White Dwarfs : The Remnants Of Stars

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White dwarfs are the remnants of stars similar to the Sun after the exhaustion of nuclear fuel. When the nuclear burning nears exhaustion, the star expels majority of its outer layers, creating a planetary nebula. The remaining core could have temperatures of more than 100,000K. Some white dwarfs gather matter from nearby stars via accretion while most others cool down over a timespan of billions of years. Soft X-ray as well as extreme UV observations are a key tools in determining the composition of these stars. [1] With the mass of around half that of our Sun yet a size just exceeding that of the Earth, white dwarfs have densities of around ~200,000 that of the Earth’s. [1] A white dwarf, in contrast to stars like the Sun is unable to create radiative pressure as all nuclear processes would have ceased. With no opposing force, gravitational pressure would compress the matter until even the electrons that make up atoms are smacked together. [1] As explained by the Pauli Exclusion Principle, under normal conditions, identical electrons (with the same spin) will not occupy the same energy level. Electrons can spin only in two directions, therefore, any given energy level could only be occupied by two electrons at a time. [1] In general gases this poses no problem as there are fewer electrons than required to fill all the energy levels. However, since the density of white dwarf is far greater, the electrons are very closely packed. Termed as ‘degenerate gas’, this type of gas
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