The Sun

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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.

The Sun is a magnetically active star. It supports a strong, changing magnetic field that varies year-to-year.

It has a diameter of about 109 times that of Earth, and its mass about 330,000 times that of Earth accounts for about 99.86% of the total mass of the Solar System.