Stars are born within vast clouds of gas and dust called nebulae. These nebulae are composed mostly of hydrogen and helium, the two lightest elements in the universe. Gravity plays a crucial role in the formation of stars, as it causes the gas and dust within a nebula to clump together. As these clumps grow larger, they begin to heat up and eventually ignite nuclear fusion in their cores, marking the birth of a star.
The Life Cycle of Stars
Once a star is born, it enters a phase where it will spend the majority of its life. This phase is known as the main sequence, during which a star fuses hydrogen into helium in its core. The balance between the inward pull of gravity and the outward pressure from nuclear fusion causes the star to remain stable. However, this equilibrium cannot last forever.
The Death of Stars
As a star exhausts its hydrogen fuel, it begins to undergo changes that will ultimately lead to its demise. The exact fate of a star depends on its mass. Low to medium mass stars, like our Sun, will eventually expand into red giants before shedding their outer layers to form beautiful planetary nebulae. The remaining core will cool and shrink, becoming a dense white dwarf. On the other hand, high mass stars will undergo supernova explosions, leaving behind either a neutron star or a black hole. This marks the end of the star's life cycle, but also the beginning of new stellar evolution processes in the universe.