The sun

Basic concept of sun

THE SUN :It is one of the stars in the milky way galaxy. It takes 224 million years to complete one circle (Revolution ) around the galactric circle called Cosmic year.The sun is 109 times bigger than the earth and weights we see , is called photosphere. Above the photosphere is the chromosphere .Beyond chromosphere is the chromosphere is the corona which is visible during eclipses.The core of the sun has the temperature about 15 million degrees k. The sun is at the centre of the solar system and all this bodies are revolving around it.Its size is Thirteen lakh times as that of the Earth it is the nearest Star to the Earth.It is an ultimate source of energy for life on earth.its diameter is 14 lakh kms. it is composed of 71% hydrogen,26.5 helium and elemants. Hydrogen and helium are the main gases present in the sun .Within the sun,hydrogen is converted to helium due to nuclear fusion releasing a tremendous amount of heat and light.It has a surface temperature of about 6000 degree centigrade, the temperature at the centre is around 15,000000 degree centigrade.The sun constantly emitting streams of its substance as protons in all directions.Sometimes these emissions are massive.Such emissions are called prominences.Sometimes these emissions roll out of the atmosphere of the sun for thousands and thousands of miles, when they are seen as solar flares. A persistent stream of protons and electrons is blowing out of the corona and sweeping over the whole solar system.This stream is called solar wind.The earth's magnetosphere acts as a shield against the ever -blowing solar wind and deflects it away from the earth. Nevertheless ,particles of solar wind sometimes piercethe magnetic shield and enter the upper atmosphere, where, like the solar flares,theycause auroral displays.In the artic region, they are called aurora borealis and in the antarctic region, they are known as aurora australis.The surface of the sun changes continuously.Bright spots called plages and dark spots called sunsports occurthere. Sunspots appear dark because they are cooler,ie, they have a temperature of about 1500 degree c.Sunspots have a periodicity of 11 years.The energy of sun comes from the fusion of hydrogen into helium.Sunlight takes eight min,16.6 sec to reach earth.Ecliptic is an imaginary annual path of sun across the sky.It age is 5 billion years and the total life is ten billion years.