Star formation is the process by which massive amounts of gas and dust collapse under their own gravity to create stars. This process typically begins within giant molecular clouds, which are dense, cold regions of interstellar matter. When localized density increases—often triggered by external forces such as nearby supernova shockwaves or galactic spiral arm passes—a region of the cloud becomes gravitationally unstable, initiating fragmentation and collapse. This collapsing material forms a protostar, which accretes mass from the surrounding envelope. As the core continues to contract, gravitational potential energy is converted into thermal energy, causing the temperature and pressure at the center to rise dramatically. Once the core reaches sufficient temperature and pressure, sustained nuclear fusion of hydrogen into helium ignites, marking the star's entry onto the main sequence and stabilizing the system.