James Stainger, of Kirkwood Intermediate School, asks :-
Why will the sun burn out?
Peter Cottrell, an astronomer at the University of Canterbury, responded.
The sun is a star, just like the billions and billions of other stars in the universe. Stars shine because of the light that they are giving out. Energy is produced in the centre of the star when four hydrogen atoms are converted into one helium atom in a series of nuclear reactions. This energy is transformed into light as it istransferred to the outside of the star.
Because there is only a limited, but very large (2 million million million million million kilograms), amount of matter in the sun it must only exist for a limited time. This is estimated to be about 10 thousand million years. From evidence of other stars in the universe we estimate that the sun is about half way through its life. It will then undergo a series of other matter conversion processes until it ends its life as a white dwarf star.
The amount of energy that is produced in these nuclear reactions can be calculated using our knowledge of nuclear physics. One kilogram of hydrogen would produce 0.9714 kilograms of helium, with the remaining matter being converted to energy, about 2.5 thousand million million joules. We would have to eat a LOT of Weet-bix to get that much energy! You might want to work out how many packets? (There are 1.4 million joules in 100 grams of Weet-bix.)