The Solar System

The Solar System consists of eight planets*. These planets all travel in circles around the sun. The four planets closest to the sun, known as the inner planets, all have hard surfaces and either no atmosphere or an atmosphere of relatively thin gasses. The four outer planets, because of their distance from the sun, have atmospheres made mostly of liquified gasses, and are known as gas giants

The eight planets, in order of distance from the sun (closest to farthest) are:

  1. Mercury
  2. Venus
  3. Earth
  4. Mars
  5. Jupiter
  6. Saturn
  7. Uranus
  8. Neptune

The Inner Planets

The four inner planets are: Mercury, Venus, Earth, and Mars. They are all close enough to the sun to have gaseous atmospheres, although Mercury is so small that it has almost no atmosphere at all. All four of the inner planets have a solid, almost spherical crust.

The Outer Planets

By contrast, the outer planets have thick atmospheres of gasses such as Hydrogen, Helium, or Methane. These planets are so cold that these gasses are all in liquid form.

Properties of the planets

Here are the planets listed with their distance from the sun, diameter, and how long it takes to orbit (length of year). Distane and diameter are given in miles

Planet Distance From Sun Diameter Length of Year
Mercury 35,983,610 3,032 88 days
Venus 67,232,360 7,521 225 days
Earth 92,957,100 7,926 365 days
Mars 141,635,300 4,222 687 days
Jupiter 483,632,000 88,846 11.9 years
Saturn 888,188,000 74,898 29.7 years
Uranus 1,783,950,000 31,763 84.3 years
Neptune 2,798,842,000 30,778 164.8 years

Notes:

* Pluto used to be considered the ninth planet, until the International Astronomical Union changed the definition of a planet in 2006. Now, we have eight planets and three dwarf planets: