Eight solar system planets,artwork. The planets are not shown to scale. Clockwise from bottom right,the planets are Earth,Mars,Jupiter,Uranus,Neptune,Venus,Saturn and Mercury. Pluto was counted as a planet from its discovery in 1930 until August 2006,when the International Astronomical Union voted to change its status to "dwarf planet". This status is shared with Ceres,the largest asteroid,and UB313,a body larger than Pluto and more distant than it,which was discovered in 2003. According to the ruling,a planet must orbit the Sun,have sufficient mass to be nearly spherical and have cleared its orbit of debris |