Triton, Neptune's largest satellite, orbits at such a distance that, from its surface, Neptune appears roughly sixteen times the diameter of our Moon as seen from the Earth. Out here, the Sun is 900 times fainter than we know it, but still brighter than 550 full Moons. However, when Triton is between the Sun and Neptune, as in this picture, the only illumination comes from the planet itself. Neptune then provides only about as much light as 0.9 full Moons, dying the Tritonian landscape a nice shade of ice-cold azure.
