Solar System Page 21
The term "Solar System" means a star as well as the planets and other objects which are in orbit around the star. Our Solar System used to have 9 planets but scientists decided that Pluto was only a dwarf planet, so now there only are 8 planets, plus our star which we call the Sun. The Solar System formed about 4.5 billion years ago. The planets except for Earth, were named after the Roman Gods, and they are Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. In between Mars and Jupiter there is an asteroid belt. No one knows how the Solar System was formed, but scientists believe that clouds of dust and gas were attracted by gravity to form the sun and the planets. Our Solar System is part of the Milky Way galaxy along with billions of other solar systems. Mars is the 4th planet from the Sun and the one most like Earth. Asteroid is a large rock in outer space.