October 9, 2013 - A tiny, mysterious moon orbiting Neptune has been spotted for the first time in more than 20 years.
By analyzing photos taken by the Hubble Space Telescope, scientists at the SETI Institute in Mountain View, Calif., have caught sight of Naiad, the innermost of Neptune's moons. The 62-mile-wide (100 kilometers) moon has remained unseen since the cameras on NASA's Voyager 2 spacecraft discovered it in 1989.
Scientists recently tracked Naiad across a series of eight archival images taken by Hubble in December 2004 after using a different technique to help cancel out Neptune's glare. Neptune is 2 million times brighter than Naiad, so Naiad is difficult to see from Earth, SETI officials said. [See photos of Neptune, the mysterious blue planet]
"Naiad has been an elusive target ever since Voyager left the Neptune system," SETI scientist Mark Showalter said in a statement. Showalter announced the new findings today (Oct. 8) during a session at the annual meeting of the American Astronomical Society's Division for Planetary Sciences, held in Denver.
This version of the image identifies all of the bodies orbiting Neptune visible in the image. Note that even the newly-discovered moon, provisionally identified as S/2004 N 1, is visible here as a faint dot. Image released Oct. 8, 2013.
Credit: M. Showalter/SETI Institute
Now that scientists have spotted the small moon again, there are other mysteries to be solved. Naiad seems to have drifted off course: The new observations show that the moon is now ahead of its predicted path in orbit around Neptune, SETI officials said.
Scientists expect that the new trajectory could have something to do with Naiad's interaction with one of Neptune's other moons that caused the innermost moon to speed up in its orbit. The exact cause of the moon's new orbit won't be known until researchers collect more data.
Neptune's slender rings are seen with remarkable clarity in this composite image taken by the Hubble Space Telescope. Image released Oct. 8, 2013.