Sterne

Stars, or Sterne in German, are luminous spheres of hot plasma predominantly composed of hydrogen and helium. They generate energy through nuclear fusion in their cores, most commonly fusing hydrogen into helium and releasing vast amounts of light and heat that radiate into space. Stars form from the gravitational collapse of dense regions within molecular clouds, progressing from a contracting protostar to a main-sequence star when hydrostatic equilibrium is reached. The Sun is a typical example, a G-type main-sequence star.

Internal structure generally includes a core where fusion occurs, surrounded by radiative and convective zones, with the photosphere marking the visible surface. The observed properties of a star—its luminosity, temperature, and color—are related in the Hertzsprung–Russell diagram and are influenced by mass.

Stellar evolution depends primarily on mass. Low- to intermediate-mass stars (up to about 8 to 10 solar masses) exhaust their hydrogen, become red giants, shed outer layers, and leave behind white dwarfs. High-mass stars fuse heavier elements and end their lives in supernovae, leaving neutron stars or black holes. These endpoints contribute to chemical enrichment and the dynamics of galaxies.

Stars are classified spectroscopically by spectral type (O, B, A, F, G, K, M) and luminosity. Distances to stars are measured by parallax and other methods, enabling studies of galactic structure and stellar populations. The term Sterne is used in German-language astronomy to denote stars.