Suppose the Sun is composed of hydrogen, and it is hot enough to run the P-P Chain. How long would its lifetime be (shining at its current intensity, at 1 L) as a nuclear-fusion powered object?

• The Sun shines with an intensity of 4 × 10 ergs per second.

• The Sun weights 2 × 10 grams.

• The available energy from hydrogen fusion (the P-P Chain) is:

  E	=	(6.4 × 10 ergs/grams) × (2 × 10 grams)
  	=	12.8 × 10 ergs

• The lifetime of the Sun with fusion power would be:

  L	=	12.8 × 10 ergs ×	1 sec
  			4 × 10 ergs
  	=	3.2 × 10 seconds
  	=	10 years

  Looks pretty promising!
  
  

  
  

• How much mass is the Sun losing through the fusion process?

  M	=	4 × 10 ergs/sec   ×	1
  			6.4 × 10 ergs/grams
  	=	6.25 × 10 grams/sec

  685 milllion tons of hydrogen is converted into helium every second!

SOHO satellite images of the Sun, highlighting huge clouds of cool, dense plasma and prominences suspended in the hot, thin corona (the outermost layer). Fusion takes place deep within the inner core, hidden from our sight. [NASA]