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The Sun

The Sun
  • The Sun is a star. It is the star around which the earth and other planets revolve.
  • It is the nearest star to the earth. It is at a distance of 150 × 106 kilometres from the earth.
  • Light travelling at a speed of 300,000 km. per second, takes about 8 minutes to reach us from the Sun.
  • The next nearest star to earth is ‘Alpha Centuari’.
  • The Sun is mainly composed of hydrogen. The glowing surface of the Sun which we see is called ‘Photosphere’.
  • Above the photospheres is the red cloud ‘Chromosphere’. Beyond the chromospheres is the ‘Corona’, which is visible during eclipses.
  • The temperature of the photospheres is about 6000°C, that of the chromosphere about 32400°C, and that of the corona about 2,700,000°C.
  • The core of the Sun has a temperature about 15 million degrees C.
  • The dark lines in the corona are called ‘Fraunhofer lines’. The emission of hydrogen in all directions is called ‘Prominences’.
  • Sometimes they roll out of the atmosphere to be seen as ‘Solar flares’.
  • The outward stream of protons flowing out from the corona are called ‘Solar winds’, which is made up of plasma.
  • The earth’s Magnetosphere or Van Allen belts, as they were earlier called, acts as a shield and deflects the Solar winds.
  • ‘Sun spots’ are dark patches notched on the surface of the Sun. They appear dark because they are cooler i.e. they have a temperature of about 1500°C.
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