Hviezdy

Hviezdy, the Slovak term for stars, are luminous spheres of plasma that emit light and heat from nuclear fusion in their cores. They form in collapsing regions of molecular clouds and evolve from protostars to hydrogen-burning main-sequence stars. A star’s mass largely determines its lifetime and fate: sun-like stars end as white dwarfs, while the most massive explode as supernovae, leaving neutron stars or black holes.

Structurally, a star has a hot core where fusion occurs, surrounded by radiative and convective zones, and a visible surface called the photosphere. The chromosphere and corona lie above it. The color and temperature determine its spectral type, from hot blue O-type to cool red M-type, and its size is described by luminosity classes: dwarfs (V), giants (III), and supergiants (I).

Observationally, brightness depends on intrinsic luminosity and distance. Parallax measurements yield distances and absolute magnitudes. Modern surveys such as Hipparcos and Gaia provide precise data for millions of stars, enabling studies of the Milky Way’s structure and motions.

Stars are central to navigation, timekeeping, and science. They are laboratories for physics under extreme conditions and trace the chemical evolution of galaxies through nucleosynthesis and, in their deaths, supernova enrichment, which seeds future generations of stars and planets.