Chapter 08

Chapter 08 - Note that the following lectures include...

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Unformatted text preview: Note that the following lectures include animations and PowerPoint effects such as fly ins and transitions that require you to be in PowerPoint's Slide Show mode (presentation mode). The Sun Our Star Chapter 8 The preceding chapter described how we can get information from a spectrum. In this chapter, we apply these techniques to the sun, to learn about its complexities. This chapter gives us our first close look at how scientists work, how they use evidence and hypothesis to understand nature. Here we will follow carefully developed logical arguments to understand our sun. Most important, this chapter gives us our first detailed look at a star. The chapters that follow will discuss the many kinds of stars that fill the heavens, but this chapter shows us that each of them is both complex and beautiful; each is a sun. Guidepost I. The Solar Atmosphere A. Heat Flow in the Sun B. The Photosphere C. The Chromosphere D. The Solar Corona E. Helioseismology II. Solar Activity A. Sunspots and Active Regions B. The Sunspot Cycle C. The Sun's Magnetic Cycle D. Magnetic Cycles on Other Stars E. Chromospheric and Coronal Activity F. The Solar Constant Outline III. Nuclear Fusion in the Sun A. Nuclear Binding Energy B. Hydrogen Fusion C. The Solar Neutrino Problem Outline (continued) General Properties Average star Absolute visual magnitude = 4.83 (magnitude if it were at a distance of 32.6 light years) Central temperature = 15 million K 333,000 times Earths mass 109 times Earths diameter Consists entirely of gas (av. density = 1.4 g/cm 3 ) Only appears so bright because it is so close. Spectral type G2 Surface temperature = 5800 K Very Important Warning: Never look directly at the sun through a telescope or binoculars!!! This can cause permanent eye damage even blindness. Use a projection technique or a special sun viewing filter. The Solar Atmosphere Heat Flow Solar interior Temp. incr. inward Only visible during solar eclipses Apparent surface of the sun Apparent surface layer of the sun The Photosphere The solar corona Depth 500 km Temperature 5800 o K Highly opaque (H- ions) Absorbs and re-emits radiation produced in the solar interior Energy Transport in the Photosphere Energy generated in the suns center must be transported outward. In the photosphere , this happens through Convection: Bubbles of hot gas rising up Cool gas sinking down 1000 km Bubbles last for 10 20 min. Granulation is the visible consequence of convection The Chromosphere Chromospheric structures visible in H emission (filtergram) Region of suns atmosphere just above the photosphere. Visible, UV, and X-ray lines from highly ionized gases Temperature increases gradually from 4500 o K to 10,000 o K, then jumps to 1 million o K Transition region Filaments The Chromosphere (2) Spicules: Filaments of cooler gas from the photosphere, rising up into the chromosphere....
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This note was uploaded on 11/04/2011 for the course PHYS 227 taught by Professor Professorroberts during the Fall '11 term at BYU.

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Chapter 08 - Note that the following lectures include...

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