Death of Stars

At the end of the "life" of a star, it can end up as a cold dark solid object of under some circumstances it can explode, forming an object called a super nova. All of the atoms inside the centre of the star are thrown out into space and mix in with the surrounding clouds of Hydrogen and Helium. Over Billions of years, stars are born and die out of the clouds of gases in the interstellar medium. All the atoms which make up the periodic table are created in stars. All the atoms which make up everything on Earth, include us, were formed inside stars.

Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. During this short interval, a supernova can radiate as much energy as the Sun could emit over its life span.^[1] The explosion expels much or all of a star's material^[2] at a velocity of up to a tenth the speed of light (30,000 km/s), driving a shock wave^[3] into the surrounding interstellar medium. This shock wave sweeps up an expanding shell of gas and dust called a supernova remnant.

Supernovae are a key source of elements heavier than oxygen. These elements are produced by nuclear fusion (for iron-56 and lighter elements), and by nucleosynthesis during the supernova explosion for elements heavier than iron. Supernova are the most likely, although not undisputed, candidate sites for the r-process, which is a rapid form of nucleosynthesis that occurs under conditions of high temperature and high density of neutrons. The reactions produce highly unstable nuclei that are rich in neutrons. These forms are unstable and rapidly beta decay into more stable forms.

The r-process reaction, which is likely to occur in type II supernovae, produces about half of all the element abundance beyond iron, including plutonium, uranium and californium.^[85] The only other major competing process for producing elements heavier than iron is the s-process in large, old red giant stars, which produces these elements much more slowly, and which cannot produce elements heavier than lead.^[86
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