# Black Holes

### By: Delwin Lam

## Im so confused! What is a black hole?

A black hole is a place in space where gravity is so intense and so strong, it pulls everything in and not even LIGHT can get out.The mass is so concentrated that nothing can escape its gravitational pull. The reason the gravity is so strong is that matter has been squeezed in such a tiny place. This is often caused when a star is dying.

## How big is a black hole?

There are two ways to describe something in size. You can describe it by its mass or how much space it takes up. Lets talk about mass now. Black holes have no mass limit. This means that Black holes can weigh up to 10 billion kilograms. Scientists predict that black holes exist because of the deaths of massive stars and therefore, we suspect that the black hole would weigh as much as the star. A typical mass for a black hole would be 10^ (to the power of) 31. That is approximately ten times the mass of the sun. Astronomers also suspect that black holes live in the centre of galaxies. These black holes are suspected to weigh 1 million times the sun. Now we will talk about the volume of a black star. The bigger the hole, the more space it takes up. If one black hole weighs 10 times more than another, its radius is 10 times as large. This radius formula was found by a man named Karl Schwarzschild and it is named "Schwarzschild radius". A black hole with the same mass of the sun would have a radius of three kilometres. Since black holes are typically 10 times the mass of the sun, that would mean that the radius of an average black hole would be 30 kilometres.

## How does a black hole form?

We discussed this earlier but it was not in depth and very brief. Here, I will describe in detail how a black hole is formed. The most common theory is when a colossal star that has three times the sun's mass reaches its end of its life, it gets crushed by its own gravity, leaving behind a compact black hole. When a star is at the final stage of its life and is about to supernova (which takes billions of years), it spends all the nuclear fuel by then which is its last resort to survive. The star stops burning and heating up and cannot create the nuclear energy required to feed the star and let it make a balance to support its own gravitational draw against the intense pressures brewing inside. Therefore, the star's stability breaks under its own gravity. The radius of the star shrinks to such a small size and it desperately tries to devour anything and everything that comes too close to it. Gravity does its job and the core of the star caves in and implodes. The outer shells of the star explode into space and the may fall into the already dense black hole making it even heavier and denser. That is how a stellar mass black hole is formed.

## When was the first black hole discovered?

Karl Schwarzschild is the man who is credited for developing the concept of black holes. In 1916, using Einstein's theory of relativity, he began to make calculations about the gravity fields of stars. Einstein's theory was to predict black holes and after Karl found the solution for the gravitational field of a point of mass and a spherical mass and he found that black holes could theoretically exist.

## Works Cited MLA format

"NASA - National Aeronautics and Space Administration."

*NASA*. N.p., n.d. Web. 18 May 2013. <http://www.nasa.gov/audience/forstudents/k-4/stories/what-is-a-black-hole-k4.html>."Black Holes FAQ." *BLACK HOLESby Ted Bunn*. N.p., n.d. Web. 18 May 2013. <http://cosmology.berkeley.edu/Education/BHfaq.html>.

"Discovery of the First Black Hole." *Discovery of the First Black Hole*. N.p., n.d. Web. 18 May 2013. <http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/971124b.html>.

"How Do Black Holes Form?" *Universe Today RSS*. N.p., n.d. Web. 18 May 2013. <http://www.universetoday.com/33454/how-do-black-holes-form/>.

"A Short History of Black Holes." *A Short History of Black Holes*. N.p., n.d. Web. 23 May 2013. <http://www.math.ucla.edu/~bon/kerrhistory.html>.