What force brings the gas in a nebula together to form a main sequence star?

also i have another question...



Which part of the EM spectrum do stars emit?



and...



List four elements present in stars and when they occur in a star's life cycleWhat force brings the gas in a nebula together to form a main sequence star?Gravity: stars form inside dense concentrations of interstellar gas and dust known as molecular clouds. These regions are extremely cold, just above absolute zero. The deep cold also causes the gas to clump. Star formation is often triggered by an external shock wave, for instance an exploding supernova. When the density reaches a certain point, the cloud collapses under their own weight.



Stars like the Sun and bigger emit mainly in visible light. For the Sun it's about 50% visible light, 45% infra red and 5% UV.

Red dwarfs emit relatively more infra red, and large stars more UV.



*All* elements are present in stars like the Sun. However for the Sun it's about 3/4 hydrogen, 1/4 helium and 2% other stuff. Over time more helium is produced and at the end of its life the Sun will even start to fusion Helium into Carbon and Oxygen.