The parent star during the combustion of hydrogen in the shell radius increases (red giant), and after separation of the outer layers to become the hot planetary nebula nucleus (formed after a helium flash), often containing mainly oxygen and carbon. The kernel is not producing energy, gradually cools by radiation of heat accumulated. Reduced radiation pressure after the termination of thermonuclear reactions in the interior makes the object collapses under its own weight, reaching an enormous density - of how to lose weight fast solar masses. After exceeding this size due to accretion of matter from the second component of the binary system, a white dwarf explodes as a Type Ia supernova, or (hypothetically) in the process of so-called. silent supernova, leaving behind a neutron star. That movement, however, must be much more intense than in the case of the new, greatly increasing the total mass of stars and enduring matter degeneration in the white dwarf, which allows the initiation of synthesis more massive elements. In a state without a valid description of the degeneracy of the state of matter in the star distribution is the Boltzmann or Fermi-Dirac, but at temperatures much higher than the Fermi temperature.
In the case of white dwarf nieakreującego matter, its temperature decreases until it ceases to be visible - it becomes a black dwarf. However, the estimated age of the universe is too short (about 15 billion years) that such objects had time to develop even of the oldest white dwarfs.
The estimated mass of the known white dwarfs are in the range from 0.17 to 1.33 solar masses, while the most common mass majority of them are from 0.5 to 0.7 solar masses [4]. So typically around the carbon-oxygen core are remaining thin shell of helium and hydrogen. Depending on the composition of the atmosphere, distinguished by many spectral types, mainly white dwarfs with an atmosphere of hydrogen (type DA) or helium (types DB and DO).