Mickey Fouts., Age 15, Of Garrett, Ky.., for his question:
What does the sun use for fuel?
Suppose the sun were a round iron stove filled with shovelfuls of coal. The gigantic furnace could swallow more than a million earth size shovels of fuel at a single feeding. And in about 5000 years, all that coal would be burned to ashes. Experts tell us that the sun has been blazing away for at least four billion years so its fuel cannot be coal.
Most of our fuels use oxygen when they burn. But there is little or no oxygen to support the fiery furnace of the sun. Until the atomic age, science could only guess what it uses for fuel, and even now we cannot prove step by step how its fuel is used. We are sure that the sun is a nuclear furnace. Its seething energy is released from the nuclei of atoms. Most experts suspect that the process is somewhat like the nuclear fusion which explodes a hydrogen bomb though no one has proved this.
The fuel of the hydrogen bomb is hydrogen, and almost certainly hydrogen is the fuel of the sun's nuclear furnace. It is the lightest of all elements, and the hydrogen atom is the smallest of all atoms. Normally, its nucleus contains one positively charged proton, and the nucleus is orbited by one negatively charged electron.
The hydrogen fuel in the core of the sun, however, does not exist under these normal conditions. It is compressed under terrific heat and pressure until it is no longer a filmy gas of free floating atoms. Most of the sun's core is hydrogen, and some estimates figure it to be 27 million degrees hot and 10 times denser than steel. All electrons are stripped from the dense fuel, and the atoms are ions.
It is thought that nuclear fusion occurs in the sun as ions of hydrogen fuse to form ions of helium. Four ions of hydrogen could combine to form one of helium, releasing in the process a tiny nuclear explosion. The seething energy of the sun would require countless numbers of such small hydrogen bombs every second.
Every second, the sun converts some 564 million tons of its hydrogen fuel into about 560 tons of helium. In the seething nuclear process, about four million tons of hydrogen fuel is released as electric energy. The sun is a fairly steady furnace, though its output increases and decreases somewhat during the 11 year sunspot cycle.
In an average hour, the hydrogen fuel squandered by the sun is more than 12 million million tons which is two followed by 12 zeros. The great nuclear furnace has been raging at this pace for more than four billion years. But our sun's hydrogen supply is so vast that its fuel is hardly diminished. And at its present rate, we can expect it to go blazing away with very little change through the next 12 billion years or so.