Mark Showalter, who works with the Mountain View-based SETI discovered the moon — temporarily dubbed S/2004 N 1 — on July 1, while studying the planet's rings, or "arcs."
According to a press release issued by SETI, Showalter had to run images, collected by the Hubble Space Telescope, through special processors in order to clearly see the moon, which is only about 12 miles across and "roughly 100 million times fainter than the faintest start that can be seen with the naked eye."
Because the moons and other debris orbiting Neptune move very quickly, pictures of the rings smear together. "The moon is too faint to be seen in individual images, but can be seen clearly when sets of 8-10 images are added together."
In total, the astronomer had to process 150 Hubble images, taken between 2004 and 2009, to determine that the moon was actually there.
After gathering that data, Showalter was able to determine the moon orbits the blue-green planet once every 23 hours.