R-Process Nucleosynthesis In Supernovae

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The star can no longer release energy via nuclear fusion because a nucleus with 56 nucleons has the lowest mass per nucleon of all the elements in the sequence.

The next step up in the alpha-particle chain would be GK (430 ke V) and this opposes and delays the contraction.

However, since no additional heat energy can be generated via new fusion reactions, the final unopposed contraction rapidly accelerates into a collapse lasting only a few seconds.

The central portion of the star is now crushed into either a neutron star or, if the star is massive enough, a black hole.

The latter synthesizes the lightest, most neutron-poor, isotopes of the heavy elements.

A supernova is a massive explosion of a star that occurs under two principal scenarios.As the star collapses, these outer layers collide with the incompressible stellar core, producing a shockwave that expands outward through the unfused material of the outer shell.The pressures and densities in the shockwave are sufficient to induce fusion in that material, and the energy released leads to the star's explosion, dispersing material from the star into interstellar space.The pressure that supports the star's outer layers drops sharply.As the outer envelope is no longer sufficiently supported by the radiation pressure, the star's gravity pulls its outer layers rapidly inward.It could be something as simple as a run away script or learning how to better use E-utilities, for more efficient work such that your work does not impact the ability of other researchers to also use our site.To restore access and understand how to better interact with our site to avoid this in the future, please have your system administrator contact [email protected] these temperatures, silicon and other elements photodisintegrate by energetic thermal photons ejecting alpha particles.Silicon burning differs from earlier fusion stages of nucleosynthesis in that it entails a balance between alpha-particle captures and their inverse photo ejection which establishes abundances all alpha-particle elements in the following sequence in which each alpha particle capture shown is opposed by its inverse reaction, namely, photo ejection of an alpha particle by abundant thermal photons: Zn photon In these circumstances of rapid opposing reactions the abundances are not determined by alpha-particle-capture cross sections; rather they are determined by the values that the abundances must assume in order to balance the speeds of the rapid opposing-reaction currents.The entire silicon-burning sequence lasts about one day in the core of a contracting massive star and stops after nickel-56 has become the dominant abundance.The explosive burning caused when the supernova shock passes through the silicon-burning shell lasts only seconds but is the major contributor to nucleosynthesis in the mass range 28-60.


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