Previous | Session 27 | Next
R.P. Kirshner (Harvard-Smithsonian CfA)
Type Ia supernovae are believed to result from the thermonuclear detonation of a white dwarf. I will review the evidence for this picture, using supernova statistics, light curves, and spectra. The variations from a single template light curve and spectrum are believed to have their origin in the amount of radioactive Nickel produced in the thermonuclear burn. I will review this connection, and the empirical methods used to determine the supernova luminosity from its light curve shape. The nearby Hubble diagram shows that these methods leave a residual scatter of about 15% in luminosity. Since SN Ia are the most precise distance indicators for extragalactic distances, we would like to push this scatter lower, if that is possible. And, since SN Ia are the tools for measuring the history of cosmic expansion to z of 1 and beyond, we would like to move beyond an empirical method to a real understanding of the origin of these effects, which may be coupled to the age of the stellar population or to the chemical abundances of the progenitor system, both of which are sure to change with redshift.
Lurking in the background is the real possibility that some variations may be due to asymmetries in the explosion itself. Perhaps SN Ia are not, in Zwicky's phrase, "perfectly spherical bastards." This session will examine the empirical evidence for asymmetries, the theoretical background from explosion physics, and the consequences for the use of SN Ia in cosmology.
Supernova research at Harvard University is supported by a grant from the US National Science Foundation.
Previous | Session 27 | Next
Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.