# Introduction – Black Holes

Gravitationally speaking, black holes are the most fascinating and powerful objects in the universe. Everybody knows them to be the devourer of worlds. These scary objects can have a mass millions or billions of times the mass of our sun. What are these beasts and is one lurking close enough to destroy our planet?

#### Intro to the Black Hole

Black holes are formed when a really massive star (>30 solar masses) ends its life in a huge explosion known as a supernova. The boundary of black holes is known as the event horizon. These objects have a gravitational pull so high that nothing, not even light can escape it. This means that anything that goes into a black hole stays in the black hole.  As no light ever leaves a black hole, they appearâ€¦..black. All the mass of a black hole is concentrated at its center in a zero dimensional point called a singularity.

#### Where can we Find Black Holes?

Black holes are more common than you think! Black Holes play a crucial role in the formation and stability of galaxies. They can be found in the center of most galaxies as that is where most of the big stars exist. Our own galaxy has a stellar black hole at its center. Its name is Sagittarius A, located 26000 light years from Earth and has a diameter of 44 million kilometers and a mass of 4 million suns.

Anything with mass can become a black hole. Even you! You just need to compress that mass to a specific size called the Schwarzschild radius. It is the minimum radius to which an object with a mass has to be compressed for it to become a black hole. For example the earth has to be compressed to a diameter of 2 cm for it to become a black hole. If you are curious to know what radius you have to be compressed into to become a black hole, you can use this formula to find out-

here, G is the universal gravitational constant and its value is 6.67x 10-11. C is the speed of light and its value is 3x 108. m is the mass of object (in kg).

#### Are these a Threat?

Is a black hole close enough to destroy our planet? The answer is no. The closest Black hole to our planet is V616 Monocerotis which is almost 3000 light years (1 Light Year = 6.9 Trillion Miles) away which is a safe distance. So you can sleep comfortably at night without having to worry about being eaten by a black hole anytime soon.