Physical Science: Big Bang Theory & Stellar Evolution PDF

Lesson 1.1 The Big Bang Theory and the Formation of Light Elements  Learn about It! Cosmology Cosmology is the body of science that studies the origin, evolution and eventual fate of the universe  Learn about It! Cosmology Religious Cosmology Religious or mythological cosmology explains...

Lesson 1.1 The Big Bang Theory and the Formation of Light Elements  Learn about It! Cosmology Cosmology is the body of science that studies the origin, evolution and eventual fate of the universe  Learn about It! Cosmology Religious Cosmology Religious or mythological cosmology explains the origin of universe and life based on religious beliefs of a specific tradition The concept of creatio ex nihilo God creating the universe as written in the book of Genesis  Learn about It! Cosmology Physical Cosmology Physical cosmology explains the origin of universe based on scientific insights, studies and experiments Nicolaus Copernicus and the heliocentric nature of the universe The expanding universe through Albert Einstein’s theory of relativity The big bang theory  Learn about It! Big Bang Theory The big bang theory, a cosmological model that describes how the universe started its expansion about 13.8 billion years ago, states that the universe continues to move and expand  Learn about It! Big Bang Theory 1. The universe began as a singularity or a point containing all space, time, matter and energy 2. It expanded rapidly in nothingness through a rapid yet peaceful process called inflation 3. The universe cooled down as it expanded  Learn about It! Big Bang Theory 4. A soup of matter in the form of subatomic particles was formed and nuclei of light atoms were created via nucleosynthesis or nuclear fusion between protons and neutrons 5. Electrons interacted with these nuclei to form actual, primordial atoms via the process of recombination  Learn about It! Big Bang Theory Evidences 1.Vesto Slipher and Carl Wilhelm Wirtz (1910) Measurement of redshift Observed that most spiral galaxies were moving away from the earth 2.Georges Lemaître (1927) Proposed alternative idea that the universe is expanding  Learn about It! Big Bang Theory Evidences 3.Edwin Hubble (1929) Calculated distances between the earth and several galaxies using redshift of light Observed distant galaxies were moving away from the Earth and one another  Learn about It! Big Bang Theory Evidences 4.Robert Wilson and Arno Penzias (1965) Discovered cosmic microwave background radiation (CMBR)—a low, steady humming noise believed to be energy remains 5.Modern astronomy (2014) Universe is estimated to be 13.8 billion years old with 5% of its composition existing as ordinary matter  Learn about It! Definition of Terms: Atoms – Smallest unit that makes up matter. Subatomic particles: Proton, neutron, electron. 2. Element – Pure substances that represent the species (Variety) of a specific atom. 3. Isotopes – atoms of the same element but with different atomic mass. (different number of neutron)  Learn about It! Definition of Terms: Element is the identity; atom shows the  Learn about It! Big Bang Theory Big Bang Nucleosynthesis Big bang nucleosynthesis (BBN), also known as primordial nucleosynthesis, is the process of producing light elements during the big bang expansion It yields two stable isotopes of hydrogen, two isotopes of helium, some lithium atoms and beryllium isotopes  Learn about It! The nuclear reactions as predicted by the big bang nucleosynthesis. Learn about It! Lesson 1.2 Stellar Evolution and the Formation of Heavier Elements  Learn about It! Big Bang Nucleosynthesis The BBN did not give rise to elements heavier than beryllium Drop in temperature resulted in insufficient energy levels for fusion reactions to push through Nucleosynthesis continued with the expansion of the universe  Learn about It! Stellar Nucleosynthesis Elements associated with both living and nonliving things mostly originated from stars Processes that occurred inside stars were responsible for the formation of these elements  Learn about It! Stellar Nucleosynthesis Elements heavier than beryllium were formed through stellar nucleosynthesis H and He produced from BBN started to combine in nuclear fusion reactions Learn about It!  Learn about It! Stellar Evolution Stellar evolution refers to the process in which a star changes through its lifetime The abundances of elements a star contains change as it evolves The course of evolution is determined by its mass  Learn about It! Stellar Evolution All stars are formed from stellar nurseries called nebulae A nebula breaks into smaller fragments as it further collapses before contracting into a protostar  Learn about It! Stellar Evolution Protostars evolve into main sequence stars upon reaching gravitational equilibrium Nuclear reactions form subatomic particles called neutrinos and positrons  Learn about It! Stellar Evolution The sun is believed to be in the middle of the main sequence phase of stellar evolution It will remain as such for at least five billion years Red dwarf stars stay on the main sequence phase for at least 100 billion years due to the slow rate of hydrogen fusion  Learn about It! Stellar Evolution Not all protostars become main sequence stars Brown dwarf stars are only able to fuel deuterium fusion reactions They cool gradually and have an average lifespan of less than a billion years  Learn about It! Stellar Evolution Main sequence stars evolve into red giant stars when all hydrogen atoms in their cores get depleted Fusion of elements in a red giant  Learn about It! Stellar Evolution Low mass stars turn into white dwarf stars when the majority of helium in their cores are consumed 1. Hot and inert carbon core eventually becomes the white dwarf  Learn about It! Stellar Evolution Low mass stars turn into white dwarf stars when the majority of helium in their cores are consumed 2. A white dwarf’s composition depends on its predecessor’s mass.  