The new moon, Neptune’s tiniest at just 19.3 km across, is designated S/2004 N 1.

The U.S. space agency has announced the discovery of Neptune’s 14th moon. The Hubble Space Telescope captured the moon as a white dot in photos of the planet on the outskirts of our solar system.

The new moon, Neptune’s tiniest at just 19.3 km across, is designated S/2004 N 1.

The SETI Institute’s Mark Showalter made the discovery. He was studying the segments of rings around Neptune when the white dot popped out, 105,250 km from Neptune. He tracked its movement in more than 150 pictures taken from 2004 to 2009.

The considerably bigger gas giant Jupiter has four times as many moons, with 67.

“It is so small and dim that it is roughly 100 million times fainter than the faintest star that can be seen with the naked eye” said the space agency.

“It even escaped detection by NASA’s Voyager 2 spacecraft, which flew past Neptune in 1989 and surveyed the planet’s system of moons and rings,” it added.

“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,” Mr. Showalter said.

“It’s the same reason a sports photographer tracks a running athlete — the athlete stays in focus, but the background blurs,” he said.

The method involved tracking the movement of a white dot that appears over and over again in more than 150 archival Neptune photographs taken by Hubble from 2004 to 2009.

On a whim, Mr. Showalter looked far beyond the ring segments and noticed the white dot about 65,400 miles from Neptune, located between the orbits of the Neptunian moons Larissa and Proteus, NASA said.

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