Neso, a moon of Neptune

Neso is one of Neptune's fourteen moons. It has a diameter of 60 kilometres (37 miles). It orbits at an average distance of 48.4 million kilometres (30 million miles) from Neptune, taking 9,374 Earth days, or 26 Earth years, to complete a full journey around the planet. It is Neptune's most distant moon and also the most distant moon of any planet in the solar system.

Neso was discovered on 14th August 2002 by teams of astronomers led by Matthew Holman and John Kavelaars. Their discovery was as part of a project to search for distant moons of Neptune. In the summer of 2001, they obtained images of areas around Neptune where moons may be located using the Cerro Tololo Inter-American Observatory and Canada-France-Hawaii Telescope. They detected six potential objects, and repeated the search again in August 2002 and August 2003, to confirm their findings. Five of those six new moons were seen again, including the moon that is now known as Neso. The other moons discovered through this method are Halimede, Laomedeia, Sao and Psamathe.

Neso is classed as an irregular retrograde moon. An irregular moon usually refers to a moon that has been captured by a planet's gravity rather than one which formed around it. A retrograde moon is one that orbits in the opposite direction of its host planet's rotation. It's likely that Neso was originally an asteroid or an object that formed in the Kuiper Belt.