The Sun, also called Sol, is the star that defines the center of our Solar System and supplies the light and heat that make life on Earth possible. It is classified as a G-type main-sequence star (G2V) and is an ordinary, middle-aged star by cosmic standards. Its energy output, generated by nuclear fusion in the core, dominates the dynamics and climate of the planets and drives the local space environment known as the heliosphere.

Structure and energy production

The Sun's internal structure is organized into concentric layers. The core, where temperatures reach millions of degrees Celsius, is the site of the proton–proton chain of nuclear fusion that converts hydrogen into helium and releases enormous energy. Surrounding the core are the radiative zone and the convective zone, through which energy moves outward by radiation and then by convection. The visible surface is the photosphere, above which lie the chromosphere and the extended corona — a million-degree outer atmosphere that becomes the solar wind, a continuous flow of charged particles that influences Earth and the other planets.

Observable phenomena

The Sun exhibits a variety of magnetic and plasma-driven phenomena. Sunspots are relatively cooler, magnetically active regions on the photosphere. Solar flares are sudden releases of magnetic energy that emit energetic radiation, and coronal mass ejections (CMEs) expel large amounts of plasma into space. These events can interact with Earth's magnetic field to produce auroras and, in strong cases, disrupt satellites, radio communications and power grids.

History, age and future

Formed about 4.6 billion years ago from the gravitational collapse of a region within an interstellar molecular cloud, the Sun has burned hydrogen in its core for most of its life. It will continue fusing hydrogen for several billion more years. In the distant future it will exhaust core hydrogen, expand into a red giant, shed its outer layers, and end its active life as a cooling white dwarf surrounded by a planetary nebula.

Importance to Earth and human life

Solar radiation provides the energy that drives Earth's weather, climate and photosynthesis in plants. The Sun's magnetic and particle emissions shape near-Earth space weather and can affect modern technological systems. Studying the Sun also helps astronomers understand other stars and the processes that govern stellar evolution.

Key facts and distinctions

  • The Sun's mass is roughly 1.99 × 1030 kilograms, more than 300,000 times the mass of Earth; about 1.3 million Earths could fit inside by volume.
  • Energy produced in the core can take thousands to hundreds of thousands of years to reach the surface, then minutes to travel to Earth as sunlight.
  • Solar activity follows an approximately 11-year cycle in which the number of sunspots and the frequency of eruptions wax and wane.

Further information

This article summarizes broadly verified facts about the Sun and its role in the Solar System. For technical details, observational data and ongoing research, consult specialized resources and mission results linked above.