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The Sun and Stars The Sun • About 150 million km away from earth • Supports all life • The sun is a large star • A star is a body of electrically charged gas, or plasma, that emits energy from nuclear reactions taking place in its core • The sun has a magnetic field that is generated by movement deep it its interior • Four important events occur on the surface of the sun: sunspots, solar prominence, solar flares and coronal mass ejections. Sunspots • A region on the Sun’s surface that is cooler than the surrounding areas • Looks darker than the surrounding areas • Indicates areas that the magnetic field is extremely strong, so the convection is slow • Sunspots come and go • Sunspots are very large, most of them is larger than Earth’s diameter Solar Prominences • A large, low energy, curved, bright stream of particles • Curved shape often forms a complete loop • Shaped by the Sun’s magnetic field • May last for several hours, or several weeks Solar Flares • A high energy, massive explosion at the surface of the Sun • Sudden release of magnetic energy that often flings hot plasma into space • Solar flares can reach their maximum energy level in just a few minutes and last several hours • An extremely powerful kind of flare is called a coronal mass ejection • When this happens, a large amount of plasma is thrown out into space at a speed of more than 1000km/hr • Sometimes, it may be pointed straight at Earth and can reach Earth about three days later. Our magnetic field protects Earth and diverts most of the plasma away from the surface • This causes the auroras (Borealis and Australis) Layers of the Sun • Corona - The corona is the outermost layer of the Sun’s atmosphere, starting at about 2100 km above the solar surface. The temperature in the corona is 500,000C • Chromosphere - emits a reddish glow as superheated hydrogen burns off. • Photosphere – lowest layer of atmosphere. It is about 500 kilometers thick. This layer is where the sun's energy is released as light and where solar flares occur. Because of the distance from the Sun to Earth, light reaches our planet in about eight minutes.