physsci1100ch14notes

physsci1100ch14notes - CHAPTER 14- THE UNIVERSE The...

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Unformatted text preview: CHAPTER 14- THE UNIVERSE The universe includes all matter, energy and space. Topics emphasized in this chapter are stars (including the Sun), galaxies, the celestial sphere and cosmology. Please do not confuse astronomy with astrology. Astronomy is a true science with conclusions based on fact and logic. Astrology is a pseudoscience. Conclusions are sometimes based on superstitions or beliefs that cannot be scientifically verified. There are no known physical quantities that could cause the effects claimed by astrologers. The Sun The Sun is a star. It is a ball of plasma(a gas consisting only of charged particles) at very high temperatures held together by gravity. The high temperatures come from energy released during fusion reactions within the star. The structure of the Sun can be explained by considering layers from the outside to the center. The photosphere is the bright, visible surface of the Sun. The temperature here is about 6000 K and it is composed of 75% hydrogen, 25% helium and very small amounts of heavier elements. On the surface of the Sun, huge patches of cooler material sometimes appear called sunspots. Sunspots appear in an 11 year cycle, increasing in number to a maximum in the middle of the cycle then decreasing until the end. Flares are sudden explosive events originating on the Sun's surface. They appear as streamers of solar material being ejected into space around the Sun. A prominence is an enormous filament of gas arching over the surface of the Sun. Both ends are normally connected to the Sun's surface. The chromosphere is a layer of hotter gas(mostly hydrogen) about 19000 km deep. Temperatures in the chromosphere reach 50,000 K. An artificial eclipse can be created using a coronagraph. This is an instrument with an opaque disk that blocks out the light from the photosphere. It is used to study the chromosphere and corona. The corona is a tenuous, white halo surrounding the Sun that is only visible during a solar eclipse or with the use of a coronagraph. Temperatures approach 1 million K. The particles in the corona have enough energy to leave the Sun. This outward flow of charged particles is called the solar wind. The solar wind extends at least 50 AU out from the Sun's surface. This region is called the heliosphere. The interior of the Sun is composed of the fourth state of matter called plasma. Complete atoms do not exist, only a mixture of high speed nuclei and electrons that move about independently as particles do in a gas. The density of this plasma is 1.4 times that of water, so it is not like any gas we are familiar with on the Earth. All of the energy we receive on the Earth originates in the Sun. The Sun's energy comes from the fusion of hydrogen to helium in its core....
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physsci1100ch14notes - CHAPTER 14- THE UNIVERSE The...

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