Star formation begins when a. gas and dust collapse inward. c. the fusion of hydrogen slows down. b. nuclear fusion starts in the core. d. the core becomes carbon and oxygen.
STEP ONE: GAS AND DUST COLLAPSE INWARD. Step Two: This mixture begins to spin and compress under its own gravity. Step Three: Once the gas and dust reaches around 15 million kelvin, nuclear fusion occurs, in which hydrogen atoms fuse, forming helium. Step Four: This forms the core, and surrounding dust and gas surrounds it, resulting in a star.