great stuff...u almost answered all my doubts...

ok a few more questions:

1. when does the collapse of a star begin? eg. for a star which has a mass of 20x of the sun compared to a star which has a mass of 100x of the sun?
which is faster?
any equations to show this?

2. how do stars form? and what factor determines the size and density of a star? if a star of a really big mass forms which HAS the potential of becoming a black hole, will it start collapsing immediately or will it start sometime(millions of years =-D) later?

pls answer these questions, i know i didnt phrase them very well, but i'll see if u guys understood my questions, if not i'll rephrase them in another post. thanks =-)