Submitted by elsbeth on Tue, 2009-10-27 16:59

The sun’s life cycle

 

The sun is a star and arose out of a nebula of gas and dust particles which came together. These particles collected around one or more central points. The sun arose out of the middle of these central points. In this phase, it is called a protostar.

Continued accretion of mass inside the protostar (core fusion) releases energy and creates radiation pressure, causing the protostar to start radiating light. In this phase (main sequence phase), the sun is known as a main sequence star.

Our sun is about halfway through this phase and is around 4.5 billion years old. Our sun will continue in this phase for about another 5.5 billion years, at which point it will move on to the red giant phase. This phase will begin after almost all of the hydrogen in the sun’s core has been consumed.

Core fusion will spread to the outer layers, which will cause the sun’s exterior to expand rapidly. This will heat up the earth until it is a ball of lava. The outer layers of the sun will also cool down, which will cause the light emitted to shift towards the red end of the spectrum. This phase is called the red giant phase. In this phase, the outer layers will break off, leaving behind a C-O core. The sun is now in the white dwarf phase and mostly emits ultraviolet radiation. Our sun will slowly cool off and eventually burn out and become a black dwarf.