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TAMU ASTR 101 - Lecture18_2009C

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Copyright © 2009 Pearson Education, Inc.Don McLeroyTexas State Board of EducationWhat is this bigger target? In the words of Phillip Johnson it is“metaphysical naturalism” or “materialism” or just plain old“naturalism”; it is the idea that nature is all there is. Modern sciencetoday is totally based on naturalism. In all of intelligent design'sarguments against both Darwinian evolution, and the chemical originof life, it is their naturalistic base that is the ultimate target. Theimportant aspect of Darwinian evolution is its naturalistic claim thatall life is a result of purposeless, unintelligent, material causes.And why is intelligent design considered a “big tent”? It is becauseanyone opposed to naturalism is welcomed into the movement. Allof us, progressive creationists, recent creationists, old earthers, andyoung earthers are welcomed in this tent. Intelligent design here atGrace Bible Church is a smaller tent than the intelligent designmovement itself. We are all biblical literalists and believe the Bibleto be inerrant. It is good to remember that the intelligent designmovement is a bigger tent. There is no reason to attack one anotherover our disagreements, though we should rigorously examine ourBible, and see how our views fit the Scriptures and how coherent acreation story they tell. Remember, naturalism is the main target.Copyright © 2009 Pearson Education, Inc.Right…E=L*t or t=E/L E is total energy liberated, L is the luminosity0.7% of H goes into energy via E=mc20.1 of Sun burns1 year = pi * 107 sMsun = 2 * 1033 gmLsun = 4 * 1033 ergs/sc= 3 * 1010 cm/sE= 0.1 * 0.007 * Msun * c2t = 0.1 * 0.007 * 2 * 1033 * (3 * 1010 )2/ 4 * 1033 seconds = 0.1 * 0.007 * 2 * 9 * 1020 / 4 = 0.003 * 1020 s / pi * 107 = 10 GyrCopyright © 2009 Pearson Education, Inc.Do you believe that an IntelligentDesigner created the Universe?• A Yes• B NoCopyright © 2009 Pearson Education, Inc.Which do you believe• A The Universe is real old, like 13.7Gyrs• B Beats the crap out of me• C The Universe is 6000 years old, as givenby Bishop UsserCopyright © 2009 Pearson Education, Inc.12.3 Life as a High-Mass StarOur goals for learning:• What are the life stages of a high-mass star?• How do high-mass stars make the elementsnecessary for life?• How does a high-mass star die?Copyright © 2009 Pearson Education, Inc.What are the life stages of ahigh-mass star?Copyright © 2009 Pearson Education, Inc.CNO Cycle• High-mass main-sequence stars fuseH to He at a higherrate using carbon,nitrogen, andoxygen as catalysts.• A greater coretemperature enablesH nuclei toovercome greaterrepulsion.Copyright © 2009 Pearson Education, Inc.Life Stages of High-Mass Stars• Late life stages of high-mass stars are similar tothose of low-mass stars:—Hydrogen core fusion (main sequence)—Hydrogen shell burning (supergiant)—Helium core fusion (supergiant)Copyright © 2009 Pearson Education, Inc.How do high-mass stars make theelements necessary for life?Copyright © 2009 Pearson Education, Inc.Big Bang made 75% H, 25% He—stars make everything else.Copyright © 2009 Pearson Education, Inc.Helium fusion can make carbon in low-mass stars.Copyright © 2009 Pearson Education, Inc.The CNO cycle can change C into N and O.Copyright © 2009 Pearson Education, Inc.Helium Capture• High core temperatures allow helium tofuse with heavier elements.Copyright © 2009 Pearson Education, Inc.Helium capture builds C into O, Ne, Mg …Copyright © 2009 Pearson Education, Inc.Advanced Nuclear Burning• Core temperatures in stars with >8MSunallow fusion of elements as heavy as iron.Copyright © 2009 Pearson Education, Inc.Advanced reactions in stars make elements like Si, S, Ca, and Fe.Copyright © 2009 Pearson Education, Inc.Multiple Shell Burning• Advanced nuclearburning proceeds ina series of nestedshells.Copyright © 2009 Pearson Education, Inc.Iron is a deadend for fusionbecause nuclearreactionsinvolving irondo not releaseenergy.(Fe has lowestmass pernuclearparticle.)Copyright © 2009 Pearson Education, Inc.Evidencefor heliumcapture:Higherabundancesof elementswith evennumbers ofprotonsCopyright © 2009 Pearson Education, Inc.How does a high-mass star die?Insert TCP 5e Chapter 17 opener (pg. 564)Copyright © 2009 Pearson Education, Inc.Iron builds upin the core untildegeneracypressure can nolonger resistgravity.The core thensuddenlycollapses,creating asupernovaexplosion.The Death Sequence of a High-Mass StarCopyright © 2009 Pearson Education, Inc.Supernova Explosion• Core degeneracypressure goes awaybecause electronscombine withprotons, makingneutrons andneutrinos.• Neutrons collapse tothe center, forming aneutron star.Copyright © 2009 Pearson Education, Inc.Energy and neutrons released in a supernova explosion enableelements heavier than iron to form, including Au and U.Copyright © 2009 Pearson Education, Inc.Supernova Remnant• Energy released bythe collapse of thecore drives outerlayers into space.• The Crab Nebula isthe remnant of thesupernova seen inA.D. 1054.Multiwavelength Crab NebulaCopyright © 2009 Pearson Education, Inc.Supernova 1987A• The closest supernova in the last fourcenturies was seen in 1987.Copyright © 2009 Pearson Education, Inc.What have we learned?• What are the life stages of a high-mass star?— They are similar to the life stages of a low-mass star.• How do high-mass stars make the elements necessary forlife?— Higher masses produce higher core temperatures that enablefusion of heavier elements.• How does a high-mass star die?— The iron core collapses, leading to a supernova.Copyright © 2009 Pearson Education, Inc.12.4 Summary of Stellar LivesOur goals for learning:• How does a star’s mass determine its lifestory?• How are the lives of stars with closecompanions different?Copyright © 2009 Pearson Education, Inc.How does a star’s massdetermine its life story?Copyright © 2009 Pearson Education, Inc.Role of Mass• A star’s mass determines its entire life storybecause it determines its core temperature.• High-mass stars have short lives, eventuallybecoming hot enough to make iron, and end insupernova explosions.• Low-mass stars have long lives, never become hotenough to fuse carbon nuclei, and end as whitedwarfs.Copyright © 2009 Pearson Education, Inc. Low-Mass Star Summary1. Main Sequence: H fuses to He in core2. Red Giant: H fuses to He in shell around He core3. Helium Core Burning:He fuses to C in core while H fuses


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TAMU ASTR 101 - Lecture18_2009C

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