The largest celestial body in our solar system is the Sun. Comprising over 99% of the solar system's total mass, the Sun is a star primarily made up of hydrogen and helium. It plays a crucial role in the solar system by providing light and heat, which are essential for life on Earth. The gravitational pull of the Sun also keeps the planets, including Earth, in their respective orbits. Its enormous size, with a diameter of about 1.4 million kilometers, dwarfs all other solar system bodies, making it the center of our cosmic neighborhood.