An exoplanet is any planet that exists outside the Earth's solar system. 539 of these planets have so far been discovered.
Types of ExoplanetsEdit
Multiple types of exoplanets have been discovered up to date. These include:
Ocean Planets, planets covered in liquid.
Rogue Planets, planets that have ceased to orbit their sun.
And many others. Many are very much like the planets of our Solar System, often containing the same chemical compounds.