Glossary
The astronomical unit (AU or au or a.u. or sometimes ua) is a unit of length very commonly used in astronomy. It is approximately equal to the distance from the Earth to the Sun. The currently accepted value of the AU is 149,600,000 kilometers (about 149.5 million kilometers).
The speed needed for a spacecraft to pull off the gravity of an object that contains gravity.
The objects, planets, asteroids, moons, dust and the Sun make up the Solar System. The Sun pulls everything to it and stops it from flying away. Each planet/dwarf planet has its own gravity to stop its own objects from pulling away.
