stellarevolution

Stellarevolution refers to the life cycle of stars, from formation in molecular clouds to their final remnants. It encompasses the structural changes, energy production, and chemical evolution that occur as stars age. The term is often used interchangeably with stellar evolution, though some writers distinguish the process from population-level dynamics.

Formation and main sequence: Stars form when clumps in molecular clouds collapse under gravity. As central temperatures rise, hydrogen fusion begins and hydrostatic equilibrium is established, placing the star on the main sequence. Massive stars shine brightly and exhaust their fuel rapidly, while low-mass stars burn hydrogen more slowly and can remain on the main sequence for many billions of years.

Post-main-sequence evolution: After hydrogen is depleted in the core, stars follow mass-dependent paths. Low- to intermediate-mass stars ascend the red giant and asymptotic giant branches, experience envelope ejection, and leave behind white dwarfs. High-mass stars undergo successive core-burning stages, end in core-collapse supernovae, and leave neutron stars or black holes as remnants.

End states and consequences: White dwarfs, neutron stars, and black holes are the compact remnants of stellarevolution. Supernovae and stellar winds enrich the interstellar medium with heavier elements, seeding future generations of stars and planets.

Observational framework: Stellarevolution is studied through the Hertzsprung-Russell diagram, spectroscopy, asteroseismology, and the analysis of supernova remnants and white-dwarf cooling sequences. Theoretical models depend on mass, metallicity, rotation, and mass loss, and remain areas of active research.