The Solar System
The Sun
The Sun is the center of the Solar System and holds the entire thing together with its gravity. You can learn more about the sun here.
The Planets
To find all the planets, we need to first define a planet. In 2006, the International Astronomical Union (IAU) defined a planet (in the Solar System) to be anything that fits these requirements:
- The object orbits the Sun
- The object needs to be similar to a sphere
- The object must have enough gravity to clear the space surrounding it
The word orbit means that planets go around the sun. It's kind of like falling towards the sun, but missing every time you get close.
Astronomers have discovered eight objects that fit the definition (the planet names are links):
Categorizing Planets
There are different ways of categorizing planets, but the one Learnmonkey uses has three categories: terrestrial planets, gas giants, and ice giants. The terrestrial planets are Mercury, Venus, Earth and Mars. The terrestrial planets are made up of rocks and metals. The gas giants are Jupiter and Saturn. The gas giants are much larger than the terrestrial planets and are made up of gases like hydrogen and helium. Finally, the ice giants are Uranus and Neptune. Ice giants have gases like hydrogen and helium, but they also have heavier elements like oxygen, carbon, nitrogen, and sulfur. Ice giants are smaller than gas giants, but are still larger than terrestrial planets.
Dwarf Planets
Dwarf planets are objects that orbit the Sun and are nearly round, but don't clear the surrounding space. Below is a list of dwarf planets (the names are also links: