how does the sun remain on fire?

Answer 1

{grrr} I spent over an hour researching this, typing my answer and giving references. I clicked the Preview button and got the Yahoo page to enter my password, then it was all gone.

I'll try again. First, the short answer:

Because there's a lot to burn. :-) Really!

The longer answer:

The sun is a ball of mostly hydrogen (the current fuel) plus helium, and finally much smaller amounts of oxygen, carbon, and other elements.

The ball is sustained by a balance of two forces. It is pulled in by gravity, which is how it formed in the first place, and which alone would make it collapse on itself. Gravity, however, is balanced by an outward pressure from hot gases and radiation in the interior.

Right now, the hydrogen in the sun is "burning" at the ravenous rate of something like half a billion tons per second. By burning, we mean not chemical burning but nuclear burning. Nuclear fusion is converting hydrogen into helium. By-products of this fusion are light and heat, which is what gives the sun its two most familiar traits!

So although the sun gulps fuel at an alarming rate, one has to consider its size to answer the question "what keeps it going?" The sun's mass, about 1.99 x 10 (to the 30th power) kilograms, makes it far larger than even our largest planet, Jupiter. To put that in terms we can understand, consider that well over a million Earths could fit inside the sun. At one of my links, below, there is a page showing nice photos of the sun, with colored balls depicting the sizes of Jupiter and the Earth.

The sun's fuel is not endless, though. Naturally the hydrogen must run out, eventually. There's no need to start making "arrangements" just yet, as it will last for about five billion more years. But as the hydrogen runs out, the dwindling outward pressure it produced, and the reduced radiation, will result in a collapse due to the now-stronger force of gravity. As this happens, the temperature in the core will increase to a point where the helium (generated in the first stage) will now become the fuel, and will be converted to carbon.

When even the helium is exhausted, the sun will become a red supergiant. Its outer edges will swallow up Venus, Earth, and even Mars. Finally there will be nothing left but a core of carbon, which will cool and become a "white dwarf."

Answer 2

The sun isn't on fire.

The sun is a densely packed ball of mostly hydrogen (with some helium in there as well.) The gravity well created by the sun is powerful enough that it causes a nuclear fusion reaction, converting the hydrogen in the sun into helium and radiating energy (which we experience as light and heat.)

Since the tremendous pressures inside the sun don't dissipate over time, the sun will continue to process its hydrogen until all of the hydrogen is spent. It will then try to consume its helium, which will cause it to expand into a red giant in five billion years.

Answer 3

Through nuclear fusion.

About 75% of the Sun consists of hydrogen while 25% is helium. The Sun is in fact one gigantic nuclear reactor. Nuclear fusion reactions in its core fuse hydrogen into helium.

Each second, more than 4 million tonnes of matter undergo nuclear fusion in the Sun's core, producing neutrinos, solar radiation and of course an enormous amount of energy (heat, fire).

Answer 4

Atomic Fusion

The sun is so massive that the hydrogen atoms are crushed together in the center by gravity. Two hydrogens make a helium atom plus excess energy. This is called fusion. This energy is emittited and absorbed countless times until it reaches the surface of the sun where it is emitted as photons(light) to reach us, 93 million miles away.

this is the best form of nuclear energy in my opinion.
stable, powerful and at a safe distance.

Answer 5

Its not fire, its superheated gas emitting light. The Sun is a ball of Hydrogen gas where the extreme temps and pressure cause nuclear fusion reactions which change the Hydrogen into Helium.

Answer 6

well,i completely agree with vanchan_london!
he has given perfect answer...its really due to nuclear fusion at the core of the sun whch fuse hydrogen into helium and as aresult produce neutrinos,and enormous amount of heat,light i.e solar radiation...

Answer 7

Because it is made up of billions and billions of Helium and Hydrogen gases? That's its basic composition, gases. Don't worry, like any other stars, it will soon come to an end, just not in my lifetime, I hope :p

Answer 8

*sings*


The sun is a mass
Of incandesent gas
A gigantic nuclear furnace
Where hydrogen is turned into helium
At tempuratures of millions of degrees

We need its light
We need its heat
We need its energy
Without the sun
Without a doubt
There'd be no you or me!