An astronomer with the SETI Institute announced the discovery of Neptune's 14th moon, spotted during a review of archive photographs taken by the Hubble Space Telescope.

With a diameter of only 19 kilometers (12 miles), the new moon, S/2004 N1, is so small that it eluded detection by NASA's Voyager 2 probe during a close fly-by of Neptune in 1989.

SETI's Mark Showalter made the discovery July 1 while studying photos taken by the Hubble telescope between 2004 and 2009.

S/2004 N1 appears in roughly 150 of those images, providing Showalter with enough material to plot the tiny moon's orbit and determine that it takes 23 hours to complete a revolution around Neptune.

Astronomers' determination in 2006 that Pluto is not a planet left Neptune as the most-distant planetary body in the Solar System.

Some experts suggest that Neptune's largest moon, Triton, was a dwarf planet captured by the gravitational pull of the larger body. EFE