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What Is a White Dwarf?

Have you ever wondered what happens when a star, or sun, runs out of fuel and energy? Then you are starting to answer the question, “What is a White Dwarf?

Stars have stages of life. They evolve and change. In the beginning of their lives, stars are formed when clouds of dust and gas are pulled together by gravity. Stars then begin to burn and shine by using fuel.

Large stars with larger amounts of mass will burn their fuel and then explode when they reach the end of their star life. Smaller stars, like our Sun, will begin to get bigger and swell. This swelling leads to them becoming a red giant. As they do this, their outer layers peel off and drop, similar to shedding.

The star begins to collapse and fall in on itself as its fuel begins to run low. Once the star is done shedding its body’s layers, then all that will be left behind is the star’s core. The core that is left behind is the white dwarf. This core that is left behind is exceptionally hot. As the white dwarf burns the last of the fuel it begins to cool down, but this could take billions of years.

The white dwarf then begins to burn the last of the fuel. Some stars are so small that they burn all their fuel, usually hydrogen, fairly quickly. The white dwarf is also smaller than its original star, but it is very dense. Imagine crushing aluminum foil into a ball. The aluminum ball is very dense and much smaller than the sheet of aluminum it came from. The same concept can be applied to white dwarfs.

Gravity pushes electrons into the tiniest space possible, making the white dwarf dense. The pressure of the electrons then stops gravity from compressing them even further, and it also manages to keep the white dwarf together. Therefore, the white dwarf is held together by the electrons rather than its fuel burning.

Once the white dwarfs burn the very last of their fuel, using up all their energy, they then they go dark.

Some white dwarfs exist in a binary system, which means the white dwarf can be bound by gravity to another star or object. In some cases, white dwarfs in binary systems begin to move closer together until they collide and merge. Sometimes these collisions cause explosions, but some are too small to cause such an explosion. Smaller ones will calmly and gradually merge together and shine like a star.

A white dwarf is one of the final stages of a star’s existence: A white dwarf is the the core left behind after a star has burned most of its energy and is near its final stages of life.

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