Stjörnuþróun

Stjörnuþróun refers to the life cycle of stars, a process that encompasses their birth, evolution, and eventual death. The process begins within vast clouds of gas and dust known as nebulae. Gravity causes these clouds to collapse, forming dense cores that eventually heat up enough to ignite nuclear fusion, marking the birth of a star. The main sequence phase is the longest part of a star's life, during which it fuses hydrogen into helium in its core. The star's mass dictates its evolution and ultimate fate. Lower-mass stars, like our Sun, will expand into red giants before shedding their outer layers to form a planetary nebula and leaving behind a white dwarf. Higher-mass stars undergo a more dramatic evolution. They become red supergiants and, at the end of their lives, explode as supernovae. The remnant of a supernova can be either a neutron star or, for the most massive stars, a black hole. This continuous cycle of stellar birth and death enriches the interstellar medium with heavier elements, which are then used to form new stars and planets.