What are the differences between a Type Ia and a Type II supernova?

A Type Ia supernova is a thermonuclear explosion of a white dwarf star in a binary star system. When a white dwarf accretes matter from a companion star, its mass may eventually reach the Chandrasekhar limit (approximately 1.4 times the mass of the Sun). At this point, the increased pressure and temperature in its core are sufficient to ignite the rapid fusion of carbon and oxygen, which leads to a runaway explosion.

A Type II supernova results from the core collapse of a massive star (usually more than 8 times the mass of the Sun). When the star exhausts its nuclear fuel, it undergoes several stages of nuclear fusion, creating heavier elements in its core. Eventually, the creation of iron in the core stops further fusion, as iron cannot release energy through fusion. With no outward pressure to counterbalance its own gravity, the core collapses rapidly, triggering the outer layers of the star to explode as a supernova.

Type Ia and Type II supernovae can be distinguished by their spectral features. Type Ia supernovae do not show hydrogen lines in their spectra, while Type II supernovae do. This is because the outer hydrogen-rich envelope of the star is expelled in Type II supernovae but has already been stripped away in Type Ia supernovae.

Type Ia and Type II supernovae also have different light curve profiles. Light curves represent the brightness of the supernova as a function of time. Type Ia supernovae have a well-defined and predictable light curve due to the uniformity of their progenitor white dwarfs. In contrast, Type II supernovae have more diverse and irregular light curves because the process of core collapse is dependent on the mass, composition, and structure of the progenitor star.

The remnants left behind by these two types of supernovae also differ. Type Ia supernovae do not leave behind a compact remnant like a neutron star or black hole because the entire white dwarf is destroyed in the explosion. On the other hand, Type II supernovae can result in the formation of a neutron star or a black hole, depending on the mass of the progenitor star's core. In summary, Type Ia and Type II supernovae have different origins, processes, spectral characteristics, light curves, and outcomes. Type Ia supernovae result from the thermonuclear explosion of a white dwarf in a binary system, while Type II supernovae are caused by the core collapse of a massive star. These differences lead to observable variations in their properties, making it possible to distinguish between the two types of supernovae.