How fast does it take for a star to ignite?

From a small star to super giant star,I imagine fusion takes place right away,setting off an outward blast of radiation therefore creating the light producing star within an split second... What do you think about this sudden birth of a once swirling disk up gas? Thank so much for your detailed... CindyHow fast does it take for a star to ignite?It takes about a couple of million years for the big massive O type stars to start fusing hydrogen to helium. For stars about 10 times the Sun;s mass that time is believed to be around 10 million years. The Sun probably took about 50 million years to start fusing its hydrogen to helium. The interior temperature of the proto star must reach around 14 million Kelvin for fusion to take place.