The Sun is the star

at the center of the Solar System.

The Sun has the diameter of 865,000 miles that is about

 same as 109 Earths. 

The Sun's color is white,

 although from the surface of the Earth it may appear yellow

because of atmospheric scattering.

Sun is brighter than about 85% of the stars in the Milky Way galaxy.  The Sun is the  star closest to Earth. The Sun is the brightest object in the sky.

An accurate scientific understanding of the Sun developed slowly, and as recently as the 19th century prominent scientists had little knowledge of the Sun's physical composition and source of energy. This understanding is still developing; there are a number of present-day anomalies in the Sun's behavior that remain unexplained.

The Sun is 4.7 million years old

 and is expected to exist for another 4.5 million years from now.