Evolution of a Star

Thursday, December 15, 2011 0 comments

It is common knowledge, that a bright star is also the hottest one and the small or dim ones are the coolest stars. Depending on this primary hypothesis, a star is studied for further information about its origin. Stars like Vega, are a huge mass of a cold and dusty clouds made up of gases. The gravitational force causes the gases to contract. The assembling of matter in close formations, leads to a rise in temperature. This rise in temperature leads to a chain of nuclear reactions in the atoms of the components present. The reason why we see luminous bodies in space is because of the energy released during chemical reactions in the stellar area.

The dusty mass consists of a large amount of hydrogen. The nucleus of an hydrogen atom undergoes a nuclear fusion reaction, to transform into helium. This conversion is accompanied by a steady release of a huge amount of energy. This is visible as a radiant light in space. This sequence of events lasts for about 10 billion years in the case of an average or medium-sized star. For instance, the Sun (which is a medium-sized star) is believed to be 5 billion years old and may live on for another 5 billion years.

Once their energy supplying elements deplete, stars slowly fade away. In the dying stages, usually a lot of stars end up as white, small and dense globes called white dwarfs. In some cases, they end up in massive explosions called a supernova, caused by the sudden collapse of a big star. The enormity of these explosions can be understood from the fact that a dying star produces more energy than what the sun can produce in millions of years. These dying stars leave behind a bluish residual mass called a pulsar. Stellar formations are usually enveloped in dense clouds of dust and gas. These cloudy envelopes block the light emitted by the stars. Infrared telescopes specially designed to detect stellar emissions are used by astronomers in such cases.

Once a single evolutionary cycle is completed, the next one begins immediately, in case of stars which end up as a nova or a supernova. The disintegrated stars end up into the constituent elements, which were synthesized earlier during their formation and radiation stages. For example, helium molecules synthesized from the action of hydrogen, returns to the original state. Only this time, the interstellar medium elements formed are heavier than hydrogen, which results in the evolution of a brighter star with the same process. The core remainder of a supernova or nova is called a neutron star. These stars exist as mildly radiating, small bodies of dust, which keep on contracting, After a stipulated time interval, these change into a black hole, from which even light radiations cannot escape. The future of stars which form a white dwarf after disintegration, is still not conclusively known. However, they turn into extremely low radiation bodies which may burn out like cinders.
This is what happens, in the entire life cycle of the stars so far and also in the years to come, as concluded by our astronomers. 


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