This is a rather crude, but easy to understand #infographic on the Stellar Evolution(evolution of the stars). While it is nowhere close to the famed Hertzsprung-Russel diagram, the infographic gives us a quick look at what might be in store for our #sun in the future.
The formation of a star
As we know (and to state in very simple language), a star is formed from interstellar clouds of dust, matter and gas - that contracts gradually because of its own gravitational attraction, and finally reaches a point-of-no-return, when the intense pressure inside leads to a rise in temperature and kickstarts the process of nuclear fusion.
Hydrogen is the most common element found in nature, because it's also the simplest element. In nuclear fusion, the fist step usually involves the fusion of hydrogen nuclei (i.e protons) to form deuterium, where one of the protons changes to neutron. From this deuterium or heavy hydrogen, the light helium of He3 (2p+1n) is formed when a third hydrogen nucleus absorbs some extra mass/energy to become a neutron. In this step, powerful gamma rays are usually released to compensate for the extra energy.
And finally, the third step sees a collision between two light He3 nuclei, which gives rise to 2 free protons to continue the chain, and 1 He4 or normal Helium nucleus.
This is the secret behind the sun's tremendous energy. Usually this is called proton-proton chain.
The stellar evolution
No matter how massive a star is, or how much hydrogen it has in store, one day it's hydrogen content will mostly have changed to helium. Then, instead of hydrogen, helium becomes the main nuclear fuel for the star. This begins the second step instellar evolution, which is called Helium Flash.
In helium flash, basic steps usually involve tri-alpha process, where three He4 nuclei fuse to form 1 C12 nucleus. This carbon, that is generated in stellar evolution, is what constitutes your body and ours. Naturally, we certainly are children of the stars in a way.
This also begins the C-N-O cycle in some stars, which involves the fusion between a C12 nucleus and a He4 nucleus, giving rise to #oxygen O16 nucleus. And this gives birth to the precious oxygen that we are currently breathing.
Death of a star
These processes continue, giving rise to ever heavier elements, and releasing energy. This energy is crucial to keep the star itself in balance - since it counterbalances the tremendous gravitational pressure that tries to pull the star inwards. In heavier stars, when too much energy is released, the gravitational pull is temporarily defeated and matter ejects out of the star's surface.
But this process cannot go on forever. So, when massive stars form iron, a deadlock is met.
The funny thing about iron is that, nuclear fusion forming elements lighter than iron give rise to more energy that is consumed in the process. But once iron is formed, to form more massive elements would mean depositing and losing extra energy. It's like a movie that doesn't manage to raise its full budget, and is termed a flop.
This gives rise to a sort of energy crisis inside the star. Temperatures rise further, as gravitational pull brings everything closer. In the case of most light stars, this is more or less the end, since they lack further energy or mass. They turn into white drawfs, which are virtually dead stars.
Larger stars, however, meet a more deadly end. Because of their immense mass, the #supernova explosion ejects out most of their matter, and following that, they collapse inwards.
This collapse produces either a neutron star (if the star's core has < 3.2 x solar mass) or a #blackhole if that isn't the case.
References: Multiple sources, primarilyhttp://cosmos.phy.tufts.edu/~zirbel/ast21/handouts/StellarEvolution.PDF
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