Monday, November 28, 2005

Black Hole

I am now into this serious topic about the Black Hole. Maybe you can't tell that someone like me will be interested in Astronomy but you are wrong. I am basically interested in everything in the universe.

At one point of my short life, i was very interested with the Black Hole. I want to know what it is so i did alot of researches from the net and from books. I have quite alot of astronomy books in my home now. :P


Mysterious name for those who do not know what a black hole is. I do not know in details about the black hole but i can generally tell you what it is.

A black hole is a concentration of mass with a gravity so great that nothing can escape from it. The gravitational field is so strong that the escape velocity is more than the speed of light. Meaning, anything that is within the gravitational field of the black hole needs to travel faster than the speed of light to escape it.

Since the escape velocity of the black hole is more than the speed of light, it means that even light cannot escape the gravity pull of black hole. Hence, we canot see anything emmitting from the black hole. It will be invisible, just black space.

This is not a photo, it is a computer generated picture.

The imaginery surface of the black hole is the event horizon. At the event horizon, the escape velocity is the speed of light. Therefore, the escape velocity inside the event horizon will be more than the speed of light.

For example, you may see a star not moving , hovering at the event horizon but it is in fact travelling at the speed of light away from the black hole. If it is travelling slower than the speed of light, it will be sucked into the black hole.

Another example, imagine you are watching an astronomer approaching the black hole. As it approaches the black hole, it starts to move slower and slower and finally it just stops there not moving.

What you saw was actually the light reflected off the body of the astronomer. The lights gets slower and slower to reach you when the astronomer reach the event horizon as the gravity pull gets stronger and stronger. Finally, the astronomer gets sucked into the black hole but you will still see the image of the astronomer at the event horizon because the light got stuck at the event horizon.

Types of black holes
Black holes are formed when stars collapsed and squashed themselves into a high density mass. It will thus increase the gravity of the space around it. For example, if our sun is collapsed into a star with only 3km radius, it will be a black hole as it deforms the space around it causing a very strong gravity pull.

There are 3 kinds of black holes:
- Stellar mass black holes
- intermediate-mass black holes
- supermassive black holes.

Stellar mass black holes have the mass of a typical star, about 5-15 times the mass of the sun.

Intermediate-mass black holes have the mass of a few thousands times the mass of the sun.

Supermassive black holes have the mass of about 1% of a typical galaxy! That is really super massive. Supermassive black holes might form when a few intermediate mass black holes collapsed into each other.

It is believed that in the centre of all galaxies is a super massive black hole, including milky way.

What will happen if someone falls into the black hole?

I have a memory that i read in a book if someone falls into the black hole, he will see nothing but then the gravity pull will tear him apart within 7 seconds.

If someone was to put his hand over the event horizon, his hand will be chopped off and pull towards the centre of the black hole.

Well.. I am not so good at explaining such stuff but i hope you guys more or less understood what i am trying to say. If you are interested, you can look them up in some astronomy books!

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