Tommy Willis, age 14, of.Lincolnton, N.C., for his question:
How fast is the sun burning up its fuel?
Everything about the sun is stupendous. We can grasp its dimensions only when we compare them with our own small world. The estimates of the size of its seething furnace, of course, are astronomical. But they, too, can be scaled down for our minds to grasp in earth sized dimensions.
Astrophysicists estimate that the sun comsumes about 564 million tons of its fuel every second. By itself, this bald figure is not very understandable. What's more it may be misleading, since only a small fraction of this material is given off as energy. Let's review the gigantic size of the sun and some of the things that go on in its thermonuclear reactor.
The volume of the sun is one and a third million times greater than that of the earth. If the trig gaseous ball were hollow, it could swallow a million earth sized planets and still have lots of room for dessert. The mass of a heavenly body is the amount of matter packed into its volume. The earth's mass is about 6 1/2 sextillion tons, which is 6,500 followed by 18 zeroes. The sun's mass is roughly 331,950 times greater.
The material in the sun is estimated to amount to about two million, two hundred thousand sextillion tons. And considerably more than half of this seething mass is hydrogen as, the fuel used to power the solar furnace. The amount consumed every second is but a fraction of the stupendous store. However, in earth sized dimensions it seems immense. In the time it takes you to count to 60, the sun uses up 33,840 million tons of its fuel. Every hour, it reduces its store of hydrogen'by two trillion, 30 billion, 400 million tons. At this rate, a helping of hydrogen equal to the earth's mass would not last the solar furnace very long.
The starry powerhouse is a thermonuclear reactor somewhat similar to hydrogen bombs in continuous explosion. Its nuclear activity is the fusion of small hydrogen atoms into larger atoms of helium. In the process, some of the material gets converted into the nuclear energy that radiates from the sun.
Hydrogen is the fuel and helium the ashes of the solar furnace. Every second, 564 million tons of hydrogen burn 560 million tons of helium. The missing four million tons of matter in this astronomical equation is converted into energy. This radiant energy is subtracted from the sun's mass. So every hour, the sun uses more than 20 trillion tons of its fuel and loses 14,400 million tons. of its massive weight.
The stupendous solar furnace can be scaled down to the size of a few small atoms. The conversion of hydrogen into helium is a lengthy process, involving a series of complicated stages. In the sun, it.is kept going continuously by countless numbers of infinitesimally small units. Each unit is the fusion of four hydrogen atoms into one atom of helium. In the process, a little less than one per cent of the matter in the hydrogen atoms is converted into nuclear energy.