The Sun

       

What is the Sun?

The Sun is a star. It is a huge glowing ball of hydrogen and helium gases. The Sun is mainly made up of hydrogen gas which is turned into helium gas through nuclear process called 'fusion'. The energy thus released is being scattered in space as sunlight. The Sun looks much bigger and brighter to us than the other stars, because it is much closer to the Earth, when compared with other stars.

     The Sun is about 149.6 million kilometres away from the Earth, while the next closest star, Proxima Centauri, is about 2,50,000 times farther away. The Sun has a diameter of 1.4 million kilometres. It is about one million times bigger than our planet Earth. More than 1,000,000 globes with the size of the Earth, could fit inside the Sun.

     Almost all the light and heat of the Sun are emitted from its surface. So, the Sun's surface is also called the 'photosphere'. The average temperature of the photosphere is about 5500 C.  All the planets in our solar system orbit the Sun, and in turn, our solar system, orbits the center of our galaxy, the Milky Way. It takes about 225 million years or one cosmic year, for the Sun and the eight planets to orbit the Milky Way once. 

     The gravitation of the Sun is far greater than that of the Earth. The Sun's force of gravity is 28 times stronger than the Earth's. The Sun emits many kinds of radiation, in addition to heat and light. Radio waves are one among them. Scientists learn a lot about the Sun by studying these waves with radio telescopes.

     Scientists believe that after hundred years, the Sun will shrink to become a white dwarf star, which will eventually fade into the cool, dark Universe.

When did the Sun originate?

     The Sun was born from a solar nebula, a vast cloud of gas, dust and debris. The birth of the Sun may have occurred 4600 million years ago. Gradually, the core of this huge cloud contracted into a 'proto star'. This proto star shrunk, and became the Sun. The planets and their moons were formed much later, from the leftover matter of the nebula. Many billions of stars were already there, before the birth of the Sun, and many more followed.

     The Sun is 149.6 million kilometres away from the Earth, and it takes more than 8 minutes for its rays to reach us. The Sun's gravity keeps all the planets orbiting around it, from flying off in a straight line into outer space.

Which are the different layers of the Sun?

      The Sun has several layers. The temperatures and the pressures increase as we move towards the center of the Sun. The photosphere is the outer layer. The temperature of the photosphere is 6000 C.

      The core is the hottest part of the Sun. As the name suggests, it is the central part of the Sun. Here, the temperature is 14000000 C. The Core is surrounded by the radiative zone. In this zone, the solar material is hot and dense enough for heat to be transferred from the core through thermal radiation. The convective zone surrounds the radiative zone.

What are the sunspots and sun flares?

     Sunspots are the dark patches seen on the visible surface of the Sun. Sunspots are caused by a strong magnetic field which blocks the outward flow of heat and energy from the core to the photosphere. Sunspots are relatively cooler regions on the Sun's surface, but they still have a temperature of about 4000 C. 

     Sun flares are the violent eruptions on the surface of the Sun. Huge quantities of heat and energy are released in these eruptions. They are caused by the collapse of magnetic field around sunspots. At times, the gigantic flame may shoot up to a height of 100,000 kilometres. Such flames are known as 'Solar prominences'.

Amazing facts about the Sun :

Age : 4,6000,000,000 years

Distance from the Earth : 149.6 million Kilometres

Diameter : 1.4 million kilometres

Surface temperature : 5500 C

Temperature at the core : 14,000,000 C

Rotational period : 25 Earth Days

Revolution Period in the Milky Way : 225 Million years.

Number of planets : 8