We know that gravity is the force of attraction by which small bodies such as earth revolves around larger bodies such as sun, which means that sun has a gravitational pull due to which earth revolves around it. In the late 1960s, astronomers discovered a star revolving around nothing due to which they were convinced that they had discovered a black hole.
According to Wikipedia, ”A black hole is a region of space time exhibiting gravitational acceleration so strong that nothing — no particles or even electromagnetic radiation such as light — can escape from it”. In simpler terms, a black hole is nothing but a black void in space, that is a place in space where gravitational pull is so higher that even light cannot get out of it. Because no light can get out, we can not see black holes.
A black hole is formed by death of a massive star. Stars are held in perfect balance by two opposite forces, first is the inward pressure of gravity, attempting to collapse the star, counteracted by the outward pressure of emitted radiation. In their core, nuclear fusion crushes hydrogen atoms into helium releasing a tremendous amount of energy. The reason for release of energy is that mass of helium atom is lesser than mass of two hydrogen atoms combined, so the remaining mass is released in form of energy. The magnitude of this energy can be calculated using Einstein’s famous mass-energy equivalence. This energy is released in form of gamma radiation and this energy acts as a outward pressure against the inner gravitational pull. As long as fusion is happening, the star remains stable. For heavier stars, heat and pressure at core allow them to fuse heavier elements, such that helium atoms are combined to form carbon and this process continues until they reach iron, and the fusion process that generates iron does not generate any energy. Iron refuses to fuse any further, that means that star is heavily fused with heavier elements. And then balance between radiation and gravity is suddenly broken. Due to this, the core collapses and star dies in a super nova explosion. If the mass of star is higher this results into the formation of a black hole.
Size of black holes may vary as they can be as small as the size of an atom, despite being smaller in size, these black holes may have the mass as that of a mountain.
Types of Black Holes:
Stellar Black Holes : These have masses that can be 20 times more than mass of the sun. Black holes formed by the collapse of individual stars are relatively small, but incredibly dense.This leads to a crazy amount of gravitational force pulling on objects around the object. Stellar black holes then consume the dust and gas from their surrounding galaxies, which keeps them growing in size. It is said that milky way contains a few hundred million stellar black holes.
Supermassive Black Holes : These black holes contains between a million and a billion times more mass than a stellar black hole. Only few supermassive black holes have been confirmed by now and those too are very far to be observed. However, according to astronomers there is a supermassive black hole located in the centre of milky way, the name given to this black hole is ‘Sagittarius A’. The mass of this black hole is almost 4 million times the mass of sun.
Intermediate Black holes : Astronomers believed that black holes are of two types only, one is Stellar and other one is Supermassive. However recent evidence from Chandra X-ray Observatory and Hubble telescope proves that mid size black are also there. These black holes are formed when stars in a cluster collides in the form of chain reaction. According to recent researches. Intermediate black holes may exist in the heart of very small galaxies. When experimented, it was found that these galaxies contains black holes having mass 36,000 to 316,000 times the mass of sun.
Fun Facts about Black Holes:
- If you fell into a black hole, theory has long suggested that gravity would stretch you out like spaghetti.
- Black holes don’t suck. Instead, objects fall into them just as they fall toward anything that exerts gravity, like the Earth.
- If a star passes too close to a black hole, the star can be torn apart.
- The First Black Hole Wasn’t Discovered Until X-Ray Astronomy was Used.
- The Closest Black Hole is Probably Not 1,600 Light-Years Away.
- Black Holes Are Only Dangerous if You Get Too Close.
It is clear that black holes are integral part of the universe and comprehending them will push us toward understanding how everything(in the universe) works together and forms and grows.
“Inside every black hole that collapses may lie the seeds of an expanding new universe.”