Triton
Triton is the largest of Neptune's 13 moons and is unique due to its retrograde orbit, meaning it orbits Neptune in the opposite direction of the planet's rotation. Scientists believe Triton was a Kuiper Belt Object captured by Neptune's gravity millions of years ago.
Source: science.nasa.gov
APODs including "Triton"
Old Faithful Meets Hale-Bopp
26/05/1997
As Comet Hale-Bopp leaves our Northern Skies, it provides us with yet another burst of joy. On May 11th the fading comet was photographed behind the famous "Old Faithful" water geyser of Yellowstone National Park, Wyoming, USA, Planet Earth. Perhaps more familiar to Earth Dwellers than the dark geysers on Neptune's moon Triton, the gas geysers on Jupiter's moon Io, and the dirty water geysers hypothesized on Jupiter's moon Europa, Earth's Old Faithful is also reliable - every 60-80 minutes it gushes a plume of water and steam high into the air. Comet Hale-Bopp will continue to be visible to observers in the Southern Hemisphere as it moves away from the Sun towards the outer Solar System.