Sindhu P Easwaran

Former Physics Teacher

The sun is the main source of energy for us. The sun continuously gives off energy in several forms-visible light, invisible infra-red, ultraviolet rays, x-rays, gamma rays, cosmic rays, radio waves and plasma. How are these energies generated in sun? What will happen to the Sun after 6000 million years? Can you imagine?


The energy is generated by nuclear fusion in the interior of the Sun. The Sun is composed mainly of Hydrogen in the form of Deuterium. These Hydrogen nuclei fuse together to form Helium nuclei and energy is released. It is calculated that the Sun consumes about a trillion pounds of Hydrogen every second. At this rate, it is expected to burnout its stock of Hydrogen in about 6000 million years.


When all Hydrogen in the core of the sun is converted to Helium, the core starts to collapse. At the same time, the Sun’s outer layer will expand to about 100 times its present diameter and cool to a red glow. Then the sun is called a red giant. It will then occupy about 25% of the horizon. The nearest planets Mercury and Venus will melt. The oceans of the Earth will evaporate and disappear. The Earth will remain as a barren rock, heated to the melting point of Lead (327.5°C). All life on the Earth will cease. The Sun will survive as a red giant, for about 100 million years more, slowly its outer layer will drift into space, exposing a hot, extremely dense core called white dwarf. This will be faint, no larger than the present planet Mars. Around this tiny star, the burnt-out Earth will continue to revolve. This tiny star will use Helium as its nuclear fuel and convert it to carbon by nuclear fusion. When the Helium runs out, the star will cool and fade forever.


Source: Arutha (60th Anniversary Magazine of Kumundhoo School, 2008)