The sun accounts for 99.85% of mass of the solar system. The immense gravitational pull of the Sun keeps the planets rotating around it in definite orbits.
- It continuously gives off energy in the form of visible light, infra red, ultra violet, X-rays, gamma rays, radio waves and plasma.
- The period of revolution of the Sun around centre is 250 million years. This period is called a Cosmic or Galactic Year.
- Like all other stars, the Sun is mainly composed of hydrogen and helium. Nuclear fusion in the core of the Sun is source of all its energy.
- The glowing surface of the Sun, that we see, is called the Photosphere, above the photosphere is the red coloured Chromosphere and beyond it is the magnificent Corona, which is visible during eclipses.
- The Sun is continuously emitting streams of protons in all directions either as persistent spiral streams called Solar Winds or as bouts of incandescent material called Solar Flares.
- The Constituent particles of solar wind are trapped by the earth's magnetic field and enter the earth's upper atmosphere as auroral displays described as Aurora borealis in the northern hemisphere and Aurora australis in the southern hemisphere.
- Solar flares being hot ionized gases pose danger to satellite communication.
- The surface of the sun changes continuously. Bright sports called plages and dark spots called Sunspots frequently form and disappear.
- Sunspots are cold and dark regions on the surface of the sun with a periodicity of 11 years. These spots greatly influence the the global climate.
- Distance from Earth - 150 m n km*
- Diameter - 100 Earth Diameters
- Core Temperature - 15 million degree C
- Surface Temperature - 6000 degree C
- Rotation Time - 25 days
- Age - 5 bn years
- Composition - H2 71% ; He 26.5% ; others 2.5% .
* Distance of Earth from Sun:-
Aphelion ( Max) - 152 mn km on July 4.
Perihelion ( Min) - 147 mn km on January 3 .
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