Lecture Summary 10

Lecture Summary 10 - EXAM II is Nov. 18 during lecture. The...

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EXAM II is Nov. 18 during lecture. The preview of lecture material 11/16 is most likely is over-optimistic. However, what is not covered will not be on the exam. Good luck studying for the exam. There will be a review in your discussion sections Nov. 16 & 17. I will conduct 2 review sessions: Wed. Nov. 17 from 2:30-3:45 in CSS 2324 and from 4:15-5:30 in CSS 1113. You bring the questions. Makeup labs will be conducted next week, so you do not have a NEW lab during exam week. Your TA should have talked to you about makeup labs last week if you are entitled to one. Talk to your TA about this if necessary. Prof. Deming Lecture Summary (11/9, 11/11, and preview of 11/16) The interstellar medium (ISM) is comprised of gas and dust. Starlight is affected as it passes through concentrations of gas and dust. There are advantages to using infrared telescopes to probe the interstellar medium. Our Sun formed in a nebula 4.6 billion years ago. Stars like the Sun are born as protostars in regions where the ISM collapses. There are many examples of star-forming nebulae, dusty disks, and infrared stars to support our theories of star formation. As gravity compressed the gas, our protosun formed. Eventually the Sun began to fuse hydrogen into helium and was able to reach equilibrium. All main sequence stars achieve stability by fusing hydrogen to helium in their cores. The Sun maintains its stability at a core temperature of 15 million K. Eventually the Sun will lose its ability to sustain itself by hydrogen fusion as helium nuclei build up in the core. With a drop in energy, the outward force cannot balance the inward force. Gravity causes collapse that heats the interior, and in a shell surrounding the helium core hydrogen fusion begins again. The outer layers of the Sun will expand at this time due to the great temperatures inside and the Sun will become a red giant. Red giants have cool surface temperatures, but much greater surface area so luminosity is greater than for a main sequence star. Stars as massive as the Sun eventually fuse helium into carbon when a core temperature of 100 million Kelvins is achieved.
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Lecture Summary 10 - EXAM II is Nov. 18 during lecture. The...

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