Main Sequence star: As the temperature of the protostar rises, it eventually reaches around 15 million degrees, at which point a nuclear fusion becomes possible. As the fusion begins, the ball of gas and dust starts to glow and the protostar is transformed into a main sequence star. New stars come in a variety of sizes and colors. They range from blue to red, from less than half the size of our Sun to over 20 times the Sun’s size. It all depends on how much gas and dust is collected during the star’s formation. The color of the star depends on the surface temperature of the star. And its temperature depends, again, on how much gas and dust were accumulated during formation. The more mass a star starts out with, the brighter and hotter it will be. For a star, everything depends on its mass. Throughout their lives, stars fight the inward pull of the force of gravity. It is only the outward pressure created by the nuclear reactions pushing away from the star's core that keeps the star “intact”. But these nuclear reactions require hydrogen which is converted to helium by nuclear fusion. Eventually the supply of hydrogen runs out and the star begins its demise. When a star is stable it means that the enregy from the core and the gravity is ballanced. Currently our sun is in this stage. At the beging of this stage the star is 'born' and at the end it is 'dead'. The Sun it formed 4.5 billion years ago and should continue to provide heat and light to the solar system for approximately another 5 billion years. |
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