Neptune's 'Enigma Moon' S/2004 N 1 Discovered By Hubble Telescope - By Accident

Despite launching all manner of satellites to look into the farthest depths of space, it appears we still haven't quite discovered everything on our own galactic back yard yet.

The latest addition to our solar system is a new moon orbiting Neptune, spotted by the Hubble Telescope earlier this month.

The reason it has gone undetected for so long is that it is no more than 12 miles across and 100 million times fainter than the dimmest star visible to the naked eye.

The new moon is incredibly dim

It even went unnoticed when Nasa'a Voyager 2 spacecraft passed Neptune in 1989.

Mark Showalter of the SETI Institute in California who discovered the planet said: "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."

Showalter examined more than 150 Hubble pictures of Neptune taken between 2004 and 2009. Looking beyond the planet's faint rings he spotted a recurring white dot, the new moon.

Currently it is called S/2004 N 1 though it will be named properly later. Showalter managed to plot an orbit for the moon which is circular and takes 23 hours.

It is the 14th of Neptune's moons to be discovered. Others include Galatea, Despina and Larissa.

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