- Astronomical Unit – the mean distance between the Earth and the Sun.
- Aphelion – the point in the orbit of a planet or comet when it is the farthest from the Sun.
- Comet – small balls of frozen gas and solids that take very elliptical paths around the Sun.
- Eclipse – an obscuring of the light, usually in relation to the Sun or the Moon.
- Geocentric – the idea that the planets and the Sun revolve around the Earth.
- Gravity – the force of attraction between all objects that have mass.
- Heliocentric – the idea that the planets, including the Earth, revolve around the Sun.
- Perihelion – the point in the orbit of a planet or comet when it is at its nearest point to the Sun.
- Sunspot – any relatively cool or dark spot on the Sun.
- Supernova – a rare event involving the explosion of most of the material in a star.
From Georgia Virtual Learning Astronomy