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What kind of pressure supports a white dwarf?
electron degeneracy pressure
What prevents a white dwarf from completely collapsing upon itself?
Further collapse of a white dwarf is prevented by electron degeneracy pressure.
Is white drawf bigger than a nertron star?
Simply, neutron star is a big nuclear - of 10km radius and solar mass (mass density about  1017- 1018 kg/m3). The material in a white dwarf is supported by electron degeneracy pressure. The physics of degeneracy yields a maximum mass for a non-rotating white dwarf, the Chandrasekhar limit-approximately 1.4 solar masses-beyond which it cannot be supported by electron degeneracy pressure. The density of white dwarf is - 109 kg/m3. So its radius is much bigger 10km, but the mass can be less, as well as bigger of solar mass.
What keeps white dwarf from collapsing under its own weight?
A white dwarf star, as well as any other stable variety of star,is held together by the pressure popularly known as "gravity".In the opposite direction, white dwarf stars are kept from collapsing completely by degeneracy pressure. Specifically, for white dwarf stars, it's electron degeneracy pressure, which arises from the fact that electrons are fermions and cannot all occupy the same energy state. For higher mass stars, the force of gravity is able to overcome this and push all the electrons into the ground state, and the star is supported by a different kind of degeneracy ... neutron degeneracy, which is the same thing but with neutrons ... and you get a neutron star. At even higher masses, even that isn't sufficient and the star collapses all the way into a black hole.
Why don't the outer layers of a white dwarf continue to be pulled inward?
Because the gravity is not enough to overcome electron degeneracy pressure. White dwarf star material is so dense that in order for it to get any denser the electrons in the atoms making it up would have to be squeezed together. For a star the mass of the Sun, this density occurs when the star becomes about the size of Earth. Stars that are more than about one and a half times the mass of the Sun do have enough gravitational pull to overcome electron degeneracy pressure, and they shrink even more, winding up a dozen miles or so across. At this density (which is comparable to the density of an atomic nucleus), they are neutron stars and are kept from collapsing any further by neutron degeneracy pressure. Stars that are even larger have enough mass to overcome even that and wind up as a black hole; once you've passed the neutron degeneracy pressure, there's really nothing left to keep you from collapsing all the way into a singularity.
Why don't white dwarfs contract as they cool?
By the time a star reaches the white dwarf stage, it's already about as compact as it's possible for ordinary matter to get... the size is maintained by electron degeneracy pressure, which is a fancy way of saying "the atoms are already touching, contracting any more would mean forcing the electrons into the nucleus."
Why do stars become black hole?
Everything star eventually has an end. A black hole is the last stage of some stars. When the fuel of star ends it converts into core and then finally into either a white dwarf, a neutron star, or a black hole.
As a white dwarf cools its radius will not change because?
The radius will not change because a white dwarf is made of electron degenerate matter, so temperature does not affect pressure or volume.
Is the final stage of a star a white dwarf or a black hole?
A black hole may only occur at the end of the life of a very massive star. Most other stars will collapse into a dense White dwarf, which will gradually become a black dwarf star over many billions of years.
What prevents a white dwarf from contracting?
The pressure within the white dwarf. The situation is somewhat different from normal gas pressure; the kind of pressure within a white dwarf is called "degenerate pressure".
What prevents a black dwarf star from shrinking indefinitely?
It is believed that black dwawfs are the burnt out hulks of white dwarfs. In its dying phase a star 1.5 solar masses or less will shrink to something around the size of the Earth, and there is no more nuclear fusion taking place , but heat remaining will make it continue to shine for several billion years. It can only shrink so far because of electron degeneracy, a condition where the electron repulsion stops them from being pushed any closer together.It will not shrink further as a black dwarf.
Could a white dwarf become a black hole?
No. A white dwarf is prevented from any further shrinkage in volume by electron pressure. Even if more gravitational pressure were exerted by a larger mass, then shrinkage would be stopped by neutron pressure -- which would mean a neutron star. Only if the mass of the star remnant were more than enough to overcome neutron pressure would you end up with a black hole.
