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ashok_bitsboymech
2005-Feb-08, 05:26 PM
hai after a long time iam keeping a query .
you all know about sun.can u think of why this sun had formed?
hwo can it be formed?
why did the sun lies in the milky way galaxy?
is is the helium and hydrogen in the sun never gets empty?
reply to me
by ur frind
ashok kumar(a living space boy to be in nasa)

bigbluestar
2005-Feb-08, 07:47 PM
Nice an oppurtunity to go back to basics. so lets start

1) HOw does a star form?
Well really the same reason all the other ones form. What starts it is the coalescing of gas. For first generation stars this will be hydrogen as its the most abundant element in the universe, and quite frankly it really has no need to change because its chemically stable. because of gravity this coalescing increases untill you get your self a protostar, A really big gas giant that would look like jupitor. The enourmout pressure on the core of this object would cause neuclear reaction. Not long after when a tempreture threashold is reached then neuclear fission starts and your star goes into main stage burn. (im skipping a bunch of steps and giving the important noes if its something athat you need the exact steps for lemmie know ill rewrite this to suite.) The excess matter usually either gets ionised, blown away, or goes through a simular step to form smaller objects like planets, moons, astroids, or just plain dust.

2) Why does a star form? What triggers the coalescing is an entirely different matter. The slowest is just plain gravity, next are supernova's or other explosive events that might compact this stuff to start the coalescing, my favourite is through galactic collisions. The gravitational tidal effects often takes Inter Stellar Material and compacts them often causing unpresidented star births.

3) Does the star fuel ever run out. Yes all the time. Once the star goes into main stage. its in a constant state of mass loss. When it does run out of fuel two different things can happens depending on the size of the star. If you are an O, B, or A type star you go Nova. A supernova is basically the pressure fromt he neuclear fission can no long resist the gravitational pull of the star. The core of the star collapses and this releases a rediculouse amount of energy violently blowing the shell of the star away. The second death a star experience is much less violent. If you are F, G, K, type star you turn into a planetary nebula (contrary to the name a planetary nebula has nothing at all to do with planets.) Basically to opposite of big stars happens, The gravity can no long withstand the pressure from neuclear fizzion and the star starts to swell. Slowly blowing its shell into space. It is also interesting to know that our sun is a second or a third generation star. We know this because first generation star don't have heavy materials such as iron. You only get these heavy element in space as the by product of a star. when a star dies it ejects its mass into space either by a nova or just puffing it out as a planetary nebula. That material coalesc's again and you have another star been born out of the heavier elements. OUr sun has some of these heavy material in it. So scientist are quite conviced that our sun is using recycled fuel.

Sorry i got carried away on that one I know some people get bored of long post but.... ah well.

astromark
2005-Feb-09, 01:42 AM
Just want to add that this universe seems to be about 13.5 billion years old. Durring that time many stars have compleated thier life cycles. This star of ours is about 4.5 billion years into a predicted 11 or 12 billion year life. In some regions of this galaxy there are star forming regions. Usually clouds of gasses we call nebulars. Thes are some times exposed to unusual forcess which can triger star formation. Some of the nebulars material could be the remnance of older dead stars. Thus the term second generation star. and as big blue star has said , our sun, Sol is one of these.