Is the sun getting bigger?
1 Answer
[1] Setting and rising Sun looks bigger. But it is an optical illusion only. [Answer by Chandramohan]
[2] Sun is not getting bigger size wise. But it is getting brighter. Today the Sun is at least 30% more luminous than when it formed. [Answer by Cosmic Defect]
Explanation:
Our brain does not have capacity to estimate size of objects which are far away,..We can only compare things.
If you measure the angular diameter of Sun in noon and in the evening it will be the same.
Why does the Sun get brighter with time?: Sun's core is the centre of power generation. Power is generated through the fusion of hydrogen nuclei on the surface of the core. The fusion product is helium which is dumped into the core. As time progresses the core size increases. As the core size increase the surface area of the core over which the fusion occurs also increase leading to a higher fusion rate and hence higher luminosity.
Sun is approximately at the middle point of its life. The main sequence phase for a Sun like star goes on for about 10 billion years, of which only less than 5 Billions have elapsed. Approximately 5 billion years from today the Sun would reach the end of its main sequence life. During the end stages the core fusion will proceed at such a high rate that the outer envelope of gas will start expanding and the Sun will expand tremendously before it ends its life as a White Dwarf at the centre of a colourfully glowing planetary nebula.
