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Overview
The stellar life cycle is the sequence of stages a star passes through from formation to its final remnant. Stars form from gas and dust, generate energy through nuclear fusion, change structure over time, and end as white dwarfs, neutron stars, black holes, or dispersed material depending largely on their mass.
Nebulae and Star Formation
Stars begin in clouds of gas and dust called nebulae. Gravity causes regions of the cloud to collapse, forming protostars that heat as material falls inward.
Main Sequence
A star spends most of its life on the main sequence, where hydrogen fusion in the core provides outward pressure balancing gravity.
Mass Dependence
Mass strongly controls a star's lifetime and fate. Massive stars burn fuel faster and live shorter lives, while low-mass stars can shine for far longer.
Red Giants and Supergiants
As core hydrogen becomes depleted, stars expand and evolve into red giants or supergiants, with fusion occurring in shells or heavier elements in massive stars.
Final Remnants
Lower-mass stars can leave white dwarfs. Massive stars can explode as supernovae and leave neutron stars or black holes.
Element Formation
Stars create heavier elements through fusion and stellar explosions. Much of the material in planets and living organisms was processed in earlier generations of stars.
Common Mistakes
A common mistake is thinking all stars end the same way. Stellar mass changes the path dramatically.
Why This Matters in Physics
The stellar life cycle connects gravity, fusion, radiation, nuclear physics, chemistry, galaxies, and the origin of elements.