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.

- 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.

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.

- 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

- What is an astronomical unit
- What are the eight planets, and what order are they in?