Thesolar system is the sun and all the planets that go round it.
Saturn is the second biggest planet in the solar system.
solar system in British English
noun
the system containing the sun and the bodies held in its gravitational field, including the planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), the dwarf planets (Eris, Pluto, Haumea, Makemake, and Ceres), the asteroids, and comets
solar system in American English
1.
that portion of our galaxy which is subject to the gravity of the sun
2.
all the matter within this portion, including interplanetary dust or gas; esp., the sun itself and its planets