https://phys.org/news/2018-07-students-foundations-massive-stars.html

"There's still a pretty open question in astronomy when it comes to massive star formation," Calahan said. "How do stars weighing more than eight solar masses form from clouds of dust and gas?"

Astronomers understand this process for stars the size of our Sun. Particles in clouds are attracted to each other and begin to clump together. Gravity takes hold and the gases flow to the center of the cloud as it collapses. Over millions of years, the gas is put under so much pressure that it begins to burn, and the star is born when nuclear fusion finally begins in the core of the compressed gas.