Black hole, the kinky hole

The black hole is one of the strangest and most fascinating objects. According to NASA, It can be referred as a place in space where gravity pulls so much that even light can’t get out. Most famously black holes were predicted by Einstein’s theory of general relativity which showed that when a massive star dies, it leaves behind a small, dense remnant core. If the core’s mass is more than about three times the mass of the Sun, the equations showed, the force of gravity overwhelms all other forces and produces a black hole.

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How is the black hole created?

In the normal life of a star, there is a constant tug of war between gravity pulling in and pressure pushing out. Nuclear reactions in the core of the star produce enough energy and pressure to push outward. For most of a star’s life, gravity and pressure balance each other exactly, and so the star is stable. However, when a star runs out of nuclear fuel, gravity gets the upper hand and the material in the core is compressed even further. The more massive the core of the star, the greater the force of gravity that compresses the material, collapsing it under its own weight.

For small stars, when the nuclear fuel is exhausted and there are no more nuclear reactions to fight gravity, the repulsive forces of electrons within the star eventually create enough pressure to halt the further gravitational collapse. The star then cools and dies peacefully. This type of star is called a “white dwarf.”

When a very massive star exhausts its nuclear fuel it explodes as a supernova. The outer parts of the star are expelled violently into space, while the core completely collapses under its own weight.

If the core remaining after the supernova is very massive (more than 2.5 times the mass of the Sun), no known repulsive force inside a star can push back hard enough to prevent gravity from completely collapsing the core into a black hole.

From the perspective of the collapsing star, the core compacts into a mathematical point with virtually zero volume, where it is said to have infinite density. This is called a singularity.

Where this happens, it would require a velocity greater than the speed of light to escape the object’s gravity. Since no object can reach a speed faster than light, no matter or radiation can escape. Anything, including light that passes within the boundary of the black hole called the “event horizon” is trapped forever.

Practically for creating real astrophysical black holes, there is main three mechanism should be known. They are:

  1. When a massive enough star burns through its fuel and goes supernova, the central core can implode, converting a substantial fragment of the pre-supernova star into a black hole.
  2. When two neutron stars merge, if their combined post-merger mass is more than about 2.5-to-2.75 solar masses, it will result in the production of a black hole.
  3. And if either a massive star or a cloud of gas can undergo direct collapse, it, too, will produce a black hole, where 100% of the initial mass goes into the final black hole.

 

The black hole can be ever seen?

It is expecting that in 2018 silhouette of the disc of the supermassive black hole at the heart of our galaxy, burned starkly against a background of superheated plasma being tossed about its enormous maw can be seen.

“One of the really nice things about this is taking an image of black hole event horizon has been beyond our reach for so long that it’s been a pleasant surprise to build upon these existing technologies and capture an image so soon,” says Monash University astrophysicist Professor Michael Brown,

“It really complements the exciting gravitational wave discoveries of merging black holes and the creation of new black holes.”

This project will start in April in this year. The NRAO says. “This process might take several months to achieve the goal of obtaining the first image of a black hole.

 

writer
Farhana Eirin
undergraduate student,
Military Institute of Science and Technology (MIST)
Bangladesh
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