The Hertzprung-Russel Diagram
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 Universe's 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 compres
As the protostar shrinks in size The central regions of a forming star become opaque and slows the outward flow of radiation. This core should eventually become a star and the disk could become planets. The Globule is cooled by emitting energy in the form of electro-magnetic waves and by the energy being used to dissociate and ionise. This can take from 10,000 to 1,000,000 years. It can takes a protostar 30 million years to reach hydrogen burning. When the protostar's core temperature has risen to several million degrees K, the fusion of Hydrogen (p-p chain) can begin( in a limited form. When the protostar is in this slower-contraction phase, it decreases in luminosity but keeps about the same surface temperature, most of the accrual of matter has slowed down to an almost non-existent level. Globules are characteristically a couple of light years in size, they possess densities of cold molecular hydrogen and dust of several tens of thousands of particles per cubic centimetre. 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. Ways in which the nebula could be cooled are by dust grains radiating away energy. The fragment collapses from a small fraction of a light year in diameter (several million solar radii) to a few thousand solar radii. The outward force exerted by the gas pressure causes the effect of gravity to be slowed down in the protostar a gradual contraction as it approaches equilibrium between gas pressure pushing outward, and gravity pushing inward. The high temperatures in the globule breaks the hydrogen molecules into hydrogen atoms (although some is radiated away) and later more energy is used in ionisation. Once it has commenced fusion and a temperature of 25,000,000 degrees F has been reached the star is now in the stable main sequence period of it's life and it will stay like this until it's hydrogen fuel is depleted and will then begin to die.
Common topics in this essay:
Kinetic Energy,
Stars Stars,
gas pressure,
protostar's core,
source energy,
clouds nebulae,
gravitational pull particles,
stars born,
gravitational pull,
hydrogen burning,
pull particles,
solar radii,
nebula begin,
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Acceptance Essays
