Is There a Ninth Planet in the Solar System?

Serious Science - . The planets of the Solar System are usually divided into several groups. First, the Inner planets – Mercury, Venus, Earth, and Mars – which have small mass and rocky composition. Next, the Gas Giants, Jupiter and Saturn, and the Ice Giants, Uranus and Neptune. However, in the past few years many scientists have come to believe that the planets of the Solar System don’t end with Neptune. In fact, there might be one more planet out there.