The armillary sphere (from the Latin armilla - "hoop") is an astronomical instrument dating back to the Ancient World. It consists of several moving rings with marked divisions that serve to determine the coordinates of heavenly bodies. Armillary spheres were used as an aid to astronomical observations and calculations until more precise devices were invented.
The example on display presents the structure of the Solar System with the planets going around the Sun in accordance with the theory put forward by Nocolaus Copernicus in the 16th century.