Sonne

Sonne is the German name for the Sun, the star at the center of the Solar System. It is a G-type main-sequence star (spectral type G2V) with an age of about 4.6 billion years. Its mass is about 1.99 × 10^30 kilograms, its radius about 696,000 kilometers, and its diameter about 1.39 million kilometers. The Sun accounts for about 99.8% of the Solar System’s total mass.

The Sun shines by nuclear fusion in its core, converting hydrogen into helium via the proton-proton chain. This energy moves outward through the radiative zone and convective zone before escaping as light at the photosphere, with a surface temperature near 5,778 kelvin. Its luminosity is about 3.8 × 10^26 watts. The outer atmosphere consists of the photosphere, chromosphere, and corona; the solar wind streams from the corona.

Surface features include sunspots and plages; the Sun exhibits an approximately 11-year activity cycle influenced by its magnetic field. It rotates with differential rotation, averaging about 25 days at the equator and longer at higher latitudes.

Gravitationally, the Sun governs the orbits of the planets and smaller bodies. It formed from a collapsing molecular cloud about 4.6 billion years ago and is expected to remain on the main sequence for roughly another 5 billion years. When core hydrogen is exhausted, it will expand into a red giant, shed its outer layers, and end its life as a white dwarf surrounded by a planetary nebula.

The Sun is the primary source of light and heat for Earth, driving climate and photosynthesis, and its activity influences space weather, affecting satellites, power grids, and communications.