by starnut » Sun Feb 17, 2008 5:39 am
OK. Let's start with a nova.
A nova is simply a white dwarf that draws matter off its red giant companion in a close binary system and accumulates too much of it on its surface. The white dwarf has a very strong gravitational force on its surface and also very high temperature, ranging from 100,000K to 200,000K (Our sun's surface temperature is only 6000K). The accumulated matter reaches a certain density and temperature (I am not sure how high) that causes a thermonuclear reaction to start, causing the surface to explode outward. This causes a spike in the brightness of the white dwarf. The brightness then dies down, and the cycle is repeated with more matter from the red giant. That video is not correct, made with the erroneous assumption that the bigger companion is the one that explodes simply because it is bigger.
A supernova can be of two kinds. In a Type 1a supernova, a white dwarf, again in a close binary system like above, accumulates more matter from its companion to the point where its mass exceeds 1.44 solar masses, called Chandrasekhar limit. This makes the white dwarf's interior unstable, initiating a thermonuclear burning that turns into a supernova explosion which destroys the white dwarf entirely. Since a white dwarf is just the carbon-oxygen core of a small star like the sun, no hydrogen has been detected in the supernova remnant. The other kind of supernova is Type II, a core collapse supernova. This happens only to stars having more than 8 solar masses. The nuclear fusion in a star of that size goes beyond helium fusion which leads to carbon-oxygen fusion which leads to oxygen-neon fusion which leads to silicon-sulfur fusion which leads to iron which cannot be fused without input of energy! The sudden cessation of fusion at the iron core causes loss of energy that has been exerting outward pressure against the inward gravitational force of the overlaying stellar mass. A catastrophic core collapse occurs until the core reaches neutron degeneracy, which stops further collapse. The rapidly infalling matter in the overlaying envelope then bounces off this neutron core, setting off a supernova explosion. Since the star still has its hydrogen envelope at the moment of the core collapse, hydrogen is detected in the supernova remnant. For a very massive star. the core collapse does not stop at neutron degeneracy; the shock of the infalling matter bouncing off the core will continue the collapse until a black hole is created.
That is a bit oversimplified explanation how a supernova occurs. You can find more info by googling supernova or reading standard astronomy textbooks. No way, can a star's iron core be fissioned (decayed) to hydrogen like Harry said! Harry likes to give short comments with oodles of links but no in-depth explanations of his own. His wacky ideas are, well, just wacky.
Sorry, Harry.
OK. Let's start with a nova.
A nova is simply a white dwarf that draws matter off its red giant companion in a close binary system and accumulates too much of it on its surface. The white dwarf has a very strong gravitational force on its surface and also very high temperature, ranging from 100,000K to 200,000K (Our sun's surface temperature is only 6000K). The accumulated matter reaches a certain density and temperature (I am not sure how high) that causes a thermonuclear reaction to start, causing the surface to explode outward. This causes a spike in the brightness of the white dwarf. The brightness then dies down, and the cycle is repeated with more matter from the red giant. That video is not correct, made with the erroneous assumption that the bigger companion is the one that explodes simply because it is bigger.
A supernova can be of two kinds. In a Type 1a supernova, a white dwarf, again in a close binary system like above, accumulates more matter from its companion to the point where its mass exceeds 1.44 solar masses, called Chandrasekhar limit. This makes the white dwarf's interior unstable, initiating a thermonuclear burning that turns into a supernova explosion which destroys the white dwarf entirely. Since a white dwarf is just the carbon-oxygen core of a small star like the sun, no hydrogen has been detected in the supernova remnant. The other kind of supernova is Type II, a core collapse supernova. This happens only to stars having more than 8 solar masses. The nuclear fusion in a star of that size goes beyond helium fusion which leads to carbon-oxygen fusion which leads to oxygen-neon fusion which leads to silicon-sulfur fusion which leads to iron which cannot be fused without input of energy! The sudden cessation of fusion at the iron core causes loss of energy that has been exerting outward pressure against the inward gravitational force of the overlaying stellar mass. A catastrophic core collapse occurs until the core reaches neutron degeneracy, which stops further collapse. The rapidly infalling matter in the overlaying envelope then bounces off this neutron core, setting off a supernova explosion. Since the star still has its hydrogen envelope at the moment of the core collapse, hydrogen is detected in the supernova remnant. For a very massive star. the core collapse does not stop at neutron degeneracy; the shock of the infalling matter bouncing off the core will continue the collapse until a black hole is created.
That is a bit oversimplified explanation how a supernova occurs. You can find more info by googling supernova or reading standard astronomy textbooks. No way, can a star's iron core be fissioned (decayed) to hydrogen like Harry said! Harry likes to give short comments with oodles of links but no in-depth explanations of his own. His wacky ideas are, well, just wacky.
Sorry, Harry.