by Qev » Fri Apr 14, 2006 6:26 pm
Iron accumulates at the core of high-mass stars due to a few reasons. First, it's produced there as the 'ash' of silicon fusion, the last fusion stage of large stars. Second, it's the most dense element being produced within the star (by fusion), so it tends to 'sink to the bottom' as it were. And third, even once fusion ceases in the core, silicon fusion continues in a shell around it, and this rains more iron down onto the rapidly growing core.
The core will remain stable until it exceeds the Chandrasekhar limit, I believe (I'm not entirely certain of this). However, once enough iron builds up, the mass of the core exceeds this limit and it
very suddenly collapses into (more or less) a neutron star. The outer layers of the star fall inward at nearly half the speed of light, crash into this surface, and rebound. This is the beginning of a supernova explosion. But what truly drives the supernova is the massive release of neutrinos from the core, as protons and electrons combine to form neutrons. This wave of particles blasts the outer layers of the star apart in a huge shockwave.
This is also where gold is generally produced, along with most of the other elements heavier than iron. This blast of neutrinos reacts with the nuclei of other atoms in the stellar material, causing nuclear reactions that build up heavier materials (nucleosynthesis). Many of these products are themselves radioactive, and will decay into other heavy elements.
Kind of strange to think that all your jewellery came from inside a dying star someplace...
I'm not entirely certain what happens in the case of a dying star where the core mass grows rapidly enough to exceed the Tolman-Oppenheimer-Volkoff limit. It should promptly collapse into a black hole, I would think. This is one of the theoretical sources of those mysterious Gamma-Ray Bursts we keep finding across the sky: a 'hypernova'.
Iron accumulates at the core of high-mass stars due to a few reasons. First, it's produced there as the 'ash' of silicon fusion, the last fusion stage of large stars. Second, it's the most dense element being produced within the star (by fusion), so it tends to 'sink to the bottom' as it were. And third, even once fusion ceases in the core, silicon fusion continues in a shell around it, and this rains more iron down onto the rapidly growing core.
The core will remain stable until it exceeds the Chandrasekhar limit, I believe (I'm not entirely certain of this). However, once enough iron builds up, the mass of the core exceeds this limit and it [b]very[/b] suddenly collapses into (more or less) a neutron star. The outer layers of the star fall inward at nearly half the speed of light, crash into this surface, and rebound. This is the beginning of a supernova explosion. But what truly drives the supernova is the massive release of neutrinos from the core, as protons and electrons combine to form neutrons. This wave of particles blasts the outer layers of the star apart in a huge shockwave.
This is also where gold is generally produced, along with most of the other elements heavier than iron. This blast of neutrinos reacts with the nuclei of other atoms in the stellar material, causing nuclear reactions that build up heavier materials (nucleosynthesis). Many of these products are themselves radioactive, and will decay into other heavy elements.
Kind of strange to think that all your jewellery came from inside a dying star someplace... :lol:
I'm not entirely certain what happens in the case of a dying star where the core mass grows rapidly enough to exceed the Tolman-Oppenheimer-Volkoff limit. It should promptly collapse into a black hole, I would think. This is one of the theoretical sources of those mysterious Gamma-Ray Bursts we keep finding across the sky: a 'hypernova'.