The Solar System (太陽系, Taiyoukei) is the proximity of celestial bodies orbiting the Sun. The Solar System is often confused with a planetary system, which refers to any system of non-stellar objects orbiting a star. The Solar System specifically defines the planetary system of the Sun, orbited by the Earth and other celestial bodies. There are billions of planetary systems within the four galaxies of the Dragon Ball universe, and there is known life among these systems.
After using the Spirit Bomb against Frieza on Namek, Goku states that "It [the Spirit Bomb] was filled with the energy of every living creature in the Solar System", referring to the planetary system of Namek.
Except for differences in Earth's geography, the Solar System in the Dragon Ball universe is parallel to the Solar System of our universe. However, only three planets from this Solar System are named in the Dragon Ball series: Earth, Mars, and Jupiter. It can be presumed that Earth and the other planets in this Solar System are parallel to our universe (as hinted by a Martian from Go! Go! Ackman making cameo in the Dragon Ball manga). Whis also mentions Pluto in the FUNimation dub of Dragon Ball Z: Battle of Gods.