Evolution of stars

In the article entitled, “Life Cycle of Stars” it talks about how stars go through a natural cycle.  Stars start out as a cloud of molecular gas, and the the cloud collapses due to its own gravity.  As it collapses the cloud breaks up into smaller and smaller pieces and each of these pieces will become a star.  A star is born when a huge section of the cloud collapses under its own gravity and ignites to form a protostar.  A protostar lifespan depends on the mass of the star.  As the collapsing gas and dust burns hotter, eventually reaching temperatures sufficient to fuse hydrogen into helium, the star becomes a main sequence star.  How long a main sequence star lives depends on how massive it is.  Next is the Red-giant stage.  After exhausting its core hydrogen the sun will expand to become a red-giant powered by rapid hydrogen fusion in a shell surrounding its core.  The temperature and pressure of the star where helium can be fused into carbon.  Once the star reaches this point, its no longer a red-giant.  The core that is left behind will be a white dwarf, a husk of a star in which no hydrogen fusion occurs.

This article goes with our 14th objective, “I can describe how stars evolve and die” in which this article did just that, from the birth to a star all the way to its dying days.  In our textbook, “The Essential Cosmic Perspective,” it also lists the stages of a low-mass star on pages 336-340.  Our lecture tutorial that we did in class entitled “Stellar Evolution” describes a stars evolution.  It says that Red-Giant stars develop when main-sequence stars are not able to support nuclear fusion of hydrogen in their cores.  Eventually, the star will shed its outer layer to produce planetary nebula, and the remaining’s of the core is called the white dwarf.

I enjoyed reading this article because it gave me a step by step look on how stars evolve and then die.  It was very helpful reading this article for the 14th objective.  I now know more about our galaxy than I did before.

 

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