Video describes how stars move in a spiral galaxy and how their speeds can be explained by accounting for dark matter. [3:17] Includes a brief quiz and a list of additional resources to explore.

Site provides a brief introduction to binary stars. Additional resources for students and teachers on this topic are offered as well as related topics.

Take this ten-question self-scoring quiz to test your knowledge of astronomy facts: age of the universe, why stars and planets are spheres, where other life might exist in the outer space, the Milky Way, and more.

A video and a short multiple-choice quiz on the Universe and what it is made up of.

Where is our Solar System? How far away is the sun? What makes up the sun? Find out all you want to know about our solar system. This is a comprehensive on-line site about space and astronomy. Check out all of the excitement!