Earth Science

The Solar System

Planets of the Solar System

Study Tip
The length of a day is related to how quickly a planet rotates, and a year is determined by how long it takes for the planet to orbit once around the sun.

Eight Planets

  • There are eight major planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune).
  • There are five dwarf planets (Ceres, Pluto, Makemake, Haumea, and Eris).
  • There are also over 150 different moons, and many asteroids and other space objects.
Study Tip
The length of a day is related to how quickly a planet rotates, and a year is determined by how long it takes for the planet to orbit once around the sun.

Orbits and Rotations

  • Distances in the solar system are measured in astronomical units, or AU.
  • One astronomical unit is the distance from the Earth to the Sun. This is approximately 150 million kilometers (93 million miles).
Planet
Mass (Relative to Earth)
Diameter (Relative to Earth)
Distance from Sun (AU)
Length of Day (in Earth Days)
Length of Year (in Earth Years)
Mercury
0.06 Earth’s Mass
0.39 Earth’s Diameter
0.39 AU
56.84 days
0.24 years
Venus
0.82 Earth’s Mass
0.95 Earth’s Diameter
0.72 AU
243.02 days
0.62 years
Earth
1.00 Earth’s Mass
1.00 Earth’s Diameter
1.00 AU
1.00 days
1.00 years
Mars
0.11 Earth’s Mass
0.53 Earth’s Diameter
1.52 AU
1.03 days
1.88 years
Jupiter
317.8 Earth’s Mass
11.21 Earth’s Diameter
5.20 AU
0.41 days
11.86 years
Saturn
95.2 Earth’s Mass
9.41 Earth’s Diameter
9.54 AU
0.43 days
29.46 years
Uranus
14.6 Earth’s Mass
3.98 Earth’s Diameter
19.22 AU
0.72 days
84.01 years
Neptune
17.2 Earth’s Mass
3.81 Earth’s Diameter
30.06 AU
0.67 days
164.8 years
Concept Check
  • What is an astronomical unit
  • What are the eight planets, and what order are they in?