Planet Facts

There are 8 planets in our solar system, they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Planets in our solar system can be divided into two main groups, Terrestrial Planets and Gas Giants. Planets that orbit other stars are referred to as Exoplanets.

Click on any planet below to find out more about it:

Facts about the Planets

  • Mercury’s craters are named after famous artists, musicians and authors.
  • Venus is the hottest planet in the solar system.
  • Earth’s atmosphere protects us from meteoroids and radiation from the Sun.
  • There have been more missions to Mars than any other planet.
  • Jupiter has more than double the mass of all the other planets combined.
  • Saturn has more moons than any other planet in the Solar System.
  • Uranus has only been visited by a single spacecraft, Voyager 2.
  • It takes like more than 4 hours for light to reach Neptune from the Sun.
  • Only 8 planets have been discovered in our solar system but there is compelling evidence for a 9th planet.
  • With the exception of Neptune and Uranus the other 6 planets can be seen unaided and all 8 are visible with a small telescope or binoculars.
  • Together the planets make up 0.14% of the solar systems mass, 99% of which is the gas giants (Jupiter, Saturn, Uranus and Neptune).
  • Except for the Earth, the planets are named after gods from Roman and Greek mythology.

Size and Order of the Planets

Size & order of the planets diagram
The planets size comparison: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune
  • The order of the planets from closest to the Sun outwards is; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and finally Neptune.
  • The largest planet in the solar system is Jupiter, followed by Saturn, Uranus, Neptune, Earth, Venus, Mars with the smallest being Mercury.

The table below shows the size of the planet, how far it is from the Sun and how long it takes to complete a single orbit.

NameDiameterDistance from SunLength of Year:
Mercury4,879 km57,909,227 km88 Earth days
Venus12,104 km108,209,475 km225 Earth days
Earth12,742 km149,598,262 km365.24 days
Mars6,779 km227,943,824 km1.9 Earth years
Jupiter139,822 km778,340,821 km11.9 Earth years
Saturn116,464 km1,426,666,422 km29.5 Earth years
Uranus50,724 km2,870,658,186 km84.0 Earth years
Neptune49,244 km4,498,396,441 km164.8 Earth years

What is a Planet?

Planets are among the many worlds and smaller objects that orbit the Sun. The formal definition of planet, as voted on by the International Astronomical Union in 2006, is as follows:

A planet is a celestial body that

  1. is in orbit around the Sun,
  2. has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
  3. has cleared the neighbourhood around its orbit.

Under this definition, Pluto is NOT a planet, but has been deemed a dwarf planet because it has not yet cleared its orbit. This definition is under discussion, particularly by members of the planetary science community, and it may yet be further refined.

Sources: https://solarsystem.nasa.gov/planets/overview/, https://nssdc.gsfc.nasa.gov/planetary/factsheet/
Last Updated: 21st July 2019, First Published: June 2012
Author: Chris Jones