What 2 forces create a star and control its size?

Answer 1

Stars are created from collections of hydrogen and helium in space. Since all matter attracts other matter, any small irregularity is distribution can result in the formation of a star as the hydrogen cloud collapses in on itself. As the forming star collects more and more material from the surrounding area it's pressure begins to rise. Due to the fact that temperature and pressure affect each other, the increasing pressure raises the temperature of the forming star. The matter continues to collapse and get hotter until the stars core reaches approximately 10 million C. At this temperature hydrogen atoms have enough energy to fuse together in nuclear fusion to form Helium. With the burning of the hydrogen fuel into Helium, a star can balance the forces of gravity (which wants to implode the star into it's center) and internal pressure (created by internal heat, which wants to expand the star outward)

Answer 2

Gravity initialises the beginning of the star (or planet) and as it gets bigger, more and more mass is attracted to it.

The size of a star (or planet) is dependant upon the other planets around it - this is known as the 'Roche Limit' (see link)

http://en.wikipedia.org/wiki/Roche_limit

A star can have massive gravitational pull even though it may only be small, for example a Neutron Star - probably around 5,000 times smaller than the size of the Earth, but can have a gravitational pull of many times the Earth (around 2 x 10^11 ms^-2) - and will also have a massive magnetic field (around 10^8 Tesla) due to its rate of rotation. (see link)

http://en.wikipedia.org/wiki/Neutron_star

Hope this helps you a bit.

Answer 3

gravity and force produced due to fusion of elements