Supernovae Types ☄️

Astronomers categorised supernovae based on star size, star system, brightness of a supernova & also on what elements are detected in the light of the supernova explosion.
 
The 1st category of supernova is caused when a binary star system exists, with one star having been turned into a white dwarf, which is very close to the companion star, which itself is in its red giant stage. Being close to the white dwarf, the outer layers of the Red Giant star slowly gets sucked into the white dwarf due to its high gravitational pull, resulting in the loss of mass of the red giant star & the almost equivalent gain of mass by the white dwarf, meaning transfer of mass from the red giant star to the white dwarf. This gain of mass by the white dwarf continues until the critical mass point also called the “Chandrashekhar Limit (1.44 Solar Mass)” where the mass of the white dwarf becomes too massive to remain stable leading to the inward gravitational push overcoming the balancing outward electron degeneracy pressure resulting in further collapse of the white dwarf ultimately leading to a super massive explosion leaving no remnant core. This process of a supernova explosion is categorised as “Type 1a supernova”. To summarise, Type 1a supernova mainly occurs when a white dwarf reaches its critical mass point, which is 1.44 times the mass of our Sun, leading to the explosion & so the brightness of a Type 1a supernova is predictable. An example of a Type 1a supernova explosion which was detected was in the “Messier 101” spiral galaxy that lies approximately 20 million light years away from Earth, 1st detected & observed in August 2011. This supernova explosion & its afterglow were observable even 04 weeks after the explosion using small to medium-sized telescopes.
 
The 2nd category of supernova explosion is caused when the core of a massive or supermassive star runs out of its nuclear fuel & the element that remains at last from nucleosynthesis in the core is mainly iron Fe with layers of lighter elements on top of it. Now, as nuclear fusion ceases in a star’s core, the outward fusion pressure from inside the star’s core drops, allowing the inward gravitational push acting upon the star’s core to take effect, and the core shrinks, ultimately resulting in the collapse of the star’s core, which leads to a supernova explosion. One needs to know that this kind of supernova explosion is more of an implosion as the outer core materials rebound off the dense Iron core after the implosion, which then gets flung out into space as an explosion. So this is type 2 supernova, which is a bit of both, meaning as the star core implodes, the outer layer explodes after rebounding off the dense star core. Also, a type 2 supernova will only occur to stars that are atleast 8 to 9 times the mass of our Sun, below which a supernova explosion will never work as after going through the Red Giant phase in the HR diagram of stellar evolution & loosing the outer hydrogen & helium shells as planetary nebula, a small or average mass star with a mass of less than 8 solar mass will turn into a white dwarf where it’s inward gravitational push will never be able to breach the outward Electron Degeneracy Pressure & so the star ends up & remains as a white dwarf for a long long time eventually turning into a black dwarf. Now, if a star has a mass of around 20 to 30 times that of our Sun, then the remaining element or material after the implosion will be so massive & so dense that even a black hole may be formed from a neutron star if the “Tolman-Oppenheimer-Volkoff Limit” or “TOV Limit” gets breached. For stars that are 40 to 50 times more massive than our Sun, once nuclear fuel in the core gets exhausted & an Iron core is formed, such stars will definitely collapse into a black hole & that too instantaneously & usually with a high probability that they won’t even produce a supernova & so for such high mass stars it becomes difficult to detect them turning into black holes without any explosion.
Note: if an astronomer detects a star having layers of hydrogen envelopes around the core, then its explosion may even be categorised as a type 1B or type 1C supernova.
 
To conclude, supernovas are important for astronomers as they provide an insight about a star’s lifetime, insight about black holes & neutron stars, insight about white dwarfs & also insight about the universe’s evolution since the Big Bang !!!