Signatures of Type Ia Supernovae Explosions and their Cosmological Implications

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Studying the cosmological expansion of the Universe requires precise determination of distances to faraway galaxies. One of the ways that astronomers do this is by using a certain type of supernova (SN), or exploding star, in a galaxy as a measuring stick. A Type Ia SN results from the detonation of an old, small white dwarf (WD) star, and because WD stars are fairly similar in size, the observable features of Type Ia SNe are similar, meaning that the relative difference in brightness between two Type Ia SNe in different galaxies is primarily due to a difference in distance. For this method to work properly to advance cosmology, it is essential that astronomers have a better understanding of the details of Type Ia SNe and the differences among them. A research group at Florida State University (FSU) will further this understanding by studying in detail the various Type Ia explosion scenarios, the structure of WD stars, the thermodynamics of the explosions, and the role of magnetic fields in supernovae. They will do this through sophisticated computer models that produce simulated SNe to compare to observations. The research team will include both graduate and undergraduate students, and the principal investigator and his team will develop and present shows at the FSU planetarium about SNe, cosmology, and related astronomy topics.Thermonuclear explosions of white dwarfs, SNe Ia, are key in cosmology due to their brightness and the apparent homogeneity of their light curves. However, the diversity of explosion scenarios and possible WD progenitor evolution with redshift pose a problem for high precision cosmology. Explosion scenarios may include a WD explosion close to the Chandrasekhar mass (M_Ch), a sub-M_Ch WD, and the dynamical merger of two WDs. For all scenarios, the team will use existing and new explosion models to calculate non-local thermodynamic equilibrium light curves, color-brightness relations, and near and mid-infrared spectra. They will use the radiation-hydro code HYDRA and include hydrodynamics and positron transport. Tools will be developed and employed for data analysis using existing observations as a benchmark.