Friday, August 17, 2012

Our Universe - The Sun

            The sun is one of the stars in the Milky Way. It looks bigger than other stars because it is the closest star to the earth. However, it is smaller than some other stars. Betelgeuse, a red giant star, is 800 times bigger than the sun.

The sun is a huge mass of gases

            The sun lies about 150 million km. from the earth. Its diameter is about 1,40,000 km. i.e., 109 times the earth’s diameter. Its gravitation is 28 times more than the gravitation of the earth.
Parts of the Sun

            The sun lies at a distance of about 32,000 light years form the centre of the galaxy. It takes the sun about 225 million years to complete one revolution around the center of the galaxy with a speed of 250 km. per second. This period is called cosmic year. The sun, like the earth, and, therefore, can rotate at varying speeds at different latitudes. It rotates once on its axis in 24-25 days at the poles and in 34-37 days at the equator.

            The sun is composed of about 75% hydrogen and almost 25% helium. It may be called a big hydrogen bomb because it release huge amount of heat and light as a result of nuclear fusion. The sun is directly
Responsible for all life on earth. It provides the earth with all of its light, heat and energy.
            The glowing surface of the sun which we see is called photosphere. It has a temperature of about 6000 degree centigrade while the temperature of the core is 15,000,000 centigrade Celsius.

            The glowing flames constantly arising from the photosphere are called solar prominences which rise up to a height of 1,000,000 km.

            The dark spots noticed on the surface of the sun are called sunspots. They are cooler than the surrounding area. The life span of sunspots varies from a few hours to many weeks. Larger sunspots may have temperatures up to 4000-5000 degree Celsius. Some of them are made of many folded layers larger than our earth’s size.

            When sunspots persist for longer periods, they cause solar flares and high solar prominences which create upheavals in the ionosphere resulting with disturbances in our radio communications.