The Sun is the largest. Jupiter is the next biggest object in the solar system. Then again, if you want to get really technical, the largest thing in the solar system BY FAR would be Jupiter's magnetosphere, which extends a radius of several million miles and nearly reaches Saturn's orbit.ars has the largest volcano in the solar system. It is called Olympus Mons, or Mount Olympus. At 375 miles (600 km) across, it would cover most of England, and at 16 miles (2 … 6 km) high, it is 3 times taller than Mount Everest. In the center is a huge, sunken crater that is 26 miles (90 km) across.