Black Holes—What are they?

By Sophia V.

There's a common myth that black holes suck everything in their path, kind of like a vacuum cleaner. However, that's not true. A black hole is essentially a region of space with a gravitational field so intense that no light or matter can escape. It is much mass squeezed down into a small point. For example, imagine a star 10 times more massive than our Sun squeezed down to a sphere the size of a small city. Theoretically, anything can become a black hole if it is crushed into a small enough space. If you crush the earth into a small enough point it could create a black hole. But, the black holes in our universe are only made from objects 10 times the mass of our sun. 

Well, how are black holes even created? To begin, averaged-sized stars like our sun will go through this process: they turn into Red Giants, then Nebulas, and lastly, White Dwarfs. Our sun is currently in the main sequence stage, where it fuses hydrogen into helium in its core, releasing energy in the form of light and heat. In about 5 billion years, as the Sun's hydrogen fuel depletes, it will change and expand into a Red Giant. During this phase, the outer layers of the Sun will grow larger and engulf the inner planets, including Earth. After the Red Giant phase, the Sun will shed its outer layers into space, creating a glowing cloud called a planetary nebula. The core that remains is the white dwarf. The remaining core of the Sun will shrink and become a white dwarf—a dense, hot object composed mainly of carbon and oxygen. White dwarfs no longer undergo nuclear fusion and gradually cool down over billions of years, eventually becoming a "dead" star. A star must be very massive when it collapses upon itself to create a black hole. Our sun would not be capable of creating a black hole simply because it is not massive enough to trap the light. 

Source: https://discover.hubpages.com/education/Life-Cycle-of-a-Star-Red-Giant-to-Black-Hole

However, stars bigger than our sun, which are massive, have a different process. 

First, these massive stars will start to form a red supergiant which will fuse heavy elements into its core, eventually collapsing under its gravitational pressure and exploding into a supernova. After this, it will turn into a Neutron Star or a Black Hole. When we have a massive star, that star will fuse heavier elements in its core, until it reaches iron, a very heavy element. This will cause the star to collapse because the iron in the core undergoing fusion will not be able to counteract the gravitational pressure since it is so heavy. As heavier molecules fuse inside the star, eventually the star can't support its own weight anymore. Gravity makes the star collapse on itself. Supernovas can also turn into a Neutron Star, which is also very dense and has a high mass with a high gravitational pull and magnetic field. Stars that are smaller in mass will turn into a neutron star. In summary, black holes are born from the deaths of massive stars, collapsing under their own gravity.