Neutron Stars and Black Holes

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jeremy_swinarton

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How is it possible for a neutron star to be composed of only neutrons? Does that mean it's made of a different element of some sort? How did scientists know it was made only of neutrons and that it was so dense?<br />I would also like to know what a black hole is made of and how it is possible that not even light can escape it. Is it even a hole? If it is, where does it lead?
 
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yevaud

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A sun is a gigantic balancing act: energetic output from fusing hydrogen pushing out, while gravity due to it's mass pulls inwards. This goes on throughout the lifetime of the star.<br /><br />When it finally dies, all of it's mass is now pulled inwards. There's no further fusion activity, so there's no longer anything to counter the gravitational pull.<br /><br />Over a certain mass (1.44 times our sun's own mass), when it collapses, the gravitational pull is enough to counter what's know as the Pauli Exclusion force. In essence, it allows the atoms to get much closer than they normally could (thanks to gravity overcoming the Pauli Exclusion Force). The proton and electrons are lost, and what's left is all neutrons, packed into a sort of crystalline matrix, with a gigantic surface gravity and tiny size.<br /><br />And a black hole is comprised of all of the matter that was once a star. To become a black hole, the star takes the next step *beyond* that of becoming a neutron star - and again, based on it's mass (about 3 times the mass of our sun, known as the "Chandresekhar limit"). As well, it's death is violent, which is to say, a Supernova.<br /><br />The gravity of the copllapsing star is enough to overcome the Neutron exclusion law, which is an equivalent law to Pauli. At the mass mentioned, it's overcome, and matter can be packed even *closer* together. So close, in fact, that it collapse all of the way down to a point.<br /><br />Gravity effects everything, including light - which is the "speed limit" for transferring information in our universe. Because in this case the star compactifies with so much mass, it collapses to the point that even light can't escape. Voila! A Singularity, which is effectively detached from our universe. We don't really know what goes on in there (except for some mathematical speculation), because if even light can't escape, no information can escape from inside.<br /><br />There is some speculation about Singularities and what they <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>
 
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rhodan

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<i>How is it possible for a neutron star to be composed of only neutrons?</i><br /><br />Protons and electrons are merged into neutrons and neutrino's after the core of a star collapses under its own gravitational force. <br /><br /><i>How did scientists know it was made only of neutrons and that it was so dense?</i><br /><br />Well, gravity may be by far the weakest of the four fundamental forces, but is has no (known) counterforce like the other three, so the effects of gravity are always cumulative. In the core of huge stars, where the pressure and temperature is high enough to fuse iron out of lighter elements, the gravitational force can become so great, that it overcomes the other three forces and the core starts to collapse on itself. This happens when the iron core has a mass 1.4 times greater than the mass of our entire Sun. This is the so called Chandrasekhar ( "Chandra") Limit. Neutron stars, like black holes, were first predicted to exist, and later confirmed by observation. Neutron stars spin incredibly fast and emit high energy gamma rays bursts. We can detect these gamma rays burst. They are more regular than clockwork. <img src="/images/icons/wink.gif" /><br /><br /><i>I would also like to know what a black hole is made of and how it is possible that not even light can escape it. Is it even a hole? If it is, where does it lead?</i> <br /><br />There still is a lot of debate of what black holes exactly are and what happens inside their event horizon. Some say they are dark energy stars, but the most accepted theory is that they contain a singularity, an infinitely small point where all the mass of the black hole is concentrated. Like a neutron star, a black hole is born from a collapsing stellar core. It contains the mass of that core. Black holes can be just a couple of solar masses. They can also be as big as billions of solar masses.<br /><br />As for the light; imagine space as a trampoline, a photon as a ping pong ball and a black hole as a bowling ball. If yo
 
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aetherius

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Is there a physical limit as to how large a star can be?
 
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yevaud

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So it was thought until recently, when a rare form of supergiant was discovered. But in general, yes. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>
 
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alokmohan

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Degenarion force keeps particles apart.When degeneration fail the particles of proton and neutron come to close and form neutrons,Degenartion force is important.
 
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fusionboy

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Why is it that when you start fusing together elements heavier than iron then the reaction is endothermic, but with elements lighter than iron the reaction is endothermic?
 
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thalion

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Iron is the most stable element, IIRC. Elements lighter than iron can fuse and release energy. Elements heavier than iron must undergo *fission* to release energy; hence the radioactive elements. Fusion of any element from iron up can only consume energy. <br /><br />Here's the gist of it--the fusion of elements from hydrogen up to iron results in products that are less massive than the atoms that went into them, resulting in energy via the familiar E = mc^2. For the fission of elements heavier than iron, the products are less massive than the original atom, also releasing energy. However, if we wanted to say, fuse the products into larger nuclei, we'd end up with atoms *more* massive than the ones we started up with, thus consuming rather than releasing energy.
 
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Saiph

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right, the reason for the different amount of energy released (or absorbed) in nuclear processes, is the nuclear binding energy required to keep the nucleus together, this binding energy is what differs between the various nuclei (and they're varying amount of protons and neutrons). <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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