Mark Showalter of the SETI Institute in Mountain View, Calif., discovered the moon, which is currently called S/2004 N1, on July 1.
The moon is less than 12 kilometres wide and at a distance of 105,000 kilometres from Neptune, it orbits between Larissa and Proteus, two of Neptune’s 14 identified moons. It takes 23 hours to circle Neptune, as reported by the CBC.
The moon is so small and dim that when the Voyager 2 observed Neptune and its rings in 1989, it completely missed S/2004 N1.
The moon is in fact 100,000 times fainter than the faintest star that is visible to the naked eye. To confirm what looked like a white dot in Neptune’s orbit, Showalter had to track just the moon’s movements while excluding everything around it.
“”It’s the same reason a sports photographer tracks a running athlete — the athlete stays in focus, but the background blurs,” Showalter said in a statement.
Showalter then identified the same white dot in Hubble pictures taken between 2004 and 2009 to determine the moon’s orbit.
Showalter also told the CBC that he plans to write a report on S/2004 N1, but it will likely take a couple of months.
More pictures of Neptune’s newly-discovered moon can be seen here.