Washington Earth Science Unit VIII Essay question

Submitted By Ivan-Vela
Words: 692
Pages: 3

Dyjuan Washington
Earth Science
Student # 191469

Unit VIII Assessment - Question #11

Discuss stellar evolution (each stage in brief). What forces are opposing one another throughout the life of a star and how do they influence the various stages in the life cycle of a star?


Stellar evolution is the lifecycle of stars. This interesting cycle consist of star birth, the protostar stage, the main-sequence stage, red giant stage and burnout and death. This cycle still has many people amazed and wondering how some forces influence various stages.

Stars are born in nebulae. These huge dark, cool, interstellar clouds of dust and gas collapse under gravitational forces, forming protostars. These young stars undergo further collapse called hydrogen burning; at some point this outward pressure balances the inward force of gravity forming main sequence stars. At this point stars age at different rates and stars expand as they grow old. As the core runs out of hydrogen and then helium, the core contacts and the outer layers expand, cool, and become less bright. This is a red giant or a red super giant depending on the initial mass of the star. It will eventually collapse and explode. The end result is that it will become a black dwarf, neutron star, or black hole depending on the original mass of the star. Two forces that oppose each other in a stars life cycle is gas pressure and gravity. Stars are in a constant fight with gravity since birth. Gravity tries to collapse and crush the star in, but the gas pressure of the star continues to push out. For most of the stars life, gravity and gas pressure fight with each other in a way that a star does not collapse under gravity or fly apart due to gas pressure until it dies (Lutgens and Tarbuck, 2008, p438-41).

The life cycle of stars is very complex. They go through five different stages until they eventually die. Gravity and gas pressure are two forces that oppose one another and influence a stars life. The next time we look to the sky, we can honestly say that we have an idea of how stars are really born.

Lutgens, F.K. and Tarbuck, E.J. 2008. Foundations of Earth Science. 5th ed. Pearson Prentice Hall. Upper Saddle River, NJ.

Unit VIII Assessment - Question #12

Describe the Hertzsprung-Russel diagram. Where on an H-R diagram does a star spend most of its life?


What is the Hertzsprung-Russel diagram? Where do most stars spend most of their life on the diagram? Einar Hertzsprung and Henry Russell developed the graph in 1910 providing a huge leap forward in stellar evolution. Let’s examine why this was so important.

According to www.newworldenclyclopedia.org The