A white dwarf surrounded by a cocoon of gas
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White Dwarfs are the remnants of stars that were massive enough to stay alive using nuclear fusion in their cores, but not massive enough to blow apart in a Type II supernova. When stars like our own sun die they will become white dwarfs. As a star like our sun is running out of fuel in its core it begins to bloat into a red giant
. When this happens to our sun (don't worry it won't happen for another 5 Billion years) the inner planets, Mercury, Venus, Earth, and Mars will all be consumed by the sun's expanding surface. Then after a few million years the outer layers of the red giant will begin to puff off and form a planetary nebula. Leaving behind only the dead core of the star made of mostly carbon and oxygen. This is the white dwarf.
A typical white dwarf is about the size of the Earth. It is also very dense and hot. The star keeps itself from collapsing under gravity by quantum mechanical electron pressures rather than the thermodynamic pressures that keep most stars from collapse. A spoonful of white dwarf material on Earth would weigh as much as a car. Strange, isn't it?
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