Learn about It! Stellar Evolution Massive stars evolve into multiple-shell red giant stars Multiple elements formed in a series of reactions in the following order: carbon → oxygen → neon → silicon → iron  Learn about It! Stellar Evolution Massive stars evolve into multiple-shell red giant stars - Stellar nucleosynthesis of elements heavier than iron is not possible due to its energy requirement  Learn about It! Stellar Evolution Massive stars evolve into multiple-shell red giant stars A multiple-shell red giant  Learn about It! Stellar Evolution Elements heavier than iron are formed after a supernova 1. An exploding multiple-shell red giant is called a supernova Happens when its core can no longer produce energy to resist gravity 2. It releases massive quantities of high-energy neutrinos Neutrinos break nucleons and release neutrons 3. The generated neutrons are picked up by nearby stars Key step in the formation of elements heavier than iron Learn about It! Lesson 1.3 The Nuclear Fusion Reactions in Stars  Learn about It! Hydrogen Burning Hydrogen burning refers to a set of stellar reactions resulting in the production of He-4 from H Responsible for producing energy in stars Two dominant processes Proton-proton chain reaction (responsible for the formation of helium cores) Carbon-nitrogen-oxygen (CNO) cycle  Learn about It! Hydrogen Burning Proton-proton chain reaction Chain reaction by which a star transforms H into He  Learn about It! Hydrogen Burning Proton-proton chain reaction 1.Beta-plus decay: two ps fuse to form a deuteron (deuterium nucleus) a positron (a positively-charged electron) a neutrino 2.Deuterium burning: D fuses with p to yield He-3 and γ 3. Fusion of two He-3 to form He-4  Learn about It! Hydrogen Burning Carbon-nitrogen-oxygen cycle Dominant source of energy in stars about 1.3 times more massive than the sun Main source of He for such stars upon recycling 12C and finishing the whole cycle  Learn about It! Hydrogen Burning Carbon-nitrogen-oxygen cycle 1.Proton capture: 12C fuses with p to form 13N and γ 2.Beta-plus decay: 13N producing 13 C, a positron and a neutrino 3. Fusion of 13C with p to yield 14N and γ  Learn about It! Hydrogen Burning Carbon-nitrogen-oxygen cycle 4.Proton capture: 14N fuses with p to form 15O and γ 5.Beta-plus decay: 15O producing 15 N, a positron and a neutrino 6. Fusion of 15N with p to yield 12C and 4 He  Learn about It! Helium Burning Helium burning refers to a set of stellar nuclear reactions that uses helium to produce energy and heavier elements such as Be, O, Ne and Fe Also responsible for producing energy in stars Two dominant processes Triple-alpha process Alpha process  Learn about It! Helium Burning Triple-alpha process Set of two-stage nuclear fusion reactions converting three alpha particles (He-4 nuclei) into 12C Creates inert carbon core found in white dwarfs and larger stars  Learn about It! Helium Burning Triple-alpha process 1. Two alpha particles fuse to yield 8 Be and γ 2. 8Be fuses with another alpha particle to form 12C and γ  Learn about It! Helium Burning Alpha processes Set of nuclear reactions that convert He into heavier elements The reactions consume He and ultimately ends at Fe 56Fe is the most stable element, having the lowest mass to nucleon (mass number) ratio  Learn about It! Helium Burning Alpha processes 1. Increases the core size and density by forming heavier elements 2. Vital in transforming main sequence stars to supergiants  Learn about It! Helium Burning Alpha processes 3. Reactions capture an alpha particle and release a γ 12C captures an alpha particle (4He) to make 16O, then 16O captures an alpha particle to produce 20Ne  Learn about It! Helium Burning Alpha processes 4. The process continues where the product captures an extra alpha particle until it produces the last atom in the series (52Fe) 5. All atoms produced are from even- numbered elements Lesson 1.4 How Elements Heavier Than Iron Were Formed  Learn about It! Limitations of Big Bang/Stellar Nucleosynthesis Fusion reactions above Fe is unfavorable Nuclear binding energy per nucleon holds the nucleus intact Smaller nuclear binding energy per nucleon Further fusion reactions with Fe require more energy  Learn about It! Limitations of Big Bang/Stellar Nucleosynthesis Nucleosynthesis of elements beyond Fe are nonspontaneous and require different pathways Neutrinos released by a supernova help in forming neutrons and protons which then get captured by nuclei residing in nearby stars Neutron or proton capture processes help in achieving higher-level nucleosynthesis  Learn about It! Neutron Capture: S-process Slow neutron capture or s-process happens when there is a small number of available neutrons The rate of neutron capture is slow compared to the rate of beta decay (hence the term slow) If a beta decay occurs, it almost always occurs before another neutron can be captured  Learn about It! Neutron Capture: S-process Slow neutron capture or s-process happens when there is a small number of available neutrons These occur mainly on red giant or supergiant stars, with each neutron capture taking a decade and the cascade of processes taking thousands of years to complete  Learn about It! Neutron Capture: R-process Rapid neutron capture or r-process happens when there is a large number of available neutrons The rate of neutron capture is fast that an unstable nucleus may still be combined with another neutron prior to beta decay (hence the term rapid)  Learn about It! Neutron Capture: R-process Rapid neutron capture or r-process happens when there is a large number of available neutrons Associated with supernovae, in which the temperatures are tremendously high that the neutrons are moving very fast Neutrons can immediately combine with isotopes that are already heavy