Why is the Sun always burning?I think its because of nuclear fission. But sun does not have oxygen i think. Without oxygen how is it possible?

Expert Answers
enotechris eNotes educator| Certified Educator

You, along with astronomers up until the 19th century, pondered this question.  By their best calculations, they simply couldn't account for how the Sun, even as massive as it is, could be able to produce heat for as long as it did.  Yesterday's astronomers did the same thing you did -- imagined that the Sun was undergoing some kind of burning process. What scientists didn't know about were the subatomic particles that compose atoms, and it is the fusion of those nuclei that create the heat that radiates from the Sun, a process unfathomable to scientists until the discovery of radioactivity.

Interestingly, the Sun starts fusing two hydrogen nuceli to create a nucleus of helium, releasing energy in this reaction.  Eventually (and this is still far in the future) the Sun's hydrogen supply will run low, and at its center it will begin to fuse soley helium, creating higher-numbered elements, then fusing those elements to create higher-numbered elements still.  Every atom that exists came from the belly of a star. Depending on the type of star, it will eventually explode, dispersing the Elements through space. Our Sun, however, being an average star of average age, will go through a process of expansion, large enough to swallow Mercury and Venus, and maybe even Earth. Certainly all life here will cease, as the solar energy will boil off the oceans and incinerate the planet, perhaps correctly reflecting the term "Global Warming."    The Sun will then contract to smaller than in is now and continue to thermally radiate a fraction of it current heat for hundreds of billions of years, as it slowly cools off.


giorgiana1976 | Student

Like any star,  Sun exists to burn!

It does not burn as you saw a fire burning, but small particles of hydrogen turns to helium particles producing nuclear energy. Every second, 700 million tons of hydrogen is turned into 695 million tons of helium and 5 million tons of energy. But Sun has a huge amount of hydrogen.

Although Sun burns every second a  so large amount of hydrogen,it has a lot of energy, still.

 It can burn another 10 billion years. Since it's appearance, the Sun has burned only half the hydrogen contained.

Scientists say that after the Sun will be consumed all hydrogen, it will begin to 'burn' helium, while transforming into a red giant star. This star will contract, at a time, throwing in space most of the material it is made from, but keeping the core, which it will become a small White Star, a star with the size of Earth but with a high temperature and a low sheen. The Sun will not explode in a supernova.

epollock | Student


Stars shine by a process quite different from that of a normal fire. Whereas a fire’s energy output is the result of a chemical reaction (wood burning), a star’s energy is released through the thermonuclear reaction of hydrogen fusing into helium and the conversion of mass into energy according to Einstein’s famous equation, E = mc2. Stars shine with a near constant energy outflow for billions of years.

Stars are born, they live, and they die through a process known to astronomers as “stellar evolution.” The critical factor that determines a star’s life cycle is its mass. Massive stars live fast and die young. Low mass stars have longer, more stable lifetimes.  

One of he defining stages of a star’s life is when it is fusing hydrogen into helium in a manner such that the outward pressure of the reaction balances the inward force of gravity in the star. This is known as “hydrostatic equilibrium” and we say the star is on the “Main Sequence.”  The Sun is an example of such a star. It has been on the main sequence for about 4.5 billion years.

krishna-agrawala | Student

It is quite right to say that the suns energy comes from thermonuclear reactions that take place at the center of the sun. However it is not quite correct to call this process as burning, which is a term used to describe the process of heat generation through process of rapid oxidation of various substances. Thermonuclear reaction produce immense amount of energy without using oxygen in the process.

The heat of the thermonuclear reaction taking place at the center of the sun cause temprature to rise to about 15,000,000 degrees C. This heat travels to the surhace of the sun, where the temperature is abour 5,500 degrees C. The energy reaching the surface of the sun is then radiated out to the space in the form of light an heat.

princessnerditia | Student

becaus in sun dea are milions of explosive gases that are constantly in reaction.

astrosonuthird | Student

Our sun is not always burning, one day it will finish its all nuclear fuels.

astrosonu | Student

hello! the sun is not always burning one day it will use up all its nuclear fuel and will become an neutron star or a black hole.

Access hundreds of thousands of answers with a free trial.

Start Free Trial
Ask a Question