New Moon Around Neptune: Planet's 14th Moon Discovered via Hubble Images

No bigger than 12 miles across, and nearly coal-black in color, a new moon discovered orbiting Neptune is so faint that it evaded detection for the 167 years Neptune has been known, even as a spacecraft flew by and discovered several of the planet's other 13 moons in the 1980s.

Finding what is now Neptune's 14th known moon was a feat of telescopic wizardry and fortuitous record keeping.

While analyzing photos of Neptune taken by the Hubble Space Telescope, astronomer Mark Showalter of the SETI Institute noticed a faint white dot on an image that corresponded to a position about 65,400 miles from the planet. Had it not been for Showalter's keen eye, the celestial speck may have been overlooked.

The dot appears about 100 million times fainter than the dimmest star visible to the naked human eye. When NASA's Voyager 2 spacecraft zoomed by in 1989, five Neptunian moons were discovered, but this moon went by unnoticed.

Showalter was studying the faint arcs, or segments of rings, around Neptune when he made the discovery on July 1.

"The moons and arcs orbit very quickly, so we had to devise a way to follow their motion in order to bring out the details of the system," he said in a press release. "It's the same reason a sports photographer tracks a running athlete - the athlete stays in focus, but the background blurs."

To do this, Showalter and his team examined existing Hubble photos of the Neptune system. The dot appeared over and over again in more than 150 archival Neptune photographs taken between 2004 and 2009.

For now, the moon is referred to as S/2004 N 1, but when it is given a common name it will likely be known after a Greek or Roman water deity, keeping in line with the rest of Neptune's moon names.

S/2004 N 1, the smallest of the moons in the Neptune system, is located between the orbits of the moons Larissa and Proteus, which were discovered in 1981 and 1989, respectively. It takes 23 hours for S/2004 N 1 to complete one revolution around Neptune.

Neptune's largest moon, Triton, is roughly the size of Earth's Moon.