life cycle of stars Essay

2519 Words11 Pages
LIFE CYCLE OF A STAR Stars are formed in nebulae, interstellar clouds of dust and gas (mostly hydrogen). These stellar nurseries are abundant in the arms of spiral galaxies. In these stellar nurseries, dense parts of these clouds undergo gravitational collapse and compress to form a rotating gas globule. The globule is cooled by emitting radio waves and infrared radiation. It is compressed by gravitational forces and also by shock waves of pressure from supernova or the hot gas released from nearby bright stars. These forces cause the roughly-spherical globule to collapse and rotate. The process of collapse takes from between 10,000 to 1,000,000 years. A Central Core and a Protoplanetary Disk: As the collapse proceeds, the…show more content…
Stars like our Sun live for about 10 billion years. Stars less massive than the Sun have even longer life spans. The energy the star gains by fusing these atoms keeps it from collapsing. If a star is massive enough, it will fuse heavier and heavier atoms -- hydrogen to heluim, heluim to carbon, carbon to ... until ... elements are fused into iron. Fusing iron to form heavier elements actually requires energy, so the star would not gain anything by continuing fusion of iron atoms. Most of the star's life is spent fusing hydrogen into helium. Our sun has been doing this for some five billion years, and is expected to continue doing it for another five billion or so years. This hydrogen burning starts from the very center of the star, and moves its way out, leaving a core of helium behind. Low Mass Stars If the star is small enough (much less than the mass of our Sun), it never gets beyond hydrogen burning. This is because its central temperature never gets high enough to start fusing helium into carbon. Once such a star has used up most of its hydrogen, it will begin to cool and collapse into a "brown dwarf". Intermediate Mass Stars Stars with masses close to that of our Sun (up to about five times the mass of our Sun) will experience helium-to-carbon burning in their cores. Outside the helium core, hydrogen will continue burning into helium. At this point, the outer layers of the star will expand to conserve energy --

More about life cycle of stars Essay

Open Document