 In the Sun , with a 10 @-@ million @-@ kelvin core , hydrogen fuses to form helium in the proton @-@ proton chain reaction : 
 In the Sun , with a 10 @-@ million @-@ kelvin core , hydrogen fuses to form helium in the proton @-@ proton chain reaction : 
In the Sun , with a 10 @-@ million @-@ kelvin core , hydrogen fuses to form helium in the proton @-@ proton chain reaction :