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Guided Notes about the Sun 1. The Sun contains more than 99 percent of all the mass in the solar system. The Sun’s mass controls the motions of the planets and other objects. 2. The solar interior is gaseous throughout because of its high temperature. The gases are completely ionized, meaning that they are composed only of atomic nuclei and electrons. This state of matter is called plasma. 3. The lowest level of the Sun’s atmosphere is the photosphere. This is the visible surface of the Sun. Most of the light emitted by the Sun comes from this layer. 4. Above the photosphere is the chromosphere, which is normally visible only during a solar eclipse when the photosphere is blocked. The chromosphere appears red because it emits most strongly in a narrow band of red wavelengths. 5. The top layer of the Sun’s atmosphere is the corona, which extends several million kilometers from the top of the chromosphere. The corona is so dim that it can only been seen when the photosphere is blocked, such as during an eclipse. 6. Gas from the corona of the Sun flows outward at high speeds and forms the solar wind. The charged particles are deflected by the Earth’s magnetic field and form 2 huge rings called the Van Allen belts. The particles collide with gases in the Earth’s atmosphere, causing them to give off light that we see as the aurora. 7. The Sun’s magnetic field disturbs the solar atmosphere periodically and causes new features known as sunspots. 8. Sunspots appear darker than the surrounding areas on the Sun because they are cooler. Sunspots typically last two months. 9. Solar flares are violent eruptions of particles and radiation from the surface of the Sun. Often, the released particles escape the surface of the Sun in the solar wind and Earth gets bombarded with particles a few days later. 10.Within the core of the Sun, where the pressure and temperature are extremely high, fusion occurs. Fusion is the combining of lightweight nuclei, such as hydrogen, into heavier nuclei. 11.In the core of the Sun, helium is a product of the process in which hydrogen nuclei fuse. The mass lost in the fusion of hydrogen to helium is converted to energy, which powers the Sun. 12. The Sun consists of about 70.4 percent hydrogen, and about 28 percent helium, measured by mass, along with a small amount of other elements. The Sun’s composition represents that of the galaxy as a whole. Hydrogen and helium are the predominant gases in stars, as well as in the entire universe. All other elements are in very small proportions compared to hydrogen and helium.
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