WILL SUN SHINE FOR EVER ?

 

Will the sun shine forever?

      The Sun shines by turning hydrogen into helium in its core. This process is called nuclear fusion. Fusion happens when lighter elements are forced together to become heavier elements. When this happens, a tremendous amount of energy is created. The famous scientist Albert Einstein discovered a formula which shows how much energy can be created from a small amount of mass. You may have heard of the famous formula E=mc2. E is energy, m is mass, and c is the speed of light. The speed of light is 186,000 miles or 300,000 km per second. So you can see that a tiny amount of matter can be changed into an enormous amount of energy. This can only happen in places which have extremely high pressures and temperatures. At the center of the Sun, the temperature reaches 16 million degrees K, and the pressure is more than a billion times the atmospheric pressure on Earth! The Sun converts about 5 million tons of mass into energy every second. This energy heats the Sun, and in turn, the Sun heats Earth and all the other planets.

 

How long will the Sun continue to shine?

 

      A shining and 'well functioning' Sun is critical for our survival on Earth. The Sun was formed almost five billion years ago. At that time, a gas and dust cloud became so condensed due to its own gravity that hydrogen nuclei began to merge with each other and release huge amounts of energy in a process known as nuclear fusion.Fortunately, the Sun's supply of hydrogen is so great that it will continue to shine for another five billion years. However, the intensity of the solar radiation will increase in the future and this will be fatal for life on Earth. As early as two to three billion years from now, the oceans will evaporate and it will become impossible to live on Earth.

Once the outward force caused by radiation pressure is absent, the solar mass will collapse inward. During this collapse, the Sun’s surface will heat up again – so much so that it will emit a significant amount of ultraviolet radiation. This will heat the matter that was previously ejected into space and cause it to glow – a 'planetary nebula' will be formed. At the nebula's center, the Sun will remain as a glowing 'white dwarf' star. The White Dwarf will be about the size of Earth, but its matter will be so densely packed together that a piece the size of a sugar cube will weigh a ton. Over the course of several more billions of years, the White Dwarf will slowly cool down – becoming a 'black dwarf' – and then our Sun will finally have disappeared.