THE MOST SPCTACULAR SUN

 ASOLAR ATMOSPHERE

A PICTURE SHOWING THE ATMSPHERE OF THE SUN

We are, indeed thrilled when we learnt about the Sunspots that exhibit a cosmic dance with      their ever changing shape. The Sun, not only throws a challenge to man forever, but also fascinates.         

Seen from the Earth the photosphere appears to us as the boundary of the Sun. The Sun,which is essentially a huge mass of gas, has no such limitation. There are two more zones above the  photosphere.They are called the Chromosphere, which is 10,000 Km thick and the Corona. Corona extends to millions of kilometres and sometimes reaches even the Earth’s orbit.In the astronomers terms, these zones are known as Solar atmosphere.

DENSITY OF THE ZONES

As these zones are far away from the centre of the Sun, the gravitational force falls rapidly. The Density of the gas also decreases to very low levels. For instance in the photosphere it is about a billion times less than the density at the core. In the Chromospheres it is less by another ten thousand times and in the Corona the density is further reduced by anther ten thousand times.

Generally when we move away from something hot, we experience the difference in temperature. It is true that we expect the same on the Sun, as the zones are far removed from the centre of the Sun. It is not so. The temperatures rapidly increase across the zones from about 5800 degree Kelvin at the photospheres to about 10000 degree Kelvin at the top of the Chromospheres and to more than a million degree in the Corona. Hence the gas in these Zones is in a highly ionized state.

Do these gases emit radiation? Yes, they do, characteristic to their respective temperatures. As they are so weak due to the low density, they are not visible to the naked eye on a normal day against the bright photosphere. However, they are visible, though for a short duration, during total solar eclipse. When the moon completely covers the photospheres, the chromospheres can be seen as a reddish ring around the darkened photospheres and the Corona as an irregular whitish halo.