The Sun is a yellow dwarf star, also known as a G-type main-sequence star. It is a medium-sized star, with a mass of about 2 x 10^30 kilograms, which is about 330,000 times the mass of the Earth. The Sun's diameter is about 1.4 million kilometers, which is about 109 times the diameter of the Earth. The Sun is about 4.6 billion years old.