Planet: A Celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, not massive enough to cause thermonuclear fusion, and has cleared its neighbourhood. i.e. Has become gravitationally dominant and there are no other bodies of comparable size other than its own satellites or those otherwise under its gravitational influence. If it has met all other criteria except for clearing the neighbourhood, then it is classified as a dwarf planet – sorry Pluto and thank you Wikipedia.
If we go even further we can simplify them into two groups: gas giants and terrestrials, for the purpose of my research I will focus purely on the terrestrials.
– Orbit: A planet revolves around the sun
– Axial Tilt: They lie at an angle to the plane of their stars’ equators, causing seasons.
– Rotation: They rotate around an invisible axes through their centre.
– Mass: the force of the planet’s own gravity forces the planet into a spherical shape.
– Internal Differentiation