The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields.
The Sun formed about 4.6 billion years ago from the gravitational collapse of a region within a large molecular cloud.
The core of the Sun is considered to extend from the center to about 20–25% of the solar radius.
The visible surface of the Sun, the photosphere, is the layer below which the Sun becomes opaque to visible light.