Jupiter hangs in the heavens behind a mountaintop on a frozen midwinter night in Lyngenfjord, Norway. Jupiter is the extremely bright ‘star’, and to its lower left and upper right are two of its moons, Ganymede and Callisto. Of the other two visible moons, Io is hidden on the Jovian disc, and Europa is just emerging on the lower left, possibly discernible as a slight elongation of Jupiter’s point of light.