Exam 3 - What process creates energy in the Sun? Source of...

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What process creates energy in the Sun? Source of Sun’s Energy The first scientific theories involved chemical reactions or gravitational collapse. chemical burning ruled out…it cannot account for the Sun’s luminosity conversion of gravitational potential energy into heat as the Sun contracts would only keep the Sun shining for 25 million years late 19 th -century geological research indicated the Earth was older than that Development of nuclear physics led to the correct answer the Sun generates energy via nuclear fusion reactions the mass lost is transformed into energy Einstein’s equation: E = mc 2 this will provide enough energy for the Sun to shine for 10 billion years Why does fusion occur in the Sun’s core? Nuclear fusion a reaction where heavier nuclei are created by combining ( fusing ) lighter nuclei. all nuclei are positively charged Electromagnetic force causes nuclei to repel each other. Remember the nucleus is full of protons! Like charges repel! for fusion to occur, nuclei must be moving fast enough to overcome E-M repulsion When nuclei touch, the nuclear force binds them together Why does the Sun’s size remain stable? Gravitational equilibrium: The outward push of pressure balances the inward pull of gravity Energy provided by fusion maintains the pressure How did the Sun become hot enough for fusion in the first place? Contracting gravity and hydrogen Know the zones of the Sun. Corona : Outermost layer of solar atmosphere ~1 million ºC Very hot, but very diffuse. You would not be burned by the corona. Chromosphere: Middle layer of solar atmosphere ~ 104 - 105 ºC Photosphere: Visible surface of Sun About 5500 ºC Convection Zone: Now we’re underneath the visible surface. Here, energy is transported upward by rising hot gas. Hotter gas rises, cooler gas falls. Radiation Zone: Energy transported upwards by photons Why is energy produced in the Sun at such a steady rate?
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Counterbalancing Why was the Sun dimmer in the distant past? Smaller in past Describe the sunspot cycle. It repeats every 11 yrs. Sun’s magnetic field switches polarity every 11 yrs so the entire cycle repeats every 22 yrs What is the solar wind? Solar Wind: When magnetic field lines break, they release the charged particles into space. This so-called solar wind escapes through the coronal holes. Electrons, protons, Helium nuclei expelled by flares How does solar activity effect humans? Changes temperature of earth
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This note was uploaded on 04/20/2008 for the course AST 2002 taught by Professor Britt during the Spring '08 term at University of Central Florida.

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Exam 3 - What process creates energy in the Sun? Source of...

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