NASA's Hubble Telescope Discovers a Tiny 14th Moon for Neptune

It looks like 13 moons simply isn't enough for our solar system's farthest planet from the sun as researchers using NASA's Hubble Space Telescope have discovered a 14th moon orbiting the icy giant.

The moon, dubbed S/2004 N 1, is so small and hard to see that even NASA's Voyager 2 spacecraft missed it when it passed by Neptune in 1989. S/2004 N 1 is no more than 12 miles across, and is 100 times dimmer than the faintest star that can be seen in the heavens with the naked eye. It completes one orbit around Neptune every 23 hours.

"This moon never sits still long enough to have its picture taken," Mark Showalter from the SETI Institute said.

Showalter discovered the moon July 1 while studying segments of Neptune's rings in older photographs. He was looking for rings further away from the planet and found S/2004 N 1 as a white dot, some 65,000 miles away. By comparison, our own moon lies almost 239,000 miles away from Earth.

"I was working with some older images from 2009 that I thought I was finished with," Showalter explained.

"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. It's the same reason a sports photographer tracks a running athlete -- the athlete stays in focus, but the background blurs."

Neptune, classified as an ice giant, is the eighth and last planet in our solar system after a 2006 ruling that Pluto was a dwarf planet, and not an actual planet.