What is a Supernova? Pt.1

So…What is a supernova? What are these intense energy explosions that radiate and emanate throughout the Universe? To answer this question In this instance well focus on the type II supernovae SNII as this is the start that died. But your probably wonder what a supernova Class I is (SNI).  In this instance the classifications that are used to describe supernovae and their properties bear no real physical significance. But to generalise, what the classifications mean, boils down to their spectra (Spectrometric properties), So for example would be that when a dying star is ready to explode, the explosion and the remnants from the explosion are analysed spectrometric ally. It is these precise chemical characteristics that determine which bracket to place the particular supernova into. Like whether an absorption line is shown in a spectral analysis. Though normally when you discover a type I SN. Normally it is similar in most ways to that of a white dwarf, though still accreting matter and slowing perishing in the cold voids of space eventually collapsing into itself. The SNI has to hit a certain threshold, a mass threshold called the Chandrasekhar limit. The maximum mass allowed for a white dwarf to be at, to avoid going supernova. A SNII is a final death phase, where the star has reached the end of its life.

 

 Fig.1 A extra terrestrial nebula that habits around Wolf-Rayet star (WR124)

Credit: van der Sluys, M,; Lamers, H. J. G. L. M. (2003).

 *Note: This Nebula is 21,000 light years across

So, now you probably asking, why and how does a star collapse in on itself? At first thought, it would seem like a difficult answer, but actually is quite the contrary.  Gravity as usual, tries to pull anything down towards the particle or object with most matter/density. For us to let go of a cup of tea in free space only for gravity to intervene and pull it straight down to the ground, likely breaking it and causing a mess. In that situation there is nothing stopping the cup from falling to the Earth, no force or energy to keep it in check. With Stars its similar, though there is a difference, energy! Energy is actually a factor with a star and gravity. With the hydrogen and helium inside burring away in a nuclear fusion reaction, intense energy is keeping gravity from crushing the star into oblivion. Now, when the star dies, meaning when it has no more hydrogen to burn and the fusion reaction is essentially gone, gravity steps in to do its business, crushing the star into its inner most core. Then the centre of the star then collapses on itself.