The Hertzprung-Russel Diagram essays

The Hertzprung-Russel Diagram essays Stars are born in the interstellar gas and dust clouds (nebulae) along our Galaxy's spiral arms (this being specific to our galaxy as being the birthplaces of stars) Observational evidence points to this. As some stars reach the end of their lives, they eject most of their mass creating new clouds of nebulae (most of this matter will be released in the form of planetary nebula). Thus the cycle continues and new stars are born from the death of the old. The gravitational pull between the particles in these nebulae is not enough on its own to cause the particles to coalesce into a star, otherwise nearly all of the matter in these interstellar clouds would have collapsed into stars very early on in the Universes history and no nebulas would remain. The gas pressure in these clouds is sufficient to balance the effects of gravity. Another source of energy in stars is the conversion of gravitational potential energy into heat during contraction. This is a small source of the Sun's energy. This contraction is a vital source of energy on which a star can draw at various stages in its life. So to begin the formation of stars the nebula needs some kind of external force to act upon it, such as the cloud being compressed which will bolster the gravitational pull between the particles to the point where this equilibrium can be broken. This compressing of the nebula can be caused by a density wave (compression wave.) This compressive force can also come from a supernova explosion, the gas shell expelled by this strikes nearby nebula and compresses it by a factor of ten (or greater). Many young stellar associations have been found within the expanding shells of old supernova remnants. But for the collapse of a nebula to begin it must be cooled so that the gas pressure would go down. Otherwise the Kinetic Energy which the particles have would exceed the pull of gravity amid each particle preventing them from coalescing. Wa ...