Põhitähtede

Põhitähtede, also known as main-sequence stars, represent the longest and most stable phase in the life cycle of most stars. Our own Sun is currently a põhitähtede. During this stage, stars generate energy through nuclear fusion in their core, primarily converting hydrogen into helium. The rate of this fusion, and thus the star's luminosity and temperature, is determined by its mass. More massive põhitähtede are hotter, brighter, and burn through their fuel much faster, leading to shorter lifespans. Conversely, less massive stars are cooler, dimmer, and can remain on the main sequence for billions or even trillions of years. The position of a star on the main sequence is plotted on the Hertzsprung-Russell diagram, a crucial tool in stellar astronomy. Stars spend approximately 90% of their active lives as põhitähtede. Once the hydrogen fuel in their core is exhausted, they will evolve off the main sequence into later stages, such as red giants or white dwarfs, depending on their initial mass. The study of põhitähtede is fundamental to understanding stellar evolution and the overall structure of galaxies.