| MadSci Network: Astronomy |
Great question. As you know, the sun is the star that Earth rotates around one time each year. Being the only star in relatively close proximity to Earth, it is the source of all of our heat and light. This massive amount of energy comes from nuclear fusion, which occurs in the Sun's core. In fusion, two atoms come together and "fuse" into a larger atom. When this happens, massive amounts of energy are released. In the sun, two hydrogen atoms fuse into helium.
Two atoms, such as hydrogen, have a natural tendency to repel each other. For fusion to occur, this repulsion must be overcome and the atoms must be moved very close together. In the sun, this is accomplished by an enormous gravitational force that pulls the hydrogens together. In addition, the sun's interior is extremely hot which gives the atoms enough energy to fuse.
The visible light that we see from the Sun is the energy escaping in the form of thermal radiation. At ordinary temperatures, below 600 C, the thermal radiation released by an object is not visible because it is concentrated in the infra-red region of the spectrum. However, at sufficiently high temperatures, the energy shifts to shorter wavelengths which we can see. A practical example of this is the red glow of heated piece of iron. At higher temperatures it becomes white, etc. Currently, much research is being done around the world to develop a reactor that would allow us to harness the energy from nuclear fusion. I hope this helps.
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