Solar system planets, order and formation: A guide

THE SUN The sun is by far the largest object in our solar system, containing 99.8% of the solar system's mass. It sheds most of the heat and light that makes life possible on Earth and possibly elsewhere. 

MERCURY: THE CLOSEST PLANET TO THE SUN - Discovery: Known to the ancient Greeks and visible to the naked eye - Named for the messenger of the Roman gods - Diameter: 3,031 miles (4,878 km) - Orbit: 88 Earth days - Day: 58.6 Earth days - Number of moons: 0

VENUS: EARTH'S SOLAR SYSTEM TWIN - Discovery: Known to the ancient Greeks and visible to the naked eye - Named for the Roman goddess of love and beauty - Diameter: 7,521 miles (12,104 km) - Orbit: 225 Earth days - Day: 241 Earth days - Number of moons: 0

EARTH: OUR HOME PLANET, FILLED WITH LIFE - Name originates from "Die Erde," the German word for "the ground." - Diameter: 7,926 miles (12,760 km) - Orbit: 365.24 days - Day: 23 hours, 56 minutes - Number of moons: 1

MARS: THE SOLAR SYSTEM'S RED PLANET - Discovery: Known to the ancient Greeks and visible to the naked eye - Named for the Roman god of war - Diameter: 4,217 miles (6,787 km) - Day: Just more than one Earth day (24 hours, 37 minutes) - Number of moons: 2

JUPITER: THE LARGEST PLANET IN OUR SOLAR SYSTEM - Discovery: Known to the ancient Greeks and visible to the naked eye - Named for the ruler of the Roman gods - Diameter: 86,881 miles (139,822 km) - Orbit: 11.9 Earth years - Day: 9.8 Earth hours - Number of moons: 79 (53 confirmed, 26 provisional)

SATURN: THE RINGED JEWEL OF THE SOLAR SYSTEM - Discovery: Known to the ancient Greeks and visible to the naked eye - Named for Roman god of agriculture - Diameter: 74,900 miles (120,500 km) - Orbit: 29.5 Earth years - Day: About 10.5 Earth hours - Number of moons: 82 (53 confirmed, 29 provisional)

URANUS: THE TILTED, SIDEWAYS PLANET IN OUR SOLAR SYSTEM - Discovery: 1781 by William Herschel (was originally thought to be a star) - Named for the personification of heaven in ancient myth - Diameter: 31,763 miles (51,120 km) - Orbit: 84 Earth years - Day: 18 Earth hours - Number of moons: 27

NEPTUNE: A GIANT, STORMY BLUE PLANET - Discovery: 1846 - Named for the Roman god of water - Diameter: 30,775 miles (49,530 km) - Orbit: 165 Earth years - Day: 19 Earth hours - Number of moons: 14

PLUTO: ONCE A PLANET, NOW A DWARF PLANET - Discovery: 1930 by Clyde Tombaugh - Named for the Roman god of the underworld, Hades - Diameter: 1,430 miles (2,301 km) - Orbit: 248 Earth years - Day: 6.4 Earth days - Number of moons: 5