Thermonuclear Supernovae

Type Ia or thermonuclear supernovae have become extremely important in recent years because their high luminosity enables them to be observed at extreme distances. This, combined with the ability to predict their intrinsic luminosity, enables cosmologists determine their distance from the observed luminosity and, along with the redshift of their light, the expansion of the universe (the Hubble relation) at their location. Advances in observations have in recent years enabled these "standard candles" to show that the expansion of the universe is actually accelerating.

These important explosions are, like novae, triggered by the transfer of mass onto the surface of a white dwarf (WD) from a giant companion star. However, in this case the mass transfer is fast enough so that the WD approaches the Chandrasekhar mass limit, initiating a thermonuclear runaway explosion that disintegrates the compact star and blows away the envelope of the companion star. There are many uncertainties about the structure of the projenitor system, the ignition process, the propagation of the burning flame in the star, the hydrodynamics of the explosion, the nuclear burning in the outermost layers that may synthesize the proton-rich heavy p-nuclei, and the amount of nickel synthesized and ejected.

Weak interaction reactions play a crucial role in the dynamics of the explosion and the isotopic composition of the ejected material. Self-consistent modeling of Type Ia supernovae requires the rates of electron capture, other weak, and strong reactions.

FRIB will enable measurements of a number of important reactions in the fp-shell necessary to advance our understanding of these complex and important explosions.

Supplemental information on Type Ia Supernovae and FRIB will soon be found on this page.