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Transcript
The Sun The Solar System Our sun is a medium sized star which is the center of our solar system. It is the closest star to the earth at about 93,000,000 miles away. It has a diameter of about 1,400,000 kilometers. The Sun is about 330,000 times as massive as the Earth. 1.3 million Earths can fit inside the Sun! The Sun by itself accounts for about 99.8% of the Solar System's mass. Its gravitational pull holds the planets, comets, etc. orbiting about it. The Sun plays a key role in the Earth’s seasons. The sun is our source of energy. Without the heat and light of the sun, there would not be life on earth. Solar energy is used by green plants for photosynthesis. Solar heating is the source of the energy of moving air. Solar energy also effects the process of the water cycle. All stars get their energy from fusion. Fusion is the combining of the nuclei of lighter elements to form a heavier element. The extra mass is converted to energy according to Einstein's equation E=mc2. Since its birth the Sun has used up about half of the hydrogen in its core. The Sun is about 4.5 billion years old. With all this intense heat and pressure, these elements exist as a plasma. The Sun has an average temperature of 10,300° F Sunlight is very bright, and looking directly at the Sun with the naked eye for brief periods can be painful. The sun is nearly all hydrogen and helium, with traces (less than 2% by mass in total) of elements with heavier nuclei. Lab: Elements in the Stars The Sun’s Layers 1: Core The Sun’s core is the place where energy is produced nuclear fusion. It's the hottest and most dense part of the Sun, having a temperature of 1.5 million °C and a density 150 times greater than that of water. 1: Core 2: Radiative Zone Around the core is the radiative zone. Though not as dense as the core, it is still so dense that photons take around 170,000 years to pass though this layer. 1: Core 2: Radiative Zone 3: Convective Zone This zone occupies the outer 1/3 of the Sun's body. It is the outer most layer of the Sun’s surface. This is a layer of less density that constantly churns and swells, driven by the enormous heat being generated below. 1: Core 2: Radiative Zone 3: Convective Zone 4: Photosphere The photosphere is made of hydrogen at the temperature of 5500°C. It is the lowest layer of the Sun’s atmosphere, the visible surface of the Sun. Most of the Sun’s emitted light comes from this layer. 1: Core 2: Radiative Zone 3: Convective Zone 4: Photosphere 5: Chromosphere The chromosphere (which means "colored sphere") is a transparent layer, just above the photosphere. The temperature of the chromosphere increases from 4300 degrees to more than 400,000 degrees. 1: Core 2: Radiative Zone 3: Convective Zone 4: Photosphere 5: Chromosphere 6: Corona The outermost layer of the Sun’s atmosphere is the corona. This layer is so incredibly hot, over 2 million° C. 1: Core 2: Radiative Zone 3: Convective Zone 4: Photosphere 5: Chromosphere 6: Corona 7: Sunspots Sunspots are "cool" regions, only 3800 K. They look dark only by comparison with the surrounding regions. Sunspots can be very large, as much as 50,000 km in diameter. Sunspots are caused by he Sun's magnetic field poking through the Sun. 1: Core 2: Radiative Zone 3: Convective Zone 4: Photosphere 5: Chromosphere 6: Corona 7: Sunspots 8: Granules Granules are the thousands of bumps on the Sun’s photosphere. 1: Core 2: Radiative Zone 3: Convective Zone 4: Photosphere 5: Chromosphere 6: Corona 7: Sunspots 8: Granules 9: Prominence Prominence is an arc of gas that is ejected from the photosphere and condenses and rains back to the surface. Also associated with sunspots are Solar Flares. The temperature of gases is around 6,000°C. During active periods in the solar cycle, large numbers of sunspots, prominences and flares occur. The Sun also gives off solar wind streaming off into space. The particles move very fast - over 150 miles per second. Thanks to the Earth’s magnetic field, you can't feel solar wind, but you can see it. Unlike the Earth, Mars does not have a magnetic shield to protect it from the solar wind, so particles from the Sun may have played a crucial role in shaping the Martian atmosphere making it a dry planet. The outer layers of the Sun exhibit differential rotation. At the equator the surface rotates once every 25.4 days; near the poles it's as much as 36 days.