Asteroid	a large rocky object that orbits a star, but is too small to be a planet
Astronomer	a person who studies stars and planets
Atmosphere	the layer of gases that surrounds a planet
Basalt Lava	a kind of rock
Carbon dioxide	a gas that animals breathe out and plants take in
Comet	a small icy object orbiting a star
Continent	a huge landmass on a planet
Core	the centre of a planet or star
Crater	a hole in a planet's surface made by a meteorite falling on it
Crust	the outermost layer of a planet's surface
Equator	an imaginary line around a planet, perpendicular to the axis of rotation
Gas Giant	one of the four outer planets made out of giant balls of gas
Hemisphere	one half of a planet's surface
Lava	molten rock above a planet's surface
Mantle	a layer of molten rock below a planet's crust
Mass	the size of something
Meteor	a small or medium sized rock from space that hasn't yet entered a planet's atmosphere
Methane	a gas that makes up most of the gas giants
Orbit	the path that an object takes around a larger object
Planet	a large celestial body that describes a well-defined orbit around a star
Rotate	to turn on an axis
Surface Area	the area on the outside of something
Terrestrial Planets	the four planets closest to the Sun
Star	a huge ball of gas that produces light itself
Volume	the size of an object