By . Mark Duell . PUBLISHED: . 20:55 EST, 15 July 2013 . | . UPDATED: . 05:47 EST, 16 July 2013 . An astronomer studying old images of Neptune found a 14th moon orbiting the planet - by accident. The National Aeronautics and Space Administration (NASA) revealed the find yesterday and said the moon, estimated to be about 12 miles in diameter, is located approximately 65,400 miles from Neptune. Astronomer Mark Showalter, from the SETI Institute in Mountain View, California, was searching Hubble Space Telescope images for moons inside faint ring fragments circling Neptune. Accidental find: This composite Hubble Space Telescope picture shows the location of a newly discovered moon, S/2004 N 1, orbiting Neptune. It's 100million times fainter than the faintest star visible with the naked eye . Neptune's . largest moon, Triton, was discovered in 1846, just days after the . planet itself was found. Nereid, Neptune's third largest moon, was found . in 1949. Images taken by . NASA's Voyager 2 spacecraft unveiled the second largest moon, Proteus, . and five smaller moons, Naiad, Thalassa, Despina, Galatea and Larissa. Ground-based telescopes found Halimede, Laomedeia, Sao and Nestor in 2002. Sister moon Psamathe turned up a year later. The expert said: ‘We had been processing the data for quite some time and it was on a whim that I said, 'OK, let's just look out further'.’ ‘I changed my program so that instead of stopping just outside the ring system it processed the data all the way out. 'I walked away from my computer and waited an hour while it did all the processing.’ ‘When I came back, I looked at the image. There was this extra dot that wasn't supposed to be there.’ Follow-up analysis of other archived Hubble images of Neptune verified the object was a moon. The tiny moon has previously escaped detection by NASA's . Voyager 2 spacecraft, which flew past Neptune in 1989 and surveyed the . planet's system of moons and rings. In space: This diagram released by NASA shows the orbits of several moons located close to the planet Neptune. Neptune's largest moon, Triton, was discovered in 1846, just days after the planet itself was found . Mr Showalter 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.' Neptune's moons and arcs 'smear out' when captured by the Hubble Telescope because of their rapid orbital motion. The astronomer re-processed the images to compensate for this smear and discovered the new moon as an extra white dot that has escaped attention before. Interestingly, the moon is too faint to be seen in individual images but was noticeable when experts looked at sets of ten images together. The astronomer has tracked the moon's movement in more than 150 pictures taken by Hubble from 2004 to 2009. He then plotted a circular orbit for the moon, which completes one revolution around Neptune every 23 hours. Mr Showalter made the discovery after he decided to focus his attention beyond Neptune's faint ring that contains its known moons (pictured). 'I looked at the image. There was this extra dot that wasn't supposed to be there,' he said . Mr Showalter and colleagues are mulling . over a name to propose to the International Astronomical Union, which . has final say in the matter. ‘We haven't really gotten far with that,’ he said. ‘What I can say is that the name will be out of Roman and Greek mythology and it will have to do with characters who are related to Neptune, the god of the oceans.’ The newly found moon, designated S/2004 N 1, is located between Larissa and Proteus. It orbits Neptune in 23 hours. The moon is so small and dim that it is 100million times fainter than the faintest star that can be seen with the naked eye. The considerably bigger gas giant Jupiter has four times as many moons, with 67. The astronomer is pondering names for the new moon but thinks that it may reference Roman or Greek mythology and be linked to characters related to the god of the ocean, Neptune. An image of the planet Neptune is pictured .
NASA says moon has 12-mile diameter and is 65,400 .
miles from Neptune .
Astronomer looked for moons inside faint ring fragments circling planet .
But Mark Showalter then analysed broader part of the sky 'on a whim'
He tracked movement of 'S/2004 N 1' in 150 pictures from 2004 to 2009 .
By . Mark Duell . PUBLISHED: . 20:55 EST, 15 July 2013 . | . UPDATED: . 05:47 EST, 16 July 2013 . An astronomer studying old images of Neptune found a 14th moon orbiting the planet - by accident. The National Aeronautics and Space Administration (NASA) revealed the find yesterday and said the moon, estimated to be about 12 miles in diameter, is located approximately 65,400 miles from Neptune. Astronomer Mark Showalter, from the SETI Institute in Mountain View, California, was searching Hubble Space Telescope images for moons inside faint ring fragments circling Neptune. Accidental find: This composite Hubble Space Telescope picture shows the location of a newly discovered moon, S/2004 N 1, orbiting Neptune. It's 100million times fainter than the faintest star visible with the naked eye . Neptune's . largest moon, Triton, was discovered in 1846, just days after the . planet itself was found. Nereid, Neptune's third largest moon, was found . in 1949. Images taken by . NASA's Voyager 2 spacecraft unveiled the second largest moon, Proteus, . and five smaller moons, Naiad, Thalassa, Despina, Galatea and Larissa. Ground-based telescopes found Halimede, Laomedeia, Sao and Nestor in 2002. Sister moon Psamathe turned up a year later. The expert said: ‘We had been processing the data for quite some time and it was on a whim that I said, 'OK, let's just look out further'.’ ‘I changed my program so that instead of stopping just outside the ring system it processed the data all the way out. 'I walked away from my computer and waited an hour while it did all the processing.’ ‘When I came back, I looked at the image. There was this extra dot that wasn't supposed to be there.’ Follow-up analysis of other archived Hubble images of Neptune verified the object was a moon. The tiny moon has previously escaped detection by NASA's . Voyager 2 spacecraft, which flew past Neptune in 1989 and surveyed the . planet's system of moons and rings. In space: This diagram released by NASA shows the orbits of several moons located close to the planet Neptune. Neptune's largest moon, Triton, was discovered in 1846, just days after the planet itself was found . Mr Showalter 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.' Neptune's moons and arcs 'smear out' when captured by the Hubble Telescope because of their rapid orbital motion. The astronomer re-processed the images to compensate for this smear and discovered the new moon as an extra white dot that has escaped attention before. Interestingly, the moon is too faint to be seen in individual images but was noticeable when experts looked at sets of ten images together. The astronomer has tracked the moon's movement in more than 150 pictures taken by Hubble from 2004 to 2009. He then plotted a circular orbit for the moon, which completes one revolution around Neptune every 23 hours. Mr Showalter made the discovery after he decided to focus his attention beyond Neptune's faint ring that contains its known moons (pictured). 'I looked at the image. There was this extra dot that wasn't supposed to be there,' he said . Mr Showalter and colleagues are mulling . over a name to propose to the International Astronomical Union, which . has final say in the matter. ‘We haven't really gotten far with that,’ he said. ‘What I can say is that the name will be out of Roman and Greek mythology and it will have to do with characters who are related to Neptune, the god of the oceans.’ The newly found moon, designated S/2004 N 1, is located between Larissa and Proteus. It orbits Neptune in 23 hours. The moon is so small and dim that it is 100million times fainter than the faintest star that can be seen with the naked eye. The considerably bigger gas giant Jupiter has four times as many moons, with 67. The astronomer is pondering names for the new moon but thinks that it may reference Roman or Greek mythology and be linked to characters related to the god of the ocean, Neptune. An image of the planet Neptune is pictured .
miles from Neptune. Astronomer Mark Showalter, images for moons inside faint ring fragments of a newly discovered moon, S/2004 N 1, orbiting tracked the moon's movement in more than 150 pictures taken by Hubble from 2004 to 2009. He Neptune. An image of the planet Neptune is