THE SOLAR SYSTEM AND OUTER SPACE
SUN

Sun
Photo courtesy of Stanford SOLAR Center

by Chris Dunn and Derek Henderson

Our Sun is a 4.6 billion years old star in the Milky Way Galaxy. The closest star to Earth, the Sun is a medium size star known as a yellow dwarf, and is the center of our Solar System. Without our own star, life on Earth would not exist. The diameter of our Sun, the largest object in the Solar System is 1,392,000 km. The distance from the Sun to the Earth is 149,600,000 km.

The temperature on the surface of the Sun is 5,800 degrees Celsius and in the Sun's core or center is 15,600,000 degrees Celsius. The Sun is made of 75% hydrogen and 25% helium by mass. In the Sun's core, hydrogen is being fused to make helium by a nuclear fusion process. A giant, spinning ball of very hot gas, the Sun has sunspots, solar winds, solar flares, and solar prominences which affect Earth's space environment and weather. The energy created by the nuclear fusion reactions in its center radiates outward to the Sun's surface 386 billon megawatts a second, and then into space in the form of heat, light, radio waves, ultraviolet, X-rays, and gamma rays.

The Sun has 4 layers; the core, the radiation zone, the convection zone, and the photosphere. As well, there are 2 layers of gas above the Sun's surface called the chromosphere and the corona. The core, the Sun's center, is the area where the Sun's energy is produced. This energy is radiated outward through the radiation zone, where particles of light carry the energy. It takes millions of years for the energy to move to the next layer, the convection zone. In the convection zone, the motion of the gases in the Sun radiates the energy outwards faster into the Sun's surface. The surface of our Sun, which rotates once every 25.4 Earth days, the poles as much as 36 days, is called the photosphere. Most of the visible white light we see comes from the photosphere. On the photosphere, there are sunspots, and magnetic storms which look like dark areas. Sunspots regularly appear and disappear in 11 year cycles. The temperature of a sunspot is about 3,800 degrees Celsius. The diameter of each spot is about 50,000 km, about as big as the Earth. The chromosphere which lies above the photosphere, and the corona also radiate white light which can be seen when the light from the photosphere is blocked out, as in a solar eclipse. The temperature of the corona is 1,000,000 degrees Celsius.

Bibliography and Additional Sources of Information

StarChild. starchild.gsfc.nasa.gov/docs/StarChild/StarChild.html



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