TOPIC:

ID Code: E2-44
Purpose: Illustrate the orbital motion of a binary star system.
Description: This common optical device consists of a hemispherical mirror with a ball hanging at its center of curvature. When the ball is displaced and started into circular motion around the center of curvature, the real image of the ball also moves around the center of curvature on the opposite side of the center of curvature from the actual ball. This would represent the orbits of a binary star system where the masses of the two stars are approximately equal. Owing to the rather ghostly appearance of the image, this model is particularly suitable for illustrating a binary system in which one of the stars (the image) is a black hole.
Availability: Available