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| Quick Facts
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Type of Object : Class G2 Star
Location : Orion arm of the Milky Way Galaxy, Center of the System
Diameter : 1.35 million kilometers (865,000 miles), or 109 Earths
Mass : 1.989 x 10^30 kilograms (4.385 x 10^30 pounds), or 1.3 million Earths
Temperature : Surface-10,000°F (5500°C)
Center-27,000,000°F (15,000,000°C)
Age : 4.6 billion years
Rotation Period : 25-36 days
Revolution Period in the Milky Way : 200,000,000 years
Density : 1000kg/m3, about the same as water
Composition of Gases : 75% hydrogen , 25% helium
Distance from Earth : 1.496 x 10^8 meters (92,957.130 miles), also defined as one astronomical unit.
Core Pressure : 340 billion times Earth's air pressure at sea level
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| Science of the Sun
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Solar Eclipse
A Solar Eclipse occurs when the Moon moves between the Earth and the Sun, covering the Sun, and casting a shadow on the Earth. At a Total Eclipse, the Sun's Corona appears around the Sun. The Sun's rays are still very dangerous during an eclipse, so you shouldn't look at the show without special protection. Eclipses were once thought to be miracles, but we now know that they are natural and can even predict when they will happen in the future down to the minute. Eclipses occur in cycles known as Saros, which means repetition. This cycle lasts 18 years and 11.333 days. A Total Eclipse can only be seen in certain parts of the world, because the path of it can only be as wide as 167 miles. The shadow of the moon moves at speeds ranging from 1,100 to 5,000 miles an hour, so eclipses can last no longer than 7 minutes and 40 seconds. Eclipses near the Earth's Equater have the longest duration.
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| Introduction to the Sun
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Our Sun is one of billions of stars in the known universe. It's just a huge ball of luminescent hydrogen, helium, and other gases, burning itself away for billions of years. It is classified as a main sequence G2 star on the H-R diagram (a chart commonly used for classification of stars).
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. This odd behavior is because the Sun is not a solid body like the Earth. Similar effects are seen in the gas planets. The differential rotation extends considerably down into the interior of the Sun, but core rotates as a solid body.
Hydrogen inside the core is packed so tightly, and the temperature is so hot, that individual atoms ram into each other, forming heavier helium atoms and releasing energy in the process. This energy takes many thousands of years to make its way to the photosphere and out into space.
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| Layers and Phenomena
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The layers and phenomena related with the sun that we'll look at below are namely the chromosphere, photosphere, corona, core, sunspots, and solar winds.
Chromosphere - The Inner Atmosphere
Huge flares and loops of hot gas often shoot into the Chromosphere, extending tens of thousands of miles above the Sun's surface. These flares shoot electrically charged particles into the solar system. When they reach Earth, the particles can disrupt radio and television signals and cause colorful displays known as the "aurora" -- the northern and southern lights. This layer is not visible to naked eye in normal conditions. However, it could be seen as red during a solar eclipse.
Corona - The Outer Atmosphere
Although it is extremely hot, gas in the Corona is spread very thin, so the only time we can see the Corona with our eyes is during a total solar eclipse, when the Moon completely covers the Sun. The Sun's powerful magnetic fields may be responsible for heating the Corona to millions of degrees.
Photosphere - The Sun's visible surface
Almost all of the visible light from the Sun comes from the Photosphere. Although it is very hot, the photosphere is much cooler than the Sun's inner layers. Cooler, dark blotches called Sunspots sometimes appear here. Spurting out of this surface are Prominences, which are glowing jets of red gas and then 'raining back' down the Photosphere.
Core - The Sun's Power Plant
Solar energy is created deep within the Core of the Sun. It is here that the temperature and pressure are so intense that nuclear reactions take place. This reaction causes four protons or hydrogen nuclei to fuse together to form one alpha particle or helium nucleus. The difference in mass is expelled as energy and is carried to the surface of the Sun, through a process known as'convection. At the surface, it is released as light and heat. Energy generated in the Sun's core takes a million years to reach its surface. Every second 700 million tons of hydrogen are converted into helium ashes. In the process 5 million tons of pure energy is released; therefore, as time goes on the Sun is becoming lighter.
Solar Wind
A constant stream of particles flies from the sun, with a temperature of about a million degrees. They fly with a velocity of about 450 kilometers per second, and this Solar Wind reaches out to at least the distance of 6 billion kilometers. The origin of the Solar Wind lies in the Sun's Corona. The Solar Wind blows gas and dust oozing out of a cometary nucleus backward, creating the characteristic `tails' of comets. Solar Wind is very irregular, and much faster near the polar regions of the Sun than at equatorial latitudes. An increased solar wind can also interact with the Earth's magnetic field and ions in our upper atmosphere, and we see this interaction as the Aurora Borealis in the northern hemisphere (often called the "Northern Lights"), and the Aurora Australias in the southern hemisphere.
Sunspots
The Sun itself operates on an eleven-year cycle, its activity ebbing and growing in a steady rhythm. This cycle was calculated after much observation in the early 1800s; the main object of examination in this experiment was the frequency of sunspots, dark spots visible on the surface of the sun. There have been many attempts at connecting solar activity to climate on Earth, but there is no conclusive evidence that sunspot activity is related to terrestrial climate. Sunspots have strong magnetic fields and usually occur in pairs or groups. In a sunspot pair, one spot has a north magnetic pole and the other a south pole, just as if there were a magnet lying underneath the surface between the spots. Most of these giant magnetic storms are larger than our Earth. The number of sunspots increases and decreases every 11 years, although astronomers are not sure why that is so.
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