csillagokat

Csillagokat is the Hungarian term for the objects known in English as stars. In astronomy, a star is a luminous sphere of plasma held together by gravity and powered by nuclear fusion in its core. Most stars form from the gravitational collapse of cold, dense regions within molecular clouds. Over time, a protostar develops an accretion disk and, when core temperatures become high enough, hydrogen fusion begins and the object settles on the main sequence.

Stars vary widely in mass, luminosity, temperature, and color. They are classified by spectral type (O, B, A, F, G, K, M) and luminosity class; the Sun is a G-type main-sequence star (G2V). The observable properties of stars—such as brightness, color, and spectrum—depend on surface temperature, size, and distance from the observer.

Stellar evolution depends on initial mass. Low- to intermediate-mass stars end their lives as red giants or asymptotic giant branch stars and shed their outer layers, leaving behind white dwarfs. High-mass stars explode as supernovae, leaving neutron stars or black holes. Throughout their lifetimes, stars synthesize heavier elements and contribute to the chemical evolution of galaxies.

Observationally, stars are characterized by apparent brightness, distance (often via parallax), luminosity, and spectral composition. Spectroscopy reveals surface temperature and elemental abundances, while variability and binarity add to the diversity of stellar phenomena. Stars populate galaxies individually and in clusters, and their formation and evolution influence galactic structure and dynamics.