The bizarre stellar graveyards

[weeman]

There are many things in our observable universe that push our comprehension and imagination to their limits. However, nothing may be as bizarre as the corpses that we see left behind from the deaths of stars. <br /><br />This is where we say, "White dwarfs and neutron stars and blackholes, oh my!"<br /><br />It is believed that our own Sun might one day die off as a white dwarf. Our Sun, being classified as a G2 specrtal type, does not quite have the mass to end its life as a neutron star or blackhole. Such things like neutron stars and blackholes, might only be the creations of larger stars in the Universe, such as Beetleguese. <br /><br />A white dwarf is a very odd object, consisting primarily of electrons, it would have the same mass as the Sun, but only be about the size of Earth!<br /><br />With white dwarfs and neutron stars we see a very interesting process going on. In a fusion star (our Sun), nuclear fusion is what keeps the star from collapsing under its own gravitational crush. The balance of inward gravitational pull, and outward energy release from nuclear fusion, is known as hydrostatic equilibrium. <br /><br />However, with white dwarfs and neutron stars, they no longer harness the power of nuclear fusion in their cores. So how do they prevent themselves from being crushed by immense gravity? Well, it is a process that has been theorized fairly recently. With neutron stars for example, the only thing that keeps it from being crushed, is that the neutrons are packed together as close as nature physically allows. This is known as neutron degeneracy pressure, and with white dwarfs, it is classified as electron degeneracy pressure. If we took a plasma, cooled it and compressed it repeatedly, we would reach a point at which it can no longer be compressed. <br /><br />Ta Da! We have our structure that is able to withstand itself against the intense forces of graviity, in theory <img src="/images/icons/smile.gif" /><br /><br />Do you find it amazing that a white dwarf can <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[robnissen]

<font color="yellow">A white dwarf is a very odd object, consisting primarily of electrons</font><br /><br />No. White dwarfs consist mostly of oxygen and carbon, the electrons of those atoms, however, are in an <b>extremely</b> tight orbit.

 

[weeman]

Ah. Thanks for the correction. I am always looking to improve my knowledge! <br /><br />So with the tight orbits of the electrons, this is where we get the idea of degeneracy pressure? Is the neutron degeneracy pressure of a neutron star the reason that neutron stars can be smaller than white dwarfs? By this I mean that since neutrons have no positive or negative charge, they do not try to repel eachother in any way. Where as with electrons they will repel eachother, meaning that they couldn't pack as close together as neutrons. <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[alokmohan]

White dwarfs probably contain degeneraed elecrons only.

 

[lukman]

There are several different types of supernovae and at least two possible routes to their formation. A massive star may cease to generate energy from the nuclear fusion of atoms in its core, and collapse under the force of its own gravity to form a neutron star or black hole. Alternatively, a white dwarf star may accumulate material from a companion star (either through accretion or a collision) until it nears its Chandrasekhar limit and undergoes runaway nuclear fusion in its interior, completely disrupting it. This second type of supernova is distinct from a surface thermonuclear explosion on a white dwarf, which is called a nova. Solitary stars with a mass below the Chandrasekhar limit, such as the Sun, will evolve into white dwarfs without ever becoming supernovae. (Wikipedia)<br /><br />What makes a massive star to decide either to be white dwarfs, neutron star or black hole? <div class="Discussion_UserSignature"> </div>

 

[alokmohan]

But degeneratin of matter is the starting point.

 

[alokmohan]

Degeneration of matter is well understood from 1920s.Fowler was the first to state this.Chandrasekhar worked it out to black hole.Eddinton killed the idea.