When are new stars formed?

New stars are formed in regions of space called nebulae, where dense clouds of gas and dust collapse under their own gravity. As the material in these clouds contracts, it heats up and forms a protostar. Once the temperature and pressure are high enough in the core, nuclear fusion begins, marking the birth of a new star. This process can take millions of years and is often triggered by events such as nearby supernovae or collisions between galaxies.