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The sun is the central object in our solar system and a huge star that shines with energy generated from deep within. It is considered to be an average size star that consist mostly of hydrogen and helium gas. The sun has a diameter of .87 million miles which is 109 times larger than the earth. Surface temperatures on the sun are approximately 12,720 degrees fahrenheit with the inner core reaching up to 27,000,000 degrees fahrenheit. At temperatures this high particles move very quickly. Since the particles are nuclei of atoms the high temperature has stripped away the electrons which normally surround the nuclei. Hydrogen nuclei are moving so quickly that they fuse together, one at a time, to make helium. This form of helium contains less mass than the four hydrogen nuclei which creates a difference that is changed into large amounts of energy. On earth we are attempting to duplicate this fusion process to make energy here.
The surface of the sun is made up of hot, bubbling gases and called the photosphere which means sphere of light. Since the sun is too bright to look at directly scientist have learned to project an image of the sun onto screens using special filters. By using this precaution they have been able to observe dark sunspots on the suns surface. Sunspots were first seen by Galileo in 1610 and are believed to be cooler areas of gas. Astronomers have learned by watching sunspots as they move across the face of the sun that it rotates on its axis about every 25 days. Sunspots appear in cycles usually lasting approximately 11 years.
Sun flares are gigantic storms that erupt on the sun. They violently fling hot gas and atomic particles into space, adding to the steady flow of particles called the solar wind. When these particles occasionally reach earths atmosphere they strike atoms in our atmosphere and cause them to glow. We see this action as the aurora borealis or northern lights. Flares have also been know to disrupt radio transmission, satellite communications and cause power black outs.
From time to time loops of glowing gas can be seen at the edge of the sun. These are called prominence. The majority of the solar corona is studied during eclipses. This is a beautiful, pearly white outer layer of the sun that contains extremely hot gas. In the direct path of a solar eclipse a person would see the moon gradually cover the sun. This event last about two hours. At the height of the eclipse a pinkish rim called the chromosphere is visible. Then the corona appears. These coronas are often studied from satellites in space. When viewed through x-ray pictures the corona is the brightest and hottest area of solar activity that can often be found even in the center of the sun. Sunspots which are very high magnetic fields are usually found in the corona region. This has led scientist to believe that the corona is heated by some form of magnetic field.