The Megasphere was gigantic artificial construct which was an exact model of the Milky Way housed at the Prometheus Science Center in 2268. Distances between the stars, nebulae, black holes, neutron stars, and other objects were to scale – though the stars and other intragalactic objects were not. All galactic coordinates for starship navigational computers and all scientific referents to galactic structure were drawn from the Megasphere. Only two originals existed – one on Earth, the other on Vulcan.