stephen Hawking