Core-collapse supernova

Collapse of a massive stellar core can launch an explosion that ejects material processed by hydrostatic and explosive burning. Whether an explosion succeeds, and how much material escapes instead of falling back, depend on the core and envelope structure. A failed supernova can retain much of the nucleosynthetic core; initial stellar mass alone is not a complete prediction.

For an initial uniform mass density $\rho$, integrate the gravitational work of the outer spherical shells from enclosed mass $M_c$ to $M_{\mathrm{Fe}}$. Since $r(m)=[3m/(4\pi \rho ){]}^{1/3}$, the positive unbinding cost is $C(M_{\mathrm{Fe}}^{5/3}-M_c^{5/3})$, with $C=(3G/5)(4\pi \rho /3{)}^{1/3}$. This includes shell–core interactions. It does not equal the final compact object's much greater binding energy. Dissociation, later recombination and overlying stellar layers add separate energy accounting.

A type Ic supernova lacks prominent hydrogen and helium features and is associated with a strongly stripped core-collapse progenitor. Line visibility depends on excitation and transfer as well as composition, so spectral classification is not an exact inventory of every element present.

A type Ib supernova is a stripped-envelope event with no strong hydrogen lines but identifiable helium features. The hydrogen-poor spectrum does not make it a thermonuclear Type Ia event.

A type II supernova has conspicuous hydrogen features in its observed spectrum and is associated with collapse of a massive stellar core retaining a hydrogen-rich envelope. Its spectral label should not be confused with a unique light-curve shape or a unique remnant type.

The process by which a stalled outgoing shock in a collapsing stellar core regains sufficient energy to expel outer material. Neutrino heating and multidimensional flow can contribute, while dissociation and radiation drain energy. Collapse does not guarantee a successful ordinary supernova.

A nonradial instability of the stalled accretion shock and post-shock flow in a core-collapse supernova. It can amplify large-scale sloshing or spiral motion through feedback between advected perturbations and acoustic disturbances. It can seed asymmetries relevant to explosion and remnant recoil, but is not itself a unique complete explanation of every neutron-star natal kick.

SN 1987A supplied a prompt terrestrial record of neutrino emission from a core-collapse supernova through its SN 1987A neutrino burst.^[ref]

The original Kamiokande paper reported a low-energy event cluster on 23 February 1987 above surrounding background. Inverse beta decay, ${\bar{\nu }}_e+p⟶e^{+}+n$, provides an electron antineutrino channel through Positron light. Neutrino-electron elastic scattering is more directional. The burst supported core-collapse supernova neutrino emission, with limited statistics and channel ambiguity.^[ref]

An original counting illustration shows why timing matters. Suppose an independently measured background is a Poisson process of rate $b$. In a prespecified window $\Delta t$, the probability of at least two background events isFor the synthetic choice $b\Delta t=0.1$, this is about $0.004679$, obtained by subtracting the zero- and one-event probabilities of the Poisson distribution. The Homestake experiment's delayed extraction cannot supply such capture-time clustering. This calculation is not a significance estimate for SN 1987A: searching many possible windows, varying acceptance and correlated backgrounds change the inference.

Core collapse can fail to produce an ordinary successful ejecting supernova, leaving a black hole and retaining much of the processed core. Some envelope material can still escape, depending on the event; failure is not equivalent to a universal zero-yield prescription.