Question

) Explain the two main physical mechanisms for supernova explosions. Explain the model for the outburst of a classical nova. Supernovae are classified observationally based on their spectra, Type I supernovae do not have prominent hydrogen lines, while type II supernovae do. How does the model of a type Ia supernova account for this deficiency? How does the model of a type II supernova explain the strong H lines?

Answer 1

Theoretical studies indicate that most supernovae are triggered by one of two basic mechanisms: the sudden re-ignition of nuclear fusion in a degenerate star; or the sudden gravitational collapse of a massive star's core. In the first class of events, the object's temperature is raised enough to trigger runaway nuclear fusion, completely disrupting the star. Possible causes are an accumulation of material from a binary companion through accretion or a stellar merger. In the massive star case, the core of a massive star may undergo sudden collapse, releasing gravitational potential energy as a supernova. While some observed supernovae are more complex than these two simplified theories, the astrophysical mechanics have been established and accepted by most astronomers for some time.

type 1 supernova do not emit hydrogen lines in spectrum because the supernovae are massive stars which lost their outer layers in a stellar wind before core collapse. Type 1 supernovae lost their hydrogen-rich outer layer, revealing the helium-rich layer immediately below.