# Heavy Element Production from Supernova

When considering super massive stars going supernova, what are the heaviest elements that are predicted to be able to be created? So if the star VY Canis Majoris (1200 suns) were to go supernova, what heavy elements would it produce and in what kinds of quantities?

• Because of nuclei binding energetics, all nuclei heavier than Fe must be made in supernova events (shock wave induced). How many would be made in a specific supernova will depend on the distribution of heavy elements in the star prior to the supernova. Obviously Ur would be the heaviest stable element that could be produced. – Lewis Miller Jan 26 '16 at 23:40
• No Uranium isotope is stable. New, as yet undiscovered, elements in the proposed 'island of stability' may be more stable than the last few found, but are also unlikely to be stable. – Jon Custer Jan 26 '16 at 23:49
• It used to be thought that all the elements heavier than Iron (Fe) were created in supernova explosions. However, the observation of a Gamma Ray Burst (GRB) on 3 June, 2013 has led to the theory, which seems to be widely accepted, that elements heavier than 140 atomic masses are mainly created in neutron star collisions and that supernova contribution is rather minor. I wrote an answer with citations in Astronomy SE. You can read it here: astronomy.stackexchange.com/q/13073 – BillDOe Jan 27 '16 at 0:11
• @LewisMiller Elements heavier than iron can and are made in stars that never reach the supernova stage. This has been known since the 1950s when the short-lived element Technetium was seen in the atmospheres of red giants. Look up s-process and physics.stackexchange.com/q/7131 – Rob Jeffries Jan 27 '16 at 0:27
• @BillOer This is still hugely debated. It has also never been thought (not since the 1950s anyway) that all elements heavier than Fe were produced in supernovae. I cannot understand why this myth persists. – Rob Jeffries Jan 27 '16 at 0:32

However, if you include the neutron star remnant that may be left behind, then much heavier nuclei can be built, with atomic masses of 300 or more. These very neutron-rich nuclei are quasi-stable in the crust of a neutron star because they are surrounded by a "sea" of relativistically degenerate electrons that block the normal decay channels. The higher the density, the more heavy and neutron-rich the equilibrium nucleus becomes, until ultimately at around $10^{17}$ kg/m$^3$, the identity of individual nuclei is lost and the crust dissolves into a sea of free neutrons (with a small fraction of protons and electrons). The following plot (from Douchin & Haensel 2000 ) shows the atomic mass and atomic number of the equilibrium "nuclei" in the crust as a function of density (where $0.05$ baryons fm$^{-3} \sim 8\times 10^{16}$ kg/m$^{3}$). Note that although the atomic number reaches a relatively modest 45 (Rhodium), the atomic number reaches 600!