• 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