Life of stars

         Stars go through the same process that humans do in the sense that they are born,live,and then die.The diffrence is that they do it far more dramatically, and take much longer time. Depending on the mass of the star, the lifetime can range from million years to trillions!.So let's get to know more about the lives of the oldest inhabitants of the universe:STARS.
     

        The universe is maily composed of gas and dust.It is in one of the clouds of gas and dust that the star will be born.Under the affect of gravity the particles of the cloud attracts each other and a mass of matter will form;Over time this mass agglomerate more and more matter and thus accumulates more and more of energy.In this way this mass heats up and begin to radiate. It will soon be a star but for the moment we call it a protostar, bacause it is not yet stable and it continues to collapse on itself.At the gradually ,While the protostar continues to be compressed on itself by gravitation, the temprature within its core rises more and more until it reaches about 10 millions degrees celsius.It is then at this very high temprature that the hydrogen atoms start to merge  giving helium atoms. This very powerful thermonuclear reaction releases a phenomenal energy outword. When its temprature is high the thermonuclear reactions  generate a very strong pressure directed outward  from the protostar, which  forces it to increase in volumes, but by expanding, the protostar becomes less dense and thus it cools, consequently to the deacrise of its temprature, the nuclear fusion decreases in intensity, and the gravity will again be able to force the star to compress on itself . This back and forth play between these two forces allows the star to stabilize. Its internal pressure compensates for gravity which prevents it to merge on itself.The star will then be able to begin its stable life. During this period of stability, which can last hundreds of millions or even billions of years , the star is in balance, it continues to produce regularely its own energy : The sun ,for example, is today in this stable phase of its live, it has been in equilibrium for about five billion years, and it will still be for the next five billion years.

          Stars are born in clouds of gas and live by slowly consuming their fuel through thermonuclear reactions; However; All the stars are not the same, there are diffrent masses.The mass of a star influences its characteristics. First of alla its color : A low massive star is extermly  hot appears in  orang-red like the sun .Inversly to the  very massive stars which are cold and appears in white or even blue .They are then called blue giants. Then the mass of the star also affects its lifespan, indeed the more a star is massive , the more it generates energy to oppose the gravity , thus it will be consumed quickly (the sun for example lives a total of 10 billion years. While a star of three times its mass can live only 300 million years, and a star of 30 times its mass can live only  60 million years.

       

         A star lives by continously producing the energy it needs to remain stable using the nuclear fusion, but at the end of its life, after having exhausted most of its fuel, the star can no longer generate the energy necessary to stabilize. While its core is still compressed under the force of gravity, the star swells and cools until it forms a red giant (ten times its initial size). In the case of a star similar to the sun: After having formed the red giant , the atmosphere  of the star will slowly be diluted in space, while its core continues to compress until it forms a white dwarf, this dwraf which inicially shines because of  its heat, will cool very slowly until it eventually dies. If we cosider a star of ten times the sun's mass, the scenario differs. Indeed bacause of the very high energy , the star exploses, its core contracts suddenly, and the rset of it remains in the space. This phenomenon is called  Supenova explosion. It is an extremely powerful and luminious phenomenon that last few days only. Seen from the earth it is the point that suddenly lights up in the sky at night. After the explosion, the star leaves a very dense residue (a neutron star) surrounded by an immense structure of mattaer, which was expelled by the supernova explosion . In this huge cloud of gas and dust will later be born other new stars. Finally, if the star is so massive for example 30 times the sun's mass, the residue which it leaves behind after the explosion , is so dense that its gravitational pull  prevents anything from escaping even light. It is a black hole.

                                            

 The supernova explosion :