7 Answers

The Sun does not "burn", like we think of logs in a fire or paper burning. The Sun glows because it is a very big ball of gas, and a process called nuclear fusion is taking place in its core. Nuclear fusion occurs when one proton smashes into another proton so hard that they stick together...and release some energy as well. This energy then heats up the other materials (other protons and electrons and such) nearby. This heating eventually grows out from the center (or core) of the star to the outside, finally leaving the surface and radiating out into space to be the heat and light we know stars emit.

People, including scientists, sometimes say that the Sun "burns hydrogen" to make it glow. But that is just a figure of speech. Hydrogen really doesn't burn, it fuses, into helium. So no oxygen is required!

source:http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question36.html

When things here on Earth burn, what is happening is that oxygen is combining with the molecules of the burning substance and releasing energy, which is the heat of the burning. Some materials give off more heat when combining with oxygen, some give off less. If a material does not readily combine with oxygen, or if the amount of energy released when it does combine is too low, we say that the material is not flammable.

What goes on in the sun, however, is not "burning" like here on Earth. There is no oxygen (or more accurately, no where near enough oxygen, there is a little) in the sun for any kind of normal burning to take place. What is going in is a process called nuclear fusion.

In the sun, hydrogen nuclei are fused together to make helium. This is similar to burning on Earth in the fact that two things are combining together to release energy, but different in every other way. For one thing, the materials invovled are different. For another, oxygen on Earth combines chemically via the outer electrons with an appropriate fuel to burn, whereas in the sun, it is the nuclei of hydrogen atoms which are combined. The interior of the sun where this takes place is much to energetic for the hydrogen atoms to even have any outer electrons. Lastly, while chemical burning on earth releases only a little energy compared to the mass of burning materials, nuclear fusion on the sun releases a huge amount of energy compared to the masses of hydrogen involved.

But just like any fire on Earth, the sun can't go on burning forever. When all of the hydrogen has been fused into Helium, the sun will change somewhat and start to fuse the helium nuclei. This does not release as much energy as the fusion of hydrogen, however. This will continue through other elements until the only thing left is gaseous iron, and the sun eventually dies. Don't worry about that, though, our sun has another good 5 billion years left before it dies!

Hope this helps.

3.5 billion years is all the time we have left….are you afraid yet?

It will explode, but not in your lifetime.

Yes, eventuality.  The Sun is a star and is dying at a very slow rate scientist say it's at it's mid point now but it's taken a kagillion  yrs. (not a word) to get there .  But happy thoughts we won't be around to worry about it.

Of course but  don't worry, you will not notice.

The sun will one day in the future, expand until it swallows all the planets and then it will become a black hole or a dead star.

AlGore said it will.. And we are the cause of it, we are killing the sun.