Astrojax is a toy consisting of three balls on a string. One ball is fixed at each end of the string, and the center ball is free to slide along the string between the two end balls. Inside each ball is a metal weight. The metal weight lowers the moment of inertia of the center ball so it can rotate rapidly in response to torques applied by the string. This prevents the string from snagging or tangling around the center ball.
Roughly, Astrojax play is a cross between juggling, yo-yo, and lasso. A wide variety of tricks and maneuvers can be performed with it. The basic maneuvers are vertical orbits, horizontal orbits and a figure-eight (butterfly) pattern.
Astrojax was invented by physicist Larry Shaw in 1987. It first appeared on the market in 1994, when it was sold through The Nature Company. Over the next several years it won a number of toy awards. In 2000 Astrojax was acquired by Active People, a Swiss company specializing in yo-yos, juggling toys and kites. In 2003 corporate chains such as Target, Walmart, KB Toys, and Toys-R-Us started to carry the product.
Active People sells several different types of Astrojax:
1. Horizontal Orbit: One of the balls is held in the users hands, the other two hold horizontal orbits underneath. The two spinning balls counterweight each other, maintaining the orbit. This is maintaided by small movements of the top ball to keep the orbits from slowing. The trick can be started by holding both the top and bottom balls (the top one directly below the bottom one), and spinning the middle ball. Then releasing the bottom ball creates a horizontal orbit.
2. Vertical Orbit: Similar to the horizontal orbit, but with the bottom and middle balls orbiting perpendicular to the ground. By tugging slightly on the ball in hand, the orbit continues however long the user desires. This is the starting movement for both tricks.
3. Butterfly: Starting with a vertical orbit the top hand is moved left and right quickly, in time with the rotation of the bottom ball. This causes the balls to move in a shape resembling a helix.
4. Switch: During a vertical orbit the top ball is released and the bottom ball is caught. The orbit now continues with their positions reversed. This trick can be performed repeatedly to add to the effect.
5. Venus: The bottom ball of a vertical orbit is pulled hard so that it travels over the users arm, followed by the middle ball. This trick can also be repeated for added effect.